Donât know about Photoshop, but using Absolute Difference Blend and on top of that using an extreme brightness curve you should be able to see the differences.
You need carefully chosen images, known to be challenging to demosaic, to be able to spot real differences. For example, sharp horizontal, diagonal and vertical patterns like fences, fabrics, fuzzy clouds or curtains, noisy pictures, saturated objects and lens chromatic aberrations.
Otherwise, when the conditions are nice, all of them perform similarly.
I disagree.
Well, if you need forensics methods digitally enhanced to make a diff picture legible, thatâs my ground truth for âsimilar performanceâ.
@heckflosse Can you tell me which of these images is significantly different to your eyes? And which two are identical? At 100% zoom please
Demosaic_try.zip (10.7 MB)
Edit: and for 10 bonus points, which image belongs to which demosaicing method.
Why should I do this (waste of time) ? You know that there are differences between outputs of different demosaicers. Do I really need to show examples? Then please provide a raw file. Then I will show the differences. Tiff (or png) files are not even worth a look, sorry
What are they for?
@heckflosse Please take note of the wink, it wasnât meant too seriously. Both you and Aurelien are correct. At pixel peeping levels there are significant differences between algorithms which may get blown up due to other processing. At 100% zoom level and using a picture taken in ânice conditionsâ, the differences are almost non-existent and certainly not bothersome.
My zip contains an illustration to that point for anyone whoâs interested. Look at 100% zoom and tell me which differences you see, then look at 400% zoom and spot the differences.
Interesting, thanks. I suppose these are simple crops from the demosaics, not resized? I hope you will say what seven methods were used.
With a quick script, I use ImageMagick to loop through each pair of images and find the largest RMSE difference. This is between images 1 and 4, with RMSE 0.011 on a scale of 0 to 1, so 1.1%. As a rule of thumb, 1% is the threshold at which I can just see that two ordinary photos are different, when the differences are evenly spread through the images.
At first glance, I canât see differences between 1 and 4. But ImageMagick (or anything similar) can point out where the differences are.
magick Demosaic-1.png Demosaic-4.png -compose Difference -composite -auto-level demosaic-diff.png
Guided by this, I know where to look. And the differences are obvious, even at merely 100%.
Thanks, the tip of the high brightness curve helped make the naked eye differences even clearer.
So, I use a âhalfâ demosaic for my proofs, as itâs quick and looks fine when downsized to 800x600. For clients that want full resolution, Iâd produce a rendition that used one of @heckflosseâs wonderful tools courtesy librtprocess. Havenât had a client in at least 30 years, howeverâŚ
Iâm also using half to process spectrum captures for SSF profiles; need RGB triplets to calculate channel averages down each image column, and half doesnât change the original R and B captures, and only does an average of G1 and G2 for G. Need as little change as possible for the downstream processingâŚ
@snibgo There are seven files, two of them use RCD (so should be identical), one is AMaZE, one is DCB, one is IGV, one is LMMSE and one is Fast. All options as named in RawTherapee.
There are no other adjustments to the image, except for a little increase in exposure, contrast and saturation - otherwise, things looked too dull.
Why not? Downsizing that much using quarter demosaic (binning)
should be good enough
Well, why using modern highres Nikon Cams then?
of @heckflosseâs wonderful tools courtesy librtprocess
Thanks, but not olny mine, also @CarVac and others were involved.
Thanks. 3 and 7 are identical, so they are RCD. Which ones are AMaZE, DCB, IGV, LMMSE and Fast?
I will also add that while differences may not be visible immediately after demosiac, the differences can be much more pronounced after processing - particularly sharpening. (At least this is true for X-Trans images)
Ok, Iâll biteâŚ
4 is clearly âfastâ, and it is significantly worse than the others. 3 and 7 are identical, so they must be RCD. From here, Iâd guess 6 and 5 are Amaze and DCB (or the other way round), whereas 1 and 2 are IGV and LMMSE (or perhaps the other way round).
How far off am I?
1 and 2 look very close to me, with 1 seeming slightly better. Whatâs your opinion?
My opinion: 1 and 2 look âcrisperâ than the others, but thatâs because the picture has no sharpening applied. In fact, 1 and 2 have (according to my eye, I might be totally off here â but it would be nice to know some amount of false detail that is typical of IGV and/or LMMSE demosaicing, which were designed for noisy images. Hereâs an example of RCD vs IGV (without sharpening):
I agree that in general the differences are minor, but itâs good to have a choice for dealing with more difficult situationsâŚ
I think youâre going to need shots of a resolution-sort of target. Something white, with linesâŚ