Filter Identify

[Guy Wayne Ulrich]

I recently latched on to a bunch of Kodak series size filters. Most are of the u sual types (K2, G, 85 Etc.), but a few I can find no info on. They are: 8N5 2D CC 6-15-24-33 (with no color code such as 33Red and so forth) What are they? What were they used for? Thanks.

[Michael S. Briggs]

My answer is based on "Kodak Filters for Scientific and Technical Uses", publication B-3.

8N5 is the combination of a #8 yellow filter with extra neutral density of 0.5 density units. 0.5 density units is light reduction by a factor of 10 to the power of 0.5 = x3.16 = 1.66 stops. So if you use this filter you need to increase exposure compared to just an 8 filter by 1 2/3 stops, or about 2 2/3 stops total.

The Kodak publication lists pale yellow filters of increasing strength 2A, 2B, 2C and 2E. It seems likely that there used to be a 2D. Interpolating between the curves for 2C and 2E, the 2D is probably greatly attenuates wavelengths blueward of about 400 nm.

CC would be color compensating.