I looked on Kodak's web site - found a nice description of filters and their uses.

http://www.kodak.com/US/en/motion/programs/student/handbook/filtration2.shtml#selecting

http://www.kodak.com/US/en/motion/programs/student/handbook/filtration4.shtml#color

So, I go looking for the 80D filter in 77mm at b&h, and I can't find it. What's the story? Nobody wants to make 80D anymore?

-- Howard Z (greenspun@howardz.com), February 20, 2001

Answers

Howard, you seem to be really into this business of colour correction. If you want to really make use of colour correction to its full, then buy a gel or polyester filter holder. Gel and polyester filters are the only source of CC filters in steps of 025 (0.025D) in R,G,B and C,M,Y, as well as some of the more obscure mired shift filters. They come in 2, 3 and 4 inch squares, mostly to special order these days, but they're still obtainable from companies like Lee filters and lighting.

-- Pete Andrews (p.l.andrews@bham.ac.uk), February 21, 2001.

Ah...I think I have found the answers.

More and more of our filters are being manufactured in Europe. Wave bye bye to the Kodak Wratten filter nomenclature like 80, 81, 82, and 85 series filters. Say hello to KR and KB.

Let's say you go to B&H and order a Heliopan 80A filter. Guess What? You don't get an 80A filter, you get a KB15 filter instead.

KB15 = mired shift value of -150

80A = -131

For 200 watt incadescent bulb an 80A plus a 82A = -152

For 100 watt incadescent bulb an 80B plus a 81A = -163

So this KB15 is fine all by itself for a 200 watt incadescent bulb, and is probably close enough for 100 watt bulb. But we go and buy a 80A but really get a KB15 because B&H says it is a 80A and we add the 82A for a 200 watt bulb and we get -170 which is too much compensation!

Same thing for taking a photograph of someone sitting in summer time shade. The appropriate filter should have a mired of 90 which is a 85C + 81, but when we order a 85c we really get a KB15 which is a 90 all by itself.

Why can't I find a 80D? It is because 80d=-56 and 82C=-45. All that is being manufactured is a KB6 which = -60. In the infinite wisdom of filter makers, the KB6 is being called the 82C, even though it is closer to the 80D. Why? Probably because the 82C is more popular - people are buying it to combine with their 80A to get -176 for use with 75 watt incadescent light bulbs. But their 80A is not -131, it is really a KB15=-150 and when combined with their 82c which is really a KB6=-60 they are getting a combined -210 instead of the desired -176.

These filter makers are trying to ruin us!

I say instead we should all switch to digital cameras with color white adjustments - which do not need filters at all. Then nobody will buy filters and we will ruin the filter makers rather than let them ruin us.

-- Howard Z (greenspun@howardz.com), February 21, 2001.

*** this bad forum software that doesn't allow corrections requires me to repost with corrections ***

Ah...I think I have found the answers.

More and more of our filters are being manufactured in Europe. Wave bye bye to the Kodak Wratten filter nomenclature like 80, 81, 82, and 85 series filters. Say hello to KR and KB.

Let's say you go to B&H and order a Heliopan 80A filter. Guess What? You don't get an 80A filter, you get a KB15 filter instead.

KB15 = mired shift value of -150

80A = -131

For 200 watt incadescent bulb an 80A plus a 82A = -152

For 100 watt incadescent bulb an 80A plus a 82B = -163

So this KB15 is fine all by itself for a 200 watt incadescent bulb, and is probably close enough for 100 watt bulb. But we go and buy a 80A but really get a KB15 because B&H says it is a 80A and we add the 82A for a 200 watt bulb and we get -170 which is too much compensation!

Same thing for taking a photograph of someone sitting in summer time shade. The appropriate filter should have a mired of 90 which is a 85C + 81, but when we order a 85c we really get a KR9 which is a 90 all by itself.

Why can't I find a 80D? It is because 80d=-56 and 82C=-45. All that is being manufactured is a KB6 which = -60. In the infinite wisdom of filter makers, the KB6 is being called the 82C, even though it is closer to the 80D. Why? Probably because the 82C is more popular - people are buying it to combine with their 80A to get -176 for use with 75 watt incadescent light bulbs. But their 80A is not -131, it is really a KB15=-150 and when combined with their 82c which is really a KB6=-60 they are getting a combined -210 instead of the desired -176.

These filter makers are trying to ruin us!

I say instead we should all switch to digital cameras with color white adjustments - which do not need filters at all. Then nobody will buy filters and we will ruin the filter makers rather than let them ruin us.

-- Howard Z (greenspun@howardz.com), February 21, 2001.

oooo, now I learned how to calculate it rather than use the inaccurate ruler method. I am so proud :)

Noon Daylight (daylight film) = 5500K. 1000000/5500=182 mireds.

EarlyAM or LatePM = 4300K. 1000000/4300=233 mireds. 182-233= -51 mired filter is needed. KB3+KB1.5=-45 or 82c=-45 or 80D=-56

Average Summer Shade = 8000k. 1000000/8000=125 mireds. 182-125= +57 mired filter is needed. KR6=+60 or 81EF=+52

75 watt incadescent = 2820k. 1000000/2820=355 mireds. 182-355= -173 mired filter is needed. KB18=-180 80A+82C=-176

100 watt incadescent = 2900k. 1000000/2900=345 mireds. 182-345= -163 mired filter is needed. KB15+KB1.5=-165 80A+82B=-163

200 watt incadescent = 2980k. 1000000/2980=335 mireds. 182-335= -153 mired filter is needed. KB15=-150 80A+82A=-152

The european method of KR and KB filters looks simpler than the Kodak Wratten system. Sometimes one Wratten filter perfectly takes the place of two KB filters, and sometimes the opposite happens.

-- Howard Z (greenspun@howardz.com), February 21, 2001.