The Infrared Zone

(The title is a play on “The Twilight Zone”. Since Rod Serling died in 1975, we’ll just have to do the best we can without him.)

I’ve written a bit about infrared digital photography before, and about how the closest you can get to it without spending a small fortune on a dedicated infrared camera is to use an infrared filter – and a lot of experimentation to get interesting results. Since what we’re really seeing is near infrared the results can be quite varied. Or random if you don’t pay attention to what you’re doing.

Here’s my first tip which can be used for more than just infrared photography: dedicate an SD card to the project, starting with making the first shot on the card the ‘white balance’ exposure so you can set custom WB suitable to the job. You can then go back and shoot more IR any time you want by skipping ahead to that first shot and telling the camera “this is white”. That’s absolutely necessary for IR shots: the camera’s normal exposure evaluation will not work through the very dense IR filter.

There are a variety of such filters, all rated in nanometers corresponding to the wavelength they allow to pass. The standard is 720nm, which allows some visible light to pass. Do not expect that to mean you will be able to see through it to frame and focus as it’s still quite effective at blocking all but the brightest light. Yes, bright light is a good idea; midday in Summer, for example. A 550nm filter will allow more visible light through, and an 850nm less. Which do you try first? How much can you afford to spend? Here’s an article that goes into depth on filters: Choosing an IR filter. In fact they have about all the info you’d want regarding infrared photography and it’s worth a read before you spend a dime. This article is just about my experiments.

For default purposes I’m using a 720nm. (Side note: I think manufacturers may go a bit overboard when blocking near infrared from the sensors, thus the reason so many cameras are strong on green-blue but weak on red.)

Step one: set white balance. Step out in the broad daylight with your camera and shoot a ‘properly exposed’ picture of the white card through your infrared filter. Okay, that “properly exposed” part is the difficult bit. We are looking at perhaps 16 stops more exposure than the standard picture would be under the same lighting. You can only open your lens up so wide (and you don’t want to, as depth of field is very helpful for getting sharp IR – more on that later), and as you increase the ISO you get more noise (your camera may allow you to increase noise reduction on high ISO – mine does, but it’s not terribly effective). That means long exposure times are inevitable, and that means motion blur is too. Best to shoot immobile objects like landscapes on a wind-free day. You absolutely will be using a tripod.

Step two: proper exposure. This step is recursive because you need the right exposure to get the white balance correct, which you need to get the exposure correct. Some (okay, a lot of) trial and error is necessary. You can start with an educated guess by taking a meter reading without the filter and then adjusting ISO, shutter speed, and aperture to increase exposure by 8 stops to begin with. I found going above ISO 400 adds a lot of noise without much gain in exposure (i.e. you’re already into long shutter time). So we get a change-up like this:

If normal exposure is ISO 100, f8, and 1/125 sec shutter speed, you add 2 stops by going to ISO 400 and 6 more stops by slowing down to ½ second. Use this as a starting point; you may have to increase to +12 stops, which would be 8 seconds exposure. I found this works most of the time, but beware: the time of day (try to shoot midday) and reflectivity of the scene will affect exposure and you have to guess at compensation as digital cameras do not have good exposure latitude. Keep in mind not all cameras are alike; some will pass more IR than others, or should I say some will block more?

Step three: frame and focus. The odds of you being able to see through the viewfinder (or even the LCD in bright light) to do this are around ‘not a chance’: if the light was that bright you couldn’t stand to be in it. So you can either take the filter off and put it on for every shot (you won’t be shooting moving subjects, remember) or you can ‘guestimate’ the scene and hope you’re right. Focus is another issue as IR does not focus at the same distance as visible light. Many old lenses were marked with an IR focus line. Rest assured new ones aren’t, and your autofocus isn’t going to work even without the filter because of this. With the filter … forget it. The trick is to try and use a small enough aperture to give enough depth of field to compensate for the variation. It helps to use a wide-angle lens which gives more depth of field for a given aperture. (Note that aperture affects other things with IR, including ‘hot spots’ the lens may have.)

Step four: post-shoot processing. Good luck. There are unlimited possibilities here, no matter which processing program you use, and the end result is entirely subjective; if it looks good to you, it’s good. I’ve got several ‘partial’ IR shots which some people might call “screwed up colour” but I quite like them.

Step five: move on or move away. You’re either going to like the results and continue, or you’re going to say “that’s not for me” and do something else. You might buy a few more different filters before you make the decision. Hopefully you won’t invest in an IR converted camera before you decide not to do it anymore.

So here are the photos. First, a series showing the initial shot and subsequent processing steps I used to get the ‘other worldy’ effect I like:

The first change is using Auto White Balance adjustment in GIMP. The second change is moving the Hue to -130. Note if you shoot in RAW and use Photoshop or Lightroom you’ll have much more control over the outcome. I don’t use this method because it is more work and time consuming, therefor an anathema to my laziness.

This next shot contradicts my own statement about taking pictures of things that aren’t going to move. What can I say? Marley is a strange dog and she stood there for 8 seconds just to have her picture taken.

IR1416

This next one came out looking almost like a normal picture. Yet there’s something just a little bit off about it:

IR1438

This one could be a fall scene or a hot, dry Summer (which we’ve had a lot of here and they can be dangerous):

IR1467

Not the typical ‘white foliage’ IR pictures, right? Well they could be if processed differently. This is just a fast, relatively easy way to get some unusual results with infrared for anyone who wants to experiment without investing a huge amount of money and time.

Of course IR doesn’t have to be in colour. I shot a few frames in B&W that look more like what you would expect. This is a nice one, I think:

IR1471

BTW if you get some unsatisfactory colour shots desaturating them to B&W may save them:

Personally I don’t think I’ll be investing any more in infrared equipment. It’s interesting to experiment with, but in the end has too many limitations to be anything more than an occasional shot for effect.

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