Using color and ND gels behind lens — Eclair ACL

[Raymond Zrike]

My Eclair ACL has a little cartridge that slides in in front of the film and behind the lens. The cartridge has a circle cutout that is about the image size of 16mm, and the intention of it is that you can load it with a circle gel to act as a filter. If I could use this feature of the camera instead of using square glass filters on the front element, I’d save about 10x the money and I’d be able to have more filtration options.

I’ve got a couple questions for those who have used filter gels like this before, though:

1. Are gel filter sheets of lower quality than glass filters? Will the image be different between using an ND filter on the front element versus using a gel behind the lens?

2. Will the possibility that of the gel not being perfectly flat (since it is flexible) affect the image quality? This is what I’m most worried about; that it would cause flares.

3. More practically, the camera I have was converted to super-16. Does anyone know if this filter holder covers the full super-16 image?

I just discovered this feature of the camera the other night since the previous owner had it taped up (which I assume indicates I should tape it over if I end up using it or not, to prevent light leaks).

[Pavan Deep]

I use an ACL, I have never used filters, I just keep it taped up.

Edited March 10, 2020 by Pavan Deep

[Raymond Zrike]

Yeah, I bought a set of gels and I don’t think they’re high enough quality to use behind the glass. Now I’m starting the tedious investment process in 4x4 NDs and the like. 

[Bruce Greene]

The advantage of behind the lens gel filters is that they allow viewing the image in the viewfinder without looking through a dark filter.  So it is easier to see through the viewfinder.   Only color correction or ND gels should be used and not diffusion filters.

But, if you have only one gel holder, then this would become kind of a pain in the neck to change filters.  You really need an entire set of gel holders to have all your filters ready to go.

And there is always the danger of dust showing up on the filter, with the same effect of dust on a digital camera sensor.  So, the filters must be kept as clean as possible.  They can not be wiped clean, so if the dust can't be blown off, the filter must be replaced.

[Raymond Zrike]

The main issue was when I did tests with the gel holder, every time I slid the holder out, the gel had been scratched all over. So I had no way of knowing if the gel was clear and fine once it was slid in, plus I’d have to replace the gel every time I change it out. Definitely too impractical.

[Gregg MacPherson]

I don't remember scratches. Maybe I wasn't looking hard enough. Gelatine filters can be really useful, so it's worth solving the scratching problem. Is it technique, or is there something about the camera? Does conversion to S16 have any effect? Checking the filter in the camera is easy. Pull the lens, pull the mag, inch the shutter....

The Wratten gelatine filters are high quality. In a jam we sometimes used lighting gells, no problem.

[Raymond Zrike]

I think the S16 conversion might have to do with it, or the filter holder is just busted. The gels are probably the best option if I want to do something dramatic, like tint the whole image dark green, then I don’t have to go out and get such a specific glass filter. On the other hand, I use NDs so often; better to have a reliable set.