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p.1 #4 · p.1 #4 · Is it normal for color to change on strobes in lower power? | |
Yes, it is normal to see a little color shift with flash power level. Most monolight studio lights get slower and more red at low power (a small few work more like speedlights). Speedlights are the opposite, they get faster and more blue at low level. Not extreme, some ignore it, either don't know or don't care, and there are other factors affecting color too, but it's easy to fix white balance.
It's just the way the flash works. A flash is a very rapid and strong pulse of power, which then slowly (2 or 3 milliseconds) trails off to nothing. A speedlight implements lower power by suddenly chopping off the light output, which truncates its trailing tail. So Full power is reddish (includes cooler tail), but chopping off the trailing cooler tail (red is cool) leaves it more blue. We might as well plan on it, because that's the way it works.
We can use a white balance card ($5 Porta Brace white balance card at B&H is a good one). Even something intended to look neutral white (like an envelope or T-shirt or church steeple) can be used, not always perfect, but often pretty good, and normally better than nothing (if we pick something actually white). We can include this card in the scene (in the same light), maybe at the edge of the frame where we can crop it off. Or more commonly, just in the first "test" picture in the situation. Then better photo software has a White Balance Tool where we just click the (neutral) card in the picture, and presto, perfect color, no color cast.
For one example, see http://www.scantips.com/lights/whitebalance.html and specifically, nearly 2/3 down the page, to the several pictures of the yellow cup, where it says "Flash color temperature varies with flash power level". The second column shows Full and 1/64 power at standard Flash WB, and one is pink and one is blue. The whole page is about correcting it.
If you have a few minutes, a more detailed view is the video on the page http://www.scantips.com/lights/shootraw.html
That is about Raw, but the WB idea is the same (raw editors process JPG too, and have real good tools).
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