Lee filters with LF lenses and ultra long exposures

[Ted R]

Perhaps you are already aware of this, and perhaps this has been covered already however I didn't see it.

High value ND filters show a problem when used with digital cameras, the filter performs as expected in the visible range but not beyond the visible range at both ends there is significant leakage. Unwanted and unpredictable color shifts occur due to sensor sensitivity beyond the visual range, especially the infra-red, unless additional band-stop filters are added. Filter maker BW makes a statement about this on their website, in the detail spec for filter families. In your film application there may be a similar effect. Might be a good idea to test for this.

[Steven Ruttenberg]

Perhaps you are already aware of this, and perhaps this has been covered already however I didn't see it.

High value ND filters show a problem when used with digital cameras, the filter performs as expected in the visible range but not beyond the visible range at both ends there is significant leakage. Unwanted and unpredictable color shifts occur due to sensor sensitivity beyond the visual range, especially the infra-red, unless additional band-stop filters are added. Filter maker BW makes a statement about this on their website, in the detail spec for filter families. In your film application there may be a similar effect. Might be a good idea to test for this.

This is why I use the Formatt-Hitec filters. They literally have no color cast at all, I do mean none. I have been using them for a very long time with no problems. The problem you get is not using the gasket between the filter and the holder as well as ensuring your camera is completely sealed from any light leakage. I have a custom set up for my 5DMKIII to prevent light from getting in anywhere. If you don't you get streaks, color shift, etc. If you have a filter that is poor IRND, you will get a green cast, soft blacks due to IR contamination etc. Make sure for long exposure you get the best filter you can afford and I recommend the Formatt filters. Especially the Ultra that they just came out with. For film, IR should not be an issue since most films are not sensitive to the IR range like a digital sensor is. Even with its IRND hot mirror installed by the factory. Given enough exposure time and bright enough sun light, you can get some IR contamination which is practically unrepaireable.

[Tim V]

Out of curiosity, does anyone know if the Formatt Fiercrest filters fit in the Lee holders? Both seem to be made out of 2mm thick glass. Wondering if the gasket on the Firecrest would fit on the filter when in the Lee holder...

I ask this because by my own calculations, for what I would like to do, it seems a 13 stop ND filter would be the best bet. The Lee 15 stop IRND would seem to be too strong after compensating for reciprocity and light level changes over the course of a day. I already have the Lee Universal hood, so it seems natural to find a way to use that so I don't need to shell out another $160+ for the Formatt holder.

Or I could simply use a 58mm circular filter with a 40.5-58mm step up ring (for use with my Dagor type 210mm G-Claron) and dispense with the hood altogether, flare be damned... That'd be the cheapest option by far with the best quality filter.

For all of the above options however, I do worry slightly about vignetting potentially caused by the step up ring, be that to attach a circular filter or the Lee hood.