Description

I love macro photography and as anyone who has ever tried it will know, extremely thin depth of field (here we are often talking about 0.1mm and below) can be a real problem as the object we are photographing is usually significantly larger. The higher the magnification you use the less of the photo ends up in sharp focus.

This problem is typically solved by taking multiple photos with a slightly different focus point and later combining them to produce the final image where everything of importance is in focus.

One such software is the excellent Zerene stacker that will do all the work for you. You still need to take a bunch of photos of the same object that differ only in the focus point - and by 'bunch' I mean sometimes more than 50! For that reason I went to design an automatic macro rail that can very precisely move a small object back and forward a few centimeters. The macro rail had to be able to:

• move in user selectable steps from 0.01mm to about 1mm
• continuously slide (fast) for the initial focusing
• memorise the start and the end positions for the focus stack
• compensate for the 'slack' in sprockets when changing the direction
• control my Canon dSLR and automatically take the photos once everything has been set
• remember some settings between the runs (step size)
• I had to build it from easily available 'junk' as I wasn't prepared to pay more than $20
• simple and quick to build - no heavy machinery required
• controlled by a smallest and cheapest micro-controller I head - the Picaxe 08m
• remote controlled to minimize the possibility of accidentally moving the camera or the subject

I actually managed to do this utilising only the parts I already had in the house (so it didn't cost me a penny while similar rails can be bought for close to $500!).

All I needed was an old, broken DVD-ROM drive (for a very nice rail it contains), a unipolar stepper motor (from an ancient 5.25" floppy drive - remember those?), the Picaxe 08m, and a few standard electronic components.

Watch the video to see the result.

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