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DPChallenge Forums >> Hardware and Software >> Mixing light types??
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 07/28/2005 11:34:35 AM · #1
Out of curiousity, if you used something like a grey card to set your white balance, how would modern digitals go working with two different types of light source eg. halogen and a tungsten? Has anyone ever had any success trying this? For instance, if you used a tungsten spotlight on a subject and a halogen light on a background or for highlighting or vice versa!

07/28/2005 11:45:22 AM · #2
In this case shooting RAW is probably the answer since both lighting sources are not falling on the subject. WB for one would probably throw it off for the other.
 07/28/2005 11:46:19 AM · #3
Yes, that's what I was thinking, with no happy medium between the two colour temps!

07/28/2005 11:51:31 AM · #4
I use a calibration target from photovision and it works great - I can set a perfect WB in any light situation.

M
 07/28/2005 11:54:03 AM · #5
Originally posted by mavrik:
I use a calibration target from photovision and it works great - I can set a perfect WB in any light situation.

M


Does that work for the situation described by Makka? Do you take several readings? Does it average the WB values?
 07/28/2005 11:57:58 AM · #6
It won't.

A good example is when mixing flash and ambient lighting as is pretty typical when shooting indoor events like wedding receptions in a hall. If you drag the shutter enough that the ambient light (usually tungsten ~3400K) illuminates the background and use flash (~5200K) to light the subject and freeze their motion, you can't just set the WB to something in the middle and get good results. You will have a blue cast on the areas illuminated by the flash and an amber cast over the rest of the scene.

You can adjust WB to correct correct either one, but it will only make the other worse.

The solution is to color balance the light sources. The easiest way is to place an amber gel over the flash and use a tungsten WB. You can also put blue gels on all the tungsten lights, but that is a lot more work.

I use the Rosco Sun gels, they are cheap and come in full, 1/2 and 1/4 strength. This means if you want some warmth to the ambient illuminated areas, you can correct the flash only partially. If you then set a custom WB using the flash, the flash illuminated areas will be correct WB and the ambient illuminated areas will have some degree of amber to them.

Where it gets tricky is if you have more than two sources, say strobes, flourescents and tungsten lights. Or if you have lights that only emit light on a narrow band of the spectrum like sodium vapor lamps.



Message edited by author 2005-07-28 12:13:24.
 07/28/2005 12:01:32 PM · #7
Ahhh I see what he is saying - no, you are going to get a funky colored bg no matter what you do in that situation. I can't imagine there's much way to fix that.
 07/28/2005 12:05:47 PM · #8

hehehe....you got me all excited there for a minute mavrik! :)

07/28/2005 12:18:24 PM · #9
Perhaps tedious, but might work (I've never tried it) if you're in a crunch is to process the RAW twice - once at the WB appropriate for the illuminated subjects and once with the WB appropriate for the background... then combine the good parts of both images.
 07/28/2005 12:21:42 PM · #10

Thanks for your help there guys! Sounds like something to experiment with!

07/28/2005 12:30:11 PM · #11
Originally posted by brianlh:
Perhaps tedious, but might work (I've never tried it) if you're in a crunch is to process the RAW twice - once at the WB appropriate for the illuminated subjects and once with the WB appropriate for the background... then combine the good parts of both images.


That would be very tedious, especially if you have to process a lot of shots.

Putting a color correction gel on the flash is much much easier.
 07/28/2005 12:43:21 PM · #12
Mixing light is a very common thing in the industry I am involved in.

HMI and other daylight sources, Zenon, tungsten, quartz, pure sunlight, mercury, sodium, blah, blah.

The effect is depending on your WB, what look your after, and what Kelvin you want to make as your base.

Correction jells are available to make say a tungsten look daylight, or visa versa.
 07/28/2005 12:47:23 PM · #13
Originally posted by Spazmo99:
Originally posted by brianlh:
Perhaps tedious, but might work (I've never tried it) if you're in a crunch is to process the RAW twice - once at the WB appropriate for the illuminated subjects and once with the WB appropriate for the background... then combine the good parts of both images.


That would be very tedious, especially if you have to process a lot of shots.

Putting a color correction gel on the flash is much much easier.


I figured, but that's what I meant by 'in a crunch' (although I guess by re-reading the original post, there's no reason to assume that the pictures have already been taken).
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