Seeking help from sensitometry gurus

[George Papantoniou]

I'm preparing to shoot the (almost) 100 year-old 9x12cm plates I have (using the adapter generously lended to me by my cousin Ole ) and I need some advice in order to save most of them for good use and not spend them all just experimenting finding the correct way to expose them.

I was thinking to work with studio flash, but I have a doubt whether those old plates will react to such short exposure times (1/500th of a second) or if the reciprocity law failure will make them insensitive to flashlight... They're ortho plates made by Gevaert and Lumiere in Belgium and France respectively in the beginnings of the 20th century, still sealed in their original packages. Their sensitivity to continuous lighting now must be about 3-6 ASA. If the same applies for short exposures, it'll work. Otherwise, I'll have to find a way to light my subjects with Tungsten lamps... Would you advise me to spend a couple of them (I don't have so many, unfortunately) for testing with flash lighting, or just drop it and try with continuous lighting right away ?

 

[Robert Hall]

Cut one in half and develop it to see what kind of fog you will be getting.

Take the other half and put it under an enlarging light with a step wedge on it. Set the lamps brightness to a 4 ev reading on a white card. See what you get. This should give you an idea if they might even work.

Anyone care to add to or correct my idea?

 

[don sigl]

Load one plate in the camera, set up your strobe lights on your subject, take a meter reading at ASA 3, turn off the modeling lights, set your shutter to B or T, turn off the studio lights, open the shutter, slide the darkslide out and pop the flash, slide the dark slide in 1/2" and pop the flash. Continue the process, increasing by 1 stop each exposure. Process and see if you have anything. Adjust if necessary and shoot the rest.

 

[epatsellis]

Don,
I'm sure you meant, 1 pop, 2 pops, 4 pops, 8 pops, etc. total exposure(or in this case it'd be 1, then 1(total 2 on first exposed piece), 2(total 4 on first exposed piece), 4, etc....)


erie

 

[don sigl]

Erie:

You are correct. It is what I meant by "Increasing by 1 stop each exposure".

 

[gainer]

Kodak makes or used to make a handy circular step wedge for finding proper print exposure. Its total density range is 1.3 or so, but the sections are labeled in seconds when the overall exposure is 1 minute. You could contact print this exposure guide on any film or plate 4x5 inches or more and could trim it to fit 9x12 cm. Put it in the camera, give a 1 minute exposure, develop and see if one of the segments is about right.

Problem: I can't tell you where to get one. Maybe another APUGer can.

 

[MattKing]

Kodak makes or used to make a handy circular step wedge for finding proper print exposure. Its total density range is 1.3 or so, but the sections are labeled in seconds when the overall exposure is 1 minute. You could contact print this exposure guide on any film or plate 4x5 inches or more and could trim it to fit 9x12 cm. Put it in the camera, give a 1 minute exposure, develop and see if one of the segments is about right.

Problem: I can't tell you where to get one. Maybe another APUGer can.

I'd try here:

http://www.bhphotovideo.com/bnh/controller/home?A=details&Q=&is=REG&O=productlist&sku=28929

Matt

 

[George Papantoniou]

Thanks guys, you gave me some good ideas to help me save some plates.

Robert, I forgot to mention that they're made of glass. I am sure there is a lot of fog, though.

I guess I'll try Don's idea so that I will test the ability of the plates to record short exposures. I'll keep you informed of the results (in a few weeks time...).