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02-13-2010, 12:44 PM   #1
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Diffraction in pentax 67 lenses

I have a lot of time in LF, not much in MF, and my small format friends are worrying about diffraction in their lenses at small aperatures.
Question: do the Pentax lenses, say 55 or 105 have diffraction problems at f22? This would show up as soft edges most likely, and some of the threads i read about the lenses talk about soft edges in some but do not say what f stop they are shooting.

02-13-2010, 01:36 PM   #2
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Well, you can always shoot them all the way stopped down and find out I shoot both those lenses at ƒ16 and ƒ19 all the time in my long exposures shots. And I know I've shot the 55 at ƒ22 several times. I didn't notice anything standing out but the edges in those shots didn't have much to show. I don't have one to post at the moment. If there is any softness on the edges, I think you'd be picking fly crap out of the pepper to find it. Big deal. And I find there are not too many situations where you need ƒ22 on the 55mm. You get around 8 feet to infinity at ƒ16 on it- on the SMC 67 generation of that lens, anyway.

My digital friend is always trying to shoot at the cherry aperture. I never even think about it. I shoot at whatever aperture the scene requires for what I want.

Last edited by tuco; 02-13-2010 at 02:04 PM.
02-13-2010, 01:39 PM   #3
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Visible Diffraction effects are format dependent. When people are complaing, they mostly complain about diffraction visibly setting in at around f/11 and smaller for APS-C sized sensors.

With a genuine 6x7 format, diffraction at f/22 should not be a really important problem. In LF (4x5 for instance) we use routinely f/32 and smaller without visible problems.

Ben
02-13-2010, 03:23 PM   #4
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Diffraction is a problem if you go looking for it.
Otherwise it's just another thing for the measurbators to get their pants wet about.

Here's an exercise for you:
Set oyur camera up on a tripod.
Take a picture at f/4 where you know the lens is performing well.
Take another picture at f/8.
Take another picture at f/16.
Take another picture at f/22.

Make prints of each file and see if you can spot the diffraction.

Get back to me with your results.

02-13-2010, 06:07 PM   #5
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I find it odd that people worry about diffraction but not so much about aberrations. They are both distructive to the image, just at opposite ends of the aperture continuum. If I were to obsses about either one while shooting, it would limit what I shoot. I don't worry about it. I shoot the 300 Takumar, 400, 600 and 90-180 zoom at f/45 on a regular basis. Having the right composition trumps diffraction loss every time. Concerning the shorter lenses at f/22; no problem.

Steve
02-13-2010, 08:37 PM   #6
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QuoteOriginally posted by desertscape Quote
I find it odd that people worry about diffraction but not so much about aberrations. They are both distructive to the image, just at opposite ends of the aperture continuum. If I were to obsses about either one while shooting, it would limit what I shoot. I don't worry about it. I shoot the 300 Takumar, 400, 600 and 90-180 zoom at f/45 on a regular basis. Having the right composition trumps diffraction loss every time. Concerning the shorter lenses at f/22; no problem.

Steve

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02-13-2010, 10:43 PM   #7
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QuoteOriginally posted by desertscape Quote
... Having the right composition trumps diffraction loss every time.
I think that about sums it up!
02-14-2010, 11:26 AM   #8
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Ok, pretty much as I suspected. My LF lenses are capable of down to f128 in some cases, but the diameter of the opening is pretty big at f32 and f45.
I think the comment about "measurebaturs" was pretty accurate.
My comment was pertinent as I am pretty new to MF and do mostly scanning for b/w.

02-14-2010, 11:41 AM   #9
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Herb I have a Schneider Super-Angulon 90mm/f8 and for an economical lens, it does great at ƒ64


Wisner 4x5 TF, TXT 4164, PMK Pyro
02-14-2010, 01:12 PM   #10
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QuoteOriginally posted by tuco Quote
Herb I have a Schneider Super-Angulon 90mm/f8 and for an economical lens, it does great at 64
Very nice image - would love to see it really large.

Ben
02-14-2010, 05:53 PM   #11
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Thanks, Ben. The largest I have is a 16x20 hanging on my wall. I need to tool up and get a 20x24 tray and easel to do that size.
02-19-2010, 10:35 AM   #12
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The more area you have to store a picture, the less perceivable effect diffraction has. You'd probably notice it if you mounted that Super-Angulon on an APS-C camera and took a shot at f64.

Another fantastic shot, Tuco!
02-19-2010, 12:33 PM   #13
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QuoteOriginally posted by tuco Quote
Herb I have a Schneider Super-Angulon 90mm/f8 and for an economical lens, it does great at 64


Wisner 4x5 TF, TXT 4164, PMK Pyro
Sweet shot !


Ansel Adams, Edward Weston and others, even had the f/64 club.
02-19-2010, 04:14 PM   #14
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QuoteOriginally posted by brkl Quote
The more area you have to store a picture, the less perceivable effect diffraction has. You'd probably notice it if you mounted that Super-Angulon on an APS-C camera and took a shot at f64.

Another fantastic shot, Tuco!
Thanks. But wouldn't the image circle projected by that lens be larger than the camera and the APS-C sensor would only be seeing the cherry center of the lens?
02-20-2010, 04:36 AM   #15
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QuoteOriginally posted by tuco Quote
Thanks. But wouldn't the image circle projected by that lens be larger than the camera and the APS-C sensor would only be seeing the cherry center of the lens?
Yes, that's correct. But diffraction is the same all over the image circle - it is not concentrated in the center.

Ben
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