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Finally - the SD rolloff bug: FIXED!!!!!

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cinefeel

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I have found a fix for this problem at last, and have informed Sigma of it as well.

These images should speak for themselves. Be sure to click on 'original' for each one. The compression on DPR really screws things up and makes them look much noisier.













"SD1 Banding Fix II" is the same is "SD1 Banding Fix I", except that I have boosted the saturation in order to make the issue as clear as possible. It seems that there is a particular shift in the hues relating to shadow noise in the SD1 processing, but it can be corrected by the following settings in photoshop:

Image > Adjustments > Hue > Settings : Yellows - 15 Reds + 5

This not only appears to fix the problem, but also improves the smoothness of shadow gradations in general. The appearance of chroma noise is also lessened.

The final image I have attached, called "SD1 Fur Color Fix", shows that this solution even fixes a hidden color inaccuracy of the SD1.

Thank goodness this issue is finally resolvable! I've been working on a shoot for work and managed to find this fix at the last minute after tearing my hair out.
 
If those settings made your image redder then you are doing something wrong!

+5 red hue should make things yellower, not redder.

Important thing is what the range is. Meaning, what falls within the band of what is considered red and what is considered yellow.

The defaults in photoshop CS5 work perfectly on my system, and across a very wide range of images.

What the default ranges are in Aperture, I don't know. I would be wary of using it because the control interface you are showing there looks somewhat less precise than Photoshop.

Either way, this clearly fixes a huge problem- one that is most obvious in my second image. I have forwarded all this to Sigma!
 
P.S.

I suppose this should be obvious, but- the better your white balance setting is, the better this fix will be.

If your white balance is way off, then this might not work right. Thankfully, I find the white balance with SD1 is pretty easy to get right- either in camera with AWB or using the dropper in SPP.

I have saved this fix to a pre-recorded action in Photoshop. I now batch-process everything with it!
 
P.P.S.

If you do want a slightly yellower result, you can use Yellows -10 and Reds -+0, but looking at the noise patterns will show that Yellows -15 Reds +5 is the optimal fix. If your results are a little off then it's the white balance that's probably to blame.

I should also point out that standard color mode is somewhat broken, in that it's much too red in the first place! At best, it would probably require a different fix. Not sure, as I never use it.

This fix I have posted I can only guarantee for Neutral color mode!
 
It does fix it..but skin tones dramatically changed...to orange...all in all, better in one way, worse in the other....

--

To understand photography, you must understand that the experience must be much more important than the result ....
Carlos Roncatti Bomfim
http://weweh.com/
because men and women are different and we humans are the same.
 
No!

The skin tone has not changed to orange.

That's just in the image with vibrance boosted +100 to show the effect!

The skin tones remain the same, minus the unnatural yellowness.

What I have now realised is that this is a general problem with a camera - it does not render these hues correctly in ANY image. This fix as presented here will make any image taken in neutral mode look more natural.

I'm currently research a bit with many different kinds of images to see whether it can be fine tuned.
 
cinefeel said:
If those settings made your image redder then you are doing something wrong!

+5 red hue should make things yellower, not redder.
Click to expand...
I go into Image-Adjustments-> Hue/saturation. I choose instead of the master channel the red channel, then for "hue" I enter "5".

Then I change the dropdown to "Yellow", go to Hue again and enter "-15".

If that is wrong, please let me know in which step I need to do something different... but my image is absolutely a bit more red, and in fact too red.
cinefeel said:
Important thing is what the range is. Meaning, what falls within the band of what is considered red and what is considered yellow.

The defaults in photoshop CS5 work perfectly on my system, and across a very wide range of images.
Click to expand...
I am also using CS5.
cinefeel said:
What the default ranges are in Aperture, I don't know.
Click to expand...
They are quite narrow which is why I increased them in my settings.
cinefeel said:
I would be wary of using it because the control interface you are showing there looks somewhat less precise than Photoshop.
Click to expand...
It's just as, if not more, precise.

The funny thing is that my changes in Aperture look much more like the ones you posted, i.e. the image actually looks more correct.
cinefeel said:
Either way, this clearly fixes a huge problem- one that is most obvious in my second image. I have forwarded all this to Sigma!
Click to expand...
That is great, I really appreciate you finding such a simple fix, but I want to understand it better and especially help people out using alternate editors like Aperture to get the same effect.

--
---> Kendall
http://www.flickr.com/photos/kigiphoto/
http://www.pbase.com/kgelner
http://www.pbase.com/sigmadslr/user_home
 
Did you start with an image shot in Neutral color mode?

Also, did you try fine tuning the yellow band? This may be necessary in an image with tones close to the false color.
 
Cinefeel, you are not looking at my images..i gave you a sample with the same problem in a thread started by you. My Sd14 photo with the problem is NOT fixed by your solution...or better yet, it fixes the problem, but gives me unacceptable skin tones....
cinefeel said:
No!

The skin tone has not changed to orange.

That's just in the image with vibrance boosted +100 to show the effect!

The skin tones remain the same, minus the unnatural yellowness.

What I have now realised is that this is a general problem with a camera - it does not render these hues correctly in ANY image. This fix as presented here will make any image taken in neutral mode look more natural.

I'm currently research a bit with many different kinds of images to see whether it can be fine tuned.
Click to expand...
--

To understand photography, you must understand that the experience must be much more important than the result ....
Carlos Roncatti Bomfim
http://weweh.com/
because men and women are different and we humans are the same.
 
I'm not sure what you're referring to...

Also, this only applies to the SD1.

Probably only Neutral color mode, even. Am I misunderstanding something?

Failing that, you may be facing the same thing as Kendall in which case maybe try Aperture instead of Photoshop.

I can promise only that this will fix SD1/SD1m images, and I'm not surprised that this is useless for the SD14 because the sensors and electronics are completely different.

I don't have an SD14 to research a fix, but you could try something similar but with different settings. Be sure to use a TIFF though, since JPEG does not have enough information.
 
I've found there is no single 'correct' set of color settings for any camera I've used---each shot is different. I've often had to start all over again from 'scratch' when my 'usual' work-flow failed to give the desired results. I shoot exclusively with AWB and use Photoshop. I start with haze elimination & local area contrast, progress to levels, then curves. First I look for and eliminate color casts, but at some point during that process I also use the color checker to look for white, black, and neutral gray colors to confirm my settings. I use un-tagged CMYK first, then RGB. I find that if you get CMYK correct, RGB is also often correct---but not always! Then I fix any problems with saturation / hue / lightness, color balance, etc. I finish with sharpening and then vibrance and a final RGB curves 'pop' adjustment (either positive or negative depending on the shot), although I often discard both adjustments as not giving an improvement or the desired effect. My final effort is to correct any blemishes.

However , your solution may be universal and brilliant for the SD-1. Thanks for sharing.
--
William Wilgus
 
You are absolutely correct that there are no 'absolute' settings.

A camera bug, however, is different!

It's pretty clear that in this case we are dealing with a bug. This is a pretty decent fix, I think, until Sigma get around to fixing it properly.
 
cinefeel said:
You are absolutely correct that there are no 'absolute' settings.

A camera bug, however, is different!

It's pretty clear that in this case we are dealing with a bug. This is a pretty decent fix, I think, until Sigma get around to fixing it properly.
Click to expand...
Good luck waiting.

It's been years since the sd9 and the yellow cast is still there.
 
My two cents about this issue: main cause is the contrast of levels in skin tones area. My work flow for portrait with Foveon:

Tiff from SPP, in ACR od CS, never touch any adjsutment here (except auto defringe and CA remove). Zoom over 300% at dark areas of portrait, sure will find typical Foveon residual noise. One pass of Topaz Denoise at very low strngth enough to clean luminance and color noise there, blur and smooth out transition of dark and bright area. Use Shadow/Hightlight - shadow off, adjust Hightlight to reduce contrast of skin tones from dark to bright. All those steps with fade can help to cure this problem. For more serious, use Portraiture with skin tones mask and many tools there.

Rgds,

Hung
 
HienPham said:
It's been years since the sd9 and the yellow cast is still there.
Click to expand...
The support of SD9 was ended many years ago, long before Foveon/Sigma understood color management.

Sigma matured regarding color understanding during the different DP camera experiments, and was finally very good when SD15 was released. Or so I think, I have not heard any major complaints regarding SD15 colors. Its clipping highlights - but that I think is an effect of treating colors correctly. With earliuer models they made some tricks to recover more highlight information. Tricks bringing in out of gamut colors into the RGB color space. Thats not possible (at least not on a massive scale) if you want correct colors.

Now --- all this experimenting was made on the same sensor, the SD14 sensor.

SD1 has a completely new sensor, that seems to have a much thicker blue layer. At least the RAW images are much bluer. So, its not surprising that they need some time to calibrate.

Of course, it hints at they not really understands color yet. If they did, I assume they would have been able to make the calibration before launch.

--
Roland

X3F tools:
http://www.proxel.se/x3f.html
https://github.com/rolkar/x3f
 
Actually, I think the SD1 is the best sensor yet in terms of color.

And no, this gradation problem CANNOT be fixed with contrast settings.
 
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