04-23-2016 07:28 PM
I believe the shutter on a 5D3 moves vertically, and at those speeds it moves as a slit, with the closing curtain trailing the opening curtain by less than the height of the frame. If the concert was using high-speed strobe lights of different colors, you'd see a band of whatever color light fired when the slit was in position to record it.
I am inclined to agree with Bob's gut instincts. Solid state lighting sources do not emit light at a continous frequency. Instead, they emit light strobocopically, meaning the fixture will quickly flash different colors, to achieve an average that the human eye will see as a constant color. For example, an LED can quickly strobe between red and green to yield what the eye percieves as yellow. Unfortunately, digital DSLRs do not allow themselves to be as easily fooled as the human brain.
04-23-2016 02:09 AM - edited 04-23-2016 02:10 AM
So I should just not shoot at high shutter speeds? I went as low as 1/640 but even then I still got the bars.
If the light that illuminates the scene is absolutely constant, you can use any speed you like. If it isn't, you risk getting artifacts at any speed at which the second shutter curtain begins to close before the first curtain finishes opening. (That's also the maximum speed at which you can use flash, because the flash can't illuminate the full scene unless it fires with the shutter fully open.) On a 60D that's probably around 1/200 second. If the ambient illumination consists of discrete flashes of different colored light (a common situation at rock concerts), the artifacts are likely to take the form of colored bars perpendicular to the direction of travel of the shutter curtains.
Think of it this way: At shutter speeds higher than 1/200 second, the two shutter curtains form a slit that travels across the focal plane. For every position of the slit, the camera's sensor will see only the lights that flash while the sensor is in that position. If flashes of red light dominate, you'll see a red bar, etc. The higher the shutter speed, the narrower the slit will be, resulting in narrower, more clearly defined bars. Depending on the frequency of the flashes, the color is apt to be purer too, since the sensor will see fewer flashes for a given position of the slit. Note that if no lights flash while the slit is in a given position, the bar will be black.
The foregoing description is a bit of an oversimplification, since the light is constantly changing color and the slit is constantly changing its position. But the probability that the various effects will cancel each other out is very low. So if you can't tolerate the artifacts, you're left with two choices: provide your own light source (e.g., flash) or use a shutter speed of 1/200 second or less. In a live concert situation, the slower shutter speed may be the only practical option.
04-24-2016 09:25 AM
"So I should just not shoot at high shutter speeds? I went as low as 1/640 but even then I still got the bars."
A simple test. Slow your SS to an unreasonable setting, maybe 1/30 and try. Don't worry about the actual photo. Also try another at 1/1000 or higher. What do you see? I think you will find out SS is not the issue. Shoot these tests in RAW.