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12-22-2010, 02:02 PM   #1
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Sharp lenses with superb IQ at small apertures, f/18, f/22, … ? Enlighten me

I would like to know which lenses, new, oldies, primes, zoom… are qualified to deliver very sharp pictures, with good to excellent resolution, colors etc, at small apertures.
The use of this lens will be mainly, for studio photography and for objects like shoes.
Now I’ m using the DA 16-45 at F/18, at zoom end, with good, but not excellent results.
The old smc m 50 f/1.7 don’t help me and I tend to believe that a 35 prime, maybe, do the job.
So, I want your opinion, with samples if possible, in full size or a crop. What do you suggest?
Thanks


12-22-2010, 02:45 PM   #2
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Focus stacking

For this kind of work diffraction is a killer. I think your best best for shooting stationary objects is to shoot as an ideal apature (f4 to f8) and then focus stack in post. A little more work, but far better results.
12-22-2010, 02:54 PM   #3
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I would recommend the Pentax M 50 mm f4 (or the optically identical K 50mm f4) or the Pentax M 100mm f4 (or again the K or A versions). These are both macro lens so they are designed to have the best sharpness as closer focusing distances as you will be using for studio work. Secondly, as they are both quite slow lenses (and macro lens to boot) they should have their optimum performance at smaller apertures (or at least hold their performance a little better) than regular fast lenses. Note that this is independent of camera, with your APS-C sensor, you are shooting beyond the diffraction limit, so all lenses are going to loose sharpness at these f-stops. You may want to look into focus stacking. Still, a quick look at photozone tests of macro lenses at f22 does certainly show noticeable differences in scores, and the slowest lens there (the Cosina 100mm f3.5, which has several other brandings you can find it in, by the way, another lens you might want to consider) does the best at that aperture.

Last edited by macTak; 12-22-2010 at 03:28 PM.
12-22-2010, 03:11 PM   #4
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What about using a tilt/shift lens to better orient the DOF to align with the objects? Just a thought...

12-22-2010, 03:43 PM   #5
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As mentioned: with apertures tighter than f/8 or f/11 on APS-C frames, you pass the diffraction limit and lose sharpness.

There are two ways optically to gain DOF on any specific frame (sensor or film): stopping down, or using a shorter focal length lens. But stopping-down leads to diffraction, and a shorter lens leads to distortion. To get around the diffraction limit, you need a larger frame. The 645D with its 55mm lens should do the trick for you. All it takes is money. I haven't checked, but I think a 645's diffraction limit is around f/16.

A tilt-shift lens gives control over the imaged plane, but it is much cheaper to tilt that plane rather than tilt the lens. I don't think any lenses on APS-C are sufficient to employ the Scheimpflug principle for here-to-infinity sharpness, but that should be possible on a 645D.

The cheap option: focus-stacking. Good luck.

Last edited by RioRico; 12-22-2010 at 05:56 PM.
12-22-2010, 05:10 PM   #6
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Is a larger format the answer? I thought DoF issues were MORE prounounced with a larger sensor... I mean, if you used a point and shoot, the DoF wouldn't be a problem at all.
12-22-2010, 05:55 PM   #7
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QuoteOriginally posted by keyser Quote
Is a larger format the answer? I thought DoF issues were MORE prounounced with a larger sensor... I mean, if you used a point and shoot, the DoF wouldn't be a problem at all.
With larger formats, DOF is more of a problem (because of longer lenses) but diffraction is less of a problem (because of larger frames). Ansel & Friends used f/64 on their 8x10" viewcams with long glass. Let's see, 'normal' on 8x10 is ~13" / 325mm, so 162mm (like my Wollensak Raptar 162/4.5) would be 'wide'. Those *must* be stopped down for decent DOF.

No, DOF isn't a problem with P&S's, because of their necessarily short lenses. But I once calculated diffraction limits for my P&S's and K20D. The numbers came out:

1.1mpx, 1/2.7" sensor, DL= ~f/6
5.1mpx, 1/1.8" sensor, DL= ~f/4.7
7.1mpx, 1/1.8" sensor, DL= ~f/3.9
14.6mpx, APSC sensor, DL= ~f/8.2

Going one stop tighter probably wouldn't affect images noticeably. A couple stops beyond there, it would likely be apparent to pixel-peepers. And a couple stops further, loss of sharpness should be visible in many enlargements.

Again, diffraction is a function of aperture, frame size, and sensor resolution; DOF is a function of aperture and focal length (among many other things); and distortion is a function of subject distance and focal length. Optimizing for all those is tricky. If it was easy, everyone would do it, eh?
____________________________________________

Anyway, macTak is on the right track: a medium-wide flatfield macro lens ~28mm at f/11 should give the sharpest results. But Pentax never made one! The closest would be a DA 35/2.8 Ltd Macro for around US$400, but it won't have the greatest DOF. It might be acceptable for shoes, though. Or look for a good Vivitar or Zeiss 28mm macro. Good luck!

Last edited by RioRico; 12-22-2010 at 06:17 PM.
12-22-2010, 06:54 PM   #8
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For product photos I use a bellows and enlarging lenses. You can also use tubes and M42 tubes are inexpensive. I have written an article on it at this post.

https://sites.google.com/site/inexpensivemacrophotography/

This was taken with a el Nikkor 105 enlarging lense



This taken with a Fujinon 135 EP enlarging lens.




Good Luck!

12-22-2010, 07:37 PM   #9
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QuoteOriginally posted by RioRico Quote
Anyway, macTak is on the right track: a medium-wide flatfield macro lens ~28mm at f/11 should give the sharpest results. But Pentax never made one! The closest would be a DA 35/2.8 Ltd Macro for around US$400, but it won't have the greatest DOF. It might be acceptable for shoes, though. Or look for a good Vivitar or Zeiss 28mm macro. Good luck!
Well, there are 28mm enlarger lenses, which one could use with an adaptor and M42 bellows. But getting as close as the OP would be getting for shoes, I dont' think the difference in DOF would be worth it (won't be very much at all, and the perspective and distortion would be negatives). I did think of the DA 35 macro, but that lens is worse at small apertures than some of the other lenses I recommended. Honestly, the loss of sharpness with a good and slow macro lens at say f22 will not be that disasterous, especially if the output size is not going to be too large.
12-23-2010, 05:26 AM   #10
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Original Poster
Thank you all for your respond.
Well, I’m thinking that the wide lenses, like 24mm or 28mm, will produce more sharpness but also more distortion. The 100mm or 135mm at the other side, will produce less distortion but also less sharpness and I have to shoot from some distance.

I believe that 35mm or 50mm are the lenses for this job.
  • As macTak mentioned, a 50mm slow lens and macro, will have his optimum performance at smaller apertures.
  • RioRico, I would like, someday, to own a 645D, until then…
  • d.bradley, tilt/shift lens is for perspective control, I don’t think that will offer anything here.
  • As for stacking a multi focus shoe, as omega leader and RioRico advice, I had it on my mind, but I would like to do less work.
Generally my thoughts matching the suggestions of macTak and I think that a M-50mm f/4 macro will help.
So at 35mm and 50mm are there any other suggestions?

Thank you again guys.

Stack photo. Grasshopper, from Tamron SP AF 90mm f/2.8 Di Macro, three shots, handheld.

12-23-2010, 06:04 AM   #11
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I keep hearing good things about F/FA50 macros. Apparently some of the sharpest lenses you can get for K mount but at the f stops you are after.. I'm not sure
12-23-2010, 07:09 AM   #12
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28mm is closest to 'normal' for APS-C (30mm is the diagonal of an APS-C frame) and should show no distortion from the distance at which you would be photographing shoes. Since sharpness is limited by diffraction and DOF, and the diffraction limit for APS-C is around f/8-11, then the greater DOF of a 28mm lens vs 35mm may be critical. Anything longer than 40mm may have DOF too thin for your needs without focus-stacking.

I like inexpensive approaches. A cheap approach would be an M42 bellows, with 28mm + 35mm + 50mm enlarger lenses, plus any needed cheap adapters. Some judicious eBaying should put that kit together for under US$75. I suggest that range of lenses because you could easily (and inexpensively) test to see what works best for you. At about US$10 each, 't'ain't no big thang, eh?
12-23-2010, 09:53 AM   #13
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Don't be fooled into thinking you will get more DOF with a shorter lens. The DOF is independent of focal length, only being determined by field of view and aperture.

This is especially observable at macro distances.

Your sort of out of luck unless you can focus stack or use a tilt lens.

Curse physics all you want, but in the end it always wins.
12-23-2010, 09:57 AM   #14
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Since your DOF increases with working distance, wouldn't the D FA 100mm Macro f2.8 (or the similar Tamron Macro 90mm) give you the greatest DOF at close-focus, allowing you to use wider apertures (f8 - f11)?
12-23-2010, 10:44 AM   #15
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QuoteOriginally posted by paperbag846 Quote
Since your DOF increases with working distance, wouldn't the D FA 100mm Macro f2.8 (or the similar Tamron Macro 90mm) give you the greatest DOF at close-focus, allowing you to use wider apertures (f8 - f11)?
No, DOF does not increase with working distance.
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