Camera as Extinction Meter?
I recently read in the Kodak Master Photoguide from 1951, that the camera can be used as an extinction meter.
By focusing on a dark object and stopping down until only slight detail remains, and consulting a chart, an accurate exposure can be made. The chart shows times for Kodak Super-XX, which shows an index of 100, that would be about ISO 200, in today's scale. From what I can find about that film, the reciprocity issues normally associated with longer exposures were virtually nonexistent.
Does anyone have any experience with this? Would only calculating the exposure from the table for your film speed and adding for reciprocity provide a correct exposure? I tried it on my digital, and got decent results.
I just wanted to see what folks have experienced before using up some film. Thanks!
Very interesting question if I understood correctly. I think you are talking about SLRs , you look from the visor and find the darkest point , set the aperture ring to a darkest visible point for the shadow and than ? Where can we find such a chart ?
Can you attach a scan ? What happens to highlights ?
The Kodak book mentions using ground glass focusing. According to the book, you focus with darkest important part in the center, and stop down until detail is just barely visible.
The chart in the book is for super-XX, and shows in order, darkest detail seen at, then exposure time and f/stop, as follows;
at f/8 expose 32 seconds at f/16
at f/16 expose 8 seconds at f/16
at f/32 expose 2 seconds at f/16
at f/64 expose 1/2 second at f/16
Other exposures and values can be calculated from there, IE at f/11 expose for 16 seconds at f/16.
The book was Kodak's Master Photoguide, printed in 1951. I tried doing that with my digital, and got decent results. The correct times may need some adjustment for the newer ISO standards, as opposed to Kodak's index of 100 for film speed. Of course, reciprocity may be an issue. With the highlights, I would assume that if the exposure is longer than, say, 8 seconds, then development change would be needed.
Thank you for your answers.
Very interesting, I will give it a go next time my self.
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This is a "rough n ready" method at best. With the current fashion of using a black T-shirt in lieu of a proper dark cloth I'd place no confidence in the results. Even using a real dark cloth, the results will depend on how well your eyeballs have adapted to the dark.
A careful worker could get decent results, but there's that word, "careful".
My concern is the reciprocity. From what little I can find, Super-XX had almost 0 reciprocity effect. Knowing the reciprocity characteristics of the old film would help target a proper exposure for the film I'm using now.
Super-xx was rated at 100, that's before the big switch, though. So the first part is calculating the speed difference, whether or not to use the stated speed or the post-change speed. After that is the reciprocity. I don't see why it wouldn't work, and do so quite reliably, once those 2 bits were known.
Practicing with my digital camera may provide some help dialing in a chart for today's speeds, as settings are controllable and the feedback is quick, although I'd like to hear from someone who's tried it rather than resort to my other camera.
I use a thick brown blanket right now, and it still takes some time to get focus spot on, so add a couple more minutes deciphering detail and values, and it could be time consuming. With practice and the right knowledge, though, it may be worth the effort. Especially when my meter is my digital camera!
I've read of this method, but never used it. I have used an old exctintion-type "meter" and can tell you this: get a proper exposure meter. A used LunaPro can be had for $50 or so. How many sheets of film does that represent?
Originally Posted by kintatsu
Actually, I use both the Gossen Sixtomat and the Sixtino, but they aren't spot meters. They both work incredibly well, so it's not an issue with no meter. Between the spot meter on my 7D and my 2 handheld meters, I'm ok, just curious about this and anyone's experience. Mightn't this be handy, with some modification and calculations, as a learning tool, perhaps? Even as a bit of an experiment in exposure calculation and lighting awareness, something can be gained.
Based on your comment about having used an extinction meter, I take it they're slightly more than useless in most situations.
I didn't mean to come across as someone who's just looking for the cheap way out, or something. I love learning something every chance I get, and learning the way things used to be done, helps bring home an awareness of the work that the old masters actually did. I even try to cook the old ways my folks made things, and teach my daughter some of it. Using old techniques and tools keeps our past richly alive for those who come after us to share in it.
BTW- $50 is about 40 sheets of film, so yeah the potential for throwing money into a bonfire could be quite high!