CTO in Place of 85B Filter

E76 · Jul 5, 2009

I have quarter, half, and full CTO gels along with bunch of tungsten slide film I would like to use outdoors, but no 85B filter. Is it possible to use a CTO in place of an 85B? What kind of results can I expect? It seems like it might work, but I cannot be sure.

Thanks.

JBrunner · Jul 5, 2009

Color wise the CTO will work fine. Optically it will depend on how good the gel is and where you put can it.

E76 · Jul 5, 2009

Any idea as to what the required exposure compensation with any of the CTO filters would be? So far I have found conflicting sources of information stating that a full CTO is identical to an 85B (+3/4 stop) and others saying a full CTO is actually warmer than an 85B, meaning the correction would be closer to +1 stop, if not more. 1/3 of a stop can make a big difference with slides!

AgX · Jul 5, 2009

From the curves I've got I deduce that a full CTO is identical in filtration to a 85B (a 1/2 CTO would be a 85C).

Peter Markowski · Jul 5, 2009

Hold a ambient meter under the gel then without, and note the difference for your stop compensation.

DanielStone · Jul 5, 2009

just meter through the gel before you expose, making sure to put the gel back over the lens though, as i inadvertently didn't yesterday, ooops. it'll be alright, slides will be a little bluer than i'd like, but the kodachrome should manage alright

-dan

E76 · Jul 5, 2009

DanielStone said:
just meter through the gel before you expose, making sure to put the gel back over the lens though, as i inadvertently didn't yesterday, ooops.

That's exactly why I don't want to do that.

Thanks for all the help guys!

CTO in Place of 85B Filter

E76

JBrunner

Moderator

E76

AgX

Peter Markowski

DanielStone

E76

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