Infrared Flash Part One

8 08 2011

Recently, J and I have been looking into infrared flash photography.
After some careful research (mostly done by J, it has to be said), we split the cost of a ten pack of Rollei Infrared from AG Photographic.

Next step was deciding on a camera, and flash, setup. In terms of flashguns, I’m currently limited to a choice between a Metz hammerhead, and the little Cobra manual. For the sake of size, I went for the Cobra. Easier to mount and carry, slightly less conspicuous (which is kind of the point) and less flash area to cover with the IR filter. Plus, it comes with a diffuser attachment, from which the piece of diffuser plastic pops in and out of, onto which I can tape the infrared filter rather than taping it directly onto the flash itself.


I’d planned to use the Yashica Electro, for the quiet shutter of a rangefinder. However, that plan was foiled by failure of the pad of death. So, since I only discovered that the evening before heading to Brighton for the weekend, and being already situated at J’s place 60 miles from home, a rethink was required. The choices were Olympus Trip 35, and two OM10s. After shooting and quickly developing a junk roll of B&W, to check my grasp of the zone focussing system, the Trip was chosen for its size. Although the flash, being about the same size as the camera itself, does create a somewhat ridiculous appearance (and means the camera refuses to hang correctly, and flips upside-down, resulting in plenty of strange looks as people try to work out what the hell is around your neck.

J bought a piece of infrared pass perspex from Ebay, from which we’ve cut ‘filters’ for three flashes, with most of the sheet left over for further experiments.

Here’s a photo of my Trip/Cobra infrared setup, after electrical-taping the hell out of the flash to remove any and all leaks of flash from the edges and gaps in the flash head. Isn’t it lovely.

So, off we went to Brighton for the weekend, to escape the crap North and take many photographs. We’d already made plans with friends down there to go to a club night on the Friday, so that provided the perfect opportunity to test our infrared ‘ninja-cams’. And, as it turns out, confuse the absolute shit out of many people 🙂

Sad to say, the experiment wasn’t entirely successful. J got a few more shots out of his roll than I did, but both rolls came out extremely thin and underexposed. After having a think, a chat, and doing a bit of further reading, we think that the problem was being too optimistic about our exposure compensation. I was overexposing by two to three stops at the very most, and I think in a dark club environment, an overexposure of several stops more would have been better. Someone has even suggested a seven stop compensation, which looking at the negatives, doesn’t seem excessive.

This is the only really visible image that came out of my roll, other than a few vague impressions of the strobe lights. Unfortunately, I suspect the lighting I’m getting in that image is mostly from the lights of the DJ booth rather than the infrared flash.

Excuse the filthiness of the negative, I forgot to do any housekeeping before scanning, and really didn’t think it was worth rescanning afterwards.

So, at this point, we have a couple of possible thoughts.

1. We’re underexposing *massively*.
2. The infrared filter we’re using is cutting off too much of the infrared spectrum for the film we’re using.

Rather than waste the remainder of our rolls testing, we decided to sacrifice a roll, with careful notes on both exposure and filter use. Some further investigation into the technical information for both the film and for the perspex led us to believe that the perpsex is simply too ‘strong’ for the films sensitivity.

Having read in various places that both negative and transparancy film can be used to filter infrared, I went through my neg files searching for offcuts of exposed and developed negative, and unexposed but developed transparancy. This yielded enough for a few flash filters.

Test camera: Ricoh 35ZF (zone focus, full control of aperture and shutter speed)
Test flash: Soliger Mk 2 (automatic, basic, relatively low powered hotshoe flash)
First filter: 3 layers of negative film.
Second filter: 2 layers of transparancy film.

We shot in sets of five, bracketing at f/2.8, f/4, f/5.6, f/8 and f/11
The shutter speed was set to a constant 1/60, as per the flash sync, throughout.
First set of five was at 3 feet.
Second set of five was at 5 feet.
Then we switched filters, and repeated the above process.
As ‘control’ shots, we also took an unfiltered flash photograph at 3 feet f/16, and 5 feet f/11.
For curiosity’s sake, we shot two tests with the original perspex filter, at 3 feet, with apertures of f/2.8 and f/5.6.
We also tried a shot unfiltered in daylight, and then the same shot with a standard red 25B filter over the lens.

Develoment details:
5 minute presoak in water.
Ilford Microphen, stock solution. 68 degrees fahrenheit.
7 minute development time. Continuous agitation for the first 30 seconds, then every 45-60 seconds thereafter.
5 minute wash in running water.
5 minute fix.

Marginally less disappointment than round one, but still fairly disappointing results. Of the 36 frames, we got 11 frames with visible images on them. Three of those frames were unfiltered flash, and two unfiltered daylight control shots, and so of no infrared interest. However, from the tests using two layers of transparancy, f/2.8 @ 1/60, from 3 feet, yielded a pleasingly clear result, and at a distance of 5 feet, apertures f/2.8 and f/4 yielded visible results. The tests with negative film didn’t come out at all, just transparant (unexposed/underexposed) negatives.

f/2.8, 1/60, distance of 3 feet.

f/2.8, 1/60, distance of 5 feet. You can just about see me in the front of the shot, the license plates behind are another couple of feet back, and reflective, so that may account for why they’re more visible than I am.

Same setup as above, but at f/4.

As a side note, the shots we took outside in daylight, with the weak (25B) red filter did show some slight infrared indication. The foliage is beginning to acquire that ‘fluffy’ effect, and there’s more of an ‘aura’ to the scene compared to the unfiltered daylight shots.

Unfiltered daylight at f/11 @ 1/125, and f/11 @ 1/250 respectively.

With the red 25B filter, at f/11 @ 1/125, and f/8 @ 1/125 respecively.

Obviously that knowledge is of no use to this particular experiment, but it’s certainly interesting to know, and may come in useful in the future.

At this stage, we’re thinking that the final issue is the flash power. As we’re getting a result wide open at a distance of 3 feet, then a more powerful flash, using the same filter material, should allow us to move a little further away from the subject.

The next stage, then, is to add a more powerful flash to the experiment. For the time being, we’re sticking with the dual layered transparancy film, since that’s what has yielded us our best (well, only) results so far. Whilst yes, it’s disappointing when experiments don’t work out right away, I do see this second roll as a success. Had it not come out at all, it would have been difficult to know how to move forward. But, since we did get a few shots from it, there’s some indication of what our next steps could be. With another seven rolls of film between us, we’ve still got plenty of room to experiment.

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