Understanding White Balance

jgs001

jgs001

Brian Cox
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I'm looking for some advice on how the camera deals with white balance when you're shooting with fill flash (I wasn't sure whether to put it here or in the lighting section)...

I was trying an experiment to see what would happen... I had the sunset behind my subject and using the popup flash compensated down a bit to fill in...

Now, the camera was in Auto white balance, it normally gets it right... but in this case seems to have lost the plot... the values reported in Aperture for as shot don't appear to be either as flash or for the conditions behind... I shoot in raw so changing the white balance to what I want is easy, but I would like to understand what you should be setting the white balance to in this sort of condition...

There are lots of things wrong with the shot, but as I said this was an experiment in fill flash and I didn't intend for them to see the light of day (as it were ;))

White Balance as shot (I was expecting this to come out as flash)
IMG_5858-Version2.jpg


White Balance set to cloudy in aperture as I wanted the warmth of the cloudy sunset light to show through.
IMG_5858.jpg
 
Well, you have two different coloured light sources in the scene, which will cause confusion for the auto WB.

The Flash, which will be balanced to somewhere around 5500–6000 K

The Sun, which at sunset, which is may be about 3000-4000 K

The flower in the foreground is obviously going to pick up more of the flash than the background and be significantly cooler than the rest of the scene as a result.

If you were to put a warming (yellow/orange) gel on the flash to bring it closer into line with the ambient light then you would get more consistent colour across the whole image.

That said, by setting the WB to cloudy, you've warmed up the flower and warmed up again an already relatively warm background, which actually works reasonably well. Custom WB in the camera could have achieved the same.

Just goes to show that sometimes WB is a creative decision as much as a technical one.

edit: http://www.cambridgeincolour.com/tutorials/white-balance.htm
 
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Musicman said:
Just goes to show that sometimes WB is a creative decision as much as a technical one.
Click to expand...

good point

Its a discussion I have with my assistants at just about every wedding. Do you shoot to get the colours 'correct' or do you shoot to get them how they look in the particular situation?

I generally shoot in RAW anyway so can make the decision in PS but it is generally down to what looks 'best' not necessarily what looks 'correct'

I'd suggest you just pick whatever you prefer
 
Thanks guys...

Thanks for the link Rob, that's explained something that always puzzled me, why it is that the camera doesn't default to flash when using attached flash... AWB guesses based on what you're photographing.
 
AFAIK the AWB always goes for the flash WB when you fire a flash... At least on Nikons.

Be a bit pointless using the flash otherwise?

In some cases you have to make two exposures (best done in PP, not at the time) with the WB for the flashed element and the WB for the background, then blend em.

Nothing worse than a normal looking person with a red or blue background, best way to scream 'this photo is an amateur snapshot!' sometimes.
 
When shooting sunset you need to set it to daylight, Remember film? it was daylight balanced when you took your holiday snaps.
WB in cameras will try and turn white to white so if you have a red sunset the white paper will look ... yes red so the camera will adjust to make it white IE taking out all the red in the light.
So s flash with a sunset put it on to flash will keep the red in the sky..
Remember when you put in your own wb at a deg Kelvin what is happen is it will compensate for this colour and push it the other end but adding the opposite colour to balance it to white.
Hope you can follow what I am saying..
 
using flash can either be the strobe only light source
or fill
or somewhere between
i use fill a lot and dont really notice a difference in the non fill shot except there is fill...hmm that sounds irish
my camera has wb setting for flash and i think photo-flood light
either the camera auto sets to flash when the flash is on
or just takes the shot on auto wb..which is my regular setting
in any event the colours seem to be natural to me without any recourse to adjusting wb settings for discrete lighting

a tree with low level flash and auto wb taken in late afternoon sun..as shot resized and sharpening mask



Uploaded with ImageShack.us
 
Lunaticsamurai said:
The biggest problem with using a flash in the day-light is the unsightly and un-natural looking shadows you get. I would have not used the flash or diffused it slightly.
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damn right...you have to get it just right and use as a 10% or so fill only..that shot above is out of hand...and the shadows prove it..
 
Lunaticsamurai said:
The biggest problem with using a flash in the day-light is the unsightly and un-natural looking shadows you get. I would have not used the flash or diffused it slightly.
Click to expand...

I don't really see much of a problem in using flash when done correctly. I can understand the problems of harsh shadows but sometimes its better to have smoother shadows when using hispeed sync flash than dealing with noise in an image.

Following image taken with flash at hispeed sync, shadows obvious in the face but I can definitely live with it.

But obviously opinions differ and each one has their own preferences.

4849672303_2ac6057d0e.jpg
 
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When you're on auto white balance, the camera defaults to flash white balance whenever the flash is switched on and ready to fire.
 
Thanks Richard, that's what I was expecting to see, but the colours seemed to be a little off with flash, it's not the first time it's happened, and I can't find anything in the settings that might have altered the basic white balance settings. I have done custom WB a few times and that's worked fine.

Thanks for the thoughts on the merits and use of flash, but that's not the concern here. I could have gone for a single off camera flash somewhere else, diffused and bounced, but I wanted to keep it simple, for a little fill light test, without having to faff about with manually setting the power output on the flash (my cheap triggers don't provide ttl I believe). Whilst the on board flash is not the ideal tool being too close to the axis of the lens etc, it's very convenient as it's always on the camera, and means I don't have to cart an armful of kit with me.
 
jgs001 said:
Thanks Richard, that's what I was expecting to see, but the colours seemed to be a little off with flash.
Click to expand...

i took some tripod shots of a group in artificial lighting

with auto wb and no flash...1/4 sec exp...the tones were quite acceptable

with flash on the results were warmer and needed some balancing in pp

using auto in photoshop the result was similar to the non flash shot
 
Thanks for the information Geoffrey, seems like the same sort of thing.
 
loplyg said:
AFAIK the AWB always goes for the flash WB when you fire a flash... At least on Nikons.
Click to expand...

And if you're using an SB-900 on the hotshoe with the supplied "smart gels", as Joe McNally calls them, to correct for shooting under other lighting conditions, it'll automatically shift into incandescent or whatever you've got in the gel holder.
 
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