f-number equivalent between m43 and FF

Started 8 months ago | Discussions thread
dethis2
Regular MemberPosts: 104
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Re: That "explanation" is so wrong...
In reply to xpatUSA, 8 months ago

xpatUSA wrote:

dethis2 wrote:

xpatUSA wrote:

dethis2 wrote:

I think you need to downsample using a good algorithm (say Lanczos) and use for this linear space instead of gamma 2.2. Gamma 2.2 is responsible for the lower mean value at the "70mm" sample.

Now that I am thinking of this .. this gamma error is in part responsible for the much less noise we percieve after downsampling as (at the dark parts like in your sample) it dampens the pixel differences much more than a correct workflow should ..

I did think about using linear export. But the last numbers I gave are from the raw data (no processing at all) and the result was similar enough, I thought.

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Cheers,
Ted

Indeed the raw result looks more "in target".

You mean that you took the raw results by selecting a n1 x n2 area in the 35 mm shot and a 2n1 x 2n2 in the 70mm one ?.

I meant what I said earlier - my last results were for the whole image. Bear in mind the image was of a white paper sheet at low exposure and the frame was full for each shot.

70mm: mean 49.7, s.dev 11.9

36mm: mean 48.4, s.dev 24.4

These last figures straight from RawDigger, whole image, no exporting involved. Numbers are un-scaled raw data values.

I was talking about the results after resampling, where the lower mean value is an indication that something went wrong.

I understand. As you know, RawDigger analyses the raw data before any post-processing. No re-sampling involved.

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Cheers,
Ted

OK Ted, I missed this part at first, thanks for repeating.

Was the light fall off same at the two shots ?. I recall Iliah mentioning to use not the whole frame but a center area for this kind of measures ..

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Ilias

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