Old 01-20-2011, 11:57 AM #1
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Question Please help with DSLR camera color rendition

I have a Canon T2i (EOS 550D) and the beam shots of my 445nm look very violet. Does anyone know how to adjust the color rendition to more accurately reflect what the eye sees? Is that white balance or some other setting? This is my first digital SLR and the number of settings and flexibility is staggering. Any help would be greatly appreciated.


See what I mean? This is a 1W 445nm Aurora C6. The deck handrail is white vinyl. The outer edges of the beam near the aperture faintly show the color I see.


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Old 01-20-2011, 12:04 PM #2
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Default Re: Please help with DSLR camera color rendition

You can adjust your white balance, but I don't know in which menu to find it on an EOS. That's a nice camera btw.
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Old 01-20-2011, 03:40 PM #3
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Default Re: Please help with DSLR camera color rendition

The 550D can take raw pictures, so why not use that? Just save them as raw files on the card, and then work on the color balance etcetera in lightroom or something similar.

You might want to under-expose your photos a bit too - the very monochromatic light from lasers can easily saturate one channel (blue in this example), and the local over-exposure will then still add to the other channels.

I suppose that is what happened in the picture above: The part where the beam is brightest seems magenta (blue saturated with red bleeding in), while color rendition at the dimmer far away part of the beam is fairly accurate.

Under exposing it one stop will only give you 1 bit of additional noise - probably not a problem on a camera like that!
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Old 01-20-2011, 10:07 PM #4
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Default Re: Please help with DSLR camera color rendition

Quote:
Originally Posted by elite ares View Post
I have a Canon T2i (EOS 550D) and the beam shots of my 445nm look very violet. Does anyone know how to adjust the color rendition to more accurately reflect what the eye sees? Is that white balance or some other setting? This is my first digital SLR and the number of settings and flexibility is staggering. Any help would be greatly appreciated.
I'm guessing that you have your camera set to auto white balance and it's giving a balance by measuring the predominant ambient light (which is mostly the artificial lights) in the scene. Those lights look like they're tungsten, but they may be mercury vapor, which can really mess with a camera's white balance. Try setting the WB manually. and make some test shots using the tungsten setting for one and daylight or strobe for another.

If the tungsten setting looks closer to correct, then, if the Canon offers a Kelvin scale, play with settings in the 2,000 to 4,000 range. If the daylight setting looks closer, play with settings in the 5,000 to 7,000 range. That's the beauty of digital. You can get instant results from your testing. And, as Benm said, the beam is overexposed and saturating some of the channels.

Sorry, I don't know the Canon menu system. I shoot Nikons myself. That's a nice shot. Good luck getting it closer to what you want.

Ed

Last edited by CoherentRays; 01-20-2011 at 10:12 PM.
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Old 01-20-2011, 11:13 PM #5
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Default Re: Please help with DSLR camera color rendition

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Originally Posted by CoherentRays View Post
I'm guessing that you have your camera set to auto white balance and it's giving a balance by measuring the predominant ambient light (which is mostly the artificial lights) in the scene. Those lights look like they're tungsten, but they may be mercury vapor, which can really mess with a camera's white balance. Try setting the WB manually. and make some test shots using the tungsten setting for one and daylight or strobe for another.

If the tungsten setting looks closer to correct, then, if the Canon offers a Kelvin scale, play with settings in the 2,000 to 4,000 range. If the daylight setting looks closer, play with settings in the 5,000 to 7,000 range. That's the beauty of digital. You can get instant results from your testing. And, as Benm said, the beam is overexposed and saturating some of the channels.

Sorry, I don't know the Canon menu system. I shoot Nikons myself. That's a nice shot. Good luck getting it closer to what you want.

Ed
Actually, the street lights are sodium vapor. The camera is new and I have not changed the default settings. I was hoping I was on the right track since it is set for auto white balance. I'll play with the settings to see what works.

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Old 01-21-2011, 03:25 AM #6
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Default Re: Please help with DSLR camera color rendition

Try stopping down the ISO. Try to keep it as low as possible. This will also help to reduce noise. Under exposing the beam will keep the colors "truer."
This particular scene has a lot of mixed lighting so I would suggest you play with the WB settings manually.

You can always edit the color balance of the raw images if you have software that allows it.
I've been experimenting with HDR post processing for beam shots and it does create an interesting effect. Check here: http://laserpointerforums.com/f48/aw...ded-58916.html
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Old 01-22-2011, 04:28 PM #7
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Default Re: Please help with DSLR camera color rendition

I think it will just take experimenting to get the best result, with help from whats been discussed so far. Since its your first DSLR, i reckon you will have to spend time going through all its possibilities, and this one sure has a lot of them

Taking beamshots pretty much requires manual settings, the automatic mode of a camera is not designed to handle such odd scenes at all.
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Old 01-22-2011, 11:04 PM #8
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Default Re: Please help with DSLR camera color rendition

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Originally Posted by Benm View Post
I think it will just take experimenting to get the best result, with help from whats been discussed so far. Since its your first DSLR, i reckon you will have to spend time going through all its possibilities, and this one sure has a lot of them

Taking beamshots pretty much requires manual settings, the automatic mode of a camera is not designed to handle such odd scenes at all.
I've been doing a lot of experimenting with ambient lighting temperature settings so far to no avail. Shorter exposures tend to lessen the violet effect but they still persist. Next I'm going to try custom white balance settings. At least I don't have to wait for printing them all to see how they came out. My wife's Nikon pocket camera seems to render the colors better but doesn't have the flexability I want. The learning curve is much steeper for this DSLR than it was for my old Minolta film camera.
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