Can an IR-pass filter block visible light from a Pentax wireless control flash?
Asked 10/13/2011
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2 answers
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I use Pentax wireless P-TTL, which relies on an optical control flash. On my K-7, even controller mode still emits enough visible light to cause reflections, and I’d like to block the visible portion while still allowing the remote flashes to see the trigger signal. Nikon sells the SG-31R for this idea, and I’m considering making a similar shield from IR-pass plastic or another filter material. Will an IR-transparent filter work for this purpose, and is there likely to be any visible red leakage?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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I have the Metz ring flash which comes with an IR shield that is fitted over the hotshoe flash for this purpose. The link has an image of it in action and it does work, allowing me to control a flash wirelessly. The reason I bring up this example is that this Metz flash is built to support Canon, Nikon, Pentax, and others out of the gate, the implication being that the blocker works for all of them.
Now, I don't imagine you plan to run out and drop ~$500 on a new flash, but the Nikon option at $15 and change seems like a very low risk choice with it already designed to fit a standard hot shoe. Since you have the K-7, which shares the tiny body of the K-5, I don't think you have worry that it won't reach. :)
So, my advice is to just buy it. Worse case, you sell at a tiny loss on Craigslist to a Nikon user.
Originally by user472. Source · Licensed CC BY-SA 4.0
user472
15y ago
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Generated from our catalog & community — verify before relying on it.
Yes — an IR-pass filter can work for blocking most of the visible light from the control flash while still allowing optical wireless triggering. Based on the shared experience here, this approach works in practice on Pentax systems.
One user reports success using IR-transparent plastic over the pop-up flash; it triggered the remote flash reliably. They did note that some visible red light still leaked through, but adding a couple of layers of Congo Blue gel reduced that effectively while remaining IR-friendly.
There are also off-the-shelf solutions made for this purpose, such as Nikon’s SG-31R, and similar IR shields bundled with third-party systems like Metz. Since these are designed specifically to block visible light but pass enough IR for optical slave sensors, they’re the simplest low-risk option.
If you want a DIY alternative, even fully developed, overexposed negative film can be used as a crude IR-passing visible-light filter.
So the short answer: yes, an IR-pass material is useful here, but some deep red leakage is possible. If that matters, add another IR-friendly gel layer or use a purpose-made shield.
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AI15y ago
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