Can't take a pic from a cyan led beam. Help please

[Energie]

I've tried to take a pic from a cyan Lux 1 beam.
The led has a strong color between green an blue.
On the camera monitor and in the pics it looks like
a very pale green/blue. nearly white.
Other colors are ok (red, green, blue).
I've tried several settings of white balance.
Anybody a suggestion?


from left: white, green, red, cyan

 

[WadeF]

Do you want it to appear blue? If so setting the camera's WB to daylight should give you close to the actual color of the LED. Also make sure you're not over exposing the shot. Even black can be made to look white if it's over exposed enough.

 

[DonShock]

I just tried doing some beamshots on a Royal Blue LuxV and had the same problem with the brightness washing out all the color. I was finally able to get the beam shape and color fairly close by dropping the exposure down a couple stops. But then the problem was that the spill beam came out totally black. I finally settled for 3 seperate pics: one to show the proper quality of the spill, a scond to show the center spot profile with a little white tinge in the brighter areas and a third to show the proper color only. All were done by changing the exposure only.

 

[cratz2]

The only color I've had serious issues capturing is the 190 lumen Red/Orange which in my beam shots, makes it appear as though the center is actually orange with a red spillbeam which isn't the case.

But I've photographed three cyans, several blues and royal blue and at least color-wise, they seem accurate. I wonder how much of the issue might be because of your monitor adjustments. I don't do anything special with the camera, other than the fact that I use manual settings for beamshots. I think the

Here are a few beamshots or beam profiles of some colored LEDs:

These are both cyan Lux IIIs, but different bins:

T3JG Green Lux III:

Royal Blue Lux III:

An old school Lux I Cyan:

The red/orange Lux III. I've seen a couple shots with color issues similar to this one. Obviously in real life, the color tint is consistant across the beam but in digital photographs, it seems to consistantly shift the color in the hotspot and the corona around the hotspot. I have to assume it is because of how the camera picks up relative brightness.

 

[LightScene]

I've tried to take a pic from a cyan Lux 1 beam.
The led has a strong color between green an blue.
On the camera monitor and in the pics it looks like
a very pale green/blue. nearly white.
Other colors are ok (red, green, blue).
I've tried several settings of white balance.
Anybody a suggestion?


from left: white, green, red, cyan

The cyan, red and green look correct to me, but the white is way off. I have the same problem with red - the hot spot appears yellow.

I had a 5 watt cyan and I got good results by putting the flashlight on a white surface.

 

[2xTrinity]

The cyan, red and green look correct to me, but the white is way off. I have the same problem with red - the hot spot appears yellow.

I had a 5 watt cyan and I got good results by putting the flashlight on a white surface.

The reason for the center appearing yellow is that the camera is overexposed. I've looked at a Luxeon Red/Orange LED through a diffraction grating, and there is a significant amount of yellow and even a tiny amount of green output in the beam. However, this is undetectable to the eye since the amounts are so small compared to the red. In the case of taking a picture though with a camera, the red portion gets overexposed, so doesn't show the center as being any brighter than the spill, however, the green sensor picks up slightly more yellow/green light in the center, and since yellow/green is far from overexposed, renders the image as yellow in the center.

 

[Energie]

Thanks all for your advices.
Great pics, craz2.
Today I have tried several cameras, different white balance, shutter speed, aperture and so on. No success with this (...) cyan emitter.

The pic below (emitter and part of the reflector) was taken at 1/2500 - 8 (80 ASA) and shows the real color.
Any brighter pic changes the colour to white.
BTW, I got this emitter from Photonfanatic and he said, its very special.

 

[gandbag]

I use some software to help correct some of the problems with digital camera exposures. You can get a free version of photomatix from photomatix.com that lets you combine 2 or more differently exposed versions of the same photo into a higher bit-depth image that is exposure corrected. Check out this image (WARNING: non flashlight related!) http://flickr.com/photos/rhizopogon/499818221/

Very often, this helps the colors a great deal, however, i'm have no idea if the problem you are having is an exposure issue, or a wavelength dependent sensor issue, or something else.

I have had a lot of problems with the results of photos of purple birds and flowers with my digital cameras. I tend to think this is "end of wavelength sensitivity distortion" of the camera sensor, but have no proof. Perhaps a RGB color sensor can't accurately reproduce purple or cyan?

 

[fire-stick]

Cyan (along with purple) is a VERY SLIM section of the color spectrum. If the white balance is off in the SLIGHTEST way the cyan color will be lost and will look more like blue or green.

 

[bombelman]

What you could do, do a manual white-balance on a white wall with the white led.
(Don't overexpose). Then try again. White should be white.
Depending on the brightness of your Cyan led, it should appear as much Cyan
in the photo, as it does in real life...

Cheers !