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DIY Transparency Slide Scanner with 3D-Printed iPhone6 Projector

This post was originally published 06.03.2017.

With this post I want to present you my self invented transparency slide scanner and give you advice how to build your own one.

The problem with making photographs from old transparency slides (36mm x 24mm) is to ensure homogenous lighting. My initial idea was, to use an iPhone 6 showing a white screen (e.g. using the App LightTable as background illumination. If you do so and lay your slide upon the white screen of your phone and shot a picture with a digital camera you will get Moiré patterns on your image due to interferences between the phone's LED array and the camera's sensor array.

Therefore you have to position the iPhone in distance behind the transparency slide in order to have it out of your lense's depth of field (DOF).

The next issue to come over is that you have to get very close to the slide in order to use the entire sensor width. But any standard lens cannot produce sharp images when getting too near to the object. Therefore it is necessary to us a macro lens, which is costly (compared to a standard lens). I helped myself with using a 21mm extension (distance) ring between camera body and my 18-55mm standard lens (working at a focal length near 55mm) on my Canon EOS D60. Of course this lens gear will not reach the quality of a professionell macro lens, but it's much cheaper.

After some trials I got the correct distance from camera (tripod thread) to transparency slide and from slide to the iPhone screen for my camera setup.

Now I needed a physical arrangement to keep the framed slide in correct distance and absolutely parallel to the camera sensor plane. I thought that this would be an ideal case for a special designed projector housing for 3D-printing. So I designed it and uploaded it to shapeways where you can also purchase it.

This model has several features to help you scanning transparency slides: - a slot to take up the iphone 6. You can also leave it empty and use daylight at your window. - a slot to take up the framed slide. This slot also contains two elastic fingers keeping the slide frame positioned exactly in fixed distance an in parallel to the camera. It also adjusts to the different thicknesses of frames (1..3mm). - a tube to avoid environmental light falling into the lens. - the projector is made from laser-sintered black material (PA) in order to avoid reflexions inside the tube - the optical axis of the projector (tube) is 40.5mm above the camera's mounting plate on which the projector should be mounted together with the camera (three mounting points). 40.5mm is the distance from a Canon EOS 60D's bottom plate to its optical axis.

To complete your setup for any other camera, please use the specific distance of the optical axis of your DSLR camera from its bottom plate (e.g. look up at panotools). Dependending on your camera, you may lay some distance washers under the three mounting points of the projector to align your camera to the height of the projector's tube.

Finally I assembled all parts and connected the camera to Canon's EOS Utility Software, so I can see the through the lens in LiveView on the screen of my computer.

I configure EOS Utility and the camera as follows:

- camera is set to Mode A (Aperture Priority Auto) and AF on

- aperture is set to F22 (in order to get the areas in the edges as sharp as possible - this is the difference to a macro lens)

- ISO 200

- LiveView is set to Quick Mode

Now you can take and save the images directly to your storage drive from the utility without touching the camera. Of course you also can catch the images directly to your camera without monitoring the lens view on a screen, nevertheless the camera control software is a very convenient option to control the scan process. As mentioned above, you can also use this arrangement without a phone's LED screen and use daylight (direct the arrangement towards a window).

The pictures below show the complete workaround for scanning slides:

Now here is a sample picture (shot in RAW and after developing and doing some adjustments in Affinity Photo):

The final depictions show the setup sheet with links to the resources and the hole pattern for mounting camera and projector to the base plate (use wood or metal).

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