Filming in a tanning bed on 35mm - flicker? fogging?

Katelin Arizmendi · May 18, 2021

I'll be shooting a scene in a tanning bed on 35mm 500T at 24fps in the US. I'm wondering if there would be any flicker issues? I plan on purchasing a Cine Check to check before as I'm sure it depends on each bed. I was also told that the UV light can fog the film. An optical flat might be able to take some of the fogging away but it would still be fogged. Has anyone had experience with this? Perhaps some fogging could look cool but ideally not too much.

Thank you

Satsuki Murashige · May 18, 2021

Hey Kate! Nice to see you around these parts, we miss you in the Bay.

Nothing I can add really, other than to maybe try to look into the specific model of tanning bed and see if there’s some kind of ballast running it?

Dunno about an optical flat, but a UV filter might help a bit. I’ve never seen one in 4x5.65, just the usual screw-in sizes.

Daniel Klockenkemper · May 18, 2021

While I don't have any experience with tanning beds - neither from filming nor otherwise - I do know that the major filter manufacturers have and do make UV filters in 4x5.65" sizes. Tiffen has a few strengths, with older filters labeled UV haze 1 or 2, and newer filters named UV-15, UV-16, and UV-17; higher numbers filter more UV. Schneider offers a UV-410 filter that claims to cut most UV wavelengths.

I haven't personally tested any of the above UV filters... I am aware of a test of stills filters, which found that B+W (owned by Schneider) was by far the most effective at actually filtering UV, while the lone review on B&H of the Schneider UV-410 filter claims that the filter added significant flare/glare. It's possible that the B&H reviewer is correct, but it's also possible that they made some mistake, like not bothering to clean the filter, or didn't mitigate it by tilting the filter...

A polarizer can help with UV exposure in landscape scenarios, but this might not be applicable in your situation, with the camera aiming directly at the UV source. I'm sorry I can't help with anything more than hearsay! But at worst the UV would cause a loss of contrast, for which you might be able to compensate somewhat in the grade.

Flicker would be my biggest concern, and it seems like you're already prepared for that. Your test with the Cine Check will be the most informative. In the absence of a test, I would film with a 144 degree shutter, assuming a 60Hz line frequency.

Edited May 18, 2021 by Daniel Klockenkemper

Katelin Arizmendi · May 18, 2021

thank you both for this info! super helpful. good to hear from you Satsuki!

Daniel - do you have any idea if any of those filters would remove some of the blue from the bulbs? that's obviously one thing we want to keep, and not have to bring in the grade.

thanks again!

Daniel Klockenkemper · May 18, 2021

Without having data for the bulbs spectrum*, my best guess is possibly a little bit, but probably not very much. The strongest UV filter I've personally seen - a Tiffen UV-2A - has a perceptible light yellow tint, which means that it does slightly filter some blue wavelengths in the visible spectrum. If the filter appears clear/neutral to the eye, then it follows that it shouldn't affect the brightness of the bulbs' output in the human-visible spectra.

To be sure, I'd recommend visiting the location with the UV filter you plan to use, and metering the bulbs through the filter. A C800 color meter might also be informative if you can get your hands on one. Of course, the only way to be really sure is to shoot a film test, but I know that's a luxury these days.

The original article I remembered about UV filter transmission is here:

https://www.lenstip.com/113.1-article-UV_filters_test_Introduction.html

There's also this more recent one from Lensrentals:

https://www.lensrentals.com/blog/2017/09/looking-at-clear-and-uv-filter-spectrograms/

* I searched a little bit for this, but the few spectral transmission graphs I could find for tanning bulbs only show the UV portion, and omit the visible light wavelengths.

Vital Butinar · May 20, 2021

Actually a really interesting question.

I'm not sure I can be much help but I do remember one time when I was working as an extra on set of a commercials to get some experience and observe. They had a bunch of tanning beds (don't know if they were real or props) but I do remember talking to a lighting technician and I think the guy told me that they put in kino flo bulbs or something like that and that there were no UV bulbs anywhere.

Good luck with your shoot.