Darkroom Exposure Times for which Reciprocity Holds?

[neil poulsen]

Out of curiosity, I'm wondering for what range of enlarger exposure times, say for Ilford Warmtone, for which reciprocity continues to hold?

[ic-racer]

Out of curiosity, I'm wondering for what range of enlarger exposure times, say for Ilford Warmtone, for which reciprocity continues to hold?

I can't say the range because I usually don't care. I usually make new test prints when I change paper sizes etc. Because, by the time it takes me to calculate the height change, calculate magnification change, consider reciprocity failure, I can have a new test strip processing

[bob carnie]

I think when I get over 20- 30 seconds I start fretting about reciprocity.

I use 250 w bulbs in my condenser enlargers to avoid exposures longer than 30 seconds. Sometimes I lose as the neg is too dense.

My other enlargers are a Durst 2000 w and a Deveere 11 x14 with tons of light power so I can stay under my 30 second warning point.

btw 250w in a omega condenser is not spec , and the bulbs do not last as long, but I have been doing this for 24 years now.

[neil poulsen]

Exactly the reason I was asking . . .

I have a Metrolux II with the remote sensor. (I currently use the Zone VI compensating enlarger timer.) The idea with the Merolux II is to take a reading with the remote sensor after changing the size of the print in order to predict the new exposure time. But I'm thinking that, this works only if reciprocity is preserved.

With that said, I suppose it's possible that this unit takes reciprocity failure into consideration, kind of like the Zone VI compensating developing timer. But, that seems a bit far-fetched.

[neil poulsen]

Thinking about it, the Zone VI developing timer isn't accommodating for reciprocity failure; it's accommodating for change in temperature, which is different.

[Jac@stafford.net]

I do what ic-racer does.

However, a little factoid: Several exposures on the same paper is less exposure than the sum of exposures.

[John Olsen]

I use scaling graphs to estimate exposure changes as I move to larger prints. I'm always a little amazed that exposures up to 60 s seem not to have reciprocity problems. (This is for Ilford MGIV) My main concern is flexing of the negative when it's under the lamp so long. Since my 4x5 carrier stretches the negative, mainly this is a concern for the smaller negatives.