Background Color is Off

[Christine Lee Smith]

Hello, so while I'm old to analog photography, I'm still growing in my digital studio lighting setups. I took a few sessions lately and the backdrop color is really off. I'm struggling to understand what's giving me such different results. Would love your ideas or suggestions.

I'm shooting with: Canon 6D / 24-70mm f/2.8
Lighting: single B10 Profoto with beauty dish (model light is off)
Backdrop: savage "blue mist" paper roll

Attaching both the background sample color photo and one of the results I'm getting.

Thank you!

 

[Christine Lee Smith]

Thanks for your feedback. Appreciate your thoughts/suggestions.

To clarify the B10 light is fixed at 6400k. The model light is adjustable, but the model light was not in use in my setting.

I’ll look into a color balance card. Other than that, is there anything else I can do to get more accurate color in camera?

The difference between the two lies primarily in the red channel which makes me believe it's about the color temperature of your light source. My guess is that it is too cold and the camera (or your RAW converter) is compensating by adding more red to get a pleasing skin tone. I just googled "B10 Profoto" and it appears that the color temperature is adjustable. I would make it warmer. If you had a grey card it would make it easier to diagnose by sampling the white balance off it.

 

[Adrian Bacon]

If you're running auto white balance, don't. Actually set it to daylight or flash, or to a kelvin setting in the 5000-5500K range. It almost looks like you're running auto white balance and it's balancing the blue out to grey.

Depending on what power setting your B10 is set to, the strobe color temperature will vary quite a bit. At full power it will be 5500-5600K. As you dial the power down, the strobe electronics will cut the duration of time that it is powering the flash tube, which results in the light shifting to a bluer spectrum as the power is dialed down because most of the red spectrum a strobe emits is during the last part of a full power discharge. You also see this behavior with speed lights. The other behavior you'll see with larger power units and older technology units is the color temperature will get warmer as the power is dialed down. This is because as you dial the power down, the electronics lower the voltage that is pumped into the flash tube, which results in the light getting warmer. Very few strobes do the necessary voltage AND power duration changes (usually it's one or the other) needed to maintain a consistent color temperature over the full output power spectrum. The ones that do, very prominently advertise that they do because it's a big deal in strobe land to have the same color temperature over the full range of power that you can set the strobe to. Most strobes either get warmer as you dial down the power or get cooler as you dial down the power depending on if they change the voltage or change the amount of time powering the tube. Smaller power units like speed lights and the B10 usually get cooler, higher power units usually get warmer.

In terms of getting correct color balance, ideally, you'd want to shoot raw, and once you determine your power level for the strobe, use a whibal card (not a grey exposure card, an actual white balance card) and take a picture of it, then proceed to shoot the rest of your photos. Once you've pulled the raw files into your converter of choice, use the white balance picker to set the white balance of that first image, then duplicate the white balance settings to the rest of the images taken at that same power level.

Other than that, if you're shooting JPEG, set your camera white balance to either daylight or flash. It'll render a little blue, but your background should come out looking a lot more correct.

 

[nmp]

If you don't have a Whibal card, try using a Teflon tape. Recently I did a comparison and the Teflon tape came very close to my color corrected Whibal card - to my surprise.

:Niranjan.

 

[Christine Lee Smith]

Unfortunately the B10 is not adjustable. I am shooting RAW.

Christine, 6400k quite cold. Is it possible to set it to at least 5500K or even warmer? Just shoot a test sequence from 3000K to 6400K in 500K increments to see what happens.



Are you shooting RAW and converting to JPEG in a RAW converter, or your camera is set to JPEG and by "in camera" you mean in-camera conversion? Either way, I would recommend a warmer light source and you should see the change you're looking for.

 

[Dismayed]

How far is the subject from the background? Have you tried metering at the plane of the background and taking an exposure to see how it looks at full exposure?

 

[Christine Lee Smith]

Adrian, you nailed it - I was in AWB. Completely forgot to change it over in camera. But as soon as I did in LR it corrected the color of my RAW images significantly. Thank you! After this experience I will be getting a white balance card set.

Also, the B10 user manual says it is 6400 straight through at all powers in normal shooting mode (unless using freeze mode and are shortening the burst time, then it gets even cooler).

Appreciate your feedback and getting me started down a better path. Thanks again!

If you're running auto white balance, don't. Actually set it to daylight or flash, or to a kelvin setting in the 5000-5500K range. It almost looks like you're running auto white balance and it's balancing the blue out to grey.

Depending on what power setting your B10 is set to, the strobe color temperature will vary quite a bit. At full power it will be 5500-5600K. As you dial the power down, the strobe electronics will cut the duration of time that it is powering the flash tube, which results in the light shifting to a bluer spectrum as the power is dialed down because most of the red spectrum a strobe emits is during the last part of a full power discharge. You also see this behavior with speed lights. The other behavior you'll see with larger power units and older technology units is the color temperature will get warmer as the power is dialed down. This is because as you dial the power down, the electronics lower the voltage that is pumped into the flash tube, which results in the light getting warmer. Very few strobes do the necessary voltage AND power duration changes (usually it's one or the other) needed to maintain a consistent color temperature over the full output power spectrum. The ones that do, very prominently advertise that they do because it's a big deal in strobe land to have the same color temperature over the full range of power that you can set the strobe to. Most strobes either get warmer as you dial down the power or get cooler as you dial down the power depending on if they change the voltage or change the amount of time powering the tube. Smaller power units like speed lights and the B10 usually get cooler, higher power units usually get warmer.

In terms of getting correct color balance, ideally, you'd want to shoot raw, and once you determine your power level for the strobe, use a whibal card (not a grey exposure card, an actual white balance card) and take a picture of it, then proceed to shoot the rest of your photos. Once you've pulled the raw files into your converter of choice, use the white balance picker to set the white balance of that first image, then duplicate the white balance settings to the rest of the images taken at that same power level.

Other than that, if you're shooting JPEG, set your camera white balance to either daylight or flash. It'll render a little blue, but your background should come out looking a lot more correct.

 

[Christine Lee Smith]

Thanks!

If you don't have a Whibal card, try using a Teflon tape. Recently I did a comparison and the Teflon tape came very close to my color corrected Whibal card - to my surprise.

:Niranjan.

 

[Christine Lee Smith]

She was about 1.5' from the background. I have not. I think it was a camera WB setting I was using mixed with the really cool light I'm using.

How far is the subject from the background? Have you tried metering at the plane of the background and taking an exposure to see how it looks at full exposure?

 

[Christine Lee Smith]

Here's the side by side screen shot after only a single edit: changing the WB to "Flash" instead of the AWB used in camera with the RAW file.

 

[Dismayed]

Here's the side by side screen shot after only a single edit: changing the WB to "Flash" instead of the AWB used in camera with the RAW file.

That's much better.

 

[Adrian Bacon]

Also, the B10 user manual says it is 6400 straight through at all powers in normal shooting mode (unless using freeze mode and are shortening the burst time, then it gets even cooler).

Ahh... very good to know! I wasn't sure if the B10s did that, though, given how much they cost, I'd certainly hope so. If that is the case, then all you really need to do is shoot a whibal card then use that to set a custom white balance in your camera, or as a preset in LR. Then when you're shooting with that flash, just put the camera in that white balance mode and away you go, easy peasy.

It might be a good exercise to run through all the power settings of the flash in full stop increments and just verify that it is consistent when in color constancy mode. One manufacturers version of consistent color may not match up with anothers. I've seen "color consistency" mode flashes vary as much as 500K from full power to minimum power and others vary by less than 50K. It really just boils down to determining what the range is and setting your Camera/LR white balance to something right in the middle of that range so that it's generally accurate, but could be slightly warm or slightly cool depending on the power setting.

Another thing to watch out for is your modifiers. They can and do affect the color temperature of the light, sometimes in unpredictable ways, especially if you're using modifiers from different brands. If you're all Profoto for everything, that's less of an issue as my experience has been they do a pretty good job of keeping all that pretty consistent.

One last thing to be mindful of: White balance is actually two axis. Amber/Blue (or Yellow/Blue), and Green/Magenta, so when you're doing the color at different power levels exercise, keep an eye out for green magenta shifts as well. It very well may not shift much in Amber/Blue, but actually shift quite a bit in green/magenta. I found that out the hard way with some flash units I was using a few years ago.

 

[Christine Lee Smith]

Another thing to watch out for is your modifiers. They can and do affect the color temperature of the light, sometimes in unpredictable ways, especially if you're using modifiers from different brands. If you're all Profoto for everything, that's less of an issue as my experience has been they do a pretty good job of keeping all that pretty consistent.

Good thoughts, Adrian! And a great suggestion. I am using PF modifiers now, but a good warning to keep in mind for the future. Thanks again for your thoughtful response!