Your lens sweet spot...explained technically

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shuttercat:
Very well explained, Mel!. As my Aussie friends would say, "Sweet".

caterpillar:

--- Quote from: gpx4 on January 18, 2008, 09:15:52 AM ---Thanks Mel. This ought to be sticky. :)

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Thanks all (raffy, john, et al). A bit wordy, but I had to be thorough. Unfortunately, I didn't do it well. I knew I should have written it, but decided to keep it as it is because it is complicated as it is. Anyway, here is the caveat.

It's not really the sensor size that is causes the diffraction. Its really the pixel size and pixel pitch (the distance between two pixels), w/c in turn lowers the sweet spot of a system. It just so happens that those with crops sensors have smaller pixels. But it could happen to the 1Ds mk-4, a 35FF sensor, once they try to go past 21mp.

If anyone can still have access to the 3mp Canon D30 (not the 30D) of vintage 2000, you will find that because the pixel size is so big, I think you will reach diffraction past f16 or f20. And yet this is a 1.6 crop sensor. Fortunately, most lenses are at their best at f8 or f11 anyway, and not f16, so we'll never know. Plus the fact that 3mp is not enough to resolve the wonderful sharpness of most lenses anyway. Which leads us to another variable that affects the sweet spot. Sensor or media resolution. It has not been mentioned in my previous post because most cameras now anyway have 8mp or 10mp by default.

There has been debates on w/c megapixel size it would take to match a 35mm film. Some say 8mp is enough, some say 24mp, some say 36-40mp, some say 100mp. But for sure, most sensors don't really do justice to what the lenses can give. Many agree though, that 24mp is about the pixel count that 35mm film matches a silicon sensor. I guess the 1Ds mk-III is very close to that now, so it will be as good as it goes. But then again, we are talking of the sweet spot and diffraction. If I am not mistaken, for this sensor, about f11 is the boundary where if we go past, the effects of diffraction will start to affect the image quality. The use of the traditional Bayer filter doesn't help either, but it is not considered a variable in the sweet spot by many assuming everything else is equal.

Unless they find some way to improve the light gathering of the sensor, or change the sensor design radically a la Foveon, the only way to go better is to go beyond the 35mm format. And this is why, even if I like Olympus and the 4/3 system and what they have done, plus the good local support here, I can't bring myself to think that as they push to 10mp, 12mp, 14mp, 16mp, due to the fact that they have 2x smaller difference in size, they are hitting the limits of physics. I am open minded about it, but unless there is some new revolutionary technology they can muster, the smaller 4/3 sensor is a dead end as far as getting more pixel for such a small real estate.

Tynn also told me he loves his D40 more than his d70 for many things. I told him it's because the pixel size is big since it is a 6mp camera. And that is why it can be so noise free compared to his d200. But then again, this is where technology comes in. The D300 has shown what can be done with low light noise handling even if you put 12mp in the same real estate. For me, the d300 is the maturity of the d100-d200 line, as the 20d is the maturity of the xxD line for canon as far as sensor capability goes and overall features to do basic photography.

This is why, unless there are other improvements in sensor design and manufacturing, expect to see changes or upgrades in other areas in future releases, regardless of brand. Expect to see more AF points, more sensitive AF points, maybe face detection, articulating LCD, higher LCD resolution, buit-in radio controlled flash commander, built-in wi-fi module, removable focusing screen, HDMI output, etc. But I think the biggest change in the dslr world, is that the future will no longer be a DSLR, but the EVIL camera. But I am already digressing too much here ;D

empoy78th:

--- Quote from: johnDong on January 18, 2008, 01:44:45 AM ---thanks for sharing!... :)

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You're welcome John! Thanks for viewing! =)