Nikon Z 24-200 f/4-6.3 compared to Canon RF 70-200 f/4

Started 8 months ago | Discussions thread
peripheralfocus Veteran Member • Posts: 4,907
Re: a little more on cross-system comparisons

jetstream wrote:

Out of curiosity, is Imatest based on Raw files or Jpeg? Does sharpening affect Imatest results or other in-camera corrections? If not, I see no reason why you cannot compare results across different systems of similar resolution.

Nearly certain that Imatest must work from a de-mosaiced image, meaning a TIFF, not raw. There are many different algorithms for de-mosaicing an image, and they can yield different levels of detail/sharpness, depending on many factors.

Yes, sharpening does affect Imatest results -- it effectively increases system MTF. The author of Imatest discusses that explicitly on the Imatest web site somewhere (I haven't read it in awhile).

Imatest evaluates the whole imaging chain, not just the lens. So that's what the results mean; they are not a test of the lens by itself.

The case of this thread shows why that's fraught with peril: the Z7II does not have an AA filter, but the R5 does, according to kenw. So the cameras are similar in resolution, but the sensors are quite different. We may be able to compare the two complete imaging chains using Imatest, but not the two lenses. Remember, however, that software (de-mosaicing + sharpening, known or unknown) are also in the mix; unless you can reliably subtract those out as a variable, then you can't even reliably compare the hardware alone.

And the R5 has an AA filter for a reason; it reduces or prevents aliasing (the recording of false data) in some cases. On the other hand, it softens the image somewhat. It's a tradeoff you can argue about both ways, but it eliminates the possibility of learning much about the difference between the Nikon lens and the Canon lens from an Imatest test.

To compare the lenses by themselves, you need an optical bench and an MTF or wavefront analyzer, or at least a collimator and a resolution target. There are organizations who can do that (mostly lens manufacturers), but they don't make their findings public (again, with the partial exception of LensRentals).

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