Are the colors based purely on their assumptions/imagination, or do the greyscale images retain some sort of data that tells what color on what part?
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They are making an educated guess. But they are often more muted than they should be. Experiments where colorized photos are compared to a control (photo taken in color) have shown that when photos are colorized they are often much less colorful than the original.
>do the greyscale images retain some sort of data that tells what color on what part?
Normal pictures don’t, but there’s one important case where it does contain some info.
Early color TV shows sometimes only survived as 16mm b/w film, because the tapes were reused. There’s some interference called “dot crawl”, an artifact of how analog color was transmitted, that also made it onto the b/w copies. From that you can restore the original color.
This restoration method was used on some Dr. Who episodes, and on some other BBC shows that only survived as 16mm b/w prints
I don’t remember the values, but there used to be a trick in Photoshop where adjusting the HSB sliders just right would do it almost on the first try, so much so that I didn’t even have to look at it while I was doing it.
i don’t believe there’s anyway to derive from grey what the original color was, because grey has no color attributes
But you can make some educated guesses.
Some colors are well known. Barns were red because the ingredients for red paint were easily available
Some colors were rare and expensive during certain times in history so they can be ruled out for all but the richest people
medieval paintings and tapestries show the colors worn by kings and peasants. the tiles and mosaics of pompeii.
museums contain clothing samples. also graves.
They don’t know, they guess based on similar illustrations, and if none are available, make up colors that look ‘good’ or seem to be correct. [These guesses in colorization are not infrequently incorrect, and there is controversy about the alteration of historical photos that colorization produces.](https://www.wired.co.uk/article/history-colourisation-controversy)
Photography has only been around for a blip of time, and humans tend to keep records and save things for reference and remembrance..So actually, when you watch such shows as The Repair Shop, they explain that many of the historical items they recover are restored using rather descriptive letters and memories from the guest owners. If you have a snippet of cloth, some old paint chips, or maybe unrestored furniture they reveal a huge amount of colors and patinas and historical processes for making dyes.
On a funny note, when we had a black and white TV there was Rula Lenska to explain why you’re using the incorrect Alberto VO5 hot oil treatment: “Hello, my name is Rula Lenska, and my hair is red, my dress is green and my eyes are bright blue. If these colors don’t look right to you then…”
Or maybe it was an ad for RCA color TVs…
My family has a ton of old black and white photos, and we were inquisitive about the colors of cars, houses, clothes, wallpaper, etc.
I would think that some one that is color blind would have it easier. All their life they have been told this is red, this is yellow, this is green. So they see different shades or grey from white to black. If only blind to certain colors (read and purple specturms look brown) that could make it hard.
There’s a lot of explanations here that mostly amount to research and guessing, some that mention specific types of film that react a little bit more to certain types of light and color, but I’d like to mention that black and white photography both older and recent can have colored panes of glass you put in front of the lens to change the image. It still takes a black and white photo.
this is lengthy but demonstrates and explains colored lenses on black and white photography. Polarizing filters also affect this.
If you as a colorizer notice certain things (the sky being very dark in a brightly lit shot) or have notes on the photo that detail the lens and film used, you can be rather certain of the hue. Some photos may have several lenses in a set taken by the photographer at the same time of the same subject, if even one other lens is used you basically can have nearly 100% certainty of the color of the photo.
In these photos, guessing and individual object research is not very necessary, but it requires knowledge of the equipment used or several techniques were used in a series of shots that you have access to.
In older portrait photography there is a pretty understood set of typical equipment and methods and others have explained well how that works, there’s probably going to be guessing involved to some extent. For well known artistic photographers taking pictures of landscapes and daily life and etc, many extensively documented (or outright invented and showed off) the equipment and techniques and guessing isn’t necessary.
An interesting sidenote is that with planned black-and-white filming or photos, colors could be chosen exclusively for their black-and-white contrast. Accurately recreating a black-and-white movie’s original colors might produce a garish mess instead of what was originally intended.
There is something called LAB colour which is the scientific way (for want of a better explanation) of how humans see colour.
It can be demonstrated in Photoshop by choosing LAB mode and then looking at the channels.
Basically the detail of an image is represented as black, white greyscale in one single channel and the colour is completely separated in to the other channels.
So you have the L channel which is the Lightness channel and is purely black and white grayscale image. So no colour information at all.
Then you have the A channel which contains Reds and Greens.
And the B channel which contains Blue and Yellow.
Already this becomes difficult to explain. But anyway, because the detail in the L channel doesn’t change you can adjust the colours to your hearts content and you don’t lose detail.
In contrast the RGB mode doesn’t have blacks grays or whites without involving all three channels together. Thus you can mess things up really easily trying to do colour restoration without switching to LAB mode.
So that’s the secret. Switch to LAB mode in Photoshop and the detail is unaffected so long as you only affect the A and B channels with colour changes.
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