How to take exposure readings for shooting with ISO 0 - 1?

[njrfoto]

Hi all,

Just a quick question regarding taking efficient and correct exposure readings for shooting with ISO 0 - 1 for making portraiture tintypes.

I have a Sekonic L-358 meter for my studio portraiture lighting but the Sekonic only goes down to ISO 3, which isnt low enough when the sensitivity of a tintype is ISO 0, or ISO 1 at best, so my question is simple; how can I take precise and useable readings using a meter (or exposure calculator) to get the right exposure settings for my camera and to set the required power output for the lights lighting the sitter?

If any one who has any experience making tintypes in a studio setting, who has already done lots of trials and sussed out the guess work, could send me in the right direction of discovering the best practice of how to get the correct exposure for studio tintype portraiture lighting that would be amazing!

All the best,

Nathan

 

[MattKing]

I'd suggest re-posting this in the Alternative Processes sub-forum, with the word tintype added to the thread title.

 

[Doremus Scudder]

Simply meter at another ISO setting and then extrapolate. Example: ISO 8 reading = f/8 at 1/2 second ISO 4 would be one stop more exposure, ISO 2 would be two stops more, ISO 1 would be three stops more.

The ISO scale is in 1/3-stop increments. The range most of us are familiar with for modern films can simply be extended for lower values.

Example: (in descending order)

400 - 320 - 250 - 200 - 160 - 125 - 100 - 80 - 64 - 50 - 40 - 32 - 25 - 20 - 16 - 12.5 - 10

Now just divide these by 10 to keep going...

40 - 32 - 25 - 20 - 16 - 12.5 - 10 - 8 - 6.4 - 5 - 4 - 3.2 - 2.5 - 2 - 1.6 - 1.25 - 1

I've highlighted in bold the one-stop increments I used in my first example. Long story short: take a reading at ISO 8 and open three stops (or change shutter speed accordingly) to get ISO 1. You could just as easily meter at ISO 4 and open two stops if your meter will do that.

Best,

Doremus

 

[Xmas]

I'd bracket as well...

 

[removed account4]

you do a reading at the lowest iso your light meter has,
and keep halving it until you get to 1
i do this sometimes when shooting paper or tin ( SG )
i read at 25 so i half it to 12 , then to 6 then to 3 then to 1-ish
so it is 3 stops difference, as a starting point.

doremus' explanaition seems a bit more accurate !

good luck with the tin !

 

[MartinCrabtree]

My Weston Master II goes down to .3. Would using it at .7 (I usually underrate ISO by 1/3) be the same as ISO 1? Just curious I've no idea what I would do to need this info but would like to know anyway.

Thanks.

 

[ME Super]

Now just divide these by 10 to keep going...

40 - 32 - 25 - 20 - 16 - 12.5 - 10 - 8 - 6.4 - 5 - 4 - 3.2 - 2.5 - 2 - 1.6 - 1.25 - 1

I've highlighted in bold the one-stop increments I used in my first example. Long story short: take a reading at ISO 8 and open three stops (or change shutter speed accordingly) to get ISO 1. You could just as easily meter at ISO 4 and open two stops if your meter will do that.

Best,

Doremus

If ISO is a logarithmic scale (100 is one stop faster than 50 and one stop slower than 200), how would one ever get to ISO zero? One stop slower than ISO 1 would be ISO 0.5, another stop slower would be ISO 0.25, and another stop slower would be ISO 0.125. You'd never actually ever get to zero! I would assume that ISO zero would be absolutely no sensitivity to light whatsoever.

 

[DWThomas]

A similar problem arises with dedicated light meters and pinhole photography, where a typical meter can't show a reading for f/325 or whatever. One common method to deal with that is to standardize on a stop, typically f/22 and generate a table (a spreadsheet is handy) to relate shutter speed reading for f/22 to that needed for f/325 (or whatever). One pinhole designer package can produce a multiplier to make such a table -- or even generate a simple spreadsheet.

One could take the same approach for ISO and build a table -- one could even have multiple columns to cover several ISOs and/or brackets. I find for pinholing I can get a large range of data on a less-than-index-card sized card to stick in a shirt pocket.

After all that windy lead-in, a number of smartphone apps provide a much broader range of values than typical dedicated hardware. I just looked at "(Pocket) Light Meter" on my iPhone and it accepts ISOs down to 0.8 (and up to 104800 !!!) I have no idea how well it functions in actual use at such extremes, although presumably it's a trivial issue of math done to light readings taken in relatively "normal" illumination.

 

[Maris]

I find doing mental arithmetic in stops a bit challenging. When I was using old infrared film that had lost sensitivity and had to be exposed at EI = 0.07 I just set EI = 7 on the meter dial and increased the suggested exposure time by 100X. How many stops is that? Still don't know.

 

[Newt_on_Swings]

I think for stuff like this it doesn't matter too much if you over expose. Just use a ton of light and see. It's kinda similar to shooting paper and litho film, it's good to just test it and get a feel for it with some rough brackets.

 

[Prof_Pixel]

If ISO is a logarithmic scale (100 is one stop faster than 50 and one stop slower than 200), how would one ever get to ISO zero? One stop slower than ISO 1 would be ISO 0.5, another stop slower would be ISO 0.25, and another stop slower would be ISO 0.125. You'd never actually ever get to zero! I would assume that ISO zero would be absolutely no sensitivity to light whatsoever.

ISO 0 is the speed of your dark slide

 

[Megan Ferguson]

Look at that the question I was about to post, has already been recently posted and a great answer, thanks Doremus. My only difference was not Tintypes but for Dry Glass Negatives. My Sekonic goes down to ISO 8 so I just need to stop down 3 stops on either the shutter speed (most likely) or the aperature.

 

[wiltw]

ISO 0 is the speed of your dark slide

No wonder I get no photo when I leave in the darkslide, I'm not exposing it nearly enough for its sensitivity, and certainly not correcting at all for reciprocity failure!

 

[removed account4]

an easy way to calculate the exposure isn't necessarily by counting down how many stops to f1 if the meter doesn't go down that far
but to use sunny 16 for exposures. iso 1 a--- 1 second at f16 in bright light ...
a 35mm film box gives a pictogram for the light-difference for open shade it works the same way. using a meter
to help educate for different lighting conditions is good, taking notes maybe, and judging the edge and harshness of
a shadow on one's hand too .. overcast, bright sun, afternoon sun ( raking ) mixed light ( bright light dark shade ) open shade &c
often times a meter isn't as helpful as one would hope when exposing liquid emulsions, home made emulsions and enlarging paper &c ..
in the end experience in judging light and different kinds of light is worth more than the most expensive of light meters especially when not shooting film but the other stuff ..