Daft question. Anyone know the speed of Kodak P.25 plates?

[steven_e007]

I was inspired by the earlier post 'Are you using your plate camera?'

I haven't taken a picture with a plate camera for a while, but I won two 2 1/2 X 3 1/2" plate cameras on eBay about a year ago. Never did anything with them... until today ;)

One is a budget cameo camera. Reasonable condition but humble lens and shutter.

The other is an ICA - must be 1920s as it has the pentagram as the manufacturers logo. Annoyingly ICA put the name of their cameras on the strap - and of course the strap has been replaced, so the camera is now anonimous. I've found that catalogue of ICA cameras from 1925 by googling - and they made about 100 different cameras!!!

It is superficially like an Ideal, but without the rack for focussing or the frame finder. It is like a budget Ideal, maybe - but strangely it has a compur dial set shutter and a Tessar lens, so not so budget optics.

Anyway, to get to the point - I happen to have a fair collection of unexposed glass plates. Over the years I have established that most of them are now completely unusable (hardly suprising) but some of the slowest ones have survived. A packet of "Wellington" process plates from about 1920 were as good as new, not a trace of fog. I expect the speed of about 1/2 ISO probably helped :D

Today (or tommorrow) I thought I'd try out some Kodak P.25 plates from the 1950s in the ICA. I assume these will be slow, so may have something left in them?

Unfortunately I have no exposure details for these plates. I've tried googling, but "P.25" gets interpreted as a document page number, so mostly anything with the word "Kodak" is displayed. I can't track down any Kodak plate info :(

Now. Does anyone know an approx ISO rating for these?
OK, they might not be exactly as per spec anymore... :p
The original ISO rating might not be so relevent, but a rough starting point would be useful. I only have a few so can't afford to waste too many plates with experiments to determine speed.

[ntenny]

Do you have a box? Kodak seem usually to have printed an emulsion number on the packaging somewhere.

I googled "Kodak P.25" (with quotes) and found a few things that indicated that it's a high-contrast emulsion that seems mostly to have been used for scientific applications. Didn't find anything that hinted at the sensitivity, but it seems like it might have occupied sort of the same niche as Tech Pan.

-NT

[rthomas]

I'm not familiar with plate cameras in any way, but I have a bit of astronomy experience. Check old astrophotography books if you can find some. Plates were in use in astronomy far more recently than most other areas, and this might have been just that sort of emulsion.

[steven_e007]

Yes, I was a bit too clever with my google searches and included '+glass' and '+plate' in the thread, which seemed to do more harm than good.

The blurb on the box implies that the plates are intended for copying colour documents (being panchromatic).

So yes, fine grained and slow. Well, no point in wasting any more time googling, they might be fogged to death anyway - I'll take a wild guestimate at 8 ASA and I'll develop in dilute Rodinal, since they are probably very contrasty and foggy and we'll see what happens ;)

[steven_e007]

Well, as a subscript to my own post -

The plates were toast. Disappointing, but not unexpected. They might be 50 years old! I was hoping the slow speed might have saved them, but maybe 'twas the panchromatic bit wot did it :(

They were very foggy and I guess at well less than 1 ISO. 5 mins in Rodinal left them very thin, too, just a ghost of an image in the fog.

Good news was that the camera seemed light tight, everything worked well and the best image, whilst very foggy, was still razor sharp. The lens must be very good and the registration of the film / focussing planes spot on. Considering the lens is quite slow (f4.5) the image is quite bright on the focussing screen, too. Must be a very nice piece of fine ground glass.

I now know that the camera is an ICA Volta 150, must be from about 1926 as it has 'ICA' on the inside, but Zeiss Ikon on the lens and rear focussing screen door. Strange, though, the ICA logo on this camera is a 5 pointed star, which alledgedly is the early logo - it was changed later on to an Angel by the time of the merger, according to cameropedia. Odd... :confused:

Shame about the plates - but I do have a roll film holder for it :cool:

Inspired by the success of the camera with the plates, even if the plates themselves were fog bound - I'm off to stick a roll through it...