New Orthoplan Flash Setup (and a problem)

[Mike]

Hello all!

I finally have a flash system that seems to work very well and maintains Kohler illumination.

The flash goes into an extra lamphouse 100 with the socket removed. There is a condenser to focus the light as well as filter holders in the front for any adjustments. This Lamphouse, as well as another with a 100W halogen, are mounted to a Mirror house 250D. There is a beam splitter in the mirror house so both the halogen and flash are directed to the imaging light path.

I use a a foot switch to shut off the halogen and then trip the flash with a remote.

The problem - all the photos have a green cast (again!) and I can't adjust it out with filters. Any ideas?

All the best,

Mike

[Kenv]

Hi Mike, the easiest way to fix the green cast would be to do a custom white balance with your camera - I am assuming that you have a digital camera. Just fire the flash and take a photograph of the light coming from the flash - no slide - and fix your custom white balance for that. That should fix it.
Kenv

[Charles Krebs]

Very nice looking set-up Mike! The green problem puzzles me. All I can think of is that perhaps there is some thick heat absorbing glass or optical element in the illumination system. HAG can be quite green. But as Ken said, you should be able to do a custom white balance. Doesn't that work?

[Mike]

Hello Ken & Charlie,

First, thanks for your comments and suggestions.

I'm not sure how to do the custom white balance; the way the Nikon Coolpix works is to do a WB Preset, requiring the light to be on during the measurement. I'll try it by manually triggering the flash during the measurement and see what happens.

Re the HAG - certainly a possibility and I will check it out. The other thought you incited is perhaps the condenser in the Lamphouse is causing some problems.

Thanks for the ideas, as I have about run out of things to check and change.

All the best,

Mike

[twebster]

Hi ya' Mike

Two things come to mind. 1) The green may be coming from the beamsplitter you are using. If the beamsplitter is a prism it may be made from just "regular" glass which will impart a greenish cast. 2) Leave the tungsten illumination on but turned down low when you make the image. The reddishness of the tungsten lamp may record just enough to offset the greenish color you are getting. I leave my tungsten illumination on when I shoot images and I don't have a problem with color casts on film. It's worth a try.

Best regards as always,

[Mike]

Hello Tom,

I thought about the beam splitter adding color; in this case the spltter is a part-reflecting glass plate, reasonably thin, (perhaps 2mm or less) and appears to be without any color cast, i.e. clear.

The idea of adding a little red with the halogen sounds like a good one, and I will give it a try.

Thanks for the input.

All the best,

Mike

[Charles Krebs]

Mike... just be careful when adding "tungsten". The whole idea of flash is to stop motion. If you keep the tungsten light too bright you can get a partial, slightly blurred "ghost image" added to the flash exposure. That said, you should certainly be able to keep the tungsten bright enough to see and focus easily without any effect on the flash image. You could probably, as Tom suggested, get enough "red" from the tungsten to offset a bit of the green...but to really correct green you need a magenta filter. If the green is coming from the glass in the optical "train" (as I think is likely the case) then you could probably take care of it with a 10 to 15cc magenta filter taped to the front of the flash. What filters have you tried? It would be ideal if you could do a custom white balance, but I don't know if that is possible with the CP 990 and flash. But with film, I have often used magenta filters over the flash when shooting through thick glass with a heavy green tint (very large aquarium tanks).

[Mike]

Hi Charlie,

Thanks for the suggestion. I agree the color cast must be coming from something in the optical train; I've eliminated about every other possibility.

Currently I am using a custom Magenta/Violet at about 25% density (printed out of Photoshop on an HP photo printer.) It does attenuate the color cast to some degree, but I think (illusion of perception?) it is skewing the reds too far and overstating them. I'll pick up some of the CCM filters to try, as they will undoubtedly provide a purer color correction.

I've made a few shots on Saturday and the combination (filter and halogen modeling light) seems to be working reasonably well. It will need to be tuned but at least it's heading in the right direction. I would prefer to not have the halogen on during exposure (I have it connected through a foot switch, so it's easy to turn on/off.

As far as I know there is no way to do a custom white balance with the flash on Coolpix cameras - I tried by doing a manual flash but No Joy! If someone out there knows how to do it, I would love to hear.

All the best,

Mike

[Mike]

To all who offered advice and help:

I finally was able to eliminate the color cast (btw - it turned out to be 'cyan' not blue) by going back to the Speedlight setting for White Balance, and 'fine tuning' it -3 (warmer/red) as well as putting a magenta color correcting filter (CCM .10) in front of the flash. (Thanks Charlie!)

This all occured in the last week after months of fighting with it. Now the Coolpix 995 gives nice neutral background and shots.

Immediately after finding the solution to the cast problem, I bought a new Coolpix 4500, receiving it on Tuesday. The 4500 obviously has a better White balance than the 995, and I am now able to pull the CCM .10 filter and use only slightly warm (-2) adjustment on the Speedlight white balance to get great shots.

It's been very trying fighting the color cast, but I think I learned a lot in working towards a solution. I hope to be posting some shots in the near future.

All the best,

Mike