Wednesday, January 21, 2009
In which I actually do the math to see how Schneider’s new CTB’s measure up to Wratten filters
A couple of people commented on my previous piece, Schneider Optics Sings the Blues, to say that the CTB numbers of the Schneider filters don’t like up with the Wratten numbers they gave me. And they were right. Next time I’ll remember to do my homework.
I calculated the Mired value for each of the filters in question. Here’s what I came up with:
80B = 113 mireds
80C = 80 mireds
80D = 54 mireds
1/2 CTB = 80
1/4 CTB = 35
1/8 CTB = 18
This is my Wratten reference, and this is my CTB reference.
They don’t really line up neatly, but that’s okay. I’ve used the 80D with great success but there doesn’t seem to be a true equivalent in the Schneider Blues, and the closest I can get to the approximately 1/2 stop loss of the 80D seems to be the 1/4 CTB. If Chater Camera’s 80D filter is in on Friday I’ll do a comparison and see what a reasonable Schneider equivalent is.
Sorry about the errors. I’ll be less trusting in the future. 
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