Topic: Rollei Retro 80S reciprocity failure

[Urban Hafner]

Now that I'm done converting my Kodak Brownie 127 into a pinhole camera (thanks Diane for the camera and Mauricio for the inspiration with your Cresta conversion) I've ordered a few rolls of Rollei Retro 80S in 127 format to test it out.

Unfortunately I wasn't able to find much information on the reciprocity failure of that film. Someone of Flickr (http://www.flickr.com/photos/22120428@N05/4868805768/#) just used the reciprocity information for Pan F+ and seemed to get good results with it. But even for that film I wasn't able to find good information on the interwebs (though http://photo.net/black-and-white-photo-film-processing-forum/00KWkF suggests "Adjusted Exp. Time = (Measured Exp. Time)^1.49" as a good approximation).

So my question is: Has anybody tried that film for long exposures? If not are there any rules of thumb you use to approximate the reciprocity failure/exposure time when using a pinhole camera?

Urban

[astrobeck]

For film:
I normally just increase the time to half as much again when I'm doing pinhole.

For example, if you determine your exposure needs to be 4 seconds, then add 2 seconds to it and expose for 6 seconds.
If the exposure is going to be 10 seconds, expose for 15 and so on.

Once I get to exposures that are 5 minutes or longer I usually double the times.

For paper I just double the times since it's so slow anyway.

This is my seat of the pants method, and so far it has worked fairly well.
Good luck and happy pin-holing! 

[Urban Hafner]

Thanks Becky. That sound easy enough. Let's see what I can get with that rule of thumb next weekend in Torino!

[edthened]

Och Urban, hav a wee lookie heer http://www.mrpinhole.com/exposure.php , an print oot yer findins fir yer camera bag, so ther   

[Urban Hafner]

Thanks Ed, I had forgotten about that page.

[Urban Hafner]

Just found a nice iPhone App that calculates long exposures and even takes reciprocity failure into account: http://leborddelapiscine.blogspot.fr/p/pinhole-assist.html

That seems to be a better solution than printing out a spread sheet for a geek like me

Urban

[LT]

the problem with that, Urban, is that each film has very different reciprocity characteristics.  Compare Acros with no failure until about 2 mins of exposure, and HP5+ required a tripling of exposure time at 20 minutes.  You'll end up with wildly different results using only one reciprocity system to calculate ...

[Urban Hafner]

That's why there's several curves that come with the app. And if you want to you can even add your own.

[LT]

good luck with it then - let us know how you get on with it.


I took a look on the website and there didn't seem to be any film specific curves fro black and white films ... looks like you'll need to do some testing for each one you use.

[Urban Hafner]

The app comes with ~ 15 curves. HP5+, Tmax, etc. But of course Rollei Retro 80S isn't one of them so I guess I'll just use one of the curves for 'traditional' emulsions (like the Ilford one).

[Francois]

One way to figure it out is to get the curves for multiple emulsions and compare their profiles. Opt for the closest match...

[Urban Hafner]

Thanks Francois. I won't be able to do that today so I'll just wing it for the first roll. But I guess I'll come back to it later.