Scott Stoness
Offline
• • • • • •
Upload & Sell: On
|
 p.3 #2 · AI for advice on choosing lens or camera | |
Z250SA wrote:
Yes, it matters. But I think you have got the proportions wrong. There are several other variables to ponder. Add the Two Great Unknowns, of which the sensor-to-RAW-magic is one, Bad Air the other.
In my testing, and I have done some through the years, my take on diffraction is as follows. We are juggling three variables in our quest for sharp images full of detail. Diffraction, noise and exposure.
1. Diffraction is physics, in practice how large the Airy disc is compared to the pixel. The disc is a point with rings around it. The pixel captures some photons of whats hitting it, pixels capturing red, green, green or blue, the Bayer array. Do we actually know how many pixels that contribute to any single point of light in the final RAW images? No! My guess is that using the actual photo site size to calculate DLA gives us too low a value. This is probably why we can get great results despite being on the wrong side of DLA.
2. Noise. Here I´m ignorant, just a user who tries to handle it as it is forced upon me. With DPP. I´m just not interested. Boring as hell.
3. Exposure, fast enough shutter to freeze action, in a second step slow enough to avoid as much noise as possible. Noise can be handled in post, motion blur not. All this while getting the correct lighting of the subject.
But the best way to get the most detail is to get the subject large on the sensor. Yet an other balance to get right. This one includes the luggability of the gear, the price of it etc. So, 200-400 or 200-800, R5 or R7? I´d take the 200-800 with the R5. I loose some reach, but I gain in lower noise. And I will carry it with ease all day long, all four hours these days.
So, yes, diffraction is one variable. But between the ice bear and the final print there are so many more variables that have far greater impact than DLA, especially DLA.
And yes, avoid f/16, perhaps f/14 (as in 100-500 + 2x). With the present day sensors, even the most demanding, the R7, f/11 is totally usable. With the R7 high ISO is the formost problem, not the DLA.
...Show more →
Analysis is usually done by freezing all variable but one and varying one variable at a time to achieve a result. So in reading your post I gather the most useful critiques of the Gemini analysis and analyses them:
Bad air (shimmer increase over longer mm) could dominate the conclusion. However I would say that's true but that just means long lens, 1.4x are not important when conditions are bad. However at good light it's not true. It's important to realize this but it does not mean defraction is important. You have to hold bad air constant at good unless its normally there - and its not.
AA filter blurring is likely important. It will result in a 45mpx body being more like a 39mpx body, resulting in higher DLA. AA bluring could increase the effective pixel size by up to two. I asked Gemini to quantify this issue and it concluded paraphrased - "it would but not more than a stop at most. eg beyond 1stop (f8 instead of f5.6). AA effect is light for r7." So I would accept that f8 is still usable rather than f5.6 which revises the analysis.
But the rest while true is not as enlightening. If I followed your logic I would stop at 24mpx and Rf200-800 because many times the 200-400 is limited by other factors. But often it is not, and I am seeking success at extremes.
Edited on Dec 14, 2025 at 04:05 PM · View previous versions
|
