How were image blending effects done before Photoshop?

Question

Before digital editing, how were two images blended together in photography? Were effects similar to Photoshop blend modes created in-camera, in the darkroom, or through printing techniques? I'm also curious whether more advanced modes like Difference, Lighten/Darken, Hue, or Saturation had practical pre-computer equivalents, or if only some blend-style effects were possible with film and chemical processes.

darkroom photoshop double-exposure film-photography blending-modes

Originally by Edward Van Crowley. Source · Licensed CC BY-SA 4.0

Edward Van Crowley

9y ago

user37321 · Answer

(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/

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.

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.

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)

Soft light

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

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.

Hard mix

Something like an ortochromatic photo printed with silk print.

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.

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.

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.