fuji s5 uniwb

[nitt]

For setting a camera to uniwb one must tweak red and blue channel to be equal to green channel. for that I look into exif of raw file WB GBGR levels. usually the green has 256 levels. But fuji s5 seems to be different beast. Exif shows that

Its levels of green is 384. Does this mean that I should aim for 384 384 384 when dialling for uniwb?

 

[TomC601]

Somethings wrong. You can only go to 255 in software. Can you post the exif info?

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Regards,

Tom

 

[nitt]

here's a link to some raw files. I hope the author does'nt mind.
http://www.jonathanpuckrin.com/photocamel/S5/

may the abnormal number levels has smth to do with the dynamic range of camera.

 

[TomC601]

There are no abnormal numbers. I downloaded one of the RAF files and it read 255,255,255 in the brightest highlight. What are you using to take your measurements?
--
Regards,

Tom

 

[nitt]

I' m talking about exif iinformation, metadata. you can have any levles on red and blue. depending on wb but green is constant. and usually 256. that's how WB works. but fuji is different it has more green levels.

I put my fuji to uniwb. It does not have so strong green bias as other cameras. For killing exessive green the FL-D filter is quite enough.

 

[nitt]

one more note. looking raf files in RPP I noticed that fuji S5 is underexpousing. and very strongly. about 4 stops. can you believ that? camera is doing 4 stops under. and then pulling with software levels up.

 

[Iliah Borg]

Yes, for UniWB Fuji S5 EXIF should read around 384 for red and blue in WB_GRGBLevels tag.
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http://www.libraw.org/

 

[nitt]

Thank you, Iljah. One question more if I may. It is about RPP. I know You have a hand in it. RPP shows fuji s5 raw files very dark. Should I compensate exposure in camera (+4 stops at least) to make files look good in RPP or just tweak dark files in RPP brighter by exposure compression?

 

[Iliah Borg]

RPP shows fuji s5 raw files very dark. Should I compensate exposure in camera (+4 stops at least) to make files look good in RPP or just tweak dark files in RPP brighter by exposure compression?

S5 has a sensor that is made of two types of pixels. Sensitivity of those are about 3.9 stops apart. It depends on the goal how we deal with that. My usual way is to address it in RPP with a mixture of exposure compensation and compressed exposure compensation; starting from compressed exposure compensation.

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http://www.libraw.org/

 

[nitt]

Thank you for confirming my suspicions.

Mixture, eh? And we don’t want our mixture too rich with those unsensitive pixels, do we. So doing ETTR with this camera one shoud rather watch for the dark end of the camera histogram and not let it creep too much to the right.