Originally posted by zoolander Okay, that sounds all well and good, but Nikon isn't the brand with the highest pixel count ........at first. Sony make the sensors and put them in their own cameras first. The A65 with 24mp came out in 2011, and the Nikon D3200 24mp six months later. Same with the Sony Arii with 42mp. But now Canon have it with the 5Dsr.
Regarding lens reviewers. The lens reviewers I look at are pretty much reviewing a lens for its absolute resolution, and not based on : "How sharp it is on 16mp or 24mp or 32mp".. I'm talking ABSOLUTE sharpness. You're talking about photozone and DXO who test at the variety of mega pixels, which isn't really testing a lens for its absolute sharpness.
I don't need to know anymore about how sharp a lens is on 16mp or 24mp, that just got confusing. You go researching 100's 100's of lenses and on this body and that body ..... No ! I want absolute resolution ........ How sharp is the lens regardless of camera mega pixels ? Thats where its at ! And that ain't where DXO or Photozone are, they are just muddying the waters with hyperbole and conjecture and "Virtual pixels" .............
There is no such thing as "virtual pixels" ! DXO are clowns, and they're making a fool of people.
You need straight up scientific analysis, and not conjecture.
Whether you use a 16mp or 24mp camera, a good lens tester can extrapolate how sharp the lens is.
99.9% of reviewers review the lens on a given camera by taking picture of some test chart and then using imatest. This procedure is dependant of many factors:
- the number of MP of the sensor of course
- the low pass filter, how strong/weak it is or if there one or not.
- the processing done on the JPEG or RAW by the manufacturer regardless of the theoretical meaning of "RAW" manufacturers apply sharpening, lens corrections and so on (Sony for example).
This is the case of dpreview, photozone, lenstip, slrgear all test lenses on a given camera or set of camera. The only one I know of that use an optical test bench instead independant of any camera is lensrental. But this is the exception.
The issue is that even if the review doesn't say it, it tested the lens on a camera and so the lens was limited by the camera used. The typical reviewer also adapt its rating based on the camera. if the camera can manage 10Mp, then 2350 lw/ph is outstanding and anything that is 2000+ is good, but if the lens is tested on a 24MP without low pass filter it would need to get 3000 lw/ph to get the results. In practice not all lenses handle the increase of Mp as well and some lenses that where reviewed as great on old sensor get a reduced rating on a more modern one. This is the case of FA43 for example.
And this is also forgeting that most reviewer test only 1 sample. The 18-135 on photozone was likely a bad one for example. Sample variation in term of performance can be quite big, in particular toward border/corner. On the review website lens A might be better than lens B but if yourself buy them both you could have you own sample of B being better than your own sample of A. The example is the 20-40. Some review find it better near 20mm other near 40mm other in the middle.
What more? An innexpensive kit lens on a high rez sensor typically does better in absolute than on a lower rez sensor... But will get lower scores by the reviewer because it might not be as near to the top performance the sensor allow. Tha's stupid but that how lenses are reviewed.
You initial point was that DxO was biased for Nikon. Do you know that nowadays the lenses that are mounted on Canon that get the best sharpness score? Well that because now 5Ds is part of the test results. The 35mm f/2 that before had 20MP sharpness score on a 5D mark III just got 34MP on the 5Ds.
An you know what? All theses FF lenses pentax has will get improved score when they will be reviewed with the FF and suddenly people look a bit too fast would think Pentax make much better lens than before.
The other reviewers they still use a given camera to perform their review. What more they don't test on all cameras but on a single one they have arround that is not necessarily the latest and great. Most reviewers use camera that are 24MP or less. This is even more visible if the review is a bit old and then the cameras are 10 or 16MP...