Tag Archives: Schwarzschild

Reciprocity for Android

Updated!

I wrote an Android App last year that I felt I needed myself when I was out and about in the field photographing long exposures. I’m happy that it has now more than 2000 active installs and I have taken all comments into account and released an updated version.
As you are well aware of, most films do need correction of the exposure time for reciprocity failure to avoid underexposing your negatives for exposure times of over a few seconds. This really gets important for night photography, when using filters and for Large Format or pinhole photography. All information is contained in the App so no data connection is needed when you’re on a photo shoot abroad, on top of a mountain or in the deep countryside without any connectivity.
I do not miss the folder with printed and weather-beaten PDFs with tables of exposure correction information for the different films that I had to rely on before. 🙂

The Reciprocity App has the following features:

  • Easy to use and usable on Android devices of most sizes.
  • Lots of B&W, colour and slide film included in the App, and this list is growing with every update.
  • Include filter factors in the exposure time calculation.
  • Include bellows extension in the exposure time calculation.
  • Built-in timer to use the calculated exposure.

See the screenshots below.

Ease of use:

Growing number of films supported:

Details about the calculation:

Built-in timer:

Reciprocity formula

In addition to the film manufacturer supplied reciprocity information, I used the findings of Howard Bond from his article in the Photo Technique magazine which had been formulated into an easy formula by Patrick Gainer.

It is a simple App, but packed with the reciprocity details of most black and white films currently being sold and a growing number of colour and slide films. Works fine on new and old Android phones as well as on Android tablets.
It’s free, make sure to grab it!

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Hi-tech pinhole photography

The fun part of pinhole photography is that it is so low-tech: No real lens involved, no focussing, great results without any hassle. Or so you might think. For me, pinhole photography means that I need to bring my Android tablet, a grey-card and Sekonic 758D lightmeter to get the job done and get a predictable exposure. It is probably as hi-tech as I need to get for all of my photography. 🙂

My technique with which I have now been able to get decent and reproducible results, comes down the following steps:

  • Use the Film Crop Assistant app to get the location of the tripod and the composition right as you cannot look through the lens, of course.
  • Use the grey-card and the lightmeter to get a reading.
  • Use the Pinhole Camera Calculator app to convert that reading into an basic exposure time that matches the f-stop of my pinhole lens.
  • Use reciprocity failure correction tables specific to the film that I use the Reciprocity app that calculates the exposure time to use for a given film and metered exposure time.
  • Use the Timer option of the Android Clock to time the exposure.

No doubt you can find similar or better tools for the Apple world.

Foma Fomapan 100 film @ EI 100, developed in HC-110 dilution H for 10 minutes, agitation: 2 inversions every 30 seconds.
Foma Fomapan 100 film @ EI 100, developed in HC-110 dilution H for 10 minutes, agitation: 2 inversions every 30 seconds.
Foma Fomapan 100 film @ EI 100, developed in HC-110 dilution H for 10 minutes, agitation: 2 inversions every 30 seconds.
Foma Fomapan 100 film @ EI 100, developed in HC-110 dilution H for 10 minutes, agitation: 2 inversions every 30 seconds.
Foma Fomapan 100 film @ EI 100, developed in HC-110 dilution H for 10 minutes, agitation: 2 inversions every 30 seconds.
Foma Fomapan 100 film @ EI 100, developed in HC-110 dilution H for 10 minutes, agitation: 2 inversions every 30 seconds.
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ADOX CHS 100 II reciprocity failure information

Now that ADOX CHS 100 II film is available on 120 format (as well as on 135 format and many, many different sizes of sheet film) it is getting really interesting. I have used a lot of ADOX CHS 100 ART on 120 format and loved the results and ADOX CHS 100 II film is said to be just as good. As a medium and large format shooter, I’m really happy that this film is now available in all formats.
ADOX provided a technical sheet for this film here, but crucially, the reciprocity failure correction information was missing. I emailed them, and they kindly obliged and provided me with the following information. I have not been able to verify any of this, I hope that you can let me know how you got on with the information below; it will certainly be a good start:

Up to 1 second, no correction required.
2 seconds: 1.5x (3 seconds)
4 seconds: 2x ( 8 seconds)
8 seconds: 2.5x (20 seconds)
15 seconds: 3x (45 seconds)
30 seconds: 4x (120 seconds)
60 seconds: 6.5x (6 minutes 30 seconds

In a graph it looks like follows (time metered on the horizontal axis versus the required exposure time on the vertical axis):

ADOXCHS100II

See also Howard Bond’s article on reciprocity departure for a really good article on the subject which is also referred to as the Schwarzschild effect.

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