I got my Q today.

Started Apr 12, 2012 | Discussions thread
Senior MemberPosts: 1,999Gear list
Diffraction. . .
In reply to Ishpuini, Apr 13, 2012

Hi Wim,

Personally, I think that each person should avoid making decisions about apertures to use just considering the math and the "diffraction limitation". It's just so easy to make rules that limit you. . . I am not disagreeing with you or being critical in this post, just stating my personal viewpoint.

Way back when the Q was announced, I was told by a number of posters that none of my K mount lenses would resolve well enough to be used on the Q -- according to the math that told them that the resolution these lenses could produce would definitely be insufficient for the pixel density of the sensor, and that the diffraction limitations of the sensor would make them very limited in any case.

The PhotoZone Q system lens tests do show that the Q Quality Line lenses seem to fall off significantly between f4 and f5.6, and it would be easy to assume that all lenses will do the same, but it's not that simple, IMO. As you stated, diffraction tends to show its effects gradually, and it must also be considered that all lenses tend to resolve better with a little stopping down. Can loss in resolution from diffraction be offset (at least somewhat) by increased resolution gained in a stopped down lens?

I don't really know, but I've tried stopping down to f8 with some lenses, and still have gotten images that were acceptable to me with a little PP. Of course, I'm not as picky as many, as I'm primarily a jpeg shooter, even with the Q, and I don't mind using PP to get final images that please me. This is especially true with the Q. I'm not one who expects the Q to produce equivalent images to my DSLRs, especially at FOV EQs that I cannot even approach with an APS-C format camera. I feel that the equivalence argument is really only relevant with formats that are reasonably similar (APS-C to 24x36, or 4/3 to APS-C are good examples), but that's just my opinion.

In any case, I've found that with a number of lenses so far, the differences between f4 and f8, let's say, are not as significant as the numbers may indicate, and it's definitely worth doing some experimentation with each lens. Also, some lenses which might not seem to have the resolution to stand up to the very high pixel density might surprise you. Some examples of surprises for me, for both optical quality and especially considering max aperture have been the DA 18-250 and the DA 50-200 at the long end where they are both slower than the "diffraction limit", and certainly not considered premium optics as a super zoom and a kit lens respectively. Both are good for what they are, but. . .

Here's one from the DA 18-250, f6.3 (wide open at 250mm), shot in jpeg, handheld (aided by leaning against a tree -- remember no SR [yet] with the Q and adapted lenses), 1/320, so over 1 stop under the 1/FL "rule".

And a couple from the DA 50-200, f5.6 (wide open at 200mm) tripod mounted, shot in jpeg, 1/200 and 1/160 respectively.

The first of the Swan shots is a vertical crop of a landscape shot. The squirrel didn't need much PP. The Swans were significantly softer, so needed more extensive work, but there was enough detail to bring back with the PP, IMO.

There's no doubt that I can do better with my K-5 and big glass, but considering the differences in price, size, and weight, the differences in IQ are pretty small. The Q + DA 50-200 is 15.5 oz. The K-5 + FA* 300/2.8 + Sigma 1.4x TC + F 1.7x AFA is @ 9 lbs. The tripod/head for the Q (CF travel tripod and very lightweight head) is 3.3 lbs, the tripod/head I use with the DSLR (CF tripod, quality ballhead, Sidekick) is 7.5 lbs. The Q kit (including tripod) costs $1250.00 USD (including the 01 Prime), and the K-5 new, lens and TCs (all used), and support gear totaled @ $5000.00 USD, and I'm cheap, so everything but the camera body were very good deals (IMO)l -- fair market would be more like @ $6500.00.

All of this is really subjective. Sometimes a keeper for me is a wastebin shot for others, and I respect that, but obviously disagree. "Saving" marginal shots with PP is a normal situation for me since I am forced to shoot in less than optimal conditions most of the time since I don't use hides or camo. PP for me is fun, and not a chore. . .

Bottom line for me is that I've learned not to just accept the "rules" and try everything. . . then let my eyes make the final decision. I think it's a good policy, and I've benefited greatly from it. It makes photography a lot more fun for me. . .


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