A recent post on the appliedcolortheory list, discussing my suggested procedure for making gross changes in the color of a product, noted that it used Filter: Blur>Average, which the poster said he never used under any other circumstances. I will now show a related use of it that can really help out certain product shots.
Just as we can change the color of a dress from orange to mauve, or a car from red to green, we can change the color of certain backgrounds, although sometimes their character would not permit it. This ability can be exploited if we choose a background color that flatters the product or whatever else is in the foreground. Or at least if we move in that direction. I will show a real-world example, but first let’s try a computer-generated graphic.
Assume, please, that we have two products as shown, one brown and one blue. We have a lot of flexibility as to the background color, but it cannot be made white, black, or anything close. The objective is to make one or both of the products really stand out.
Following are four examples. Please state the one you would pick if you are instructed:
1) That the brown product is much more important than the blue one.
2) That the blue one is much more important than the brown.
3) That the two are of equal importance.
My answers, which I assume are yours also, are that (A) is best for the blue object, (C) for the brown, and (D) if the two are considered of equal importance.
How were these backgrounds chosen? We know that the greatest contrast is found between a color and its complementary—its opposite, its opponent. There are various definitions of complementary floating around, but the most accurate for our purposes is to select the color in LAB and invert it. To test, you can put one color on top of the other at 50% opacity. If you really have complementaries, the result is always 50% gray. Note: if you are playing around with complementaries, much of the time you’ll have to use Color mode to avoid damaging detail.
How do we find the complementaries in this graphic? Just sampling the squares with the eyedropper won’t necessarily work, because they are textured. That’s where Filter: Blur>Average comes in. To make (A) I selected most of the blue square, and applied Average. The texture is now gone, as every pixel within the averaged area is identical. I find it is 36L(6)a(42)b, which I set as the Foreground Color. Then I cancel the averaging, select the background only, fill it with the Foreground Color, and Invert. This yields (approximately) 64L6a42b, a light yellow-brown. Just the thing to make the blue square pop, but it makes the brown square harder to see.
To get (C) I did the reverse, selecting and averaging a piece of the brown square and inverting it to get a blue strongly tending to cyan. Now we see the brown square perfectly, and the blue one not so well.
What if both these squares are important, but neither more so than the other? You might think that the best background would be a gray, as in (B). Not so. A concept known as Schönfelder’s Law suggests that the best background would be the complementary of the average of both colors. To find it is simple. Select a piece of the brown square, then Shift-select a piece of the blue one. Then, run Filter: Blur>Average, which can run through multiple selections.
The average of the brown and the blue is a grayish purple, 45L6a(6)b. Inverting it creates the greenish-yellow-gray of (D), which makes the two squares stand out better than the pure gray background of (B).
Now, let’s consider a real photograph. (E). I assume that the three varieties of grapes are the focus, and that each is as important as the others.
I don’t know why the photographer chose this strong magenta-blue background. Perhaps he was looking for something that was totally different from any of the three types of grapes. However, it makes the light green ones stand out unduly, because they are the most dissimilar to the background.
Nothing in the composition prevents us from substituting a new background color. The procedure is:
On a layer that can be discarded, make roughly equal selections of each of the three grapes, then Filter: Blur>Average (F). This results in a yellowish brown, 38L8a15b. Inverting it produces a cyan-blue.
This inverted value cannot be inserted as the new background without destroying the current texture. Instead, it goes on a layer set to Color mode, with whatever method you like to exclude the objects in the foreground. The result is (G). Note how much better defined all the fruit is.
In this particular image the background has nothing that identifies it as being of one color or another, so we can feel free to substitute whatever we like. This isn’t always possible, so it should be pointed out that even moving in the direction of the complementary will make an improvement. In (H) the move is only halfway toward the background color of (G) and still things are working out for the better.