Sunday, May 11, 2008

Cameras and infrared. 1 - Film

I go on about this a lot, but it’s important. Standard photographic film reacts to a similar range of wavelengths as the eye. It does pick up more ultraviolet than we can, which is what causes that overall ‘haze’ on photos taken in bright sunlight. Fortunately UV doesn’t travel well through glass so the lens stops most of it. You can clear the problem with a simple UV filter, which is a good idea anyway. They are cheap, and if your camera takes a head-on knock, you’ll find it much cheaper to replace a UV filter than a scratched lens.

So all my cameras have UV filters.

Infrared is a whole different game. If you want to take photos in the infrared on film, you have to buy special infrared film. Note that you don’t need a special camera, just special film BUT…

…some camera backs reflect infrared and will mess up your photos. Watch for that.

Using infrared film is a lot of fuss, even if you can find a shop that sells it. There are no local suppliers where I live now and I won’t buy it by post. There are some things you have to know about that film before you hand over your cash.

It has to be stored cold. If you ask for it, and it doesn’t come out of a fridge, don’t buy it. Infrared film is very heat sensitive. It can be fogged before it ever goes in a camera if it’s not properly stored. If you get some, rush home and keep it in the fridge until you’re ready to use it.

Now comes the interesting part. The film must be stored cold, but if you put cold film in a warm camera you’ll get condensation on the film. So you need to bring it up to ambient temperature before loading it.

Right. Your camera is loaded with infrared film. Now you need an infrared filter, which will block all visible light. This means that when you look through the viewfinder, you see nothing. Okay, slide the filter out of the way, frame and focus the shot, slide the filter back and shoot, right? Wrong.

Infrared light does not focus in the same place as visible light. If you have a good SLR camera, you’ll notice every lens has a red dot or mark, a little to the left of the centre mark. Focus your shot, look at the lens and the centre mark will tell you the focusing distance. Move that to align with the red dot, and you’re focused for infrared.

Okay. Now you can slide that filter back into place and take the shot. Assuming whatever you were shooting at is still around. Did I mention you should do all this on a tripod? Well, you should.

Let’s say you’ve been through that ten times and taken ten shots. Your film isn’t finished but there’s nothing else to interest you. Pack up and go home, leave the film in place and try for more tomorrow?

Nope. That film has to be stored cold, remember. You MUST finish it now. Use the whole film, rewind, take it out of the camera and put it back in its cool-box. When you get home, keep it in the fridge until you’re ready to process it.

If you’re taking it to be processed, find a specialist. Don’t fall for ‘Oh, we can do that. It’s just like black and white film’. Not quite. The processor needs to keep it in the fridge. If they don’t they’ve ruined it.

Whether you process yourself or have someone do it—no safelight. When developing film, usually you can have a very dim red light on, just enough to see what you’re doing. Not with infrared. Total darkness, or you’re screwed.

So, to summarise:

Infrared film must be kept cold, warmed up to use, used all in one session and then kept cold again.

You can’t see through the filter, and if you focus with the filter out of the way, it’ll be wrong.

If any internal component of the camera reflects infrared you’re screwed. If you have one of those that uses an infrared light and sensor to track the frame number, you’re totally screwed.

Developing it requires an ability to work without sight. No, you can’t use infrared night-vision goggles. Obviously.

Infrared film is expensive and extremely difficult to use. I gave up on it, because you’d need to take many, many shots to have a chance of getting a seriously good ghost photo, and even then it’s just too easy to ruin the film. Plus, setting up the shot takes so long that whatever you were aimed at will have wandered off. Too much expense, too much trouble, for too little return. Not worth the bother.

Then along came digital. They see infrared all the time, and you can even frame a shot through a filter. I’ll deal with them next.

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