We have a lot of slides that have been sitting in the basement for a long time. We have now decided to digitise them. While we do own a reasonable scanner that can scan four slides in one go, it is rather slow (i.e. over a minute per slide) and manual. Inspired by a c't article from 12/2015, we decided to photograph each slide as it was illuminated by our old projector. The blog by PeschiMo also documents a similar setup. The website by thomas on analogue photography also gives a comprehensive introduction.
We used:
- Revue universal 600 AF
- Pentax K-50, with a 50mm F1.8 Pentax prime with a macro ring
In contrast to the equipment used in the c't article, our projector does not have an inbuild timer for automatically advancing the slides, but a wired remote control. Hence we used a relay and a Raspberry Pi to automatically advance the slides, and also to control the DSLR using gphoto2.
This project contains the code to control the projector and the DSLR. You can:
- Take a batch of pictures, automatically advancing the slides
- Manually move the slide tray forward or backward
- Set the shutter speed settings of the camera (required since the Pentax K-50 cannot determine shutterspeed itself when controlled via gphoto2. Annoying, but this is the only DSLR we had available).
- Pictures are automatically downloaded from the camera to a location of your choice, a network share in our case.
A picture takes between 7-8 seconds including automatically advancing. Digitising a slide tray of 36 slides around 4 minutes 20 seconds. The quality is more than good enough, our slides from 1960-1990 lack in initial picture quality and craftsmanship anyway.
In order to facilitate development outside of the Raspberry Pi, the GPIO and gphoto2 are mocked when unavailable. The Pipfile only tries to install them when on a linux system running on armv7l. gphoto2 requires compilation of the system libraries before the python library can be installed.
We have now finished scanning our entire slide collection, so I don't expect this project to receive any further updates. But may it be helpful for someone else in future.