Kodak E100 reciprocity failure data
Something I wasn't able to figure in Kodak E100G/V/.. datasheets:
what is the reciprocity failure dependency for this particular emulsions ? Any hints where to find such (likey to be graph showing exposure extensions needed to compensate as a functtion of time exposure).
The datasheets claim that up to 1 sec (or was it 10 sec ?) no correction is necessary, however do not mention what is happening above these times.
Long exposures are of particular interest to me cause night scenery if one of my particular interests.
I haven't tried this particular film, I'm mainly a Fuji guy, but according to Kodak's website no filter compensation or exposure compensation is necessary for exposures from 1/10,000 second to 10 seconds.
I primarily use either Fuji Provia F100 or Velvia F100 for nighttime exposures. With Velvia F100, no filter compensation or exposure compensation is necessary for exposures up to 1 minute; with the Provia F100 the range is up 128 seconds. These numbers are all according to Fuji, but my experience is that they are accurate.
Yes, that is.
10 sec is said not to require any reciprocity failure-wise precautions, but longer then 10 sec exposures aren't that rare in night scenic photography, especially with LF. I wonder why Kodak doesn't mention this data...
Well, I have a large stock of E100S/G/V stuff that needed to be disposed (i.e. shot out) prior to switching back to Fuji (hopefully Velvia 100 (non F) will then be readily available..) :-), albeit just a quick check of my first four properly exposed E100S slides reveals that this stuff isn't bad at all either....
I'm not sure where you would get your film from in Israel, but Velvia 100 is pretty well available here. I only use the F100 for nighttime work, I'm not fond of it for my regular work - there I use either the 50 or 100.
Yeah Robert, I don't expect from you to be aware where it can be bought in Israel :-), its OK.
I know it is available in US, but for some reason it has yet appeared in my country (it may take up to half year for a new Fuji ilm stuff to reach our corner while Kodak is here almost instantly). I was looking for a good deals for a Fuji 100 stocks on Ebay, nothing so far (unlike even fresh Kodak - lots of E100S/G/V can be picked considerably cheaper then the new (as much as twice))
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The Ektachrome 100 emulsions were mostly rated for a Schwarzschild exponent of about .95 to .97 (where 1.0 is no reciprocity failure) a few years ago by Robert Reeves in Wide-Field Astrophotography. The emulsions have been modified since, but I expect the reciprocity characteristics to be about the same.
For practical use, plug the Schwarzschild exponent into Michael Covington's modified Schwarzschild formula where t= time in seconds and 'p' is the Schwarzschild exponent. The value for 't' on the right of the equation should be your meter's indicated exposure time in seconds.
Corrected exposure time = ((t+1)^(1/p))-1
See these threads for more discussion that you might find interesting:
Wow, thank Lee, will have to go over all of these...
However, still, somehow manufacturers own data would certainly provde the most reliable info, too bad Kodak didn't consider that for some reason ...
I don't know why Kodak has decided to drop the compensation curve graphs from their reciprocity information. But you can graph your own curve or make up a table from the Covington-Schwarzschild formula using a computer spreadsheet. The thread on the Gainer method of reciprocity failure compensation will provide some graphs as well, all you'd need is to determine a factor for a specific film that works for you.
There are several astrophotography books that lay out methods for determining a Schwarzschild exponent for a particular film. I posted the info on those books in a thread I mentioned earlier: