Help me understand how shutter speed affects colour so much!

[Ett]

First off, this is my first post on the forum after I got my first SLR

Anyway guys, here's the deal:

I've been playing around with some photos and I'm trying to understand something about the colour in my photos. Here are two photos that I just took. The lighting conditions were exactly the same, and the camera settings didn't change (f/1.8, 50mm, ISO 200), except the first photo was taken at 1/350, and the second at 1/250:

First one: 1/350:





Second one: 1/250:





Now, I can understand why the first one is a little darker, but why on earth does it look so much more red? The white balance was set to fluorescent (my lighting was a fluorescent light), so the WB didn't chance at all, only the shutter speed.

Any help would be appreciated

Thanks!

[zona5101]

the light changed.... flourecent blubs have cycles where the color is different in different parts of the cycle.

[candleman]

Bruce got it..

To keep a constant WB under flourecent you need a slow shuterspeed so that it takes in the whole cycle of colour.
I think electrical supply in NZ is 50Hz, so in theory it should be anything slower then 1/50th should give a full colour cycle. Your country may be different. but generally speaking... the slower the better.

[jml79]

Originally Posted by zona5101

the light changed.... flourecent blubs have cycles where the color is different in different parts of the cycle.

+1. Gotta love flourecent lights. The cycle speed is almost always 60hz so if you use a shutter of 1/60 you will catch one full cycle and always have an even colour. Slower multiples also work so 1/30 and 1/15 will give even results. Anything else could cause a colour shift.

[Ett]

Ha! What a simple solution. So in theory, I could have gotten that red effect on the 1/250 photo as well, I was just lucky not to?

Now tell me, if I slowed the shutter down to 1/60, the photo would be over exposed at f/1.8. How would I compensate for that? Would I have to be sure to take the photo in RAW and adjust the lighting after? Or is it just not possible to take a photo at f/1.8 in those lighting conditions?

Man, what a simple solution. Thanks guys, I appreciate it!

[jml79]

1/60, f2.8 and ISO 100 should do it. 1/60 is about 2 stops slower than 1/250 so you need to compensate both the ISO and Aperture unless your camera allows an ISO of 50. Or shoot in Raw and just re-balance the colour in PP.

[kirbinster]

Not that you are asking about this, but it looks like you have dirt on your sensor in the upper right of both pictures.

[Ett]

Originally Posted by kirbinster

Not that you are asking about this, but it looks like you have dirt on your sensor in the upper right of both pictures.

Nope, that's actually a spot on the while surface at the back :P

[corvus2606]

easiest solution to increase shutter time while leaving everything else the same is a ND filter, I have one that cuts the light by a stop, makes outdoor long exposures much easier.