How photographers can use histograms to nail their exposure
A Cheetah Stands Ricebowl RB-120 during a color temperature test. The modifier had no effect on the light’s color temp.
Useless information alert… well maybe it’s not useless, because after all you clicked on the link, so you probably thought it might help your OCD. I tend to obsess over, what some photographers may consider to be small things, in my quest to perfect my vision for portrait photography. Then once I find what I think are the answers, I feel more confident in my photography technique.
Recently I started thinking about color balance after buying three new to me softboxes. Two of them were Profoto RFi 1 x 6′ Strip Softbox
Portrait of fitness model Matthew Cuff photographed with a Profoto D1 with a dome placed in the CheetahStand 48″ RiceBowl RB-120 Deep Para Softbox with no baffles and the Chopstick in the medium position.
Initially I wanted to make sure that the Cheetah Stands Rice Bowl produced neutral colored light, but I quickly noticed that when you used both baffles, the light was quite warm… which got me thinking and the question I wanted to answer had two parts. 1. What are the color temperatures of all of my modifiers? 2. Does it really matter? So I decided to test the color temperature of one of my Profoto D1 Air 500 Monolights and then every single modifier I own. The results were actually quite shocking. Partly because testing took forever, since I’m the photographer version of a hoarder and own more than 17 modifiers, which I guess I should have realized when my closets were over flowing…
To test the performance of each, octabox, softbox or umbrella, I set the monolight at full power and repeatedly took a photo of a gray card and a few other objects on my dining table with a Canon EOS 5D Mark III
Profoto 1×6′ stripbox modifer color temperature test. The softbox warmed the light 1300K.
The color temperature of the monolight was 5850K, which was very similar to the color temperature I measured in other tests, where I found the following. The D1 stays between 5850k and 5700k from 500ws to 65ws respectively (power 10-7). Then it decreases 100k as you decrease power a full stop until it bottoms out at 5400k (power 6-4).
Surprisingly, I found that all of my modifiers either had no effect on the color temperature or warmed the light source. I did not notice a magenta or green shift in any of the modifiers. Originally I thought silver modifiers cooled the light source, but found that some of them didn’t warm or cool the light, and some only warmed the light by a few hundred degrees Kelvin, I also found that few of my “white” modifiers warmed the light by over 1000 degrees kelvin.
Below is a chart showing all of the modifiers and their effect on color temperature. You will see that affect measured as a negative number because my baseline was 5850K and when the modifiers were attached the color temperature decreased, which is the same thing as warming.
Modifier |
Kelvin Shift |
| CheetahStand 48″ RiceBowl RB-120 Deep Para Softbox | 0 |
| Beauty Dish | 0 |
| 60″ photek | -250 |
| 60″ photek with sock | -300 |
| Profoto 3′ ctabox | -400 |
| Chimera 4×6 | -400 |
| Elinchrom Rotalux 100cm Deep OctaBox with inner baffle | -400 |
| CheetahStand 48″ RiceBowl RB-120 Deep Para Softbox inner baffle | -550 |
| Profoto 5′ octabox | -600 |
| Deep Octa both baffles | -700 |
| Chimera Medium Stripbox | -750 |
| Chimera 1×3 stripbox | -900 |
| Plume Wafer 75 softbox | -900 |
| Chimera 1×1.3 softbox | -900 |
| CheetahStand 48″ RiceBowl RB-120 Deep Para Softbox with both baffles | -1000 |
| Profoto 1×6′ stripbox RF | -1200 |
| Profoto 1×6′ stripbox RF | -1300 |
This 4 light portrait I took of Oakland Raiders quarterback Connor Cook for Panini America had modifiers that varied by 500K.
I couldn’t believe that the color temperature could vary so greatly between the modifiers. There was a point in my career that I decided to sell all of my Paul C Buff Alien Bees and then buy two Profoto 7A 2400 packs, because I believed that I needed greater color consistency across all of the lights, while photographing beauty for a cosmetology client. Then after a while, I realized that having two packs, 5 heads and some extension cables didn’t give me enough flexibility when shooting environmental portraits or shooting multiple sets on location. In addition the system was so powerful I ended up shooting at f11 all of the time. So I decided to sell everything and buy 6 Profoto D1 Air 500 Monolights, which have served me well over the past five or so years. However, I recently acquired a Pro6 1200 pack to use as my main light source after testing the eveness of the light produced by the D1 in large modifiers.
This color balance test really caused me to question whether or not changing lighting brands made any sense. I began to think about a recent series of headshots I did for a client showcasing hairstyles and grooming on a set where I used up to 7 different modifiers and various power settings on a total of 6 lights. Resulting in a color shift of up to 600K.
You can see in this behind-the-scenes image, from the shoot mentioned above, a mix of modifiers that resulted in a color shift of 500K. However, the image was captured with these very same lights, and yet a color shift is not visible.
This image has lights hitting the model from 4 angles and when you look at the final picture it doesn’t look like one part of her neck is blue or her hair is too warm, it just looks right. The strip softbox striking her from behind on the right is -900k, her face is -300k, the top of her head is -900k and the the back of her head is -400.
All of this called into question everything that I considered previously about color temperature and fash photography.
I think you could use this information to your advantage and but I’m really not sure yet how I feel about things. For instance, I noticed before that if I tried to fill an outdoor picture shot late in the afternoon and I used a modifier and light that emitted of 5850K temperature, that my shadows looked blue. So after taking all of the information from my test in to consideration, I probably need to use something that is -900k to fill late afternoon sunlight. Also it sort of makes sense now why my beloved Elinchrom 39″ Rotalux Deep OctaBox with both baffles looks so good out outdoors, because the resulting color balance with a D1 near full power is 5150K, Therefor it’s very close to the color temperature of sun light.
Shot with a Elinchrome 39″ Deep OctaBox and Profoto D1 500 air at 250 WS. Jayne Watson poses for a portrait at Greenbriar Hills Country Club in Kirkwood, Mo. on Thursday, Dec. 1, 2016. (Copyright USGA/John Gress)
I could also foresee a problem if your fill source is a lot cooler than your main source, but luckily for us fill sources are often soft modifiers on low powered lights, thus increasing their warmth, or passive cards reflecting the main light source.
In addition, after testing a Profoto Acute2 1200 I found that the light was 5450k from 1200ws to 150ws, and then it dropped 200k when I set it to 75ws and 37.5 ws. So using it at low power with a warm modifier and a slow shutter speed for an environmental portrait in a warm ambient environment would probably result in a very pleasing image since the main lights temp would be around 4300k and the natural fill would be a warm 3200k. I must say the color temperature of the Acute concerned me, until I did this test and realized that a 600k shift in color temperature between all of my Profoto lights isn’t a big deal.
I also purchased a Pro6 1200, after my Acute2 1200 pack burned out, and completed a white balance test with the 6 and my trusty gray card and found that the color temperature output only ranged from 5750K at low power to 5850K at full power, even though I expected a 400 degree swing from using the master variator.
After considering all of this, and I could be totally wrong, I believe this test shows us that a600-degree shift in Kelvin probably really doesn’t matter that much in a “real world” studio environment. However, I’ll let you know if lightning strikes and I end up with a 1900k swing that ruins the whole shoot. Although given their vastly different brightness, I’m not sure how I’m going to pair a large strip at low power with a beauty dish at high power. =)
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