Nikon DSLR and Blown out reds - a Color Space issue

<p>I have seen many treads about the Blown out reds issue using Nikon DSLRs. I am convinced that this is a problem related to using a small Color Space and not an issue with the cameras. In this case even AdobeRGB qualifies as a small Color Space and I´ll try to show why.<br>

In a simplified way, a color space is defined by the position or coordinates of the primary colors, commonly Red, Green and Blue.<br>

In the following image (created by Jeff Schewe, obtained <a href="http://en.wikipedia.org/wiki/File:Colorspace.png">here</a> , where it states that it is Ok to use it for this purpose) the visible color and the most common color spaces are shown<br>

<img src="http://upload.wikimedia.org/wikipedia/en/3/37/Colorspace.png" alt="" /><br>

The first thing to notice is that the red and blue primary colors are the same for sRGB and Adobe RGB. Second, there is a considerable area of reds outside of the sRGB and AdobeRGB that will result in blown out reds.<br>

The diference between sRGB and AdobeRGB is in the green primary, which has an important effect in the blue-green colors.<br>

If you want to be able to capture the reds or any color outside the AdobeRGB color space, you should use a large color space like ProPhotoRGB<br>

Now lets see this effect on a real photo. Following is a series of the same picture, taken with a Nikon D300 in RAW, opened in Adobe Camera Raw 4.6, with camera profile set to "Camera Vivid" in ACR, where the only difference between them is the color space</p>

<p>The first image is with sRGB color space. It almos completely bown out. You can see the spike at the right of the histogram showin this</p><div></div>

<p>If we change to AdobeRGB, the problem with blown reds is almost the same</p><div></div>

<p>When we use the ProPhotoRGB color space the problem is solved. Also notice that the spike in the histogram has disappeared and now we have some tonality in the high reds</p><div></div>

<p>One more image. Here I`ll try to show why underexposing is not the best approach. I have taken the impage in AdobeRGB color space and underexposed it by 1.25 stops using the exposure slider of ACR. Even if now the reds are not blown out, in the histogram you can see that the high reds are a spike (compared to the histogram of ProphotoRGB) so you are loosing tonality</p><div></div>

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<p>"I have seen many treads about the Blown out reds issue using Nikon DSLRs. I am convinced that this is a problem related to using a small Color Space and not an issue with the cameras."</p>

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<p>Agreed. In nearly every case where I've read this complaint it was almost invariably due to user inexperience with editing. The few exceptions included photographing under unusually difficult lighting, such as gelled stage lights.</p>

<p>Thanks for the write-up. Francisco, if you edit your image in ProPhotoRGB in NX2, and need a JPG for web-based exhibition, you still need to convert it back to sRGB. How much clipping and blow-out will that cost? Perhaps, an image or two to show that will be great.</p>

<p> </p>

<p>Arthur, what you need to do is to convert the image to sRGB using a perceptual rendering intent. I don't know how to do it in NX2, but I can try to do it later tonight in NX (I don't have access to it now). I use PS CS3.<br>

The purpose of the perceptual rendering intent is to map the colors proportionately from one space to the other, so the tonal transition will be smooth. It may be that the colors won't be accurate but pleasing.<br>

This is the case where the main subjects or large areas of the images have original colors outside of the final color space.</p>

<p>In the case where only small portions of the image colors are outside of the final color space, you may use a relative colorimetric rendering intent, which will keep most of the colors inside the color space unaltered.</p>

<p>Is ProPhoto RGB available on Nikon cameras? I shoot in AdobeRGB.</p>

<p>Ok, I'll admit to being inexperienced with editing, but when I go to the color management drop down in NX2, I do not find "ProPhotoRGB". Where do I find ProPhotorRGB in NX2? Francisco, I'm not sure what software you're using, but I assume it is PS. This has been a most helpful series of threads, and I thank everyone for their help.</p>

<p>Dan, ProPhotoRGB is not available directly on Nikon Cameras. The reason I may think of is that the definition of a color space in camera is used only for Jpeg images. RAW images are not affected by it. You choose the color space in the RAW converter.<br>

I would not recommend to use ProPhotoRGB with Jpeg because they are 8 bit per color, and it would no be a good choice for a huge color space. Actually if your end result has to be jpeg, you should first convert to a color space like sRGB or AdobeRGB, then convert to 8 bit and finally save as jpeg.</p>

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<p>I am convinced that this is a problem related to using a small Color Space and not an issue with the <a href="00V23x#" target="_blank" >cameras</a> .</p>

 

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<p>If so, then this would affect all cameras. Not just Nikons. So, why haven't I had this problem with my Nikon, Canon or Leica?</p>

<p>Clarification about profile conversion: Even if in theory if you use a perceptual rendenring intent to convert from a large profile like ProPhotoRGB to a small one like sRGB the colors should be mapped proportionately, in practice this does not happen and the out of gamut colors of the small space get clipped. Basically what happens is that even if you can select a perceptual rendering intent the conversion is done with a colorimetric intent.<br>

This is caused by the way working profiles are defined, called "matrix profiles". I found out testing conversion in PS3 and confirmed it in articles available on the web.<br>

Some of the links:<br>

<a href="http://www.josephholmes.com/propages/AboutRGBSpaces.html">Joseph Holmes</a><br>

<a href="http://www.colorwiki.com/wiki/Color_Management_Myths_21-25">Color Wiki</a><br>

<a href="http://www.earthboundlight.com/phototips/matrix-profiles-perceptual.html">Earthboundlight</a></p>

<p>As a result of this, if you really need to produce a final output in a smaller color space, you will have to edit your image (i.e. reduce saturation) before converting color space</p>

<p>The rendering intents do work when you convert or soft proof to printer profiles, since they are defined in a different way (table-based)</p>

<p>I tested the conversion also in Capture NX with the same result, so it is not exclusive of PS</p>

<p>Douglas,<br>

It may affect other cameras, I just don´t have other brands to test. This is not a common problem since it happens only with really saturated colors as in some flowers or birds.<br>

Some times it is even difficult to detect, especially if the saturated areas are small or do not have detail. Also if it is not a primary color, maybe only one channel is saturated and you still see detail or texture from the other channels</p>

<p>Capture NX users:<br>

This is based on NX since I don´t have NX2<br>

To open NEF images in ProPhotoRGB<br>

Edit->Preferences->Color Management<br>

In the dialog box: Default RGB space: Choose ProPhotoRGB and check "use this instead of the embeded profile"<br>

Note: The captions may be slightly different since I´m translating from a spanish version of NX</p>

<p>To convert an image (after editing it) to another profile:<br>

Adjust ->Color profile<br>

In the dialog box check "Convert to profile" and choose the desired color profile</p>

<p>Speaking of ProPhoto RGB. I shoot in Adobe RGB but for NEF files it's meaningless as you can open them in any profile you like.<br>

I have some Kodachrome slides that were put on a PhotoCD back in 1997. When I open in sRGB or AdobeRGB, it looks like this:<br>

<img src="http://hull534.smugmug.com/photos/289065465_UBSF5-L.jpg" alt="" /><br>

San Francisco, 1996, Nikon FE2 and 50mm f1.8 AIS lens</p><p>Here is what the same file looks like when opened in ProPhoto RGB:<br>

<img src="http://hull534.smugmug.com/photos/572076614_buFgE-L.jpg" alt="" /><br>

Much better, and much closer to reality as I remember it.</p>

<p>Well, well, it really does help to edit properly and use a bigger color space, no doubt about it. but even if you shoot raw and are not aware that the histogram you are looking at is a JPEG conversion not a real RAW histogram people can be easely decieved that they are capturing the right exposure and then , OOPs blown reds. this has to do with the design of the Bayer array, twice green filters over the photosites compared to the red and blue channel, AND is not Nikon exclusive.<br>

Remember you are capturing RAW and then can edit on any color profile you like best or need. if you use a MUTED W/B profile when shooting raw you will notice, first an image that looks green like HULK, and second a histogram with a more accurate red channel, Then on PP correct the white balance and you have captured an image with no clipping and good tonality.<br>

I use UNIWB as WB profile when shooting RAW.</p>

<p>@ Gary Payne, not long ago you had a thread about your D700 and some red flowers where I posted an answer to that problem, did you give it a try?<br>

My point is Fransisco is right a bigger color profile gives you a better latitude for PP , but is important to have an image that has captured the right ammount of information to start with.</p>

<p>I wonder how many ppl really follow aup after they post.</p>