Fumbling towards a correct exposure for Dry Plates

[Drew Bedo]

Please help me think this through:

I have splurged on a box of 4x5 glass plates from Lane. They say these plates are sensitized to about ISO 2. I am trying to get a handle on what I can do for an initial set of test exposures.

If I assume "Sunny sixteen" conditions, I would expose an ISO 100 film at 1/100 sec and f/16.

By counting on my fingers, ISO 2 is something like six stops slower than ISO 100. Figuring back from f/16 to my widest available aperture of f/5.6 and slowing down to 1/10 sec I ran out of fingers.

Do I have that right?

Are these equivilant exposures under bright conditions?

f/16 at 1/100 sec
f/5.6 at 1/10 sec

[Tin Can]

I think you are correct, but I would add one more stop and don't forget bellows factor

[jim_jm]

I found that I got better results by rating Jason's "regular" plates at ISO 1, rather than 2. This was with an older batch of plates from around a year ago, but they seemed to benefit from a bit more exposure.
Using sunny-16 for midday landscape and building shots, that would mean 1 sec @ f16, 1/2 sec at f11, 1/4 sec at f8, or 1/8 sec @ f5.6. With a shutter that has speeds like 1/5, 1/10, etc. I just use the closest speed, usually erring towards overexposure.

If you're shooting indoors or in dimmer light where you have to meter, remember to compensate for reciprocity if your speed is longer than a few seconds. I asked Jason for his reciprocity recommendations last year, but can't remember his specific suggestions right now.

[Two23]

Wouldn't Sunny 16 be 1/2s and f16? What am I missing here? I've been shooting them for the past year & half and find my Minolta meter works reasonably well as a starting point, but better exposure comes with experience in reading the light.

"Sunny 16" is f16 and 1 over the ISO, so f16 and 1/2s.


Kent in SD

[Drew Bedo]

I intend to shoot with an ISO 100 B&W film, then shoot the same composition with the lane dry plates. I do not intend to do much in the way of multi-second exposures. I'll get an idea of the spectral response as well.

[Two23]

I intend to shoot with an ISO 100 B&W film, then shoot the same composition with the lane dry plates. I do not intend to do much in the way of multi-second exposures. I'll get an idea of the spectral response as well.

OK. but you'll have to shoot the plate five stops slower (more exposure) than the film. And, remember that the plates are ortho--only sensitive to blue and UV light. I don't know of any meters that are right on the money with that.


Kent in SD

[Drew Bedo]

OK. but you'll have to shoot the plate five stops slower (more exposure) than the film. And, remember that the plates are ortho--only sensitive to blue and UV light. I don't know of any meters that are right on the money with that.


Kent in SD

Thanks for that.

You are right on every count . . .except maybe the five stops. If I rate the plates at 1 or two as some recommend, the difference will be more like 7 or 8 stops if my finger counting is right. . . .and that is a part of the exercise. With ten plates in the box, multiple bracket shots will be made.

The T-Max cover shots are intended to help me understand the properties of the plates; exposure, dynamic range, spectral sensitivity and so on. With some confidence in using this medium, spending money on 8x10 plates will make more sense.

[BradS]

100 = 2^6.644
So, ASA100 is about 7 stops faster than ASA1 and about 6 stops faster than ASA2.

[Two23]

The older plates were slower. The newer ones seem closer to rated speed. Keep in mind the wild card is they are only sensitive to blue and UV light.

I will add, don't use any filters.


Kent in SD

[Doremus Scudder]

The ISO scale goes in approximate third-stop increments. Here's the list from 100 down (I've indicated whole stops going down from ISO 100 in bold), just count the total difference between extremes and divide by three or count whole and third stops:

ISO 100 - 80 - 64 - 50 - 40 - 32 - 25 - 20 - 16 - 12 - 10 - 8 - 6 - 5 - 4 - 3 - 2.5 - 2 - 1.6 - 1.2 - 1 - 0.8

So, ISO 100 to 2 = 5 2/3 stops. ISO 100 to 1 = 6 2/3 stops. Increasing exposure by 6 and 7 stops respectively gives you just 1/3-stop overexposure; a good safety factor IMO.

Reference: https://en.wikipedia.org/wiki/Film_s...nt_system:_ISO

Best,

Doremus