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Lens Cell Cleaning
On 2/9/2011 10:41 AM, Cheesehead wrote:
And the rear has a ring holding it in place, which should be removable easily with a spanner wrench. I'm not sure what you are saying here but do NOT remove the glass itself from it's mount but unscrew the whole cell from the shutter to clean the front/inner surface and you can also clean the rear of the front element while you are there by opening the shutter. Stephey |
Lens Cell Cleaning
On 2/10/2011 12:47 PM Cheesehead spake thus:
I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. That said, the rear should be a single piece of glass. But it is not. If it is a cemented piece, then it is not a true Tessar and the fogging may be in the cement. That would be bad. I've not found the formula out there to describe the lens. In the mean time I've been searching for a replacement rear cell. It's not clear you've tried to remove and clean the rear cell; have you? If not, you should. What've you got to lose? If in fact the cement is clouded (which I think is probably unlikely), you've got to replace the thing anyhow (or have it recemented), so why not just pull it out and clean it? It ain't rocket surgery, you know. -- Comment on quaint Usenet customs, from Usenet: To me, the *plonk...* reminds me of the old man at the public hearing who stands to make his point, then removes his hearing aid as a sign that he is not going to hear any rebuttals. |
Lens Cell Cleaning
On 2/10/2011 3:47 PM, Cheesehead wrote:
I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. Not sure who told you that but it's not a tessar, it's a triplet. A modern version of the classic cooke triplet. And a rather good one I might add. Stephey |
Lens Cell Cleaning
On 2/10/2011 7:54 PM, Cheesehead wrote:
I have, of course, unscrewed the cell from the shutter and observed that the fogging is inside the rear cell. Hmm that's odd. It should be a single element so hard to imagine there being fogging inside it? Stephey |
Lens Cell Cleaning
On 2/10/2011 4:54 PM Cheesehead spake thus:
On Feb 10, 4:53 pm, David Nebenzahl wrote: It's not clear you've tried to remove and clean the rear cell; have you? If not, you should. What've you got to lose? If in fact the cement is clouded (which I think is probably unlikely), you've got to replace the thing anyhow (or have it recemented), so why not just pull it out and clean it? It ain't rocket surgery, you know. I have, of course, unscrewed the cell from the shutter and observed that the fogging is inside the rear cell. Well, did you try to clean the outer surfaces? Sorry, not clear from your postings. -- Comment on quaint Usenet customs, from Usenet: To me, the *plonk...* reminds me of the old man at the public hearing who stands to make his point, then removes his hearing aid as a sign that he is not going to hear any rebuttals. |
Lens Cell Cleaning
On 2/10/2011 10:14 PM, David Nebenzahl wrote:
On 2/10/2011 4:54 PM Cheesehead spake thus: On Feb 10, 4:53 pm, David Nebenzahl wrote: It's not clear you've tried to remove and clean the rear cell; have you? If not, you should. What've you got to lose? If in fact the cement is clouded (which I think is probably unlikely), you've got to replace the thing anyhow (or have it recemented), so why not just pull it out and clean it? It ain't rocket surgery, you know. I have, of course, unscrewed the cell from the shutter and observed that the fogging is inside the rear cell. Well, did you try to clean the outer surfaces? Sorry, not clear from your postings. I'm confused on his post as well. It's a triplet and as such the rear "cell" would be a single element. I suppose the glass itself -could- be bad and have fogging inside the single element itself? Or the coating is screwed up? Stephey |
Lens Cell Cleaning
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Lens Cell Cleaning
On 2/11/2011 8:27 AM, Cheesehead wrote:
that also has me puzzled. It is described as a Tessar, but I am only going by what I can find. Where did you see that? EVERY source I found, except people saying they are guessing at the formula, like you are here, say it's a triplet. http://www.apug.org/forums/forum44/1...8-geronar.html http://www.hevanet.com/cperez/test/BigMash210.html http://www.bhphotovideo.com/c/produc...nar_Copal.html http://greenspun.com/bboard/q-and-a-...?msg_id=002Owe http://en.wikipedia.org/wiki/Rodenstock_GmbH#Geronar http://photo.net/large-format-photography-forum/003EZO The rear cell *looks like* it has two elements in it. Not sure how that is possible. Stephey |
Lens Cell Cleaning
"Cheesehead" wrote in message ... On Feb 9, 11:41 pm, "Richard Knoppow" wrote: If its a standard Triplet the back cell will be a single lens so there is no need to remove the glass. The front cell will have two elements. Usually in larger lenses there is a threaded back cap on the cell but it may have a retaining ring on the front which is more common for smaller lenses. If a back cap its easy to remove. The elements are clamped between concentric edges in the cell so are automatically centered. If the cap is too tight for removal with simple finger grip use one of those rubber jar grippers. It won't mar the surface. If you grip too tightly it will clamp it and make it even harder to remove. I agree with the others about cleaning but if the lens is oily the standard optical cleaner is pure acetone followed by dry isopropyl alcohol. Window cleaner like Windex may streak the lens if not followed by alcohol. The newer butyl alcohol "streak-free" cleaners are better. While ammonia is alkaline and strong alkalies can dissolve some kinds of glass there is no real danger from the very dilte ammonia in Windex and similar cleaners. If you use acetone be careful of the edge paint, if any, and of the paint on the cell because it will dissolve both. I do not recommend cleaning inside elements when in a shutter because there is too much danger of getting the cleaning fluid into the shutter, take the cell out. -- -- Richard Knoppow Los Angeles, CA, USA I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. That said, the rear should be a single piece of glass. But it is not. If it is a cemented piece, then it is not a true Tessar and the fogging may be in the cement. That would be bad. I've not found the formula out there to describe the lens. In the mean time I've been searching for a replacement rear cell. I think you mis-typed, a Tessar _does_ have a cemented rear component, a Triplet does not. I also don't remember what a Geronar is but think it may be a Dialyte. Have to look it up. If it is a Dialyte its a four element air spaced lens. Both front and rear cells will have two lenses with an air space between. There should be a back cap on both cells allowing access to the inner surfaces. If its actually a Tessary type and there is haze inside the rear component its due to the cement being damaged. Most old lenses were cemented with Canada Balsam. This has good optical properties but is subject to damage from low temperatures, which will make it milky. It also tends to dry out at the edges unless very well sealed, so that its common for CB cemented lenses to show a yellow ring of oxidation at the edge. If this goes on long enough the cement at the edges may crystalize. While a small amount of oxidation at the edge (its not true separation) does little harm it can cause problems if it progresses far enough. Most of these lenses can be recemented. Modern cements are synthetic, either binary cements similar to common epoxy or UV curing cements. Some lenses built in about the 1950s have an earlier synthetic cement of a type cured by heat. Some of these show degradation or true separation due to problems in the cementing process. I've seen a number of Kodak lenses that seemed slightly hazy but on close examination with a magnifier and correct light, it was evident that the cement layer had become reticulated, having a sort of orange-peel look. Some Zeiss lenses and some Wollendak lenses from this period have actual large bubbles in the cement where it has completely separated from the glass. All these can be recemented if they are thought valuable enough. One can try it at home using a makeshift method of centering but any valuable lens should be submitted to someone like John van Stelten who has the proper equipment to do it the right way. -- -- Richard Knoppow Los Angeles, CA, USA -- -- Richard Knoppow Los Angeles, CA, USA |
Lens Cell Cleaning
Cheesehead wrote:
Cheesehead wrote: On Feb 9, 11:41 pm, "Richard Knoppow" wrote: If its a standard Triplet the back cell will be a single lens so there is no need to remove the glass. The front cell will have two elements. Usually in larger lenses there is a threaded back cap on the cell but it may have a retaining ring on the front which is more common for smaller lenses. If a back cap its easy to remove. The elements are clamped between concentric edges in the cell so are automatically centered. If the cap is too tight for removal with simple finger grip use one of those rubber jar grippers. It won't mar the surface. If you grip too tightly it will clamp it and make it even harder to remove. I agree with the others about cleaning but if the lens is oily the standard optical cleaner is pure acetone followed by dry isopropyl alcohol. Window cleaner like Windex may streak the lens if not followed by alcohol. The newer butyl alcohol "streak-free" cleaners are better. While ammonia is alkaline and strong alkalies can dissolve some kinds of glass there is no real danger from the very dilte ammonia in Windex and similar cleaners. If you use acetone be careful of the edge paint, if any, and of the paint on the cell because it will dissolve both. I do not recommend cleaning inside elements when in a shutter because there is too much danger of getting the cleaning fluid into the shutter, take the cell out. -- -- Richard Knoppow Los Angeles, CA, USA I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. That said, the rear should be a single piece of glass. But it is not. If it is a cemented piece, then it is not a true Tessar and the fogging may be in the cement. That would be bad. I've not found the formula out there to describe the lens. In the mean time I've been searching for a replacement rear cell. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average: 4.74, 4.81, 4.76 On Feb 9, 11:41 pm, "Richard Knoppow" wrote: If its a standard Triplet the back cell will be a single lens so there is no need to remove the glass. The front cell will have two elements. Usually in larger lenses there is a threaded back cap on the cell but it may have a retaining ring on the front which is more common for smaller lenses. If a back cap its easy to remove. The elements are clamped between concentric edges in the cell so are automatically centered. If the cap is too tight for removal with simple finger grip use one of those rubber jar grippers. It won't mar the surface. If you grip too tightly it will clamp it and make it even harder to remove. I agree with the others about cleaning but if the lens is oily the standard optical cleaner is pure acetone followed by dry isopropyl alcohol. Window cleaner like Windex may streak the lens if not followed by alcohol. The newer butyl alcohol "streak-free" cleaners are better. While ammonia is alkaline and strong alkalies can dissolve some kinds of glass there is no real danger from the very dilte ammonia in Windex and similar cleaners. If you use acetone be careful of the edge paint, if any, and of the paint on the cell because it will dissolve both. I do not recommend cleaning inside elements when in a shutter because there is too much danger of getting the cleaning fluid into the shutter, take the cell out. -- -- Richard Knoppow Los Angeles, CA, USA I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. That said, the rear should be a single piece of glass. But it is not. If it is a cemented piece, then it is not a true Tessar and the fogging may be in the cement. That would be bad. I've not found the formula out there to describe the lens. In the mean time I've been searching for a replacement rear cell. I thought a Tessar had four elements, the rearmost was a cemented doublet. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average: 4.74, 4.81, 4.76 |
Lens Cell Cleaning
On 2/12/2011 12:33 PM, Jean-David Beyer wrote:
Cheesehead wrote: I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. That said, the rear should be a single piece of glass. But it is not. If it is a cemented piece, then it is not a true Tessar and the fogging may be in the cement. That would be bad. I've not found the formula out there to describe the lens. In the mean time I've been searching for a replacement rear cell. I thought a Tessar had four elements, the rearmost was a cemented doublet. Lot of confusion in this thread.. A 210mm f6.8 Geronar -IS- a triplet. The rodenstock sales booklet at the time these were sold stated this. http://www.bhphotovideo.com/c/produc...nar_Copal.html A tessar has a cemented doublet but this lens isn't a tessar. http://en.wikipedia.org/wiki/Tessar Someone along the way may have swapped out the rear cell from some other lens into the sample he has or something odd, I have no idea. Maybe he is confusing a coating problem with fogging inside the cell? I have no idea on that either.. But the rear cell on a normal 210mm f6.8 geronar is a single piece of glass. Stephey |
Lens Cell Cleaning
Lots of snipping here................................
"Jean-David Beyer" wrote in message ... Cheesehead wrote: Cheesehead wrote: On Feb 9, 11:41 pm, "Richard Knoppow" wrote: I'm not absolutely certain about the Geronar formula. It is reported to be a Tessar. That said, the rear should be a single piece of glass. But it is not. If it is a cemented piece, then it is not a true Tessar and the fogging may be in the cement. That would be bad. I've not found the formula out there to describe the lens. In the mean time I've been searching for a replacement rear cell. I thought a Tessar had four elements, the rearmost was a cemented doublet. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average: 4.74, 4.81, 4.76 That is correct except that it is possible to have a "reversed" Tessar with the cemented component in the front. Also, some Tessar types have the iris in the front air space instead of the rear even though the cemented component is in the back. However, the Geronar is a Cooke Triplet, a three-element, air-apaced lens with no cemented surfaces. Its of high quality and such lenses are capable of good performance at moderate stops. -- -- Richard Knoppow Los Angeles, CA, USA |
Lens Cell Cleaning
On 2/13/2011 3:22 PM, Richard Knoppow wrote:
However, the Geronar is a Cooke Triplet, a three-element, air-apaced lens with no cemented surfaces. Its of high quality and such lenses are capable of good performance at moderate stops. From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P It's multicoated, comes in a modern, reliable shutter and is small/lightweight. It actually folds up in my super graphic. Given most LF lenses are used around f22, the wide open edge performance isn't an issue for most people. I've actually done some portraits with mine on 4X5 at f11 and they look great. The only disadvantage I see with this lens is the smaller image circle compared to the much Larger/heavier/more expensive plasmat types. If I had to choose this over some vintage lens that has questionable coatings and flaky/ancient shutter, I would get this one in a heartbeat. Stephey |
Lens Cell Cleaning
On 2/14/2011 8:37 AM, Cheesehead wrote:
Thanks all. It looks like my understanding of this lens is in error and that the rear cell needs to be replaced. Bummer. Honestly, you're probably better off just getting another lens. From what I've seen these don't sell for a lot of money and I'm not sure where you would even find a replacement rear cell. Maybe find one with a smashed filter ring or damaged front element (so you can use the one you have) if you are looking for a cheap way out? Stephey |
Lens Cell Cleaning
In article ,
wrote: From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P Well, at least in the 1990s when the question arose for me, it was more like "who wants that when you can buy a nice clean used Commercial Ektar"? Though, actually, knowing what I know now, I'd have gone for a 203/7.7 or a WF Ektar instead, if I were shopping in the Geronar price range and could only afford one lens. I suspect most of these that were ever sold were sold with the Calumet/Cambo kits that bundled them with a moderately priced monorail camera. I learned with exactly such a kit and it was perfectly good. But when it came time to buy my own equipment I was strongly advised to buy a quality used lens instead of a new Geronar, and I think that was the right advice to give. -- Thor Lancelot Simon "We cannot usually in social life pursue a single value or a single moral aim, untroubled by the need to compromise with others." - H.L.A. Hart |
Lens Cell Cleaning
On 2/14/2011 5:37 AM Cheesehead spake thus:
Thanks all. It looks like my understanding of this lens is in error and that the rear cell needs to be replaced. Bummer. Whoa just one second. Before you toss the lens, let me bug you just one more time. It seems to have been established that that rear cell is a single element, not a cemented doublet. In which case any fogging would actually be on the surfaces(s) of the cell, not internal. What did you use to clean the lens? Maybe you need to try something stronger, like acetone, which can dissolve just about any kind of crud. Might be worthwhile, even if, as others have pointed out, the lens is not that great: at least you'd have something to shoot with in the meantime. -- The phrase "jump the shark" itself jumped the shark about a decade ago. - Usenet |
Lens Cell Cleaning
On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote:
In , wrote: From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P Well, at least in the 1990s when the question arose for me, it was more like "who wants that when you can buy a nice clean used Commercial Ektar"? I actually replaced a "nice clean" commercial ektar of the same length with this lens and got much better results at my shooting apertures of f16-f22. Maybe my sample was a bad one but the geronar has much higher contrast and "snappyness" to the pictures, especially in difficult lighting. Add to that a much better shutter, I don't think I'd want 50 year old lens with marginal coatings in one of those old supermatic shutters over this one. Like I said, this lens gets a bad rap and I suspect most of the people saying this have never tested or even used one.. |
Lens Cell Cleaning
On 2/14/2011 3:57 PM spake thus:
On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote: In , wrote: From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P Well, at least in the 1990s when the question arose for me, it was more like "who wants that when you can buy a nice clean used Commercial Ektar"? I actually replaced a "nice clean" commercial ektar of the same length with this lens and got much better results at my shooting apertures of f16-f22. Maybe my sample was a bad one but the geronar has much higher contrast and "snappyness" to the pictures, especially in difficult lighting. Add to that a much better shutter, I don't think I'd want 50 year old lens with marginal coatings in one of those old supermatic shutters over this one. What do you mean, "marginal coatings"? Do you think they flake off or something? Sorry, but it sounds to me as if you've bought the marketing hype hook, line and sinker when it comes to "advanced, space-age" coatings. The only "marginal" here is that modren coatings are marginally better than the old ones. Hell, even *uncoated* lenses (horrors!) can perform extremely well (under certain conditions). -- The phrase "jump the shark" itself jumped the shark about a decade ago. - Usenet |
Lens Cell Cleaning
On 2/14/2011 8:52 PM, David Nebenzahl wrote:
On 2/14/2011 3:57 PM spake thus: On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote: In , wrote: From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P Well, at least in the 1990s when the question arose for me, it was more like "who wants that when you can buy a nice clean used Commercial Ektar"? I actually replaced a "nice clean" commercial ektar of the same length with this lens and got much better results at my shooting apertures of f16-f22. Maybe my sample was a bad one but the geronar has much higher contrast and "snappyness" to the pictures, especially in difficult lighting. Add to that a much better shutter, I don't think I'd want 50 year old lens with marginal coatings in one of those old supermatic shutters over this one. What do you mean, "marginal coatings"? Do you think they flake off or something? Sorry, but it sounds to me as if you've bought the marketing hype hook, line and sinker when it comes to "advanced, space-age" coatings. The only "marginal" here is that modren coatings are marginally better than the old ones. Hell, even *uncoated* lenses (horrors!) can perform extremely well (under certain conditions). I guess you missed the "difficult lighting? And yes those early coatings were good, just not as good as later ones. And yes I do use uncoated lenses too so understand your point here. In tough lighting the ektar created low contrast chromes. I didn't make this judgment based on marketing. I wouldn't have bought a geronar at all if I wasn't having issues with the commercial ektar of the same length. I have a 135mm WF ektar and the images it makes are nice and crisp compared to the ones I was getting with the comm ektar, hence I looked for a replacement. I have never considered replacing the 135mm WF ektar, it works just fine so don't thing older coating are rubbish. Sorry if posting that -in my experience- this "novice" lens performs much better that my old commercial ektar did- rocks the boat of people who are sold on those old lenses are somehow some sort of religious experience. I could see nothing wrong looking at the commercial ektar, maybe it was a bad one? I can only base this on my experience. It was a -sharp- lens but didn't have the contrast/snappyness this geronar has. So to say "-Blank- old lens is a better choice" didn't work out for me. Stephey |
Lens Cell Cleaning
wrote in message ... On 2/13/2011 3:22 PM, Richard Knoppow wrote: However, the Geronar is a Cooke Triplet, a three-element, air-apaced lens with no cemented surfaces. Its of high quality and such lenses are capable of good performance at moderate stops. From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P It's multicoated, comes in a modern, reliable shutter and is small/lightweight. It actually folds up in my super graphic. Given most LF lenses are used around f22, the wide open edge performance isn't an issue for most people. I've actually done some portraits with mine on 4X5 at f11 and they look great. The only disadvantage I see with this lens is the smaller image circle compared to the much Larger/heavier/more expensive plasmat types. If I had to choose this over some vintage lens that has questionable coatings and flaky/ancient shutter, I would get this one in a heartbeat. Stephey A carefully designed Triplet is capable of excellent performance and Rodenstock is noted for making good lenses. I am not sureprized it works well. Somewhere around f/22 is the "optimum" stop for many LF lenses. The limit of a Triplet is that they are hard to correct for either high speed or wide angle, if it isn't required to be either it can perform entirely satisfactorily. -- -- Richard Knoppow Los Angeles, CA, USA |
Lens Cell Cleaning
wrote in message ... On 2/14/2011 8:52 PM, David Nebenzahl wrote: On 2/14/2011 3:57 PM spake thus: On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote: In , wrote: From my use, it's a very nice lens given a bad rap mainly because it was sold at a low price as a "novice lens". Who wants that when you can buy a pro lens? :P Well, at least in the 1990s when the question arose for me, it was more like "who wants that when you can buy a nice clean used Commercial Ektar"? I actually replaced a "nice clean" commercial ektar of the same length with this lens and got much better results at my shooting apertures of f16-f22. Maybe my sample was a bad one but the geronar has much higher contrast and "snappyness" to the pictures, especially in difficult lighting. Add to that a much better shutter, I don't think I'd want 50 year old lens with marginal coatings in one of those old supermatic shutters over this one. What do you mean, "marginal coatings"? Do you think they flake off or something? Sorry, but it sounds to me as if you've bought the marketing hype hook, line and sinker when it comes to "advanced, space-age" coatings. The only "marginal" here is that modren coatings are marginally better than the old ones. Hell, even *uncoated* lenses (horrors!) can perform extremely well (under certain conditions). I guess you missed the "difficult lighting? And yes those early coatings were good, just not as good as later ones. And yes I do use uncoated lenses too so understand your point here. In tough lighting the ektar created low contrast chromes. I didn't make this judgment based on marketing. I wouldn't have bought a geronar at all if I wasn't having issues with the commercial ektar of the same length. I have a 135mm WF ektar and the images it makes are nice and crisp compared to the ones I was getting with the comm ektar, hence I looked for a replacement. I have never considered replacing the 135mm WF ektar, it works just fine so don't thing older coating are rubbish. Sorry if posting that -in my experience- this "novice" lens performs much better that my old commercial ektar did- rocks the boat of people who are sold on those old lenses are somehow some sort of religious experience. I could see nothing wrong looking at the commercial ektar, maybe it was a bad one? I can only base this on my experience. It was a -sharp- lens but didn't have the contrast/snappyness this geronar has. So to say "-Blank- old lens is a better choice" didn't work out for me. Stephey Both the Geronar and Commercial Ektar have the same number of glass-air surfaces, six. Neither is a high flare lens even uncoated. Multiple coating does reduce flare and has much better anti-flare properties for color than a single coating. The effect is more for color purity and saturation than for overall contrast. While its possible the coatings account for the difference I think something else must be happening. What I suspect is that the cement in the rear element of the Ektar may have become hazy. This is a peculiar effect that I've seen in other Ektar lenses. When examined under magnification, and using grazing incidence light, you can see that the cement layer has developed a sort of orange-peel texture. You can see it using transmitted light as a light haze but its effect on contrast is enormous. Check your Ektar for this. FWIW, the Commercial Ektars were designed especially for color work and are almost apochromatic. Kodak was using them to promote the sale of color film. -- Richard Knoppow Los Angeles WB6KBL |
Lens Cell Cleaning
On 2/15/2011 8:24 PM, Richard Knoppow wrote:
While its possible the coatings account for the difference I think something else must be happening. What I suspect is that the cement in the rear element of the Ektar may have become hazy. This is a peculiar effect that I've seen in other Ektar lenses. When examined under magnification, and using grazing incidence light, you can see that the cement layer has developed a sort of orange-peel texture. You can see it using transmitted light as a light haze but its effect on contrast is enormous. I used the wrong term saying "marginal coatings", this was more what I was referring to and since I sold this lens long ago, I have no way to know what the actual problem was. The other issue I had was right after purchase I had to have the old shutter repaired. Like I stated in another post, I love my 135 WF ektar so it's not like I hate old lenses.. I guess what I was trying to get across is: in my experience this "novice" lens produced MUCH better results, especially on color slide film, than my commercial ektar did so some statement that one of these old "classics" is always a better choice didn't pan out for me. Nor have I seen anything in the results from this lens that would have me go look for a replacement. Whatever was wrong with that ektar lens wasn't obvious but I don't doubt there was likely something like you stated wrong with it. Given their age, I also wouldn't doubt others have this same issue, that doesn't sound easy or cheap to resolve. I would suspect that finding a good working sample of a geronar would be more likely that finding a good sample of a lens that is many years older, YMMV. Stephey |
Lens Cell Cleaning
wrote in message ... On 2/15/2011 8:24 PM, Richard Knoppow wrote: While its possible the coatings account for the difference I think something else must be happening. What I suspect is that the cement in the rear element of the Ektar may have become hazy. This is a peculiar effect that I've seen in other Ektar lenses. When examined under magnification, and using grazing incidence light, you can see that the cement layer has developed a sort of orange-peel texture. You can see it using transmitted light as a light haze but its effect on contrast is enormous. I used the wrong term saying "marginal coatings", this was more what I was referring to and since I sold this lens long ago, I have no way to know what the actual problem was. The other issue I had was right after purchase I had to have the old shutter repaired. Like I stated in another post, I love my 135 WF ektar so it's not like I hate old lenses.. I guess what I was trying to get across is: in my experience this "novice" lens produced MUCH better results, especially on color slide film, than my commercial ektar did so some statement that one of these old "classics" is always a better choice didn't pan out for me. Nor have I seen anything in the results from this lens that would have me go look for a replacement. Whatever was wrong with that ektar lens wasn't obvious but I don't doubt there was likely something like you stated wrong with it. Given their age, I also wouldn't doubt others have this same issue, that doesn't sound easy or cheap to resolve. I would suspect that finding a good working sample of a geronar would be more likely that finding a good sample of a lens that is many years older, YMMV. Stephey Well, results is what counts! It would be interesting to know if the Ektar had something wrong with it. Coating in general should not affect sharpness so but does affect contrast and color purity and saturation, all of which are interepreted by the eye as sharpness. OTOH, its possible that this Geronal is just a better lens than the Commercial Ektar you had. If your Wide-Field Ektar has satisfactory contrast and color rendering its a good indication that the problem with the C-E was not the coating. The WF Ektar has the same coating plus it has _four_ glass-air surfaces. -- -- Richard Knoppow Los Angeles, CA, USA |
Lens Cell Cleaning
On 2/17/2011 2:32 AM, Richard Knoppow wrote:
If your Wide-Field Ektar has satisfactory contrast and color rendering its a good indication that the problem with the C-E was not the coating. The WF Ektar has the same coating plus it has _four_ glass-air surfaces. That's true and I do use a LOT of cameras from that time period with single coated and even uncoated lenses so I'm not sure what the issue was. Another experience, I ran into the same sort of problem with a 135mm xenar LF lens. It was a -horrible- lens where the 75mm xenar on my rolleicord is a wonderful one. So just because a lens has more elements in my experience doesn't mean it's always a better performer. Stephe |
Lens Cell Cleaning
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Lens Cell Cleaning
wrote in message ... On 2/17/2011 2:32 AM, Richard Knoppow wrote: If your Wide-Field Ektar has satisfactory contrast and color rendering its a good indication that the problem with the C-E was not the coating. The WF Ektar has the same coating plus it has _four_ glass-air surfaces. That's true and I do use a LOT of cameras from that time period with single coated and even uncoated lenses so I'm not sure what the issue was. Another experience, I ran into the same sort of problem with a 135mm xenar LF lens. It was a -horrible- lens where the 75mm xenar on my rolleicord is a wonderful one. So just because a lens has more elements in my experience doesn't mean it's always a better performer. Stephe I had a chance to test a 135mm, f4.5 Xenar as supplied on some Speed Graphics, it had a problem similar to the Wollensak Raptar/Optar in that while the center was quite sharp the corners never got completely sharp even when stopped down all the way. This problem seems to be uniform throughout the Rapar/Optar line, including the enlarging lenses, but not for the f/5.6 lens made for the Graflex Super-D or the Wollensak telephoto lenses, both of which are very good. I also have Rollei cameras with f/3.5 Xenars and they are extremely sharp with good corner performance. All I can think is that the same prescription was not used for other focal lengths or for other speeds. Its very odd. So, I don't know if you got a dog or if all of the Xenars are that bad. More elements give the designer more resources to make corrections. The Cooke Triplet has six surfaces, two spacings, and three powers, just enough to correct all seven of the primary aberrations and maintain focal length. More complex lenses allow for correction of secondary aberrations so they are valuable where one needs a faster or wider angle lens. Also, by using a symmetrical design the lateral aberrations, lateral color, coma, geometrical distortion, are, at least to some degree automatically corrected by the symmetry. While the Triplet is a simple lens it is _not_ cheap to make because the element spacing is very critical so that the mount has to be precision made. The Tessar was not inspired by the Triplet but the Heliar was. Hans Harting, of Voigtlander, tried to correct some of the secondary aberrations of the Triplet by compounding the two end elements. His original design was not successful but later designers did much better. The Voigtlander Heliar (which became a different design than Harting's original), the Dalmeyer Pentac (of Booth), and the Kodak Ektar used on the Medalist camera, and the Kodak Enlarging Ektar lenses of 50mm and 75mm are examples of excellent lenses based on this general design. However, other lens types offer more possibilities to the designer so the Heliar type has not been popular. -- -- Richard Knoppow Los Angeles, CA, USA |
Lens Cell Cleaning
In article ,
wrote: Another experience, I ran into the same sort of problem with a 135mm xenar LF lens. It was a -horrible- lens where the 75mm xenar on my rolleicord is a wonderful one. So just because a lens has more elements in my experience doesn't mean it's always a better performer. Most LF Xenars were "press" lenses, which really means budget: small circle of coverage, never the best coatings (newspaper printing amps up the contrast plenty), in some cases questionable quality control. Schneider had a much higher-end series of lenses for similar applications, the Xenotar. Perhaps this is has something to do with why the Xenars are so uncharacteristically bad for Tessar formula lenses in those lengths. On the other hand, maybe it's not "uncharacteristic". Wollensak made some awful Tessar lenses and so did a few others. Maybe Richard knows: is there something about the Tessar design that makes is particularly prone to manufacturing or Q/C error? There are some truly awful Schneider large format lenses as well as some very good ones. The 90 and 120mm Angulons in particular seem to have been either misdesigned or systematically mismanufactured, while by the time they started multicoating (for example, the earliest Symmar-S-MC lenses) they seem to have gotten their act together. The Schneider web site says they made the large-format Xenars until the mid 1990s (this is a surprise to me). I wonder if the later ones were any better. -- Thor Lancelot Simon "We cannot usually in social life pursue a single value or a single moral aim, untroubled by the need to compromise with others." - H.L.A. Hart |
Lens Cell Cleaning
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Lens Cell Cleaning
On 2/18/2011 2:15 PM Donn Cave spake thus:
Quoth (Thor Lancelot Simon): ... | On the other hand, maybe it's not "uncharacteristic". Wollensak made | some awful Tessar lenses and so did a few others. Maybe Richard knows: | is there something about the Tessar design that makes is particularly | prone to manufacturing or Q/C error? I believe one way to make a Tessar awful is to use it for LF applications that require a larger circle than it really delivers. While comparing the reputations of various Tessars, it might be interesting to correlate with the absolute coverage circle - that's not the right word, I mean the farthest extent of any kind of coverage, irrespective of optical quality. My hunch is that identical glass could have a better or worse reputation depending on artificial cutoff from its mounting etc. Interesting you should mention coverage as it relates to Tessars. Some time ago I did an experiment (a successful one as it turned out) with a Tessar that was "too short" for the format. Not sure it qualifies as LF, but I was shooting 9x12 (cm) film with the "next smaller size" lens, a 105mm (made for 6x9) instead of the usual 135mm or so. (The lens was a Carl Zeiss Jena f/4.5 Tessar). It covered beautifully, sharp and tasty looking from corner to corner. Not an extreme example, I'll grant you: the 9x12 image circle is 150 mm (nominal), while the 6x9 is 110 mm. And I believe that these older, uncoated lenses are exceptionally well-made, high-quality examples of the species. -- The phrase "jump the shark" itself jumped the shark about a decade ago. - Usenet |
Lens Cell Cleaning
"Thor Lancelot Simon" wrote
The Schneider web site says they made the large-format Xenars until the mid 1990s (this is a surprise to me). I wonder if the later ones were any better. If the mid 80's sample I had was anything to go by the later LF Xenars were every bit as horrible as Schneider's earlier output. Quality of Angulons was probably worse, but some rather good samples did manage to escape the factory. -- Nicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/da-main.htm n o lindan at ix dot netcom dot com |
Lens Cell Cleaning
On 2/18/2011 5:15 PM, Donn Cave wrote:
Quoth (Thor Lancelot Simon): ... | On the other hand, maybe it's not "uncharacteristic". Wollensak made | some awful Tessar lenses and so did a few others. Maybe Richard knows: | is there something about the Tessar design that makes is particularly | prone to manufacturing or Q/C error? I believe one way to make a Tessar awful is to use it for LF applications that require a larger circle than it really delivers. The xenar I am talking about looks bad on 6X9. A 135mm tessar should easily cover that sharply when stopped down. This one won't. Stephey |
Lens Cell Cleaning
On 2/18/2011 6:10 PM spake thus:
On 2/18/2011 5:15 PM, Donn Cave wrote: Quoth (Thor Lancelot Simon): ... On the other hand, maybe it's not "uncharacteristic". Wollensak made some awful Tessar lenses and so did a few others. Maybe Richard knows: is there something about the Tessar design that makes is particularly prone to manufacturing or Q/C error? I believe one way to make a Tessar awful is to use it for LF applications that require a larger circle than it really delivers. The xenar I am talking about looks bad on 6X9. A 135mm tessar should easily cover that sharply when stopped down. This one won't. I guess some lenses are just born bad ... -- The phrase "jump the shark" itself jumped the shark about a decade ago. - Usenet |
Lens Cell Cleaning
"Nicholas O. Lindan" wrote in message m... "Thor Lancelot Simon" wrote The Schneider web site says they made the large-format Xenars until the mid 1990s (this is a surprise to me). I wonder if the later ones were any better. If the mid 80's sample I had was anything to go by the later LF Xenars were every bit as horrible as Schneider's earlier output. Quality of Angulons was probably worse, but some rather good samples did manage to escape the factory. -- Nicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/da-main.htm n o lindan at ix dot netcom dot com I have a prototype Angulon, its awful. It has severe color fringing, something a lens of this type should not have at all. My lens designer friend tell me that the prescription in the patent shows up pretty bad when set up in a lens optimization program. Later Angulons do not seem to have this problem so it must have been changed in some way. The Angulon is similar to a Dagor but uses a different order of powers in the cells. It also has some power shifted from being exactly symmetrical to improve its correction for distant objects. It should be no worse than a W.A.Dagor but it is. Originally Schneider claimed 105 degree coverage. In fact, the lens has a circle of illumination that large but the image quality beyond about 90 degrees is pretty bad. The Dagor claims 97 degees but also isn't good beyond about 90 even the WA Dagor. Modern WA lenses are much better than these things but are also much larger and heavier. My impression is that Schneider was not a quality brand before 1945 but their lenses after that were very good to excellent. However, I've checked a couple of f/4.5 or f4.7 Xenars for Speed/Crown Graphics which showed excessive something, maybe coma or maybe oblique spherical aberration leading to smearing of highlights away from the center. This is very similar to the problem with Wollensak Raptar/Optar lenses for press cameras. Even when stopped down to f/32 the marginal image is not sharp. -- -- Richard Knoppow Los Angeles, CA, USA |
Lens Cell Cleaning
"Richard Knoppow" wrote
I have a prototype Angulon, its awful. The two good samples I have had were both 'Linhoff' branded on the shutter and were late production. -- Nicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/da-main.htm n o lindan at ix dot netcom dot com |
Lens Cell Cleaning
On 2/21/2011 3:55 PM, Nicholas O. Lindan wrote:
"Richard wrote I have a prototype Angulon, its awful. The two good samples I have had were both 'Linhoff' branded on the shutter and were late production. The 135mm xenar I had was in a linhoff shutter too. It was abysmal.. Stephey |
Lens Cell Cleaning
In article ,
Nicholas O. Lindan wrote: "Richard Knoppow" wrote I have a prototype Angulon, its awful. The two good samples I have had were both 'Linhoff' branded on the shutter and were late production. Interesting. I had a 90mm Angulon which I would characterize as just barely acceptable -- but not truly awful like the contemporaneous 120mm Angulon I tried around the same time. Mine too said "Linhof" on the shutter. I know at some point Linhof started doing very stringent re-QA on every lens they sold. Supposedly they duplicated the entire QA setup that Rodenstock used at the end of their production line, and supposedly they did actually reject some lenses that had passed manufacturer QA (though it is not clear whether this means the manufacturer had actually tested the lenses that failed, or just a statistically significant sample of lenses from the same run). I wonder if this was because of spotty quality from one or more suppliers earlier on. -- Thor Lancelot Simon "We cannot usually in social life pursue a single value or a single moral aim, untroubled by the need to compromise with others." - H.L.A. Hart |
Lens Cell Cleaning
On 2/22/2011 11:47 AM, Thor Lancelot Simon wrote:
In articleiq6dnXcmLK1HTf_QnZ2dnUVZ_qOdnZ2d@earthlink .com, Nicholas O. wrote: "Richard wrote I have a prototype Angulon, its awful. The two good samples I have had were both 'Linhoff' branded on the shutter and were late production. Interesting. I had a 90mm Angulon which I would characterize as just barely acceptable -- but not truly awful like the contemporaneous 120mm Angulon I tried around the same time. Mine too said "Linhof" on the shutter. I know at some point Linhof started doing very stringent re-QA on every lens they sold. Supposedly they duplicated the entire QA setup that Rodenstock used at the end of their production line, and supposedly they did actually reject some lenses that had passed manufacturer QA (though it is not clear whether this means the manufacturer had actually tested the lenses that failed, or just a statistically significant sample of lenses from the same run). I wonder if this was because of spotty quality from one or more suppliers earlier on. I have heard this same thing but question this given the 135mm xenar I had, that was horrid, was in a linhof shutter. Obviously some other lens other than the original one could have been put in this shutter by someone along the way to make it appear to be a better lens than it was. I suppose seeing the linhof brand on a shutter could help "prove" it's a good sample but given the age and unknown history, it's not a fact cut in stone anymore. Stephey |
Lens Cell Cleaning
In article ,
wrote: I suppose seeing the linhof brand on a shutter could help "prove" it's a good sample but given the age and unknown history, it's not a fact cut in stone anymore. Right. At one point in the mid-90s, the Linhof factory rep for the U.S. used to very loudly hold forth here about the special Rodenstock testing machine Linhof had acquired for this purpose, etc. etc. -- but then again, he was also the Rodenstock factory rep. He didn't typically respond to questions about what might be wrong with Rodenstock's own quality control such that Linhof felt they needed to repeat it! (Of course, this was a little unfair, since Linhof did not relabel *only* Rodenstock lenses... but it was fun to yank the guy's chain.) I suspect Linhof was badly burned by questionable lenses at some point and decided on this testing program to reduce warranty costs or brand image problems. That would imply that after some point, Linhof-marked lenses were particularly good, while before that time, they may well have been particularly bad. Since for Linhof's main competitor, there were always both budget (Wollensak) and premium (Kodak) lenses available, someone having an awful experience with a Raptar was not likely to abandon the Graphic or Graflex cameras entirely. But if Linhof was getting all or most of their lenses from Schneider at some point and Schneider was churning out Xenars of poor quality -- which seems to have been the case! -- then they would need some way to escape the damage this could do their brand. -- Thor Lancelot Simon "We cannot usually in social life pursue a single value or a single moral aim, untroubled by the need to compromise with others." - H.L.A. Hart |
Lens Cell Cleaning
"Thor Lancelot Simon" wrote in message ... In article , wrote: I suppose seeing the linhof brand on a shutter could help "prove" it's a good sample but given the age and unknown history, it's not a fact cut in stone anymore. Right. At one point in the mid-90s, the Linhof factory rep for the U.S. used to very loudly hold forth here about the special Rodenstock testing machine Linhof had acquired for this purpose, etc. etc. -- but then again, he was also the Rodenstock factory rep. He didn't typically respond to questions about what might be wrong with Rodenstock's own quality control such that Linhof felt they needed to repeat it! (Of course, this was a little unfair, since Linhof did not relabel *only* Rodenstock lenses... but it was fun to yank the guy's chain.) I suspect Linhof was badly burned by questionable lenses at some point and decided on this testing program to reduce warranty costs or brand image problems. That would imply that after some point, Linhof-marked lenses were particularly good, while before that time, they may well have been particularly bad. Since for Linhof's main competitor, there were always both budget (Wollensak) and premium (Kodak) lenses available, someone having an awful experience with a Raptar was not likely to abandon the Graphic or Graflex cameras entirely. But if Linhof was getting all or most of their lenses from Schneider at some point and Schneider was churning out Xenars of poor quality -- which seems to have been the case! -- then they would need some way to escape the damage this could do their brand. -- Thor Lancelot Simon The curious thing is that Wollensak's prices were no lower than Kodak's for their "premium" lenses. I think there was some sort of design blunder made on the design for the Raptar/Optar lenses used on press cameras and the Enlarging Raptar lenses, which are also pretty bad. Kodak's Ektar lenses are uniformly excellent as are the Enlarging Ektars. Even Ilex lenses, also not cheap by any means were head and shoulders better than Wollensak. Now, another curiosity is that the Optar lenses made by Wollensak for the Series-D Graflex are excellent. A different design even though still a Tessar. They were offered as an alternative to the Ektar lenses for these cameras but the price was about the same. I think Wollensak got the reputation for being cheap because they made a lot of OEM lenses for cheap cameras. So did Ilex for that matter. Wollensak shutters OTOH are excellent and, since they use all hair-springs, can be rebuilt with new parts. -- -- Richard Knoppow Los Angeles, CA, USA |
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