Color Accuracy vs. Art in Photo Post-processing, the Case for HDR

I see that question a lot posed online, in discussion groups, even under photos. To me liking Photoshop but not liking HDR would be analogous to liking wrenches but not liking hammers. Sure, many people wield HDR poorly, but many carpenters wield a hammer poorly too… what could that have to do with hammers? In other words, what does the existence of poor results have to do with the potential (value or utility) of the tool?

Many people vilify HDR; I don’t get it. Most people play guitar poorly, but that won’t keep me from enjoying the work of many talented guitarists. Of course everyone’s entitled to their opinion and their own tastes. If classical music fans want to say, “Ugh, I think I hear a guitar in that piece!”, or photography fans want to say “Ugh, Galen Rowell used graduated neutral density filters!”, that’s their privilege. Surely HDR software will get better and better at expanding dynamic range while producing unobtrusive results, and as that value is delivered for more and more shots, I’ll have terabytes of exposure-bracketed images to draw upon.

I find HDR a useful tool about 80% of the time, with maybe 5-10% of all shots I choose to keep being simply not possible without it.

My example above is pretty obvious and results like that may be an acquired taste, but can you identify which of the following photos was shot with HDR and which were not?

Perhaps more to the point, which do you like better? If you can’t tell how an image was produced, does the process or tool used matter?

As for whether or not a result matches an original scene, no photograph does (unless the entire scene is pure white or pure black).

Consider the scene’s brightness. An original scene contains light in a range of up to 17 stops, our eyes can handle 13 stops, a film camera can handle about 11 stops, the best full frame digital cameras at most 8-9 stops. Most of the digital cameras with small format sensors that most people shoot with are probably closer to 4-5 stops. How do you restore some fraction of the shadow and highlight detail in those 8-9 lost stops of light, if not with High Dynamic Range techniques?

Then consider the color. The camera’s CCD sensor has one range of colors that it can sense. The proprietary RAW format each camera saves the file in has another range of colors that it can store. The monitor you display it on has yet another. You may edit and save in a format with a lot of colors like TIFF.  Eventually the image tends to get converted to 8 bit JPEG format for printing or display online, trying to represent the infinite shades of natural color in only 256 levels of color for Red, Green, and Blue (RGB). But the printer typically uses a subtractive CMYK color scheme of Cyan, Yellow, Magenta and blacK, which doesn’t match or directly overlap any of the other color spaces used along the way. Color accuracy is a great concern for graphic artists and the fashion industry, so the Pantone™ system was developed to provide 700 calibrated colors.across scanners, monitors and printers.  Even back in the Sony Trinitron™ cathode ray tube days, a calibrated monitor could often display 16 million colors, so even using color calibration systems we’re 15 million colors and change short of having a truly accurate end-to-end result across all the technologies and color maps your images will pass through.  I worked for years as an applications engineer at the world’s leading color printer manufacturer.  You’ll hear a lot about how vivid colors are, perhaps how many colors a monitor or printer can accept as input, but rarely will you hear about how many colors can be printed at a given spot on the paper, the challenges of color space mismatch as an image moves from device to device, color representation bottlenecks (such as JPEG), or the general lack of calibration and accuracy at every step along the way.

Fortunately human perception is very forgiving.  It was important for use to be able to discern between millions of colors, but we never developed much ability to remember them accurately.  Cognitively we group colors into roughly 11 categories, but we have little ability to remember even distinctly different colors from memory, let alone subtle shades of them.

Our brains also distort color, and try to assign the brightest thing in a scene to be white. That’s we have to have our cameras and software adjust images to a certain “white balance” (strictly a human perceptual distortion). The ambient light available when viewing an image (outdoors in sun, shade, under incandescent light, flourescent, etc) seriously affects our perception of the result as well.

Our eyes and brains are not carbon copies from person to person. Some people report noticeably different perception even from eye to eye. There’s truly no such thing as “reality” when it comes to white balance and human color perception.

So given the essentially insurmountable issues at every step of the process, how can anyone claim to have produced an accurate copy of any given moment? What would that even mean… accurate to an electronic device, to one person, or to which subset of people, and under which ambient lighting conditions for viewing?

Must we “go with the flow” and pretend with the charlatans that accuracy is possible (or even a desirable goal), or is it safe to observe that the “this is just as it happened” emperor has no clothes?

To each his own though… everyone is entitled to like or not like something for any reason or for no reason. HDR simply happens to be one tool that I find not just extremely useful, but indispensable. I’d sooner part with even basics like UV filters and circular polarizers.

If photographers aspire to be some sort of sterile recording device, s sort of walking copy machine, then they can be replaced by webcams nailed to trees or doorjambs. Most definitions of “art” require human involvement and influence… a departure from sterile reality. Accept the inaccuracies of color capture and representation, the massive distortions inherent in human color perception, the lack of human color memory, and recognize the opportunity to free yourself to exercise your human side, your artistic side.  Any departure from the fruitless pursuit of perfection will set you free.

Update in early 2013: Wow, what a turnaround… after getting a full frame camera in early 2009 and starting to use Lightroom, I began to have far more success with single exposures and far less need or desire to go to the extra time and effort required to use HDR.  I take less time per photos while having far more control over the result… great example of why it’s useful to remain open to new techniques and to periodically evaluate new tools.  I’ve even seen great improvements when moving form Lightroom 3 to 4, which I only noticed by going back and trying to edit in 3.  The color translation tables to interpret RAW files seem to be much better in Lightroom 4.  But man, that must be a mind-bender to people who were absolutely convinced that they had end to end accurate color.  How did they choose between an “Adobe” or “Camera Standard” interpretation of the RAW file originally, and if the color translation for that setting changed for their camera from Lightroom 3 to 4, which is accurate?  There are other choices… Camera Landscape, Camera Neutral, Camera Portrait… it’s quite possible that our color perception varies so much over time and by viewing conditions and by subject type that different color translations are best in each unique situation. 

I should also clarify that a lack of accuracy is not necessarily an argument against monitor calibration, which helps you get more predictable prints (if you manage color profiles all the way through to printing), and discern more colors while you edit.  That won’t fix the inherent end to end accuracy problem and color space translation issues or the inherent mismatch between digital imaging and the human perception system… there’s no one right or wrong approach.  Fight our human failings and try to impose order and reason on them, or accept imperfection and embrace the freedom to create; it’s entirely up to you to decide.