Room color temperature

Question

Gday.

In my room I have a monitor that I feel is good for color accuracy. It's not the best but it's the best i've had. It's an LG 24MP76.

I like processing my photos, so I bought some LIFX light bulbs. With these ligthbulbs I can control the color temperature of my ambient light, in my room, while I am processing my photos.

What is a good colour temperature for evaluating my photos on the monitor?

Currently, in my workflow I turn off f.lux, and max out the brightness in the monitor. I don't own color calibration hardware for my computer - like Spyder or similar.

Thank you.

Answer 1

The industry standard for viewing color prints is 5500⁰K. I think that this fact is moot when viewing images on a monitor. Becasue the human eye/brain combination has a built-in white balance mechanism, the brain automatically adjusts the sensitivity of our vision system. This occurs all the time but you are likely unaware.

Try this test: Procure some deep colored filters (red, blue, green etc.). Candy wrappers or gift wrapping cellophane will work. Cover one eye with the filter and stare out the window at a sunlit vista or at a lamp in the room. Keep the filter on your eye for 2 to 4 minutes. Now remove the filter and look about, for a few seconds with one eye closed. Now switch eyes. You will see that the once filtered eye has drastically changed its color balance. This experiment will reveal the extent of this human automatic white balance. It makes you aware because each eye is controlled by the brain independently. Do try this experiment; it tells you a lot about human color vision.

Note: The photo industry and the lighting industry adopted the Kelvin temperature scale. This is the Celsius scale, however it starts at -273⁰C. The idea is, the Kelvin scale, starting at absolute zero (lowest possible temperature) has only positive values. Also, as all materials are heated, they glows first yellow-hot, then red-hot, then white-hot, then blue-white-hot. Potters, glass blowers and metal smelters judged the temperature of the material by its color. Early photo lamps were glowing tungsten, and the temperature of the glowing metal correlates to its color output. Films were formulated to operate under different color illuminates identified by their Kelvin temperature.

Answer 2

This began as a comment and grew enough to become a potential "answer."

Here's a bit of physiological trivia that might throw some light (!) on why ~5000K was chosen as a good "correllated colour temperature" standard for critical colour comparison. At that wavelength, human eye receptors in the retina are optimal for red, green, and blue radiation.

Viewing light intensity is the second critical factor when dealing with colour. The light must be bright enough for your visual apparatus to function optimally too. The goal is even diffuse illumination at 500 lux on the surface of a print image to be examined/compared. Not many are aware of this necessity and it often goes ignored. When this is set properly, fix the settings so they won't change. Eliminate any variable natural source of illumination. The goal is consistency and stability. When using fluorescent sources, strive for a CRI (colour rendering index) as high as possible with a minimum of 90%.

When you are working with colour on a monitor, the ambient light colour temperature and intensity can be a factor due also to an "adjacency effect" in non-neutral coloured environments.

TIP: Sitting in front of your monitor OFF in your workspace with the normal working lights ON, what do you see? If you see reflections of yourself and what's behind you, remember that this reflection is additive—and is added to your image when the monitor is on. This will affect your perception of your monitor's output NO MATTER HOW CAREFULLY YOU CALIBRATE IT. Adjust your room lighting so that reflections do not interfere with your onscreen image. Many who work with colour wear black to minimize unwanted colour contamination during evaluation.

There are several fixed "standard" points of colour temperature along the "white" Planc curve on the ICC Colour chart. D65 (daylight) is one. D50 was chosen as another one for reasons mentioned above.

Aside: Printing press operators are accustomed to having a higher ambient colour temperature for more easily seeing low contrast (yellow ink on white) subjects for image alignment. The actual colour management is done electronically in a reserved area of the plant set aside for colour evaluation.

Now, you are ready to turn on your monitor to set its brightness level. While it is warming up a minimum of 30 minutes to stabilize, create a file using something like Photoshop that is 100% Red, 100% Green, and 100% Blue. Display this "document" on your screen while viewing a blank white paper beside your monitor. Shield the monitor from the paper illumination and the paper illumination from the monitor. Adjust the monitor (not the file) to match the subject brightness at 500 lux.