Wednesday, November 11, 2009

Comparison: Color Shift from Light Modifiers (Why it pays to buy quality)

Color Shift from Light Modifiers

Why it pays to buy quality

In this posting we are going to explore the difference between some light modifiers of various styles and brands. This is not a review or an endorsement for any particular product. Instead, we are going to take a look at how different manufacturers light modifiers affect the color temperature of light. This important aspect of light modifiers seldom gets any kind of attention, yet it is just as important as any other characteristic, especially when mixing light modifiers. My goal is to point out just how dramatic the differences can be. There also appears to be an implication that the savings from buying cheap Chinese products, does come at a price. 

The idea to test for color shift came about when viewing some photos from a shoot. I noticed that there was a distinct blue hue in the shadows for some of the photos. Reaching for an explanation, I realized that I had been using my Chinese knockoff of the Eclipse Plus umbrella for fill on those photos. It didn't take too long to set up and prove my theory and indict the guilty party, er, umbrella. That was back in January, 2009. Today, while browsing my photo collection, I happened upon this experiment and decided that it would make a good post for Studiography, so here we are. Enough said on that, let's get down to business so you can see for yourself what I'm talking about.

Test Methodology
For this test, I am shooting a QP Card white balance card, which has three patches, near black, medium gray, and near white. For each photo I have taken three readings from near the center of each patch, presented. I have approximated the distance that each modifier would typically be used at. Since a bounce umbrella cannot be as close as a softbox, by necessity the distance from the subject to the back of the umbrella will be farther. The flash power was set to compensate for the efficiency of each modifier. As you may know, monolights tend to shift their color a bit with changes to the power settings. I did not take that into account for this simple test, but can assure you that any color shift from the monolight will have been minor because the power settings were not dramatically different and my studio lights (JTL Mobilight 300) have not been prone to significant color shift in the years that I've been using them. One last note, I donot usually use a reflector with my umbrellas, even when bounced, so or these photos, the monolight was pushed forward so that the flash bulb is inside the umbrella.

You will not see any photos of the light modifiers or commentary about build quality, design, or other aspects of their performance. In this posting we are only looking at color shift, so we will only be looking at photos of the QP Card to assess the color shift relative to a bare bulb. I will first present the photos with the summary and patch readings, and then wrap up with the conclusions.

The Results

Bare Bulb

38" subject to light (mounting plate)
RGB Patch Readings (dark, med, light)
096, 096, 096
132, 132, 133
240, 241, 242

This is the reference to which all the other photos are compared. I performed a custom white balance based on this shot and used this white balance for all of the other shots. As you can see, it is nearly perfect for all three patches.

7" Reflector
73" subject to light (mounting plate)
RGB Patch Readings (dark, med, light)
112, 112, 112
132, 135, 136
237, 239, 241

I was interested to know if my 7” standard reflector would cause any color shift. It seems highly unlikely that it would, but inquiring minds want to know. Based on this shot I would rate it as neutral.

30" Photoflex umbrella(bounced)
53" subject to back of umbrella
8" light (mounting plate) to back of umbrella
RGB Patch Readings (dark, med, light)
104, 100, 099
134, 131, 131
240, 239, 239

Photoflex are known for producing professional level equipment. I consider them entry level, but professional, nonetheless. This 30” umbrella I picked up used and have no idea how old it is or in what environment it has spent its prior life. The RGB readings show a very slight shift toward red, but essentially it is neutral.

42" Photoflex umbrella (bounced)
55" subject to back of umbrella
11" light (mounting plate) to back of umbrella
RGB Patch Readings (dark, med, light)
107, 103, 102
136, 132, 132
240, 239, 240

This Photoflex umbrella was also picked up used. It too shows a very slight shift toward red, but for all practical purposes, it is neutral.

43" B'osh Eclipse Plus umbrella (bounced)
53" subject to diffusion layer
8" light (mounting plate) to diffusion layer
RGB Patch Readings (dark, med, light)
105, 107, 122
137, 140, 157
241, 245, 253

This umbrella is a Chinese knockoff of the Photogenic Eclipse Plus and is the cause for wanting to perform this lighting experiment. I bought it new back in 2002 thinking that it was the real Eclipse Plus. They not only copied the design, but the name as well, which probably fooled a lot of people. This product has since been dropped and my guess would be that the lawyers had something to do with it.

You can easily see that there is a significant shift toward blue and the RGB numbers confirm what our eyes already know. My guess is that the diffusion material contains optical brighteners, which add a little bit of blue to fool the eye into thinking a white is a brighter white. This is one of the significant differences between a cheap copy and professional gear, and it is not obvious until it creates a problem, as it did for me. I will say though that when the two umbrellas are used together they work fine and they do a great job of diffusion, so it is a mixed bag. They are good by themselves, but cannot be mixed with other light modifiers.

32"x24" Amvona Softbox
39" subject to front diffusion layer
RGB Patch Readings (dark, med, light)
110, 108, 118
134, 134, 137
238, 241, 250

Amvona are known in some circles as makers of the cheapest softbox you would ever want to use, and I kind of feel the same way. They really do offer a lot of value in that they are very inexpensive, but perform fairly well and come with valuable extras: circle mask, rectangle mask, grid (egg crate), and speed ring (S-mount). The down side is that they do cause significant color shift toward blue. Not as bad as the Chinese Knockoff of the Eclipse Plus, but enough to warrant not mixing them with other light modifiers for critical work. I plan to replace my Amvona softboxes with Photoflex over the next year or two, primarily for this reason.

45"x33" Photoflex Softbox
39" subject to front diffusion layer
RGB Patch Readings (dark, med, light)
108, 106, 098
135, 135, 128
241, 241, 238

This was my first Photoflex softbox. The Photoflex design sports quick release corners that make setup and tear-down extremely fast. They are probably not as rugged as Chimera, but are just fine for me at a fraction of the price. The other good thing about them is their lack of color shift. The patches look good and the RGB numbers confirm that they add only a slight bit of warmth. I would not be afraid to mix this with any other quality light modifier, but obviously mixing this with the Chinese umbrellas would be a disaster.

47" Photek Softliter
39" subject to front diffusion layer
RGB Patch Readings (dark, med, light)
101, 098, 096
136, 132, 131
241, 240, 240

I love Photok gear. Okay, I'm biased and I admit it. Regardless, they do offer some unusual designs and come up with decent, if not outright good implementations. I have the Photek PeoplePopper with background stand, posing bench, and two of their velour backgrounds. I also have the 45” and 60” Softliters. One can argue that they are not be the best, but it would be a loosing debate to say they are anything less than good. The eye and the RGB values back me up in this case, as this is about as good as it gets with only the slightest bit of warmth added.

At the end of the day, it becomes clear that the good stuff really is better in more ways than just build quality or even design. You may pay more to get the good stuff, but if you need to mix and match light modifiers, which is part of the fun, then the extra cost is simply the price of admission to the game.

In terms of color shift, assuming one would mix & match light modifiers, here is my rating (excluding the standard reflector).

  1. Photek Softliter – First rate and suitable for professional use.
  2. Photoflex umbrellas – Suitable for professional use.
  3. Photoflex softboxes – Suitable for professional use.
  4. Amvona softboxes – Okay for amateur use in non critical lighting, professionals should avoid.
  5. B'osh umbrellas – Limited amateur use only. Just fine together, but don't even think of mixing with anything else.
Feel free to derive whatever conclusions you wish. If you have done similar experiments, I am interested to know if your results agree with mine. If you have found this posting useful, please leave me a comment.

Until next time...


No comments:

Post a Comment

Your comments are greatly appreciated, but please be kind. Kudos are always welcome! Please note that due to comment spamming, all comments are moderated, so it may take a little while before yours appears on the page.