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IR Flash — progress!

So, I finally leveled up with this IR flash mess I’ve been working on. I’ve got actual, honest to goodness results.

Warning: This is going to be very nerdy and tech-y. If IR photography isn’t your thing, just look at the pictures and move on, unless you want a serious soporific. I’ll put up a less geeky post on IR street photography later.

I’m not going to do a whole tutorial write-up thing on how to go about this, because there are already a couple of good ones here and here.

The first one does a great job of explaining how to go about putting a gel on your flash with a bit of space to prevent, you know, melting. However, the filter mentioned there has a non-optimal cutoff for IR film currently in production. The second one (which will be of particular interest to XA shooters) provides a film/filter pairing which is currently available and works great: Ilford SFX gel filters and Rollei IR400 film.

I tried this combination out with my Nikkormat FT-2, 2.8cm f/3.5 Nikkor-H (a great lens for IR work), and a Nikon SB-24.

Nikormat FT-2 with SB-24

Shooting wide open with the flash at full power produces usable exposures for subjects in the 8-15′ range, give or take, with some definite (but acceptable) overexposure for subjects close up.

This is reasonably consistent with the flash’s calculations for ISO 12 (which is what I normally rate IR400 at when shooting with an R72 filter), which suggests I may be able to engage auto mode — or, if subjects aren’t too distant, I may even be able to shoot safely at f/5.6, which would be lovely from a DOF standpoint.

With the Nikkormat and 28mm f/3.5, I’m shooting blind, because I’m working with an opaque infrared filter over the lens. (Note: for night photography, this can be omitted. However, since current IR films are sensitive to visible light, using them for flash work without a filter on the lens during the day is likely to be somewhat counterproductive.) However, with a 28mm lens, even wide open, I have enough DOF to scale focus reasonably well, and guessing the composition isn’t too hard.

BTW, if you’re curious about how scale focus works, this may be helpful:

Scale Focusing with the 2.8cm f/3.5 H

Anyway, after all that technical mumbo-jumbo, what matters is, it works!

BART, Richmond Line Commuters

I’m even reasonably pleased with that photograph as such — successful test aside.

The one downside to this setup is that it tends to let through a little more visible light than I’d like — the SFX gels are a little loose in that regard. Not so much that I’m blinding people, but it bugs me just a little.

So, I’m also still fiddling around with alternative options. One not-really-successful setup is this:

Bessa R with Sunpak 622

It’s a thick eBay 89b filter intended for Cokin-type filter holders which I’ve taped to the front of a wonderfully cumbersome and powerful Sunpak 622. This setup works quite well for digital IR flash with my unmod’d D40, and emits very little visible light, but is completely useless with Rollei IR400. However, initial tests on a less powerful flash provided some exposure with Eke IR820. (Which suggests that the eBay filter isn’t a true 89b equivalent.)

I was hopeful that the Sunpak (which I got specifically for this project) would enable me to shoot with this filter/film combination through sheer power. And it does, sort of, but unfortunately the working distance is still too short to be really useful in the majority of situations.

Aura-135-004-23

That was shot at f/1.7, and you can see that even just at about 8′ feet or so, it’s already significantly underexposed. So, while this is not a failure, as such, it’s obviously of very limited practical usefulness unless I’m willing to get truly in-your-face. I’ll continue experimenting with different filtration options and see what I can get on this front.

2 Responses to “IR Flash — progress!”

  1. ault Says:

    Does the gel completely eliminate the flash’s visual output?

  2. Nick Says:

    Not completely. It’s nearly unnoticeable with the eBay 89b filter. It’s noticeable but still fairly weak with the Ilford SFX gels on the SB-24. However, when I tried the SFX gels on the Sunpak at full power, it was quite blinding. : )