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Before computers, to blend two pictures into one, I'd imagine they'd have used some sort of mirror setup to reflect the one picture onto a mirror containing the reflection of the other picture. Does that sound right?

What about different blending modes that Photoshop has, like "Difference," "Pin Light," etc. What are the pre-computer origins of these?

Example of blending modes

migrated from hsm.stackexchange.com Sep 20 '16 at 11:51

This question came from our site for people interested in the history and origins of science and mathematics.

  • 1
    This question might get more traction on Photography.SE -- in addition, although it is a question of prior technology, it seems to miss the historical importance focus that I would expect in this forum. – K7PEH Sep 19 '16 at 4:48
  • Ok, I will move over to that side – Edward Van Crowley Sep 19 '16 at 4:52
  • If Photography doesn't want this Graphic Design will take it. – RyanFromGDSE Sep 20 '16 at 12:59
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(I still need to post a test with a black and white image...)

Interesting question.

Before digital manipulation, you needed to do things by hand. Some blending modes could be reproduced in camera, some during develop or chemically and other could be reproduced in a photographic print and some more on a commercial print. Some others I am not sure that could be reproduced directly because they are using different channels to analyze pixel values.

I am not doing a rigorous approach on what calculations the blending mode does, but an "empiric" approach of the results. I am not sure in all cases because I have the feeling some blending modes are not using direct proportions but some kind of logarithmic progressions.

What are the pre-computer origins of these?

I am not sure that all have a pre-computer origin. On the contrary, a blending is in principle a way of computing color values. You could not do that before a "computer".

I can not cover all blending modes. But here I go with a couple.

The test image

This has some characteristics. It has a similar color of the one we are superimposing (r255g128b0) and some complementary one (blue jeans)

I also included a test band, with white, middle gray, black, the exact same orange we are using and the complementary blue.

Original photo: https://pixabay.com/es/lectura-libro-chica-estudio-515531/

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes.jpg

The orange band

Using your example with an orange band:

Multiply

This is the same as if you print a color photo and you print a band of transparent orange tint on the top of it. Take a look at this post: https://graphicdesign.stackexchange.com/questions/77703/preparing-design-for-duotone-printing/77708#77708 I use it to simulate a duotone. (Print)

Keep in mind that inks are transparent, so they mix of complementary colors still is transparent.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-01-Multiply.jpg


Linear burn

This could be as if you print on an absorbent orange paper. It also could be as if you put a strong color filter on your lens.

The difference is that the complementary color is neutralized to black.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-02-LinearBurn.jpg


Screen

The complementary color is not completely washed out, but the general result is this:

Instead of printing a grayscale photo with black ink you put orange ink. A monotone. (Commercial print)

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-03-Screen.jpg


Soft light

Using a color gel, either as a filter on the lens or the source light.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-04-SoftLight.jpg


Hard light

This could be duplicated with a duotone, but instead of black, you could use a (theorical) oversaturated version of the orange ink and a lighter version of the orange... yellow.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-05-HardLight.jpg


Hard mix

Something like an ortochromatic photo printed with silk print.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-06-HardMix.jpg


Hue

The result is similar to a duotone using black ink + the color. The amounts of color depends on how the complementary color is neutralized.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-07-Hue.jpg


Color

A sepia photo was archived changing some silver crystals with other ones. In this case, the result is a change on the middle grays but leaving the shadows and hlights alone.

But if you use a color different from the orange you probably could not find a suitable crystal.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-08-Color.jpg


Using the same image

But the blending modes get more complicated when you use for example the same image. Then they could react as an overexposed slide or overexposed positive print.


Multiply

Similar as the orange band, could be the same as printing several times on an inkjet printer the same image.

enter image description here

Test Image http://otake.com.mx/Foros/Color/BlendingModes-11-Multiply.jpg

  • Screen could be an over exposition. I am not sure but probably one full stop.

enter image description here Test Image http://otake.com.mx/Foros/Color/BlendingModes-13-Screen.jpg

Pure brute force computation

  • Diference is a total analitic blending mode, but could be at some extent a matt mask principle on a blue screen.
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Just to add a couple:

  • Darken is the minimum of the foreground and background
  • Lighten is the maximum of the foreground and background

I don't know enough about printing to tell you how you would achieve that in print. If you know how to do one, though, the other is easy. Let's say you know how to do "Lighten". To do "Darken" you could start with the negatives of the foreground and background, apply the "Lighten" mode and then take the negative of the result.

Hue and Saturation probably can't be done easily with traditional methods. They take either the hue from the foreground, but the luminance and saturation of the background, or the saturation of the foreground but the hue and luminance of the background.

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You could do this by double exposing the negative or double exposing the paper, then perhaps flashing it, developing it in different ways, or toning it...

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