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#1
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F-stop Sweet Spot
I read recently that the best F-stops for lens both camera and enlarger are F8
and F11. I realize that depth of field comes into play, so putting that aside how does F22 suffer in either cameras and/or enlargers. If the sweet spot is F8 what do I lose with my camera when I have it set at F22 aside for longer exposures? If the sweet spot is F8 for my enlarger what are the costs at F2.8 or F22? Are the differences perceivable? Does the complexity of lens factor in here? |
#2
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F-stop Sweet Spot
"ATIPPETT" wrote in message
... I read recently that the best F-stops for lens both camera and enlarger are F8 and F11. I realize that depth of field comes into play, so putting that aside how does F22 suffer in either cameras and/or enlargers. If the sweet spot is F8 what do I lose with my camera when I have it set at F22 aside for longer exposures? If the sweet spot is F8 for my enlarger what are the costs at F2.8 or F22? Are the differences perceivable? Does the complexity of lens factor in here? The sweet spot depends somewhat on the size of the lens. For example, on a large format lens with largest aperture of f/8 and minimum of f/64, the sweet spot is closer to f/22. On my digital camera, which has an f/2 lens with minimum aperture of f/8, the sweet spot is closer to f/4. For MF lenses, the sweet spot probably is close to f/8 or f/11, but it does depend on the lens. This partly determined by the design of the lens. Another important factor is the inherent fact that all lenses suffer from diffraction limitation when stopped down, which means as the aperture gets smaller, the theoretical maximum resolution of the lens decreases. Do a google search on diffraction limitation for more info. As you mentioned, the smaller the aperture, the better the focus is at the film plane and the better the depth of field of the subject matter. Schneider has some good MTF charts which document the sweet spots on their enlarging lenses: http://www.schneideroptics.com/photo...oto_enlarging/ |
#3
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F-stop Sweet Spot
There are often diffraction effects at very small apertures (f22 +) with
multi-element lenses. Most f2 camera lenses seem to look best at f5.6. |
#4
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F-stop Sweet Spot
Every lens is different. Test yours and make your own choice.
"ATIPPETT" wrote in message ... I read recently that the best F-stops for lens both camera and enlarger are F8 and F11. I realize that depth of field comes into play, so putting that aside how does F22 suffer in either cameras and/or enlargers. If the sweet spot is F8 what do I lose with my camera when I have it set at F22 aside for longer exposures? If the sweet spot is F8 for my enlarger what are the costs at F2.8 or F22? Are the differences perceivable? Does the complexity of lens factor in here? |
#5
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F-stop Sweet Spot
ATIPPETT wrote:
[...] Does the complexity of lens factor in here? Absolutely! While some lenses may indeed perform best at, say f/8, others will not. Some even will perform best fully opened. What happens, always, with every stop that a lens is closed down is that maximum achievable resolution is reduced. About halved every two stops a lens is closed down. Diffraction is the cause of that. So would we be dealing with diffraction only, all lenses would perform best wide open. Alas, most lenses are troubled by all sorts of faults, reducing resolution too. The effects of these aberrations are lessened by stopping down (using more and more of the central bit of the lens, which shows least faults). So stopping down is a balancing act: while the aberrations are reduced, limiting the resolution limiting effect of those, the limiting effect on resolution by difraction increases. So as long as aberrations are worse than diffraction, stopping down imporoves resolution. How far a lens must be stopped down to reach that point depends, of course, on how much lens faults there are. And that is a matter of lens design. And since not all lenses are created equal, a "rule" like the "f/8 sweet spot" thingy is rather, well... useless. |
#6
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F-stop Sweet Spot
db wrote:
There are often diffraction effects at very small apertures (f22 +) with multi-element lenses. Diffraction is always present, and it gets worse the same when going from f/16 to f/22 as it does from f/2 to f/2.8. And i'm afraid it's not restricted to multi-element lenses either. |
#7
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F-stop Sweet Spot
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#8
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F-stop Sweet Spot
In article ,
"db" wrote: There are often diffraction effects at very small apertures (f22 +) with multi-element lenses. Most f2 camera lenses seem to look best at f5.6. Hum????? How to respond to a general statement?????Hum? If you like shalow DOF? Something missing "L" :-D -- Duzz that A moose you ? |
#9
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F-stop Sweet Spot
"RSD99" wrote: Every lens is different. Test yours and make your own choice. With my Mamiya 645 lenses and a 60x microscope, I could _maybe_ persuade myself that wide open and f/22 were _slightly_ worse than the other f stops. The "sweet spot" bit is more of an issue for people who shoot test charts than for real photography. David J. Littleboy Tokyo, Japan |
#10
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F-stop Sweet Spot
Any Moose Poster wrote in message ...
snip You know, I think those standards are over rated. I have shot 10,000 plus images in my 22 plus years. I can attest that 35mm f/22 negatives and slides are sharper than f/8 for exosures in camera,....a good aligned enlarger set up properly will give you a sharp print regardless of apeture on the lens,.....but a good lens is essential. No fricked up elements, or milky optics. You know what come to think of it 400 asa film is alot sharper at f/22 than 100 at f/5.6 Um, are you sure? I ask because my 55/2.8 and 105/2.8 MicroNikkors, both bought new in 1986, are noticeably sharper in the plane of best focus at f/8 than at f/22. In fact, the 55 is best in the plane of best focus below 1:1 at f/5.6 and reversed above 1:1 at f/4. I shoot them at apertures smaller than f/8 only to gain depth of field. Could you be confusing sharpness in the plane of best focus with sharpness in depth? We give up some sharpness in the plane of best focus to get more DOF, but every lens has an aperture beyond which stopping down loses sharpness overall. Cheers, Dan |
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