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#11
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Soft edges on C330 shots
Peter Chant wrote:
Alan Browne wrote: Do you think it is lens softness wide open or solely focus? I don't think I'd expect enough softness to be seen on a lowish res scan with a MF lens. Am I thinking along the right lines? Could be softness from being wide open. Tripod? Shutter speed? Release cable? Bad scan? Can't be the tripod, wasn't using one... Shutter speed, probaly 1/60th, may have been chancing it at 1/30th... Actually amazed that with the 55mm lens I have gotten away with 1/15th on occation. Release cable, bit silly if you are hand held... Duh, but I didn't know it was hand held. I know - I'm going to get the tripod lecture - I really must take it out on a tripod and see what happens some day! That's it - beat yourself up before I get a chance. The 'rule-of-thumb' speed is only good for smallish prints, IMO. Present that photo screen size and it starts to look a bit soft. I'd put most of the softness to being handheld. I'm wondering about the scan. Would explain why the bottom left of the building is unsharp when the top is. Plane of focus? -- -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. -- usenet posts from gmail.com and googlemail.com are filtered out. |
#12
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Soft edges on C330 shots
Alan Browne wrote:
I'm wondering about the scan. Would explain why the bottom left of the building is unsharp when the top is. Plane of focus? I doubt it. Even at f2.8 the differences in slant distance between the bottom and top of the building would not be that large. Pete -- http://www.petezilla.co.uk |
#13
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Soft edges on C330 shots
Peter Chant wrote:
Alan Browne wrote: I'm wondering about the scan. Would explain why the bottom left of the building is unsharp when the top is. Plane of focus? I doubt it. Even at f2.8 the differences in slant distance between the bottom and top of the building would not be that large. So what is it: lens? -esp. near wide open. lack of tripod? I'd tend to think the tripod... -- -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. -- usenet posts from gmail.com and googlemail.com are filtered out. |
#14
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Soft edges on C330 shots
RolandRB wrote:
Peter said he was probably using 1/60th sec and possibly 1/30th so assuming 1/60th sec then the picture should have looked sharp at the size he was showing it and at 1/30th should not have looked as soft. So at full aperture my suspicion is the focus is out between the viewing lens and the taking lens and if you know these cameras then this should be no surprise. Something for me to re-check. I originally checked it with my 135mm, the lens that is used least. I'll have to dig out the calculations but depth of focus (ie at the film) does not depend on lens focal length. IIRC it is something simple like 2*fstop*circle of confusion, but I need to check that. Pete -- http://www.petezilla.co.uk |
#15
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Soft edges on C330 shots
RolandRB wrote:
You need to tape a broken piece of ground glass to the back rails of the taking lens and using a lupe, adjust the focus to infinity while looking at a distant scene. If your broken piece of ground glass is from an old camera and it has a split prism then so much the better. Then make the ground glass in the camera at the top be in focus with this scene by using spacers or adjusting screws to adjust the ground glass distance from the viewing lens. If you have one of these old TLR Mamiyas then there is no point in using it unless you know the adjustment for this is correct. It is often wrong for any camera you might buy on ebay. I've done it once. I found a maintenance manual for the 220 on line. The 220 uses shims but the 330 is much easier as it has three little adjustment screws. I used a couple of sheets of newspaper taped flat to a cardboard box at about six feet distance - this seemed to replicate the set up in the maintenance manual. Not having a loupe I used a 50mm lens of a 35mm camera. Question is, has it drifted since then or perhaps the 135mm lens, my least used, was a bad one to adjust the screen with. I should have used the 55mm or 80mm which I use most. Any reason for picking infinity rather than a closer target? For the ground glass screen I used a piece of glass and an oil stone. A tedious job! Pete -- http://www.petezilla.co.uk |
#16
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Soft edges on C330 shots
RolandRB wrote:
No, you can pick a closer target so long as it stays in the same place. The 135mm lens would be a good choice as it would amplify any incorrect focussing. Using a 50mm or a 35mm lens from a 35mm camera as a loupe should be adequate. It would be worth using the same setup again to check that the focussing coincides. Pulled out my sums: Depth of focus = 2 x circle of confusion x aperture From this, with a 0.06mm circle of confusion we get: f D o Focus (mm) 2.8 0.34 3.5 0.42 4.0 0.48 5.6 0.67 8.0 0.96 11.0 1.32 16 1.92 22 2.64 32 3.84 Depth of focus does not, surprisingly to me, depend on lens focal length. -- http://www.petezilla.co.uk |
#17
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Soft edges on C330 shots
RolandRB wrote:
So at full aperture of f2.8 the film distance has to be accurate to within a third of a millimeter. That would take some very careful adjustment on your part. If you have adjusting screws then once you "get it right" and then tighten the screws (if that is what you have to do) then the very act of tightening them might shift the distance by that amount and throw it out again. When I last did it I adjusted the three screws a quarter of a turn at a time, being careful that all were turned the same amount and checking that I had focus over the whole screen. There is no locking mechanism on the adjusting screws. They are reasonably stiff to turn and with the new foam in the screen holder there is a fair bit of pressure on them so, as I don't change screens, little reason to suspect that they rotate. The more I write the more urgent I feel the need is to check them for piece of mind with the more usual lenses. Also ought to go out with a tripod and see what I get at f22. -- http://www.petezilla.co.uk |
#18
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Soft edges on C330 shots
RolandRB wrote:
On 11 Feb., 20:31, Peter Chant wrote: RolandRB wrote: So at full aperture of f2.8 the film distance has to be accurate to within a third of a millimeter. That would take some very careful adjustment on your part. If you have adjusting screws then once you "get it right" and then tighten the screws (if that is what you have to do) then the very act of tightening them might shift the distance by that amount and throw it out again. When I last did it I adjusted the three screws a quarter of a turn at a time, being careful that all were turned the same amount and checking that I had focus over the whole screen. There is no locking mechanism on the adjusting screws. They are reasonably stiff to turn and with the new foam in the screen holder there is a fair bit of pressure on them so, as I don't change screens, little reason to suspect that they rotate. The more I write the more urgent I feel the need is to check them for piece of mind with the more usual lenses. Also ought to go out with a tripod and see what I get at f22. --http://www.petezilla.co.uk I don't suppose there is any chance that somebody has been handling the camera and dropped it? I would look to ensuring the negative/transparency is flat when you scan, is it soft at the edges when viewed directly (perhaps on a light box)? Given the odd pattern of softness you describe I would doubt the film plane is off, |
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