magenta brown tint on coollights cdm150

J Davis

J Davis

Veteran
I'm seeing a magenta or brown cast on scenes lit with the coollights cdm150. Anyone else get this?
 
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Which globes are you using, the 3200 or daylight? The daylights have a bit of a green spike.

I generally set a "auto" white balance when using the CDM 150w which cancels out the color shift. I love my 150w, I've had them for years and just returned from a multi-country shoot in Asia. The universal ballasts are great, no issues striking on the various mains power standards.
 
I've got two daylight CDM150's.

I see green of their flos and LED's which I correct with 1/4 magenta or 1/2 magenta. But both my CDM's don't seem to have a green spike, if anything its the opposite (magenta spike). The above linked videos had white balance at daylight preset.
 
J Davis said:
But both my CDM's don't seem to have a green spike, if anything its the opposite (magenta spike). The above linked videos had white balance at daylight preset.
Click to expand...

Interesting. I have two, they are about 3-4 years old, first gen, I've replaced the globes a few times. Always a green spike, slightly more than the typical 1200w SE HMI, yet less green vs the Cool Lights LED600. Generally if I WB to the 150w, the other daylight lamps go slightly magenta, but it's never been an issue. I would estimate between 1/8 and 1/4 minus green correction.

NYC - Any referrals for a good set PA in Manhattan? I have a small shoot in town, 2 days in Jan. PM me if it's not too much trouble.

Cheers.
 
The current generation of bulbs have no green spike and its been corrected in the bulb. I don't see the issues you are talking about in your videos.
 
I see a magenta cast on the posted videos. Which camera, & Scene File, was it captured on? Was the light modified?

My six month old CDM150's burned roughly 50 hours, & the color meter shows it running 4900*/+1 Magenta.
 
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Its canon DSLR with daylight balance preset.
Both my CDM150's have had minimal use, just the two videos linked above and this one which also has a magenta/brown cast http://vimeo.com/31754082
CDM150's were the only lights used in all 3 videos. I would say that they have had 3-4 hrs use with me being generous with my estimate
 
1). Color meters don't work reliably with discontinuous (non full spectrum) sources like CDM, Fluorescent or LED.

2). In addition you shouldn't be mixing a lot of sources of various color temperatures or types especially is some or all of them are discontinuous.

3). Even slight differences in color temperature if multiple sources are involved will make custom white balance difficult and won't be able to do its job in removing whatever cast your camera might be seeing.

4). Don't use daylight or tungsten presets, custom white balance is what it takes to correct green/magenta bias.

5). Different cameras / sensors have different reactions to various kinds of lighting. There is no hard and fast rule, you have to find out what works best for your camera by testing and seeing what you can get away with and how to best use each kind of light--taking into account whatever limitations they have.
 
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Hi Richard, while you were posting I was taking a shot so that you could see. Borrowed my kids lego as I don't have a color chart to hand.

Here are some temporary links for a RAW file to download, you might have to right click (or control click on a mac)
and select save file

raw file
http://dl.dropbox.com/u/23768853/_MG_5132.CR2.zip

jpeg
http://dl.dropbox.com/u/23768853/_MG_5132.JPG.zip

6541947475_24cb2a0edb_b.jpg
6541947261_1f0efbcabb_b.jpg


6541948739_6fa8756d95_b.jpg
 
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#4 above in my post. Never use daylight presets unless your out in real daylight. Always custom white balance for simulated daylight like flos, LEDs and CDM/HMI.
 
TEST the hell put of your lights. Try to get a photographic gray card. Test each light. Eyedropper the footage in AE and look at the RGB levels.

Actually, I find CMYK a way more useful numerical system to visualize how your lights differ. Drop screen grabs into photoshop and check the readouts. If a gray has higher values in Y and C, you need some magenta (minus green) to sort it out - and so on. But you can just layer up gray shots in AE (with a good monitor) and see which lights have a cast. Basically, you want RGB numbers to be fairly close, within 10 digits or so, for a neutral gray.
 
Cool Lights said:
Never use daylight presets unless your out in real daylight. Always custom white balance for simulated daylight like flos, LEDs and CDM/HMI.
Click to expand...

Thats why I provided a link to the raw file, when I custom white balance or color correct the video I get the brown cast
 
Actually when I bring in the RAW to photoshop and go to 5450 kelvin and -18 toward green tint then it looks natural.
Could that rather large need for green mean that I have old bulbs?
Or is the correction for the green spike that you introduced to the bulbs a while ago, be over compensating?


edit:
thanks for the advice michael carter

2nd edit:
It's almost 2am here I better get some sleep before work 2morra
 
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A thought I just had made me get out of bed to post here.

The crux is that often I want to use the CDM's in conjunction with other lights like the coollights LED's and the coollights flo's.
EXAMPLE a cdm150 with 1/4 diffusion so I get a great shadow off the actress. Then a dimable flo for fill and led on a boom for hairlight.

If I set my white balance and in camera tint correction to add extra green for CDM's ... then how can I bring in flo's and led's when they are already green heavy?
 
I generally wouldn't make a key and fill two different kinds of instruments like a flo and an LED, as I said in #2 above, many discontinuous sources don't mix well. I would more use a flo as key and a smaller flo as fill then LEDs for accent. Or LEDs as key and fill and a fresnel projecting a pattern on the wall behind and another fresnel for accent lighting. If you do mix, you have to pay attention to small differences in them and equalize those differences as much as possible using things like minus or plus green. That's more trouble so you may want to keep the key and fill the same type light in most cases.
 
J Davis said:
Actually when I bring in the RAW to photoshop and go to 5450 kelvin and -18 toward green tint then it looks natural.
Could that rather large need for green mean that I have old bulbs?
Or is the correction for the green spike that you introduced to the bulbs a while ago, be over compensating?
Click to expand...

Any compensation for green in discontinuous lighting may look like over correction. If you have to go one way or another I would prefer to err towards the magenta side as it looks good with skin tones--certainly more so than green does.

Since color meters aren't reliable with discontinuous lighting you can't rely on what a camera records as color temperature and passes in RAW. Thus you may have to tweak the color temperature and tint settings manually. The bulb is 5400K so that's why it seems more natural to set it at 5400K then manually set the tint.
 
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