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Achieving true color with Canon EOS 5D Mark II

John Forney , Feb 27, 2010; 07:43 a.m.

I have just bought a Canon EOS 5D Mark II and have been disappointed with the trueness of the color of some images to the point I am thinking about returning or exchanging the camera. I am not sure if it is a problem with the sensor and I need to exchange the camera for another one or if this is normal. How can I tell if the problem is the camera or if this is normal?

The shades of some things are off quite a bit (the corner of my lens case that is aqua (blue-green) looks light blue, a rusty color looks more red, etc). The reason I bought the camera was for good, true images. I contacted customer support and was told that I need to use a grey/white card and manually calibrate a custom white balance for each shot and in addition buy third party software.

To quote the response from canon: “Your EOS 5D Mark II should be quite capable of capturing true to life colors, but stock settings on your gear may not cut it. First-set a Custom White Balance (CWB) by picking up a gray/ white card and filling most of the viewfinder with it IN the light you are shooting. This will allow the camera to sense what color temperature is best as per the scene you are shooting. Then use the CWB function to set this as the WB and THEN re-shoot the scene. The colors may look subtly different but they should be accurate.

Next step is finding a way to calibrate your color profile on the monitor so they match print output. This usually requires the use of third party equipment, but is crucial to get correct color output.”

Responses


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Matt Laur , Feb 27, 2010; 07:53 a.m.

Well, that sounds correct. When you say the colors don't look right, are you talking about on your computer display, or in prints, or both?

Yes, you need to have your white balance correct for the light in which you shoot, or record a shot of a white balance target in that light, for use in RAW processing afterwards in post production. And then you MUST have your display calibrated, using a hardware calibration device and the accompanying software. Otherwise, you have no way of evaluating what you're seeing. And when you print, you must be using the the right printer profiles, taking into account the paper stock, which must match the profile.

Ken Schwarz , Feb 27, 2010; 08:25 a.m.

"True color" is an elusive goal. I've been at this for 5+ years and I'm still improving my technique. I suppose that taking formal training would accelerate the process, but this is just a hobby for me, so part of the pleasure is the discovery itself. Anyway, here's a summary of what I've learned.

White balance is certainly a big part. I always shoot RAW so that I have flexibility to adjust it in post processing. Note that white balance is not simple. Your light sources probably aren't simple. I find that fluorescent lights are the worst; it's just impossible to get colors to look right. But even if I use a controlled photo-quality light such as flash (which is much easier to balance), light bounces off of colored walls, flooring, etc. These all contribute to the complex color puzzle.

In Lightroom, you get to choose one white balance for all tones in the picture. In PhotoShop you can adjust for casts in shadows, midtones and highlights separately. Pray that this isn't necessary because it is a real PITA to do. My advice if you go there is to use a light touch of adjustment; it's all too common that I toss out the final result because when I look at it later it looks all wrong.

Then there is the matter of interpreting the RAW image data. There's no one "right" answer...you have choices. In the camera, you get choices such as standard, landscape, portrait and so on. These are used to generate the JPEG output but dont' affect RAW output. Lightroom seeks to mimic those and gives you its own. Compare them and see how they subtly change the colors. I find that "Canon standard" red is hotter than Adobe's red, for example. Faithful tames it further.

Next there are adjustments of contrast curves, which can be done in Lightroom for all colors together, or in Photoshop for the colors separately. I often find that I need to use Photoshop's contrast controls to get the best results, although they can usually be approximately quickly using the various color sliders in Lightroom.

One last point--and maybe the easiest and may be the most important for you: when you increase exposure in post processing (I find it necessary in almost every shot with my 5D2), watch out for pushing reds too far. Your RGB histogram is your guide here. I have made it routine practice to tweak the Lightroom "recovery" slider to pull back exposure of the bright areas (just a bit) as needed to restore natural fleshtones when reds are pushed too far. It's a simple technique for keeping reds natural.

Juergen Sattleru , Feb 27, 2010; 09:11 a.m.

Canon is absolutely right - learn about color management! You need to calibrate your entire workflow - Display, Printer and WB in camera. Btw, "true color" has always been an elusive goal - just look back at the film days and all the different print results (or even slides) of various film manufacturers.

Dan M , Feb 27, 2010; 10:25 a.m.

Your 5DMkII is probably fine. It is not a point-and-shoot, intended to be used on automatic. It is a high-end camera designed to give you control over your images. If you are worried about custom white balance, you are not taking advantage of the camera. To get control of color, you have to start at the beginning and continue all the way through. Shoot RAW (which makes the camera's white balance irrelevant, except that some software will use it as a default in reading the image). Use a gray card, at least under difficulty lighting conditions, and adjust WB in post-processing. In some cases, you will have to adjust color beyond that. E.g., shots over long distances, especially in humid conditions, are often too blue. Reds are often too intense in some shots of flowers. Your brain compensates when you view these things in real life, but not when you see the photo, so you have to adjust.

And yes, calibrate your system. The odds are pretty high that the color balance on your monitor, if you have not calibrated it, is wrong.

BTW, I agree with Ken--I find Canon's 'standard' picture style to be a little too red for my taste, so I use Adobe's as a starting point. Just a matter of taste. But you can adjust color balance as well starting with any of Canon's picture styles. And just like WB, picture styles are just a starting point if you shoot RAW. If you shoot JPEG, they are built into the file, and adjustments are much harder.

These same issues came up, in different forms, back in the film days. For example, people who knew what they were doing chose between kodachrome and ektachrome partly on the basis of their different color balances. People used filters to accomplish some of the things that we can now do with software.

Ben Goren , Feb 27, 2010; 10:27 a.m.

John,

Welcome to the rabbit hole.

First, start with an acceptance that the ultimate goal is physically impossible to achieve. One can, however, come acceptably close.

The basic reason is that the light that reaches your camera’s sensor is composed of a broad spectrum of wavelengths. Your camera, however, only records the intensities of three fairly narrow wavelengths, in the portion of the spectrum named “red,&rdquo “green,” and “blue.” This works because the pigments in your eye are sensitive to similar narrow bands of wavelengths.

Your monitor has, effectively, millions of tiny lightbulbs that have filters on them so they emit light that’s, again, similar to the colors your eyes are sensitive to.

Your printer, on the other hand, works by laying down ink that, ideally, absorbs all light except for those magic three colors, which reflects off the (mostly) white paper. In reality, the ink works much differently. Yellow ink, for example, reflects back equal amounts of orange and red light in addition to yellow.

By now the problem should be obvious. Not only is everything working with only a subset of the spectrum, not only do all these devices record or reproduce that limited portion of the spectrum in limited ways, but those devices that are nominally very similar can, themselves, have significantly different characteristics. The red color of one monitor will not be an exact color match for the red of another; neither will be an exact match for the red in your eye; and the proportion of the intensity of the red in relation to the green and blue will vary as well. And that’s just comparing two monitors! A camera and a printer are so radically different in their operation I’m constantly amazed that it even works at all.

The good news is that there’s an excellent mathematical model for describing the human visual system. The model says that, if you shine light of such-and-such a combination of frequencies of light, almost everybody will perceive it as such-and-such a color, and that color can be represented with three numbers. No, not the RGB values you’re familiar with, but X, Y, and Z, which are a very close match for the relative electrical signal strengths that get sent down your optic nerve.

The process of color management starts by performing a spectral analysis of an input or output device. This is done by taking a picture of a set of color patches with known spectral properties, or by measuring the spectral response of a set of designated device values. The ColorChecker is one well-known camera target, though its usefulness in modern times is somewhat limited. The ColorMunki is a wonderful new, inexpensive device that can measure both monitors and printers to see what spectrum, exactly, is produced when you tell the device to display, say, R=42 G=69 B=144.

The next step for cameras is to calculate a map that says that the camera records such-and-such an XYZ value as RGB this-and-that. Monitors and printers are the revers: such-and-such RGB outputs this-and-that XYZ.

An ICC profile is then created from that data. The profile defines some sort of a mathematical transformation that one applies to that device’s RGB values to get the corresponding XYZ, or vice versa. The more measurement points one has (and, of course, the more accurate and precise the measurements), the better the final approximation.

The computer’s color management software then, automatically and on-the-fly, makes all the necessary adjustments. When it all comes together, it truly seems like magic.

Enough theory.

With the 5DII, you’re actually pretty lucky. With even illumination of objects that isn’t causing reflective glare and an accurate white balance, the Faithful picture style is, out-of-the-box, a decent quality colorimetric match. You could stick with that and be confident that you’re in the ballpark.

If you want to do better, get yourself a ColorChecker SG. There are other options; my preference is Argyll CMS…but you still need a target, there’s a steep learning curve and…well, the ColorChecker SG is an excellent choice.

(If you really want to go insane, there are techniques that involve shooting a scene multiple times through different carefully-selected color filters; museums do that for archival art reproduction. And that’s the easy way….)

Of course, even if you get a superbly-profiled image from the camera, if your monitor and printer aren’t equally-well profiled, the output won’t match. As I mentioned, the ColorMunki is a great tool for both. If you have somebody else do your prints, you can save a bit of money by getting a display-only profiling device. The results will be good, but not quite as good as what the ColorMunki will do.

And, lastly, the ambient light at your computer as well as the light you view your prints in will have a very significant impact on your color perception. Ideal for color evaluation is a small windowless office with 18% gray walls and subdued D50 overhead lighting. That’s also a rather unpleasant environment to spend the whole day in, so consider just pulling the blinds during the critical bits, and opening them to evaluate the prints in (high-quality by nature) sunlight.

Good luck…

b&

Joe C , Feb 27, 2010; 10:55 a.m.

Unfortunately, even with perfect color management, you can never get all possible colors to appear correct unless you adjust some by hand. The problem is that the red, green and blue response curves of the camera do not match the response curves of human eyes, so when you correct some colors, others will be wrong, and vice versa. The results would probably be good enough, though.

You should definitely calibrate and profile your monitor, and then use color managed software to view the photos before deciding that the colors are way off. Or if you are looking at prints made from unmodified JPEG files, then the same would be true of the printer and print software.

I do not know how good the color correction is for JPEGs from a 5D2, but you might try the Faithful picture style which is meant to be color accurate under direct sunlight.

You might also get better results using RAW instead of JPEG and handling color correction entirely in the RAW converter software. This is probably more flexible, if not more accurate.

And finally, white balance does not affect the colors as much as one might think, but it helps a little to get it correct. That's another advantage of RAW, where the white balance can be changed after the fact instead of having to get it right while shooting.

John Forney , Feb 27, 2010; 11:28 a.m.

Thank you for the advice and explanations. I have been adjusting the settings and have very good results now. I see that I have a lot of options to fine tune things to get very good photographs.

Joe C , Feb 27, 2010; 11:47 a.m.

The red color of one monitor will not be an exact color match for the red of another; neither will be an exact match for the red in your eye;

This is true, but the red in your eye is not a single color, rather it is a range of wavelengths. It also overlaps significantly with green ( http://en.wikipedia.org/wiki/Cone_cell ).

but X, Y, and Z, which are a very close match for the relative electrical signal strengths that get sent down your optic nerve.

I actually wish they were a closer match. I've been schooled on photo.net before for assuming that they were identical. Specifically I don't like the peak at 450nm in X ( http://en.wikipedia.org/wiki/CIE_XYZ_color_space#Color_matching_functions ).

I should propose to ICC that they support a color space based on SML. It wouldn't help with camera color correction, but it would improve monitor and printer profiling.

Summer Leif , Feb 27, 2010; 12:09 p.m.

John, people have been giving you good advice. However, I would like to give you a few quick tips.

Shoot RAW and then load your CR2 files into Adobe Lightroom software to adjust the color and other parameters to your liking for each photograph.

For most situations use auto-white-balance. However when shooting at night, set your white-balance to somewhere around 2500K-2700K. Again, shoot RAW and load the CR2 files into Adobe Lightroom software for adjustment.

Get a "greta macbeth card" for critical situations so that you can have a test shot with known colors that you can make adjustment to in Lightroom later.

But as others have probably hinted, the chance that the problem is the camera are about 0.001%.

There is another set of standard color adjustments that you can make in your custom settings. Take some photos of a standard color card and fine tune the custom settings while using auto-white-balance, to optimize it for standard situations.

In conclusion, don't expect perfect color until you have fine tuned your photographs in Lightroom, and always shoot RAW to produce CR2 files you can work with in software afterward.


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