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Velbon slider modification

 

I have used a Velbon Super Mag Slider with up to 3× magnification without problems, but when going to larger magnifications I could not get small enough steps to make it work for focus stacks. So I decided to modify the slider to see if it would be possible to get smaller steps in a controllable way, and the result is shown in the pictures below. An obvious modification would of course be to motorize the system. More about safe stepping sizes for focus stacking can be found here.

 

Calculations:

• One turn of the main knob of the Velbon Slider gives a displacement of 4 mm.

• The worm and worm system gives a 1:30 transmission.

• The 15/60 teeth gear wheels give a 1:4 transmission.

 

This gives 4000/(30×4) = 33.3 µm for a full turn of the second gear wheel (the one with the stripes drawn on it). So with this set-up, a quarter of a turn of the second gear wheel moves the slider with 8.3 µm, which is suitable for enlargements of up to 10×. I have used this set-up to do focus stacks at 10× magnification and it works very well and consistently.

 

 

 

 

 

 

An example taken with this set-up at 10× magnification (63 pictures stacked).

 

A crop from the same photo, at 100%.