Monday, November 14, 2011

ColorHug

OK, so you're into photography. Like most of us, you download your pictures from your camera, or you scan your negatives, then process them on your computer. Nice. Fun. Convenient.

But frustrating. Why? Because of color. As in, the color you saw in the scene is not what you see on your computer screen, which is not what you see on your other computer screen or what people will see online or what you end up with from your printer.

Coffee Break
This is one solution to color problems, of course. I love black and white; and with no color there is no problem with color casts.

Maiko at Shochikuza theatre in Osaka.

There's lots of reasons. Your camera doesn't really capture the "true" color (if you shoot negative film you know just how malleable "true" really is). A printer can't really reproduce all colors your camera can capture or your screen can show; it fudges things outrageously just to give you a vague impression of similarity.

But one frustrating reason is that your screen isn't neutral. Pretty much all screens have a color cast — they're bluish or reddish, or a green tint, or have some odd color shift between lighter and darker colors. And monitors change as they get older. The backlight changes color with age, and the screen pixel colors themselves can change with years of exposure.

So you carefully edit your pictures to look great on your computer. But if your screen is, say, a bit blue, then you will have added extra red to your pictures to compensate for that. They'll look reddish on other peoples screens, and come out red-tinted on your printer. Of course, their screens and your printer have color casts of their own, making things even worse.

You can't do much about other peoples screens. But at least you can do something about your own. Most image-related software today can handle "color profiles". That is, a file that describes how your monitor (or camera, or printer) handles color, and lets the software compensate for it. If you have a good color profile for your particular screen then your software can take it into account. Everything will look "right", that is neutral, as you work with it. It won't fix other peoples screens of course, but at least they get a nice, neutral, well-balanced image without color casts to begin with. It should look better, at least, if not great.

Yodobashi - Color
Why can't we just eyeball the color cast ourselves? Because we are really, really bad at evaluating color accurately. Any hint of the right color and we "fill in" the rest ourselves. The picture above is black and white. I added a few areas of solid color tint to it — red, green and blue areas for the signs in the background, muted orange for skin areas, a few splashes on clothes and bags. All colors are solid tints, and just vaguely similar to the real colors. Most of the image is still in black and white, with no trace of color.

Still, at first glance it looks like a natural color image to most people, and some refuse to believe it's largely black and white until you explicitly cover up the colorized parts. Our brains see the hints of color and fills in the rest by itself.

How do you create a color profile? You use a "colorimeter" — a device that measures the color on a screen, or paper — together with software that takes the measurement and generates a color profile from it. There's a few such devices for sale out there like the Pantone Huey or X-Rite ColorMunki. They work well enough. But the software is not open source, so you're dependent on them to support you in the years ahead. If the company goes bust or they decide to discontinue support for newer OS version your expensive device ends up as a paperweight. They also typically work only on recent Macs or Windows machines.

Enter ColorHug. It's a colorimeter, built as open hardware (schematics and the firmware is available for you), and with open source software for Linux. It's a fair bit faster than other systems, and less expensive too. The developer is gearing up for a first production run, and has just announced an advance order program that gets you a unit at a discount in exchange for helping out with reporting bugs and issues.

This is very useful for Mac and Windows users too by the way. The software is for Linux, but the color profile files are the same for every operating system. You get a bootable CD with a Linux system, so you can boot the CD, calibrate your monitor, then use the profile in your own operating system with no problem. And of course, the client software is open source, so somebody is bound to port it to both Windows and Mac if there is enough interest.

I've sent in my preorder already. Interest seems huge, though, so I can only hope I'll actually get one.

6 comments:

Richard said...

I love the effect of that B&W photo with some colours filled in. Like you say, I didn't notice it wasn't all in colour at all - just thought the lighting in the subway was making everything look a bit washed-out or something. Makes everything look quite sterile, like in Mirror's Edge.

George said...

Interesting. At first, the subway photo really fooled me. I didn't realise it was color until I read the post.
I haven't tried serious digital (all digi I've used is P&S), because I'm too cheap and rather use film. However, I've liked your article as it will be useful if I get some serious digi or scan color film.
As of calibration, our class projector is an example. The small PC screen is totally different compared to what the projector gives, the latter washes out everything, and a light cyan or yellow appears white!

A bit off topic, I see you now use a GF670. It must be a nice machine, but I won't be able to afford it, neither I would use it that much. I'd like however, to go up in format. I believe that for using the camera once or twice a month, it better be MF.

Janne Morén said...

Richard (Hi, by the way!), yes, we don't need much in the way of hints. Lossy image and movie formats like Jpeg take shameless advantage of it; they use formats with one luminance channel and two color channels, then save the color channels in much lower resolution and lower compression than the luminance channel.

George, the GF670 is a _very_ nice piece of equipment (it had better be ^_^). I wanted one ever since they were announced and I finally decided to splurge on one. I don't have much in the way of habits or expensive hobbies otherwise so it was doable; I'm certainly not going to afford another piece of equipment for a long while though.

If you want to get in to medium format (and you should - it really is a different kind of experience) then now is an excellent time. There's still plenty of high-quality used stuff floating around since most professionals went digital. I got my Pentax 67 for a song, comparatively speaking; less than the cost of the CLA.

Richard said...

Hi!

I particularly enjoy compression algorithms that are not only clever mathematically, but also exploit what we know about perception. Good stuff.

Aside: I have some Surströmming in my fridge that I will attempt to eat soon. I will play Abba and have one more beer while doing this.

Janne Morén said...

Open the can outdoors, under water. Rinse the filets, and find out a place beforehand to dump the wastewater so you don't get into trouble with the neighbours.

And remember, it's only the smell that's a little pungent; the taste is fine. Once you've rinsed them, most of the smell is gone.

George said...

Hi again.
Yes, it's a great time for getting into MF (or film in general). In these two weeks I've seen very nice bargains but I believe I will postpone my entry into MF until Nov, next year. Perhaps as a self present for my 18th anniversary.
I just hope the price doesn't begin to suddenly rise in this time.

About compression: It's interesting how we can "fool" our perception, still, if possible, I prefer lossless (esp. for music).

As of Gastronomy: Surströmming doesn't catch my attention (I'm not a fan of strong food) but I remember having eaten a can of something called "sprotid" from Latvia. I assume it's smoked herring. It's delicious.