Demosaic - optimal choice for different Fujifilm Super CCD EXR modes?


I have a Fujifilm FinePix S200EXR which uses a “Super CCD EXR” sensor. In contrast to the Bayer square layout, it uses a diagonal sensor pixel layout where some sensor pixels can be “binned” to optimize for either a larger dynamic range or for a better signal-to-noise ratio in low light scenes.

Due to this rather unique layout, I wonder if any special demosaic algorithms would be recommendable. Or are the diagonals just hiding that there is still a Bayer pattern, and I don’t need to worry?

As a new member, I am not sure whether I am able to link images yet… but you will surely find several examples searching for images by keywords like “super ccd exr sensor” or similar.

RT supports extracting frame one or two (both having 6 MP) and the SN-Mode where the two frames are combined to reduce noise (not for more resolution). DR mode is not supported by RT.


Left using only one frame (frame 1), right using the SN mode (average of both frames).

So, apparently the HR mode is not really supported either, which would require to handle both raw sub images like a kind of 2D interlacing…

Correct, apart from the normal mode only the SN mode is supported.

I am quite disappointed to learn that different EXR cameras seem to produce different raw image content, related to their operating mode. My S200EXR creates RAF HD with two images, and only Fujifilm and Adobe seem to know how to (re-?) construct 4000×3000 pixels from their resolution of 2824×2128 stored raw pixels. Applying SN averaging where resolution interpolation was desired is not an optimal solution.

In contrast to other reports, RAF SN and DR created by the S200EXR have only half the file size of HD; dcraw reports only one image, so I have to assume they contain an already averaged image in SN mode, or an already combined HDR result in DR mode.

I linked a sample archive in your HDRMerge github project.

I tried with this raw which is from an S200EXR in whatever mode (it contains two equaly exposed 6 MP frames). RT definitely can access both 6MP frames in this file and also can combine them.

Other EXR modes are not supported by RT

If an SN RAF created by an S200EXR contains two images, then a HR RAF must contain four to have twice the file size?!..

Let’s do quick maths: 2824 * 2128 ~ 6Mpx, 16 bit/px = 2 bytes/px, so ~12 MB per RAF provides only room for one image…

Just download the file (which has a size of ~24MB), combine it in RT using SN mode and you will get one 6MP output with less noise.

Your image has a size of ~24 MB. So it must have been shot in HR mode (not in SN mode).

If I take a shot in SN mode, the RAF file has only a size of ~12 MB. So I have to assume that the camera already did the averaging and saved one raw image with the averaging result.

If I take a shot in HR mode, the RAF file has a size of ~24 MB. So I have to assume that the image is not supposed to be averaged, but to be interpolated to a high resolution instead.

I wish I knew how to interpret RAF header data to see if any flag in it might give a hint in which mode the camera was set up.

From RT perspective, it doesn’t matter what’s in the exif of EXR files concerning shooting mode.
If there are two frames in the raw, RT can access each of them and also average them. Not more, not less. If the two frames have different exposure (for example this file) averaging them does not make sense, but you still can do it, because there are two frames in the raw.

Solution found … in the free Adobe DNG Converter!

Set up a custom conversion preset: DNG 1.4 + :ballot_box_with_check: Linear (mosaic free) — and voila, RawTherapee 5.6 reports: 24.0 MP (5640x4248) … from here, the camera apparently scales down to 4000x3000.

That of course has the downside that you can’t use for example rt raw ca correction for this files.
Just wanted to mention…

Okay, I’ll have to discover how important that feature may be to me… thank you for now, for your patience. :sweat_smile:

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