contact print exposure

[pingu666]

probably stupid question, but im going to try contact printing some paper negs onto paper,
the paper with dark grey messed up neg seems to be 6 stop nd on my light meter, and im planning to just stick them sandwhiched together under glass or milky perspex, and use the ceiling light and time it.

but how do i work out the exposure? as i dont have f4 + nd 6, as i dont have a lens to start with, would that be f0? the meter goes down to f1

the paper iso is 3, for what its worth

 

[joxby]

Do a test strip, as if you were making a print on an enlarger.

Use a full sheet of paper, cover it with card or something to block out the light and then shift it across in half inch steps at say 2 seconds per exposure.
develop the paper and choose the step and thus exposure time from that..



oh wait......."paper negs" ???

in fact reading your post again, i'm not certain i know what you're doing with what, so apologies if a test strip is not suitable

 

[pingu666]

yeah was hoping to work out a time to start with

 

[abdoujaparov]

I'm not sure either, but I do know f0 would be infinite, so it's not that

Presumably you have a figure for ISO3 paper and traditional negs - double that six times, that would be my starting point, assuming that ND6 is accurate.

 

[StephenM]

The brightness of the image equals the brightness of the object at an aperture of f/0.5 for a perfect lens, so you can take that as the starting point of the aperture scale.

Contact printing times depend on the brightness of the bulb and the distance. I'd start at around 10 seconds using light from my enlarger, and considerably less if I were using the room light in my darkroom. A test strip is the only way to allow for all the variables in your setup.