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09-12-2018, 05:26 AM   #1
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K1 II Red color cast in flash photos

Switched to using flash for headshots and am finding that with AWB setting on camera there is a red color cast that makes development difficult and time-consuming to correct.
I used Pentax 50mm FA 1.4 lens lit with a 40" octabox loaded with 2 Cactus flash units. I didn't notice the issue when using fluorescent or LED light sources. Red/Purple cast can be lessened in post but even with Lightroom 6 color control, it is difficult to maintain true to life accuracy of skin tones.

The other issue is it is not a consistent result. Withing one session a few shots require little if any color adjustment.

I also use Portrait Pro software to finish the sessions but it only makes matters worse. I am open to any suggestions regarding getting superb quality headshots or portraits with my K1 II and flash light sources.

I have included a few shots as examples. Any instruction or assistance will be greatly appreciated.

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09-12-2018, 06:16 AM   #2
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I hope you're shooting in raw! In Lightroom just over the white balance adjustment sliders there's a profile selector that starts at "As Shot." There's a setting called "Flash" and also "Daylight" that might be good. Neither will probably be perfect since the light modifiers and the walls the light is bouncing off of may not be perfectly white. It might be a good place to start and you can tune it from there.

You can also go to one of the images that looks good and write down the temp and tint values, then paste those into the others. You can copy and paste those settings to all of the photos in a shoot to avoid having to do it by hand.

Another thing you can do is have the model hold up a grey card in the first shot. You can take a white balance reading with the eyedropper tool in Lightroom and paste that into the rest. If you don't have a grey card a piece of white paper should work, but sometimes they have a color cast to them. You may not like the finished look, but it can give you a neutral starting point.

You still might have to do some individual adjustments even after all of this, but hopefully you'll be at a better starting point. At work I use Einstein strobes and one of the selling points is shot to shot color consistency at any power level. The implication is that color temperature can change at different power levels with other flashes, but I haven't tested it. Just something to think about.

Hopefully this helps!

Mars
09-12-2018, 06:48 AM   #3
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QuoteOriginally posted by Mars V Quote
Another thing you can do is have the model hold up a grey card in the first shot. You can take a white balance reading with the eyedropper tool in Lightroom and paste that into the rest.
^^^ This. Or, in fact, take one shot of the grey card and set a custom white balance in-camera on that area.

As mentioned in the previous response, shoot raw to provide maximum latitude for white balance adjustment in post-processing. But if you set the custom white balance in-camera using a grey card reference, you should get accurate-looking shots in both JPEG and raw straight out of the camera...
09-12-2018, 07:04 AM   #4
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I may be wrong, but I always thought the grey card should be used for exposure and a white card used for WB...

09-12-2018, 07:23 AM - 1 Like   #5
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QuoteOriginally posted by CarlJF Quote
I may be wrong, but I always thought the grey card should be used for exposure and a white card used for WB...
Technically, the 18% grey card is for exposure adjustment - but it works just fine for white balance, and saves carrying two references.
09-12-2018, 07:33 AM   #6
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What other lights do you have in the room? What color are the walls on the right side of the room? The side of the face away from the octobox will be lit by those other lights or by flash reflected off the right-side walls.

The other possibility is that the color cast is coming from the translucence of the skin being lit from the side.

A white reflector at some distance on the right side might help provide some white light into those skin-lit shadows.
09-12-2018, 07:35 AM   #7
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Flash color might vary when used in very short sync- What version of firmware for your Cactus and camera are you running on? Check if those are up to date. I find mine cactus RF60X very stable and consistent in terms of color cast even with HSS and power sync(thing that I can't say about Fomei Panther that got "screaming pink" cast all over below 1/256s).

Last edited by Reed; 09-12-2018 at 08:10 AM.
09-12-2018, 07:49 AM   #8
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QuoteOriginally posted by Mars V Quote
I hope you're shooting in raw! In Lightroom just over the white balance adjustment sliders there's a profile selector that starts at "As Shot." There's a setting called "Flash" and also "Daylight" that might be good. Neither will probably be perfect since the light modifiers and the walls the light is bouncing off of may not be perfectly white. It might be a good place to start and you can tune it from there.

You can also go to one of the images that looks good and write down the temp and tint values, then paste those into the others. You can copy and paste those settings to all of the photos in a shoot to avoid having to do it by hand.

Another thing you can do is have the model hold up a grey card in the first shot. You can take a white balance reading with the eyedropper tool in Lightroom and paste that into the rest. If you don't have a grey card a piece of white paper should work, but sometimes they have a color cast to them. You may not like the finished look, but it can give you a neutral starting point.

You still might have to do some individual adjustments even after all of this, but hopefully you'll be at a better starting point. At work I use Einstein strobes and one of the selling points is shot to shot color consistency at any power level. The implication is that color temperature can change at different power levels with other flashes, but I haven't tested it. Just something to think about.

Hopefully this helps!

Mars
Thanks for your input. I always shoot DNG on manual, but on next outing will go back to LED's just to see if the Cactus flash units are the inconsistent light source causing the issue. Since the camera converts the white to grey a card for white balance is a good idea. When adjusting theatrical lighting we do something similar. So far I have found you can't remove the red cast. I have adjusted Hue, Saturation, and Vibrance and been unable to come close to the original. I use LR6, Elements and Portrait Pro for editing in any combination or alone. Becomes a bit frustrating. I believe setting the WB individually may be best avenue.

09-12-2018, 07:53 AM   #9
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QuoteOriginally posted by Reed Quote
Flash color color might vary when usend in very short sync- What version of firmware for your Cactus and camera are you running on? Check if those are up to date. I find mine cactus RF60X very stable and consistent in terms of color cast even with HSS and power sync(thing that I cant say about Fomei Panther that got "screaming pink" cast all over below 1/256s).
I used RF60's and find them to be solid performers, however not sure about firmware update.
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09-12-2018, 09:38 AM   #10
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Even if you set the white balance, be careful - the camera may think it is smarter than you are. You may need to some options(s) in the C menus (C3/15 seems to be the one for the K1 (same for the K1 II? don't have that manual)).

I had a somewhat similar problem with flash white balance a while ago: Wacky white balance with remote trigger studio flashes for K5 - PentaxForums.com
09-12-2018, 10:06 AM - 1 Like   #11
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QuoteOriginally posted by BigMackCam Quote
Technically, the 18% grey card is for exposure adjustment - but it works just fine for white balance, and saves carrying two references.
I have read claims going both directions regarding gray vs. white cards for white balance. It should be noted that, technically, a proper exposure of a white card may actually be clipped for one or more colors, making evaluation and adjustment difficult. That is one reason why the "eyedropper" control in Lightroom for white balance will fail with an error if a "too white" area is chosen. A properly printed gray card will reflect red, green, and blue equally.


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09-12-2018, 11:29 AM   #12
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Granted, my laptop monitor is not calibrated, but I don't see the red cast in the whites. Those appear quite proper. I would look to your lighting. You might also want to set white balance on the camera to match the color temperature of the flash (should be in the specs). AWB from the preflash may be leading the camera wrong.Edit: Obviously did turn on brain before typing...


Steve

Last edited by stevebrot; 09-12-2018 at 11:40 AM.
09-12-2018, 01:40 PM   #13
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QuoteOriginally posted by stevebrot Quote
Granted, my laptop monitor is not calibrated, but I don't see the red cast in the whites. Those appear quite proper. I would look to your lighting. You might also want to set white balance on the camera to match the color temperature of the flash (should be in the specs). AWB from the preflash may be leading the camera wrong.Edit: Obviously did turn on brain before typing...


Steve
These are best I could do to normalize using Elements, LR6, and Portrait Pro. Not up to par regarding vibrance of colors and contrast. If I had to review the shots I would reference them as overworked. I have a few days and will keep at it, however, I plan to do some number matching. The issue isn't consistent but happens enough to be a royal pain and renders my work substandard.

Thanks for the input.
09-12-2018, 01:45 PM   #14
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Some other examples... note the red blotches on the right side of his face. I will have to go in and surgically re-color that area.
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Last edited by MPDSr; 09-12-2018 at 01:49 PM. Reason: added examples
09-12-2018, 02:16 PM - 1 Like   #15
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QuoteOriginally posted by MPDSr Quote
Some other examples... note the red blotches on the right side of his face. I will have to go in and surgically re-color that area.
Just out of interest, have you tried a different raw development tool? The K-1II is still relatively new, so it's not outside the realms of possibility that the camera profile for your software is causing this issue.

I'm running Darktable under linux. If you like, I'd be happy to take a look at one of your affected RAW files to see if I get the same problem. Just a thought...
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