SIGMA's Garish Red Problem ...

Guest .

Banned
Hi all,

most SIGMA users already know, that pictures that contain large-scale and bright garish red picture elements often cause severe problems.

In these cases, the very sensitive red-channel overflows.

The best way to handle this problem is to "underexpose" these shots when shooting them. Later, when developing the image, one might correct exposure to the necessary extent .... then things are done with!

But ... what can be done, when such a (problem) shot was taken without exposure correction.

Coincidentally, I happened to find a solution to recover such shots ...:)

Let us have a look at the issue:

sample 43.JPG

Well, I took this photo with my SD14 with NO exposure-corrections (multi spot metering). As expected, the red channel strongly overflows ... as the histogramme clearly indicates ....:eek: All SPP sliders are in "0"-position.
The rose does not look nice ... somehow washed out ... no fine details in the rose's petals ....

sample 48.jpg

The only options to correct the histogramm are first to darken the image until the red cahannel performs correctly (let us forget this!) or to reduce colour-saturation to the necessary extent ... let us watch this option...

sample 44.JPG

Well, now we have detailed structures in all petals but ... the rose looks pale and flat now ... no real solution, I think.

sample 50.jpg

As I found out ... the X3F-RAW-file is not the problem! It contains the necessary image information ... In this case it is the SPP converter, which cannot handle this problem.
I took another converter ... namely RAW-PHOTO-STUDIO.
First the RAW with NO corrections ....

sample 46.JPG

The problems now are exactly the same compared to SPP! The red channel overflows absolutely .... as the histogramme indicates, too.

But, RPS provides the option, to adjust different colours differently and independently. So, you can adjust the red colour range independently as far as colour saturation and brightness are concerned. This is, what I just did in the next step ... a very small correction of the image contrast ... and ..

sample 47.JPG

Now watch the detailed structures of the petals, colour saturation and the histogramme.
Done, I would say.

sample 49.JPG

See you with nice pictures

Klaus
 

amaxgraph

Banned
I don't konw german then i download today ARCSOFT PHOTOSTUDIO DARKROOM (the same of your software but in english), because i've the same problem on develop saturated red channel on SPP and LIGHTROOM 2, but i don't find anything for view full red channel of my X3F than a normal control of RGB. If you are so gentle to tell me how do you do, because i think to change my SD14 with a SD9 or SD10 for this problem.
I'm waiting for your response.
regards
 

dirk

CI-Founder
Hallo amaxgraph,

welcome in the Sigma User Forum! Unfortunately, I do not use ArcSoft software, so I can not help you with this question.

Klaus is on vacation until 9th of October as far as I know, so it will take some time until he can access internet again.

best wishes
 

Guest .

Banned
I don't konw german then i download today ARCSOFT PHOTOSTUDIO DARKROOM (the same of your software but in english), because i've the same problem on develop saturated red channel on SPP and LIGHTROOM 2, but i don't find anything for view full red channel of my X3F than a normal control of RGB. If you are so gentle to tell me how do you do, because i think to change my SD14 with a SD9 or SD10 for this problem.
I'm waiting for your response.
regards
Hello Maxograph,

welcome to the forum!

In fact, there is a difference between Arcsoft Darcroom and RAW-Photo-Studio!

Both softwares are similar ... but not the same! Arcsoft Darkroom was first, before they sold there software to "IMAG MASTER". So, RAW PHOTO STUDIO is Darkroom's progression.

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Here, Carl Rytterfalk shows basic functions .... :)

The "Garish Red Problem" can only be solved with RAW-Photo-Studio ... as I showed above! Darkroom does not have the selective colour menue, which was added with the later RAW-Photo-Studio!

So ... get you RAW-Photo-Studio to replace Arcsoft Darkroom! :)
Follow the steps, I indicated above! Most probably, you will be successful!


See you with nive pictures

Klaus
 

amaxgraph

Banned
thanks Kluas, i'm testing in this day RAW PHOTOSTUDIO (i have many problem with the german language), and i've viewed immediatly the benefit. this situation have create more problem (than resolve it) on my workflow. I'm explain that i would say, i'm using LIGHTROOM 2.1 with all my camera (EOS30D, LUMIX DMC-L1, NIKON D1), i've just calibrated this camera with a colorchart target (with significant improvement of colour in Canon and Panasonic camera), but my mode of shot (only RAW in every camera), can't combine with RAW PHOTOSTUDIO and LR21. I search to expplain better my problem, to export a photo with optimal colour developed by RAW PHOTOSTUDIO i colud convert this in TIF file (8/16 bit), but in LR21 i loose the info about colour temperature and other, then now for SIGMA file i take even the X3F and a copy (colour correct) of TIF. This as a significant improve in dimension of my catalog and i can't have only a program (because RAW PHOTOSTUDIO can't have the database capabilities) for do my work. If you have info about a new version of SPP or a method to export a DNG (the DNG convert in RAW PHOTOSTUDIO is with a camera raw of ADOBE then reply the problem of read my X3F in LR21) with read X3F of RAW PHOTOSTUDIO i can't sell my SD14, if aren't solution about i'm selling this ASAP.
 

Guest .

Banned
Hi Amaxograph,

Well, language should be no problem with RAW-PHOTO-STUDIO. There is an English version available! It is a very nice tool indeed!

It is no problem to convert SIGMA X3F into the DNG-Format!

Just go for Adobe's DNG-Converter for Windows ... it will do the job! Then you can use any RAW-converter available.

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See you with nice pictures

Klaus
 

amaxgraph

Banned
Maybe i don't explain well my problem (or we don't know that i'll ask you), the gear for ADOBE Product (DNG converter, Camera Raw, LightRoom that i call LR21 - LightRoom 2.1 candidate version) it's the same, then if i can't covert well my X3F with LR21, nothing of other software product by ADOBE that work different (final result it's same). If you know (but know really), a method to convert in digital format (every format but not TIF - tag informed file format or JPEG) that have inside every info generate by EXIF of my SD14, i'll thank you, if you haven't this knowledge don't respond to this question.
regards
 

LUIS A GUEVARA

Well-Known Member
Dear Amaxgraph . The most advanced degree of control over RAW conversion can only be found with
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This little gem of software will allow you to convert to any Image file format ,with or without Gamma Encoding , to any Color Space with or without Color Balance and a lot more and it is free.

Output Options
0 Raw color (unique to each camera)
1 sRGB D65 (default)
2 Adobe RGB (1998) D65
3 Wide Gamut RGB D65
4 Kodak ProPhoto RGB D65
5 XYZ

This image for example is an SD9 X3F file processed in dcRAW-X , the Mac version , as a LINEAR CONVERSION . That is without Gamma encoding and Tone Mapped in Adobe Photoshop CS4.

8140473-md.jpg




Luis
 

Steaphany

Well-Known Member
Sunset with overly Strong Red

Yesterday, I was trying to shoot the Sunset. The Sun was already below the horizon, so all the red was the glow reflecting off the clouds.To boost the color saturation and contrast, I tried Uncompensated as well as both -1EV and -2EV settings. The photos were far from perfect, but the most striking difference between the SD14 photos and how I saw the sky was the intensity of reds captured. I saw subdued pastels, my SD14 captured intense and vivid crimson.

These images have not been adjusted. I converted them from X3F to 16 bit TIF with SPP, and then resized and saved as JPG with IrfanView.

ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 8

SDIM0311.jpg

ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 11 ( -1EV )

SDIM0312.jpg

ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 14 ( -2EV )

SDIM0314.jpg

Apart from a slight need to shift the color balance away from Magenta, the high red sensitivity brought results which were not visible to the eye.
 

LUIS A GUEVARA

Well-Known Member
Yesterday, I was trying to shoot the Sunset. The Sun was already below the horizon, so all the red was the glow reflecting off the clouds.To boost the color saturation and contrast, I tried Uncompensated as well as both -1EV and -2EV settings. The photos were far from perfect, but the most striking difference between the SD14 photos and how I saw the sky was the intensity of reds captured. I saw subdued pastels, my SD14 captured intense and vivid crimson.

These images have not been adjusted. I converted them from X3F to 16 bit TIF with SPP, and then resized and saved as JPG with IrfanView.

ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 8

View attachment 941

ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 11 ( -1EV )

View attachment 942

ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 14 ( -2EV )

View attachment 943

Apart from a slight need to shift the color balance away from Magenta, the high red sensitivity brought results which were not visible to the eye.
Very nice shots Steaphany , and thanks for a very interesting and valuable posting about the peculiarities of digital sensors that have prompted many to say that , particularly Foveon sensors, behave more like Transparency Film , where slight underexposure brings out Increased Saturation.

Your keen observation :

.......... the high red sensitivity brought results which were not visible to the eye.

also points to another interesting fact , this time about the high sensitivity of the Foveon sensor to Infra Red , and the , somewhat insufficient Infrared Cutoff Filter.

Hope that somebody picks up on this , perhaps Tony C or Kakou.

Luis
 

Steaphany

Well-Known Member
Has anyone ever tried using cyan color compensating filters to reduce the intensity of the red while preserving the blues and greens ?

I have been looking to see whats available and I'm leaning towards getting a Cokin P Series filter holder, a 77mm adapter ring to fit my Sigma 28mm EX DG Macro, and a set of Cyan P700-P709 filters.
 

LUIS A GUEVARA

Well-Known Member
Has anyone ever tried using cyan color compensating filters to reduce the intensity of the red while preserving the blues and greens ?

I have been looking to see whats available and I'm leaning towards getting a Cokin P Series filter holder, a 77mm adapter ring to fit my Sigma 28mm EX DG Macro, and a set of Cyan P700-P709 filters.
Not me . I prefer to work color and tone in software . It is easy to work color saturation, intensity and contrast independently , per channel ,in Photoshop RGB Color Mode and even more in the intrinsic Color independence of CIE Lab Color Space.

Cokin Color filters were great and the only alternative for Film, but with digital Imaging we have non destructive infinite interpretative possibilities.

Luis
 

Guest .

Banned
Hi Steaphany,

that sounds at least interesting. :) The crucial question might then be, whether the camera's wight balance would accept this measure?? The camera's reaction should be to amplify the remaining red intensity hitting the sensor, to balance towards neutral white.
If this should not work within the camera, it has to be done on the computer.

Amplyfing the red channel could result in stronger picture noise.

Just try it! :)

See you with nice pictures

Klaus
 

kakou

Active Member
I've found that a colour balancing filter such as an 80A or 82A helps reduce blue channel noise when the lighting is reddish, such as with incandescent light.

For sunsets you want to preserve the red or it will look rather bland. :)
 

Steaphany

Well-Known Member
Klaus,

You bring up a good point and I was intending to set a custom white balance to compensate. The only unknown will be to experiment to see just how strong a cyan correction would be needed and if this would vary by scene or could be relatively fixed.

Luis,

I started with analog or film based photography back in the 1970's and it has always been my view that the greatest photographic control occurs when the shutter is open. If information is lost, as being addressed by this thread as the Foveon imager saturates the red levels, whether working with analog or digital, you can't bring it back. Additionally, some effects can not be reproduced in software, the effects of a poliarzing filter is a good example.

Since we have no control over the Foveon imager, the support circuitry, or what image processing occurs in the camera, then only two options remain, either software post processing as Klaus described above, or to reduce the level of red light by use of a cyan color compensating filter. The effect on the final image may be the same, but until we can do a side by side comparison of the techniques, we're only guessing.

When I get the filters are run the experiments, I'll be posting the results. If anyone else here is inclined to try, go right ahead. As more work is done to develop techniques to maximize the potential of our cameras, everyone will benefit.
 

LUIS A GUEVARA

Well-Known Member
Klaus,

You bring up a good point and I was intending to set a custom white balance to compensate. The only unknown will be to experiment to see just how strong a cyan correction would be needed and if this would vary by scene or could be relatively fixed.

Luis,

I started with analog or film based photography back in the 1970's and it has always been my view that the greatest photographic control occurs when the shutter is open. If information is lost, as being addressed by this thread as the Foveon imager saturates the red levels, whether working with analog or digital, you can't bring it back. Additionally, some effects can not be reproduced in software, the effects of a poliarzing filter is a good example.

Since we have no control over the Foveon imager, the support circuitry, or what image processing occurs in the camera, then only two options remain, either software post processing as Klaus described above, or to reduce the level of red light by use of a cyan color compensating filter. The effect on the final image may be the same, but until we can do a side by side comparison of the techniques, we're only guessing.

When I get the filters are run the experiments, I'll be posting the results. If anyone else here is inclined to try, go right ahead. As more work is done to develop techniques to maximize the potential of our cameras, everyone will benefit.
Steaphany If you are getting any channels saturated ( Or burned out in Film ) during the taking of the photograph , you are not handling your exposure properly .

You do have control over the "Foveon imager and the support circuitry" Sigma cameras have a Good Display to instantly see the resulting images and the effect of your corrections ,plus an extremely useful Histogram that was put there just for that purpose. And of course it has IN CAMERA MENUS TO CONTROL SATURATION LEVELS PER CHANNEL AS WELL AS CONTRAST AND SHARPNESS.

As you can see you can adjust YOUR CAMERA SATURATION , SHARPNESS AND CONTRAST ,right at the Scene .This is called controlled Photography , as oposed to Snapshooting with Factory Defaults settings. , later you can Fine Tune your images during POST PROCESSING.

LCD Display info.jpg

These controls never existed in Film cameras . You are right , what you didnt capture you cannot bring back , that is why controlling the camera during exposure is so important.

Of course using absortion color filters to compensate your camera response to a given situation will do some good , but remember that sensors use only 3 colors to derive all the spectrum ,so changing one of them will afect the rendition of others that are NOT MEASURED , BUT CALCULATED , such as YELLOW, for example , or Violet , or Purple, etc etc.

When , and only when , you have exhausted the tools that were implemented in your camera , would it make sense to try other solutions. One of the major obstacles to digital Imaging is reluctance of film photographers to let go of the old analog Paradigm.

Luis
 

Steaphany

Well-Known Member
Luis,

Let me clarify what I meant by "no control over the Foveon imager, the support circuitry, or what image processing occurs in the camera".

Sigma has not, as of writing this post, published an SD14 Application Programming Interface to allow software developers and photographers to write their own versions of the SD14's internal operating firmware. Nor has Sigma published the electronic schematics to allow electronic engineers the ability to open up their SD14 and replace the electronic circuitry. We are stuck with the black box SD14 just as Sigma engineers designed. I can not change or control what they provide to me, except for the adjustments which they implement in firmware.

Also, look at the title of this thread. This thread is a discussion on the means to address the propensity of images of a subject with significantly high percentage of red hue photo sites having the red pixels pushed into saturation when green and blue are fine and when the exposure is accurately set. This phenomenon does not occur in all situations, hence the need to be aware of the potential and to find way to resolve the problem when it occurs.

As far as I'm aware, I can not control the camera image saturation level, or gain, of the individual red, green, and blue channels. If it did, I'm sure this thread would have been reduced to someone saying RTFM.

As for what you describe by "sensors use only 3 colors to derive all the spectrum", this is exactly how human color vision works. It's called metamerism, the matching of an apparent color with different spectral power distributions. You also have to remember that color does not exist in nature. A electromagnetic wave with a wavelength of 550 nm is no different than one at 2 m, both are waves possessing a polarization, a wavelength, and intensity. It is only the 550 nm photons interacting with the photosensitive proteins of the human retina that cause a signal to be sent to the brain where the conscious awareness sees green. The 2 m photons pass through the retina, completely unseen, and only detected by an appropriately tuned radio.

The design of color film (Yes, color films have red, green, and blue photosensitive layers) as well as all forms of electronic imaging, where the application is to photograph or record an image close to what the human eye sees has it's foundation in the tri-stimulus or trichromatic theory of human color vision. This was first postulated by Thomas Young in 1802, was developed further when three different retina cone cells were proposed by Hermann von Helmholtz in 1850, first standardized by the CIE in 1931, and actually proven as fact in 1983 when measurements from a single retinal cell were possible.

References:
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BACK ON TOPIC:

It is my philosophy that changes performed during exposure provide a greater level of control than by software manipulations done after the exposure was taken.

Color Compensating filters are available in primary colors, Red, Green, Blue, Yellow, Cyan, and Magenta. They come in a range of transparencies typically .05, .10, .20, .30, .40., and .50 which can be used singly or in combination to achieve what ever correction is desired.

Cyan filters reduce the intensity of photons in the band corresponding to Red, allowing the remaining visible spectrum through. By adjusting the camera's white balance to custom, it will accept the bias that the filter causes and simply reducing only the red to correct the propensity of the reds to become saturated.
 

LUIS A GUEVARA

Well-Known Member
Luis,

Let me clarify what I meant by "no control over the Foveon imager, the support circuitry, or what image processing occurs in the camera".

Sigma has not, as of writing this post, published an SD14 Application Programming Interface to allow software developers and photographers to write their own versions of the SD14's internal operating firmware. Nor has Sigma published the electronic schematics to allow electronic engineers the ability to open up their SD14 and replace the electronic circuitry. We are stuck with the black box SD14 just as Sigma engineers designed. I can not change or control what they provide to me, except for the adjustments which they implement in firmware.

Also, look at the title of this thread. This thread is a discussion on the means to address the propensity of images of a subject with significantly high percentage of red hue photo sites having the red pixels pushed into saturation when green and blue are fine and when the exposure is accurately set. This phenomenon does not occur in all situations, hence the need to be aware of the potential and to find way to resolve the problem when it occurs.

As far as I'm aware, I can not control the camera image saturation level, or gain, of the individual red, green, and blue channels. If it did, I'm sure this thread would have been reduced to someone saying RTFM.

As for what you describe by "sensors use only 3 colors to derive all the spectrum", this is exactly how human color vision works. It's called metamerism, the matching of an apparent color with different spectral power distributions. You also have to remember that color does not exist in nature. A electromagnetic wave with a wavelength of 550 nm is no different than one at 2 m, both are waves possessing a polarization, a wavelength, and intensity. It is only the 550 nm photons interacting with the photosensitive proteins of the human retina that cause a signal to be sent to the brain where the conscious awareness sees green. The 2 m photons pass through the retina, completely unseen, and only detected by an appropriately tuned radio.

The design of color film (Yes, color films have red, green, and blue photosensitive layers) as well as all forms of electronic imaging, where the application is to photograph or record an image close to what the human eye sees has it's foundation in the tri-stimulus or trichromatic theory of human color vision. This was first postulated by Thomas Young in 1802, was developed further when three different retina cone cells were proposed by Hermann von Helmholtz in 1850, first standardized by the CIE in 1931, and actually proven as fact in 1983 when measurements from a single retinal cell were possible.

References:
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BACK ON TOPIC:

It is my philosophy that changes performed during exposure provide a greater level of control than by software manipulations done after the exposure was taken.

Color Compensating filters are available in primary colors, Red, Green, Blue, Yellow, Cyan, and Magenta. They come in a range of transparencies typically .05, .10, .20, .30, .40., and .50 which can be used singly or in combination to achieve what ever correction is desired.

Cyan filters reduce the intensity of photons in the band corresponding to Red, allowing the remaining visible spectrum through. By adjusting the camera's white balance to custom, it will accept the bias that the filter causes and simply reducing only the red to correct the propensity of the reds to become saturated.

Too much ado about nothing . Just make sure you dont oversaturate any chanel during capture and restore the image likeness during post processing . Adobe Lightroom has individual control over Intensity and Saturation Individually of all the colors that you mention . The fact that the red over saturation occurs in some situations and not in others is showing a camera marginal rejection of unwanted NON VISIBLE colors , possibly by overly IR reflectivity of some organic dyes in Nature or Fluorescense of others due to excessive UV.

There are filters that combine both . The B&W 486 and 486 W is an UV/IR -cut , Interference filter that completely blocks unwanted UV and IR radiation , specially designed for digital cameras. The B&W 415 , absorbs UV and prevents Fluorescense that happens right at the LENS CEMENT ( In cheap lenses , that is )without introducing any color imbalance in the capture .

Also please note that this thread belongs to the DIGITAL DARKROOM , for practicioners and not for Engineers.

Luis
 

Steaphany

Well-Known Member
I just confirmed something that I suspected and want to see if anyone else has noticed this aspect of the Garish Red Problem.

Sigma Photo Pro handles Red better than IrfanView.

Here are two versions of the same X3F Sunset shot at ISO: 100, White Balance: Sunlight, Shutter: 1/10, f: 8 (No exposure compensation)

This was what SPP produced:

SDIM0311.jpg

This is what IrfanView produced:

SDIM0311_IrfanView.jpg

Both images show far more red than what I was able to see, but IrfanView saturated the colors where SPP was not as severe.

Has anyone else noted this type of discrepancy between SPP and their other software tools ?
 

kakou

Active Member
As you can see you can adjust YOUR CAMERA SATURATION , SHARPNESS AND CONTRAST ,right at the Scene .This is called controlled Photography , as oposed to Snapshooting with Factory Defaults settings. , later you can Fine Tune your images during POST PROCESSING.

These controls never existed in Film cameras . You are right , what you didnt capture you cannot bring back , that is why controlling the camera during exposure is so important.
Sure they did. It wasn't as easy as clicking a button on a computer, but it was possible to control them by choice of film, paper, exposure, development chemistry & temperature, enlarger type (condenser or diffused), etc.

Of course using absortion color filters to compensate your camera response to a given situation will do some good , but remember that sensors use only 3 colors to derive all the spectrum ,so changing one of them will afect the rendition of others that are NOT MEASURED , BUT CALCULATED , such as YELLOW, for example , or Violet , or Purple, etc etc.
All colours are calculated from the three primaries. That's how pretty much any colour imaging device works. Also, Foveon doesn't actually measure RGB, but calculates it from the three layers.




As far as I'm aware, I can not control the camera image saturation level, or gain, of the individual red, green, and blue channels. If it did, I'm sure this thread would have been reduced to someone saying RTFM.
True. About the best you can do is use Dave Coffin's dcraw and alter his source code. Or, you could extract the three layers with it and come up with your own transform. A couple of people on dpr have done that.
 
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