Pop Quiz: What is the color temperature of the light hitting your monitor right now?
Followup Question: Do you know why it matters?
Many people do not give much thought to the light hitting their monitor while editing photos. Yet it is critically important if color accuracy is important in the least. Let me show you the importance with a few shots. See if you can guess the color temperature of the light hitting the each screen. Know that my office is a small 5′ x 8′ room, off-white walls and a skylight overhead. (Exposure of each shot was balanced in post production with only the exposure setting itself increased to match other shots.)
- Indirect Daylight off to the side, from above (4650K)
- Cloudy light from above (5450K)
- Direct Daylight (5001K)
- Direct Daylight with a white fabric placed over the skylight opening (4100K)
- Indirect Daylight with a white fabric placed over the skylight opening (4300K)
- Direct Incandescent/Tungsten light bulb at night (2750K)
Each photo is clickable for a larger 1200 pixel wide shot. I balanced the shots according to a white card test of the light (shot separately) except the last image which was left at the camera chosen 5250K, otherwise the 2700K renders far too blue.
Our brain takes the light coming in and, in essence, auto corrects it. If viewed in a complete black environment, a screen can be color calibrated and show colors as true. This is fine and should be done. How our brain perceives colors coming from the screen will also be influenced by the color temperature of the light available at the time. Most manufacturers suggest calibrating your screen with the anticipated ambient light sources available (and the best calibration tools are able to balance for this light).
For the first image, I was going to use the shot without my reflection as a more pure example. But I thought it important to leave in because most of us don't realize what effect we have our images. If light is coming from behind you (in this case, there was direct sunlight on the wall to the side of the iMac, which was reflected off the rear wall as well) then your shadow can make a large difference. I could have done the same for the last shot, where the bulb is clearly visible in the corner.
Some suggestions to help make sure colors stay true:
- Calibrate your screen in, ideally, a black environment. If your calibration tool of choice does not measure ambient light, just ensure there is not an over abundance of one light source or another. If it does measure ambient light, use the source you anticipate being available while editing (or make multiple profiles for each light source).
- Edit your photos in the likely light source they will be viewed under when printed.
- Be aware of the color of your walls.
- Only have one light source hitting your screen at a time while editing.
- Use indirect light when possible and do not place your light source behind you.
- Realize light reflected off items viewable from the screen's reflection will influence results.
The second item can be very important. If your screen is calibrated correctly and you edit photos with a tungsten light source, your brain is adjusting for that source. In that case you make white look as you percieve white to be in that instance. Now, when you print that image (let's assume the printer is properly calibrated and you used an ICC profile to soft proof) and present it in indirect day light, the colors will not match what you saw on your screen. Likewise if you took it into direct sunlight. But it will come closer when viewed at night with a tungsten source.
It's important to edit, on a calibrated screen, with a light source as anticipated when the print itself is viewed. Baring a known source, Indirect Daylight is the best bet.
If you need information on calibrating your monitor, DPS has a post for that here.