BW - color conversions

A while back there was a post about using channel mixer to take a color shot down to B/W. There were some starting settings for the RGB to get in the ballpark. Does anyone remember what they were.

Michael,

This is really more of an imaging question. If you'd like I can move it there, or you can simply repost...

BTW, if you do a quick look-see through the DI Forum, you're almost sure to find this issue in several archived threads.

To give you a quick answer, normally you want the three channels of the color mixer to add up to 100%. Your starting settings will depend on your original color image, so a rule of thumb would be to subtract from one when you add another.

Still, I find just looking at the image as I work is enough for me to decide what adjustments to make...

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Originally Posted by MJS

A while back there was a post about using channel mixer to take a color shot down to B/W. There were some starting settings for the RGB to get in the ballpark. Does anyone remember what they were.

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Thanks Steve. I've got a re-shoot for some friends on a portrait for their wedding invitations. I had one other question while your there. I just got a pair of the Alien Bee 1600's for main strobes with silver/white umbrellas and might add a second pair of less powerful unitsfor back ground/hair lights. Do you think that the 400's would be enough for that purpose?

Thanks again as always,
Michael

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Originally Posted by MJS

Do you think that the 400's would be enough for that purpose?

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...I'm probably not the best one to ask about this. One, because I've never used ABs (although I'm sure the 400 have enough power for what you mentioned), but mainly because I'm not big on using a lot of lights, period.

I like asymmetrical and indirect lighting, and generally use one key with a reflector fill. Sometimes I use the spill from the key as a partial bg light, too, but if not never use more than one seperate bg light.

So, I guess what I'm saying is that many times I use only one light, occasionally two, never more than three. To me, four units is overkill... :D

I guess that's the problem with new toys, I always seem to want more. I'll give the less is best approach a try.

I was just thinking about mixing 1600s with 400s. If you want to use the proportional modeling light feature, and you want it to be consistent through all the lights, wouldn't you have to put 150 W bulbs in the 1600s and 40 W bulbs in the 400s? 40 W seems awfully weak for modeling light especially when you consider that 40 W would only be used when the 400s are set to maximum output.

Maybe you don't use the proportional feature. I don't. But I only have one light. :)

I wouldn't worry a whole lot about modeling lights wattage, especially with a digital camera...

I think folks that don't have much experience with electronic studio flash put much too great an emphasis on modeling lights. Really, the only thing I use them for is so I can see what I'm doing as I work and then so I can focus on my subject while I'm shooting.

The main adjustments to my lighting are always done by evaluating meter readings, then the photo itself, whether with a polaroid (back in the OLE days), or by viewing a digital image and its corresponding histogram.

I would never trust modeling lights to be a truely accurate representation of what the image will look like when lit with the flashes. Just a real general guideline.

I agree. I just use the modeling lights to focus with. I keep them jacked up to full power so my tired old eyes can see my subject.

Well, that's good to know. Who knew I was actually doing it right? I only have one "real" light but I use a Nikon SB-30 to throw some light on my background. The SB-30 of course has no modeling light. I have a Sekonic flash meter that I sometimes use to try to put some numbers on my contrast ratios, but I honestly usually just wing it. Instant feedback has to be the best part of digital photography.