If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#31
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
yes, ditto my topcon 35mm SLR, with great lenses but a hard to maintain leaf shutter in body ;-( However, a very large number of 35mm rangefinders from the 1950s and 1960s had fixed lenses and leaf shutters, provided flash synch at any speed, but without danger of getting dirt or damaging shutter during lens changes (as just one fixed lens was used). a number of leaf shutter oriented MF SLRs feature an adapter which can be machined to take other non-leaf shutter lenses. In effect, this combination is a MF SLR body with a leaf shutter mounting into which you can adapt other lenses. A similar setup is used with microscopes and telescopes. I have described how to adapt an existing low cost leaf shutter lens by removing the glass etc., largely because the kowa shutter adapter is rare and costly and busted lenses are lots cheaper ;-) (see http://medfmt.8k.com/mf/kowafaq.html). the trend seems to be the other way in many cases. For example, the 4x5" and miniview graphic cameras usually used leaf shutters in the lenses, but then added models with focal plane shutters in the camera body which could be used instead of the leaf shutters with barrel lenses (i.e., lenses which do not come with leaf shutters for view camera use etc.). the hasselblad 200/x series provide focal plane shutters in the camera body, but allow you to use leaf shutters in the lenses as well. ===== Personally, I have wondered why nobody has created a MF RF with leaf shutter and convertible lenses, as with the old contaflex and kodak retina examples, see http://www.photo.net/bboard/q-and-a-...?msg_id=003HSZ I would think that with modern glasses and precision mounts, such a system could provide very good performance, while minimizing cost and weight. Instead of paying for 3 lenses, complete with three shutters and three lens mounts, you had one lens and three lens front elements. Swap these out, and you get a wide angle, normal, or telephoto lens effects. The cost for a three lens kit would be minimal over a similar 3 lens kit model which required three separate lenses, complete with three machined mounts and integral leaf shutters in each lens, yes? ;-) but I think the mfgers would rather sell us two additional lenses at full markup than provide us with a few extra front lens elements as part of the kit, yes? ;-) grins bobm -- ************************************************** ********************* * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* |
#32
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
Bob Monaghan wrote:
yes, ditto my topcon 35mm SLR, with great lenses but a hard to maintain leaf shutter in body ;-( However, a very large number of 35mm rangefinders from the 1950s and 1960s had fixed lenses and leaf shutters, provided flash synch at any speed, but without danger of getting dirt or damaging shutter during lens changes (as just one fixed lens was used). But none of these ever reached the image quality levels of Leica, which makes me wonder if my earlier proposition that focal plane shutters yield sharper results isn't true. Personally, I have wondered why nobody has created a MF RF with leaf shutter and convertible lenses, as with the old contaflex and kodak retina Why hasn't this approach been used more frequently in 35mm as well? I would think there would be lens design limitations with this approach. I just saw a camera on eBay (I forget the brand) that had an integral rangefinder/lens combination which was interchangeable. That is you pulled off the lens *and* the rangefinder assembly off of the camera body simultanaously and then swapped it wiht another lens/rangefinder assembly. Neat idea. I've always wondered why advanced flash features found on say the Konica Auto S3 haven't found their way onto MF cameras. Or even Minolta's new "D" lens range where focusing distance enters into the flash formula? Obviously MF cameras are used to shoot weddings and parties all of the time. I scratch my head as to why they don't have the latest and greatest automatic flash features. |
#33
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
Bob Monaghan wrote:
... Personally, I have wondered why nobody has created a MF RF with leaf shutter and convertible lenses, as with the old contaflex and kodak retina examples, see http://www.photo.net/bboard/q-and-a-...?msg_id=003HSZ I would think that with modern glasses and precision mounts, such a system could provide very good performance, while minimizing cost and weight. Instead of paying for 3 lenses, complete with three shutters and three lens mounts, you had one lens and three lens front elements. Swap these out, and you get a wide angle, normal, or telephoto lens effects. I've been thinking about it as well, except that I'd like to see a TLR with such lenses. The savings would be even more obvious. -- Lassi |
#34
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
|
#35
|
|||
|
|||
Focal plane vs. leaf shutters in MF SLRs
Hi,
I would like to try to answer the original question - shutters need to be designed such that the exposure time of each part of the image is more or less the same to get an evenly exposed image. The location of the leaf shutter needs therefore determined in such a way that its opening and shutting mechanism produces an evenly exposed image on the film plane. It therefore can only be positioned in one certain place within the lens, where its mechanism works with the light flow in the mentioned proper way. On top of it, by definition, it is circular and therefore would require more space if positioned close to the film plane than if it is placed between the lens elements. Usually it also is located very closely to the diaphragms of the aperture and they can only be located where the have to be optically - again same reason - uniform image exposure. And by definition the diaphram need to sit in or very close to the aperture plane or one of the conjugated planes of it. If you place the aperture not in the correct plane, you get not only uneven exposure in the film plane but also vignetting etc. If you like to know more about it and in detail, email me directly. I presume that the full explanation would be not really of interest for most readers as it would involve more details about lens design and I am not sure if readers would like to read a lot of theory.... Regards George Nyman Dean Hoffman wrote: There have been SLRs with a leaf shutter incorporated into the body. The Kowa 35mm slrs come to mind. Unfortunately these involved complex linkages that were prone to failure. "KM" wrote in message ... I was cleaning my RZ and began wondering why each lens must incorporate its own leaf shutter, then began wondering why we find leaf shutters only in lenses. I understand why the shutter has to be in the lens for rangefinder systems (proxmity of wide-angle rear elements to focal plane = insufficient space), but why couldn't they be incorporated into SLR bodies? In current leaf-shutter systems like the Bronica ETR and Mamiya RB/RZ, doing so would make the lenses smaller and lighter. In focal-plane systems like the Pentax 645N, you'd get flash synch at any speed. I'm sure there's a perfectly good explanation I'm overlooking.What is it? |
#36
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
|
#37
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
wrote in message ... Why hasn't this approach been used more frequently in 35mm as well? [...] Funny this should come up. One of my student workers just now returned my Contaflex, which as you know is an SLR that with a Prontor leaf shutuer and X,M synchro, and of course it has interchangable lenses. It remains one of my favorite miniature cameras with the 30mm lens. Why wasn't it used more? For one, it's expensive and entails rather strident limitations. To make this Contax system work there is one common lens behind the shutter and all the lenses use it as the rear element. I can post some pictures of the lens system if you like. |
#38
|
|||
|
|||
Focal plane vs. leaf shutters in MF SLRs
"Georg N.Nyman" wrote in message ... Hi, I would like to try to answer the original question - shutters need to be designed such that the exposure time of each part of the image is more or less the same to get an evenly exposed image. [...] And obviously, the larger the leaf shutter, the more limited the top shutter speed. Look at the Copal #0 with 1/500th compared to the *gasp* Ilex #5 which has a (nominal) 1/50th top speed (which I find is actually closer to 1/30th). |
#39
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
yes, I should clarify that I am NOT saying that my proposed convertible lens Med Fmt camera would require the highest performance levels possible requiring equaling leitz or contaflex or mamiya 7II optics. ;-) Rather, I would like a decent MF camera where you have low cost (as three lenses for little more than cost of one leaf shutter with swappable front elements) and light weight (three lenses weighing little more than one), a RF for low weight and ruggedness with lower costs than a mirror and prism SLR, perhaps even a folding RF (cf. old folders, fuji..) design for compactness for travel. There have been convertible lenses in LF for ages, and there have been examples of this design approach (as with the cited Contaflex, Kodak Retina..) which worked quite well. Given that most of the lens cost is in the shutter, iris, and mounting mechanics, a design which eliminates these costs by substituting interchangeable lens fronts for different focal lengths seems pretty direct design for a low cost low weight camera option. I understand exotic lenses would be problematic, but I am just looking for the relatively modest standard lens trio (50/80/150mm) in MF. If some of the MF fuji zoom lenses had a longer zoom range, this might not be such an issue. But it looks like fuji is getting out of that business ;-( regards bobm -- ************************************************** ********************* * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* |
#40
|
|||
|
|||
convertible lens RF? Focal plane vs. leaf shutters in MF SLRs
yes, quite true, but I wasn't thinking in historical terms but in terms of operationally useful examples like the speed and crown graphics rather than the old hood viewing models (http://medfmt.8k.com/mf/graflexb.html) in most cases, you pay quite a bit extra for a camera with a built-in focal plane shutter over a similar model limited to leaf shutter lenses; there are also issues of repairability and shutter speed variations (esp. at maximum speed end and so on). So I think most users today tend to opt for leaf shutter lenses and a simple body, and mainly those who expect to adapt or use barrel lenses will seek out the more complex and costly and often heavier bodies with the focal plane shutters built-in. I have seen a few bodies offered for sale where the individual stripped out the focal plane mechanics (and RF) in order to save weight, but can't recall anyone adding a focal plane shutter to a non-f.p. body ;-) ;-) grins bobm -- ************************************************** ********************* * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Formula for pre-focusing | Steve Yeatts | Large Format Photography Equipment | 9 | June 22nd 04 02:55 AM |
zone system test with filter on lens? | Phil Lamerton | In The Darkroom | 35 | June 4th 04 02:40 AM |