At the risk of being pedantic, I'll explain it too you in another level of detail. First, lets backup though.

shawnc 19 hours ago | link | parent | flag

These are so amazing. The world wasn't sepia toned a hundred years ago! As silly as that statement is, my brain is actually having a hard time really believing these photos are from 100 years ago. I'm in awe.

OK. This was the original statement. The somewhat minor but technical point I was making is as follows. There is a simple explanation. The world then looked like it does today. And the image itself is modern, so it looks modern. Thats it. The Awe of this? Its called the "uncanney valley". Its kinda-almost-sorta-perfect-but-off-a-bit.

How did they do this then? Easy, the colorwork is done in photoshop, using contemporary techniques. PS allows them to exploit the latent image data, and map it onto one of many "style" outputs. [1]

You can debate this or not. But its cited in the footnotes above. If you havent read them, take a look.

I understand all of that you say?

Ok. You so, you are now in "awe of photoshop".

The technical reasons for this are not hard.

I'll stop here, because I think any more technical is not going to help you.

I've done a fair amount of photography...

Again, I would encourage you to do research on colour theory. If you do your own work, it will help you immensely, to make the most of your images. And if you really are an expert in this already, you know how trivial it is to produce "contemporary" style images from these formats, given the datasets you have to play with.

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Edit: For the general reader

[1] Style. In the sense i'm using it here is a mix of overall color, texture, tone, sharpness, saturation, hue, tint, noise, and other basic image editing techniques. Without getting into a discussion about "color" (ie, not "accuracy" but more correctly temp, tint, gamut, etc), its important to understand that the "look" has a lot of potential. Think about instagram. All of those filters are just "style" presets. But they don't look alike. Some are contemporary, some are retro, etc. It only requires a certain base image quaity to "take" the style (ie, good enough to not be ruined at the pixel level). So you might have an image which out of iphone looks "OK" and then in instagram is "Cool" or whatever. But the look of the "instagram" is independent of the landscape (which always looks the same, sepia toned on your phone or not). Now, the question is, what limits the "style"? And thats where the color technicals come in. If your input is messed up, your gamut and balance and tint will not let your image "take" a style. Because the transitions (ie, curves, etc) will destroy your pixel base. The size of your gamut, will determin the range you can execute. Now, with film, the color-setting step is a one-shot deal. There are no 12 instagram settings - you get just one - film/chemistry setting. You gett a little bit of flex at the print (color mix, etc) but not much. If you scan the film, then you are opening up to 12 syles (or whatever). So, now we get to the point. None of the film emulsions (prior to NC portra) really give you a contemporary look. To get that, you have to bring the image into digital. The temp/tint/contrast levels are just not there. Thats why its "odd" seing an old image looking like NC portra film or like a 2000+ PJ photoshop. And you can double check by looking at the details, if your an expert. The monochrome seperations have good tonal information, which is a credit to the guys back 100 years ago. But the modernists of that era were some of the best photogs ever, and among the most technically brilliant in monochrom image capture.