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_speed#Current_system:_ISO

Best,

Doremus

[Drew Bedo]

A lot of good stuff here. Thanks everyone.

Now another few questions:

I understand that the spectral response is deep in the blue end, perhaps even near Ultra Violet. If that is so, is any exposure compensation requirted to account for that? If a scene is metered for ISO 100 film (and I make an exposure on that film) , then adjust for the nominal ISSO 1 speed of the dry plate , as discussed above,. . .is any further adjustment needed for the loss of half the spectrum?

I assume that best exposures will come at high sun angles (say, 10AM to 3PM), as the "golden hour" just at sun-up and sun-set will be strong in the red end.

Lenses to be used are "modern" , mid-1990s vintage from Rodenstock, Fuji and Nikon. Can I assume that these are corrected enough to avoid a blue shift in focus (getting really modern "APO" lenses is off the table).

[Tin Can]

Can't really help on that Drew

I bought about 4 boxes of the glass negs, shot a few and put them away for a while

Most likely I shoot more this summer, AFTER I see what you do!

Get in the water, they do work and I think you are covering most of the issues.

Be very gentle processing them, I use trays

[Two23]

A lot of good stuff here. Thanks everyone.

Now another few questions:

I understand that the spectral response is deep in the blue end, perhaps even near Ultra Violet. If that is so, is any exposure compensation requirted to account for that? If a scene is metered for ISO 100 film (and I make an exposure on that film) , then adjust for the nominal ISSO 1 speed of the dry plate , as discussed above,. . .is any further adjustment needed for the loss of half the spectrum?

.


Exposure can vary by a stop depending on cloud cover. Usually it seems to follow visible light close enough that a meter is a help.


Kent in SD

[Drew Bedo]

Processing: That's another one.

I am visually impaired and haven't processed any film since the mid 1990s. Setting up a dark room of any kind in our house is not practical . . .you would have to be here . . . .take my word for it. I have looked at that for years with multiple misses.

So part of this project will be to find a lab somewhere (anywhere) that will process the exposed plates.

I am still working on how to handle exposed plates when unloaded from film holders. Post processing storage is yet another issue to be delt with.

[Drew Bedo]

Exposure can vary by a stop depending on cloud cover. Usually it seems to follow visible light close enough that a meter is a help.


Kent in SD


A help? Good to know!

I intend to shoot duplicates of a scene with the dry plates and T-Max 100, so we will see how much "help" a meter is.

[Two23]

1.Setting up a dark room of any kind in our house is not practical.

2. So part of this project will be to find a lab somewhere (anywhere) that will process the exposed plates.

3. I am still working on how to handle exposed plates when unloaded from film holders.


1. They can be processed in a Stearman SP-445 with special available holder or in the SP-810 that doesn't need a holder. Two at a time in SP-445, four at a time in the SP-810. Load them in an interior bathroom or even closet at night. You can use red safe light with these. I originally process them in trays in my bathtub, using red light. Interior bathroom no windows and lights off in adjoining room.

2. Blue Moon in Portland does them.

3. In dark closet or interior bathroom at night with lights off in adjoining room, load them into 4x5 box. Put a piece of the glassine paper that comes with the plates between each and also the top one so they don't scratch the emulsion.


Kent in SD

[Jim Noel]

AS it says on the front of the box, the plates are orthochromatic. In other words, they are most sensitive to blue light and basically insensitive to red. In the middle of the day , from about 2 hours after sunrise to about 2 hours prior to sunset, expose as you do with panchromatic film using your regular meter. early and late in the day there is more red in the spectrum , thus less blue. Increase the exposure at least a stop in these cases. I have used so much Ortho filmin my life I can Pretty well judge the necessary adjustment. I began photography when most film was orthochromatic. A CD can act as a prism to show you approximately the %age of red in the spectrum. Simply bounce the light off it and look at the bands of color.
The instruction in the box concerning development are excellent. Follow them and don't vary until you get experienced with the product, at least 2 or 3 boxes. This is exactly the direction I give to my students who want to try the plates.

[Drew Bedo]

Jim: Thanks for that. Great info. and concise . . .without speculation; great. Glad to hear that time available for shooting is a bit extended beyond my gues. Thanks too for the experiential tip on extending exposures into the later afternoon.
The CD tip is new to me. I will give it a go. I will be using a changing tent for handling film and plates.

Processing; Yeah. Our house has one interior room. It is a small closet stuffed with hanging clothes. I have been told that it is off limits for wet chemistry or anything else photographic. Same goes for our one bathtub and the room it lives in.

Two23: Blue Moon it is then . . . . for as long as the money holds out!

[Tin Can]

The plates I have, have thin paper interleaving, be sure to save this for use again for outbound shipping to Blue Moon to avoid scratches.

I also think you could find an opaque container or a used SP-445 (they out of stock at Steerman) to be used in your dark tent

I say this because you already plan to load holders in a tent and a SP-445 of other DIY thing could be made and do one plate at a time, in the same tent

I realize the closet is out of bounds! For very good reasons

I do only one plate at a time in a 3 5X7 trays. Using the water stop tray twice, the second time for washing, very gently

I have a dedicated small plastic spatula, I use for for putting the plates in and out of the trays under red safe light

I have read in the distant past before electricity everywhere, windows were temporarily covered with rubylith for wet plate and maybe more


Also all wet plate users make a portable tiny darkroom


https://www.largeformatphotography.info/forum/showthread.php?99161-Material-to-block-windows-of-portable-darkroom-boxes-for-wet-plate-collodion&p=980254&viewfull=1#post980254

[Kiwi7475]

The plates I have, have thin paper interleaving, be sure to save this for use again for outbound shipping to Blue Moon to avoid scratches.

I also think you could find an opaque container or a used SP-445 (they out of stock at Steerman) to be used in your dark tent

I say this because you already plan to load holders in a tent and a SP-445 of other DIY thing could be made and do one plate at a time, in the same tent

I realize the closet is out of bounds! For very good reasons

I do only one plate at a time in a 3 5X7 trays. Using the water stop tray twice, the second time for washing, very gently

I have a dedicated small plastic spatula, I use for for putting the plates in and out of the trays under red safe light

I have read in the distant past before electricity everywhere, windows were temporarily covered with rubylith for wet plate and maybe more


Also all wet plate users make a portable tiny darkroom


https://www.largeformatphotography.info/forum/showthread.php?99161-Material-to-block-windows-of-portable-darkroom-boxes-for-wet-plate-collodion&p=980254&viewfull=1#post980254

Only the SP-445 rev 3 is out. Rev 4 is available.

https://shop.stearmanpress.com/collections/photography/products/rev-4-sp-445-compact-4x5-film-processing-system

(No affiliation)

[Doremus Scudder]

... If that is so, is any exposure compensation required to account for that? If a scene is metered for ISO 100 film (and I make an exposure on that film) , then adjust for the nominal ISO 1 speed of the dry plate , as discussed above,. . .is any further adjustment needed for the loss of half the spectrum?
... Can I assume that these are corrected enough to avoid a blue shift in focus (getting really modern "APO" lenses is off the table).

Keep notes shooting and bracket on the side of overexposure a stop for the first shot or two. When you find the best E.I. for your plates, you can adjust your meter accordingly.

Any modern lens is well color corrected into the blue. As far as UV goes: most lenses don't transmit light that is very far into the UV, it takes special glass to do that. It doesn't matter if your plates are sensitive to those wavelengths or not; they won't see them since they won't make it through the lens. Focusing should be fine. The "old timers" didn't bother with focus compensation...

Doremus

[Jimi]

As an aside, does anyone know if rubylith (or some equivalent material) is available in Europe? I'd like to get some to cover a small window, but I don't even know where to start looking.

[RLangham]

When you solve Sunny Sixteen for a given film speed, it remains accurate down to ASA 1 and below. (With the exception of Doremus Scudder's post above, I've never actually seen speeds below ASA 1 given as an ASA number. When such speeds were common there were other scales.)

Given f/16, shutter speed = 1 / rated film speed. That is to say, f/16 (on any lens at any time, barring filters, bad transmission of the lens optics and bellow factor) is the point at which the film speed is equal to the reciprocal of the shutter speed, under typical sunny conditions.

Take the reciprocal of the film's original rated speed, or "box speed," 2, and you do indeed have 1/2 = 1/2 second. It's not necessary to count by stops when you know that the math works consistently. F/16th is just a convenient constant where the math works out, but believe me, it does, so I trust it implicitly.

The way I would expose those plates, if I were dying to expose them at box speed, would probably be f/11 at 1/5th or f/16 at 1/2, but that's just me. Under most conditions, I would probably actually rate it @ ASA 1, giving an exposure of, say, f/16 at 1 second. Shooting half box speed gives you a valuable margin for error and makes printing/scanning easier in most cases. In Mississippi summer sunlight half box speed sometimes burns the neg a bit, and in the summer I shoot at box speed.

For more convenient shooting, J. Lane does have Speed Plates rated @ ASA 25, which are what I have. Now I just need to figure out how to tray develop without a safelight, or else order a safelight!

[Two23]

When you solve Sunny Sixteen for a given film speed, it remains accurate down to ASA 1 and below. (With the exception of Doremus Scudder's post above, I've never actually seen speeds below ASA 1 given as an ASA number. When such speeds were common there were other scales.)

Given f/16, shutter speed = 1 / rated film speed. That is to say, f/16 (on any lens at any time, barring filters, bad transmission of the lens optics and bellow factor) is the point at which the film speed is equal to the reciprocal of the shutter speed, under typical sunny conditions.



For more convenient shooting, J. Lane does have Speed Plates rated @ ASA 25, which are what I have. Now I just need to figure out how to tray develop without a safelight, or else order a safelight!


I've processed the ISO 25 plates under a very faint, indirect red light and things went well. As for "Sunny 16," right now on the Northern Plains it's "Sunny 22."


Kent in SD

[RLangham]

I've processed the ISO 25 plates under a very faint, indirect red light and things went well. As for "Sunny 16," right now on the Northern Plains it's "Sunny 22."


Kent in SD

I need to just get one. I've wondered if I can very indirectly light my darkroom with an old "infrared" heater floodlamp I used for a lizard cage back in the day... I'd worry about it having blue or yellow in its spectrum and fouling things up, though. J. Lane himself told me that it would be a long shot, but that I should try it.

[Drew Bedo]

I've processed the ISO 25 plates under a very faint, indirect red light and things went well. As for "Sunny 16," right now on the Northern Plains it's "Sunny 22."


Kent in SD

ISO 25 dry plates? Can you direct me to a source?

[Drew Bedo]

When you solve Sunny Sixteen for a given film speed, it remains accurate down to ASA 1 and below. (With the exception of Doremus Scudder's post above, I've never actually seen speeds below ASA 1 given as an ASA number. When such speeds were common there were other scales.)



Thanks, and the rest of your post is an excellent explanation of the Sunny sixteen rule.

ISO below 1? Fifteen years ago, I took a Daguerreotype workshop with Jerry Spagnoli at the Photogrpaher's Formulary in Montana. The exposures were something like 30 seconds wide open at f/5.6 in sun or overcast. I started counting backwards and came up with an equivalent "ISO" on the order of 0.005 or something equally useless . . .but it was interesting to do. The sensitized Dag plates were so blue sensitive that UV penetrating the overcast was effective in exposing the plates. . . .so any direct comparison to film was not useful.

[BradS]

......right now on the Northern Plains it's "Sunny 22."


Kent in SD

:) :)

Brad (who grew up in Minnesota)

[Daniel Unkefer]

ISO 25 dry plates? Can you direct me to a source?

Contact Jason. Or buy from photo dealers, like this one:

https://www.freestylephoto.biz/181450-J.-Lane-Pre-Coated-BandW-Glass-Speed-Plates-ISO-25-4x5-10-Pack

[RLangham]

Contact Jason. Or buy from photo dealers, like this one:

https://www.freestylephoto.biz/181450-J.-Lane-Pre-Coated-BandW-Glass-Speed-Plates-ISO-25-4x5-10-Pack

He has an Etsy store and he communicates very cordially and informatively on there...

[RLangham]

Thanks, and the rest of your post is an excellent explanation of the Sunny sixteen rule.

ISO below 1? Fifteen years ago, I took a Daguerreotype workshop with Jerry Spagnoli at the Photogrpaher's Formulary in Montana. The exposures were something like 30 seconds wide open at f/5.6 in sun or overcast. I started counting backwards and came up with an equivalent "ISO" on the order of 0.005 or something equally useless . . .but it was interesting to do. The sensitized Dag plates were so blue sensitive that UV penetrating the overcast was effective in exposing the plates. . . .so any direct comparison to film was not useful.

Yes, I wouldn't want to get my portrait taken with a Dag!