Custom Camera Profiles for Different Locations

     

by Brenda K. Hipsher – April 15th, 2010

by Joe Brady

Since creating custom camera profiles has become so easy to do with the introduction of the ColorChecker Passport, I find myself creating new profiles frequently. Now I don’t want to end up with hundreds of profiles in my system, but I do want to have the best possible color reproduction for each scene.

I’ve spoken about how white balance and the camera profile are two different but necessary components for great color, but understanding the color distribution of the type of light may help you to decide when you really need to create another custom camera profile. I don’t want to get overly technical here. So let’s talk about this in a practical, easy-to-follow way.

I do recommend having a custom camera profile for each of the basic light types you encounter – Studio Lights, On-Camera Flash, Tungsten, Daylight and Shade. If you need to photograph in mixed or variable light sources, I would create one here too. The reason for this is that the light does not have a continuous spectrum of light. Simply put, there may be spikes of certain colors and holes where other colors are suppressed. So even though two images might share the same color temperature when using a neutral reference for white balancing, the spectral distribution of the light may be different. For two quick examples, think office fluorescent tubes and standard incandescent light bulbs.

Standard fluorescent tubes (not the daylight or cool-white kind) generally have a strong green spike in their light output, but your eyes adjust to it immediately. However, since green light cancels out its opposite – in this case magenta – a print containing magenta and deep red viewed under these lights will make these colors seem dulled. The same thing happens with incandescent light bulbs. We can see that when dimmed, these bulbs become obviously yellow, but they have a strong yellow output even when very bright. The opposite of yellow is blue, so when looking at the same print, any areas of blue will appear dulled and desaturated. Having a custom profile for these types of lights will correct for these effects.

The question that I needed answered however was do I need different profiles for daylight?

If you have ever traveled to the southwest, you have surely noticed how a clear sky seems to be a much deeper blue compared to the east coast. Is this simply color temperature or is something else going on? I selected two shots that were taken with the exact same color temperature and white balance at roughly the same time of year and same time of day – one from Miami and one from Wyoming and compared them. Despite a cloudless day in both locations, the Wyoming sky appeared much darker. When I sampled the sky in Photoshop using the Color Sampling Tool, the Wyoming sky displayed a different ratio of red, green and blue compared to the Miami South Beach view.

In order to compare similar brightness levels, I then sampled points of cloudless sky and adjusted the levels in the Eagle shot until the Blue numbers matched in both images – in this case when blue reading was matched in each image, the Wyoming Eagle sky averaged around 13 more points of red and an average of 5 points of green compared to the Miami sky.

The Mars Exploration Rover with an inset image of the Color Calibration Chart. The two "eyes" at the top of the Rover are two of its cameras.

The reason for this is mostly based on the atmospheric conditions, and in this case humidity. Miami is a very humid place, while Northern Wyoming is extremely dry – enough to sometimes cause nosebleeds in us easterners. The water in the air absorbs some colors of light and results in a different blue to the sky. Think about underwater photography. What is the first color to go? Red, of course! To have this confirmed, I asked my partner Diane who works for the Astronomy Department at Cornell University to ask her Atmospheric Science colleagues if this is what was happening. Since this crowd designed the camera system on the Mars Rovers, they had to take atmospheric conditions into account and designed a color reference chart to place on the Rover for color calibration. On Mars, they were dealing with frequent dust storms and had to correct for the color absorption caused by the iron oxide filled dust.

What prompted this entire exercise for me was that I noticed when I applied my standard daylight camera profile and then a profile created on location in Wyoming that the color response was slightly different. Now this was not an enormous change, but the location specific profile did produce a perfect result. The conclusion to this story is that if you are going to an exotic and beautiful location far from home, take the 30 seconds you need to create a custom profile and get the best color possible for your efforts.

I’ll leave you today with what to me is one of the most incredible images I have ever seen. At first glance, it looks like a dim, dusty sunset shot with a wide-angle lens. In actuality, this is a view of the Martian sunset captured by the Mars Rover “Spirit” on April 23, 2005 – I’ll say that again – Sunset on Mars – enjoy!

Categories: Ambient, Cameras, ColorChecker, Education, How-To, Lighting, News, Perception, Profiles, Viewing, Vision, White Balance | Tags: , , , , , , , , ,

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