DXOMARK.com, did you notice

Started Jan 28, 2014 | Discussions thread
Anders W Forum Pro • Posts: 21,466
Re: DXOMARK.com, did you notice

Steen Bay wrote:

Anders W wrote:

Steen Bay wrote:

Anders W wrote:

Steen Bay wrote:

Dr_Jon wrote:

I was just saying you don't know the lens resolution so it's no lp/mm on the sensor but lp/mm the sensor can resolve with that lens. A Canon 500 f4 might resolve 120 lp/mm on a sensor, but no-one has a sensor to see that (so it isn't relevant yet).

Cameras like the E-M1 and D7100 have almost the same pixel size/density, and both are without AA-filter. Could be used to compare the resolution of mFT and Nikon FF/APS-C lenses measured in lp/mm (think that the D7100 should have app. 26mp in order to make it a totally fair comparison).

Sure you can do that but in what sense would such a comparison be "fair"? In my view, it would be just as unfair (in the opposite direction) as one where we'd compare resolution in lp/mm without taking the size of the image circle into account. To me, a fair comparison is one where we measure lens resolution on a per-image basis using sensors with the same per-image resolution.

It would be 'fair' as a pure lens (not system) comparison. Like testing the lenses on an optical bench. It's often claimed that mFT lenses are sharper than FF/APS-C lenses, which I believe is correct, but we don't really know, so think that such a lp/mm comparison could be interesting.

No it would not be fair as a pure lens comparison. In your suggested comparison, the FF/APS-C lens enjoys the advantage of higher medium (sensor) resolution per image.

Yes, but we compare lp/mm, not lp/ph.

If we compare lp/mm, the comparison is fairer than it would be if we compared lp/ph but still not as fair as in the comparison I suggest. The reason is that the disadvantage for the larger sensor of using lp/mm would not be properly balanced by the advantage of higher (on a per-image basis) sensor resolution. The effect of the former is linear and proportional whereas the latter is not (even if we measure sensor resolution linearly rather than in terms of pixel count).

Testing on an optical bench does not imply such an advantage. If I understand things correctly, it implies testing on a medium with infinitely high resolution, so that the lens can show what it can do without being in any way restricted by the resolution of the medium.

Not sure how an optical bench works, but if a mFT lens has a higher resolution (lp/mm) than a FF lens when tested on sensors with the same pixel density, then the mFT lens will also have the highest resolution (lp/mm) if tested on a sensor with unlimited MP count.

Sure. But even if the MFT lens has the highest resolution in lp/mm, that does not necessarily mean that it has the highest resolution on a per-image basis, which is what we (at least I) am ultimately interested in.

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