[quote name='PuxaVida' date='05 June 2010 - 10:51 AM' timestamp='1275727861' post='240']
Regardless of it's AF performance, any comments on the rumours that the 7D requires high quality lenses because of it's high pixel density?... When it comes to %100 views I suppose...
Serkan
[/quote]
Hi Serkan,
I think you have to look at it in another way: 100 % view is a view you can use to spot the smallest defects in a lens. That is useful in order to know what you can and can't do with your equipment, but serves no other purpose than that.
Essentially, in my view, digital shooters need to get over two trends which are common, namely the one where you always have to look at 100 % from a close distance to apparently view a photograph at its best, and the other where we apparently have to expect nothing but perfection from lens and camera manufacturers, at any price point.
When it comes to the first point: 100 % was ok up to about 12, maybe 17 MP in FF (60 - 70 lp / mm), and about 6 MP to 10 MP in APS-C (translated to FF that is 40 - 55 lp / mm, at 1.6X enlargement of course). Why is this you may ask? Simply because as very good amateurs using colour negative film we would get 20 - 40 lp / mm from our colour negative films in print. Professionals would get 60 lp / mm, maybe a little more. We had film like sharpness then, so it didn't matter all that much. There was a nice transition from sharp to unsharp when going out of DoF, and there was quite a bit of fall-off from centre to extreme border too. And we were all quite happy with that.
This changed with digital when the first newness wore off. MTFs looked flat, from centre to extreme corner, unlike with most pictures taken on film. This was due IMO because of the different characteristics of the sensor vs film, for one caused by the difference in thickness of the medium (0 of the sensor vs 0.2 mm of the film), the even distribution of "particles" on a sensor, the direct integration of sensor with camera and enlarging equipment (computer and printer), and the sensor assembly, which cut off high frequency resolution drastically. We also saw sharpness come in very rapidly close to the DoF zone, stya more or less th esame, and then disappear quite fast again.
It is much easier to see any defects now then we ever could see with film as a result, although I can assure you that with film it also has been visible all the time, if you cared enough to look. This also gets me to the second point, namely that in t e past we would do occasional 20 x 30's, sometimes a 40 x 50, and often that was it. Most stuff, even today, was printed and viewed on 10 X 15 or 13 X 18 (all cm of course). With 100 % viewing, at 72 dpi, or even at 90 dpi if that is the definition of ones display, you are looking at an image of more than 1 by 1.5 m with most modern cameras, including a 7D, and preferably from 30 or 40 cm away.
The latter is not proper viewing distance. The diagonal X 2 is. If you look from that distance, a proper viewing distance, I can assure you that many of the defects become totally irrelevant.
Coming back to high pixel density: because the combination of high pixel density and AA-filters which cut off only frequencies that are much higher than before, we start seeing the response with sensors we used to see with film, namely a clear or clearer transition from centre to extreme corner, even with the best of lenses, and especially the wider the AoV of a lens is. This is optical laws at play here, we are back again at the normal interaction of optics and medium, no longer screened off as it were from an artifical cut off, which made us believe things looked better than they actually were.
However, things are actually becoming much better than they were, basically because optics still get better, be it at a price. Modern optics from a specific class are better than most stuff produced in the past, and that is not only true for professional lenses, but also for consumer or advanced consumer lenses. Examples are the new 15-85 IS vs the 17-85 IS, the range of 20-35 -> 17-35 -> 16-35 -> 16-35 II, etc , and a bunch of others too, inclusing lenses of other brands.
The things we used to do in the past, and that is IMO where we are right back now with 15 MP+ APS-C cameras and 20 MP+ FF cameras, is to learn to use the camera-lens combinations we own to their best advantage, and/or make use of their weak points to our advantage. Do note that although some lenses may get to "only" 1200 or 1400 lines per image height in their extreme corners when used wide open, this is stil a lot more than we ever got out of film.
And a camera like the 7D is one that ups the level quite significantly again in APS-C land, especially considering all its other characteristics (with the exception of my own pet hate, caused by my eye problems, the frame in the VF which I can't see in one go <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />).
Finally, although the 7D has upped the ante with regard to resolution another step, as it has the staggering resolution of ~120 lp/mm in APS-C format, it still doesn't come close to what the best lenses are capable of, yet. 400-450 lp/mm is what a really good lens can do at F/4 (and theoreticall better at larger openings, although only specialist lenses, designed for monochromatic light, manage that , generally speaking). And according to the lens formula that means that combined resolution is about 90 - 100 lp / mm. And this is what we seem to be achieving.
I do expect, however, that by the time we get to similar resolutions as we get from the lenses by themselves, we will have sensor sites that are photon counters, however, no longer traditional well sites. When you get to sites that are the same as or relatively close to the dimensions of the wavelenght of light, it is likely we need to have a different type of sensor to capture anything at all without capturing just noise from the electronics.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....
' />.![[Image: smile.gif]](http://forum.photozone.de/public/style_emoticons/default/smile.gif)
... I understand that the high quality lenses produce way better resolutions than the sensor can.![[Image: rolleyes.gif]](http://forum.photozone.de/public/style_emoticons/default/rolleyes.gif)
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