03-11-2011, 09:04 PM
A few related things I'm wondering about:
[size="2"](particularly since Marcus posting yesterday that you'd "like the D7000 to have a bit less resolution, as some lenses struggle near the borders...")[/size]
I haven't worked out how all the variables interact, though I think I almost understand some of Wim's post a while back..! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/huh.gif' class='bbc_emoticon' alt='
' />
[quote name='wim' timestamp='1287530403' post='3699']
...
1) Lens quality.
The best lenses out there, generally are diffraction limited by about F/4. Think the best Zeiss glass, Canon L primes, the Nikon professional range, the better Sony (Zeiss) glass. This means that these lenses will resolve right to the physical limit possible, which is about 400 lp/mm (line pairs per mm) at F/4, and the criterion being the Rayleigh criterion, which states that this is at 9% contrast, IOW, much less than the 50% MTFs we are looking at from manufacturers, but resulting in higher resolution than on those 50% charts. Do note that "lesser" lenses may not be diffraction limited, but modern prosumer lenses are often close anyway. 250 lp/mm is considered to be excellent.
2) Sensor, or medium (film, sensor, whatever) resolution.
The higher the number of pixels or silver halide crystals or photon counters, or whatever per square unit of area, the higher the resolution...
Do note that final negative or RAW resolution is inversely proportional to the inverse individual resolutions of sensor and glass, or if said in a different way, 1 / total recorded resolution equals the sum of 1 / lens resolution at a specific f-stop + 1 / maximum recording resolution. You can express this in pixels per image height, as is done on this site, or in lines / mm, or as we used to do in the past, lp/mm, as one needs a minimum of 2 lines in order to depict an edge or line.
Due to the nature of the above formula, it follows that in order to get out the maximum of the one element in that formula, resolution needs to be infinite for the other component...
...Note that for a 200 lp/mm end result, we need both the lens and sensor being capable of resolving 400 lp/mm, as follows from the formula above. If you work it out, we are talking here about a ~550 MP sensor in that case. Since we are still rather far from such resolutions, I do think we stil have along way ahead before we even get close.
...Finally, at these resolutions it becomes increasingly impossible to get the ultimate sharpness from the negative, whether RAW or film, for the simple reason that the smallest of vibrations or of deviation from perfect focus WILL influence the end result much more than an increase in resolutions, as is already being experienced by medium format shooters at 50 and 60 MP. You'll need heavy tripods, MLU, remote switches, etc. to get the most out of the system.
...
HTH, kind regards, Wim
[/quote]
[size="2"](particularly since Marcus posting yesterday that you'd "like the D7000 to have a bit less resolution, as some lenses struggle near the borders...")[/size]
- If there are any plans to start testing on the D7000? (I noticed you've been testing at 15MP on Canon APS-C for quite a while.)
- What would be the effect on resolution figures from a given lens tested on two different APS-C sensors?
- What are the implications for D7000 owners re lens choices? Other than "buy the best you can afford", is there a sort of 'cut-off' point in resolution below which it's not worth buying, because the image quality probably won't be acceptable to most people (who've bought the camera), although I appreciate that's subjective.
How applicable are the test results from one (APS-C) sensor to another?
I thought I could use both the Nikon D200 and the Canon 15MP (for third-party lenses) APS-C tests for choosing lenses, weighted on the basis of optical quality.
Now, I'm a bit confused (again...!) <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />
I haven't worked out how all the variables interact, though I think I almost understand some of Wim's post a while back..! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/huh.gif' class='bbc_emoticon' alt='
' /> [quote name='wim' timestamp='1287530403' post='3699']
...
1) Lens quality.
The best lenses out there, generally are diffraction limited by about F/4. Think the best Zeiss glass, Canon L primes, the Nikon professional range, the better Sony (Zeiss) glass. This means that these lenses will resolve right to the physical limit possible, which is about 400 lp/mm (line pairs per mm) at F/4, and the criterion being the Rayleigh criterion, which states that this is at 9% contrast, IOW, much less than the 50% MTFs we are looking at from manufacturers, but resulting in higher resolution than on those 50% charts. Do note that "lesser" lenses may not be diffraction limited, but modern prosumer lenses are often close anyway. 250 lp/mm is considered to be excellent.
2) Sensor, or medium (film, sensor, whatever) resolution.
The higher the number of pixels or silver halide crystals or photon counters, or whatever per square unit of area, the higher the resolution...
Do note that final negative or RAW resolution is inversely proportional to the inverse individual resolutions of sensor and glass, or if said in a different way, 1 / total recorded resolution equals the sum of 1 / lens resolution at a specific f-stop + 1 / maximum recording resolution. You can express this in pixels per image height, as is done on this site, or in lines / mm, or as we used to do in the past, lp/mm, as one needs a minimum of 2 lines in order to depict an edge or line.
Due to the nature of the above formula, it follows that in order to get out the maximum of the one element in that formula, resolution needs to be infinite for the other component...
...Note that for a 200 lp/mm end result, we need both the lens and sensor being capable of resolving 400 lp/mm, as follows from the formula above. If you work it out, we are talking here about a ~550 MP sensor in that case. Since we are still rather far from such resolutions, I do think we stil have along way ahead before we even get close.
...Finally, at these resolutions it becomes increasingly impossible to get the ultimate sharpness from the negative, whether RAW or film, for the simple reason that the smallest of vibrations or of deviation from perfect focus WILL influence the end result much more than an increase in resolutions, as is already being experienced by medium format shooters at 50 and 60 MP. You'll need heavy tripods, MLU, remote switches, etc. to get the most out of the system.
...
HTH, kind regards, Wim
[/quote]