Tuesday, May 25, 2010

DIY Macro Filter

I've a 70mm f=500mm (astronomical grade) objective sitting idle from a finished experiment, so I was always thinking how could I use it in the best way.

When I heard that a macro filter is just an optical lens to bring the focus point closer, I begin to think that it might be just a converging lens! For example, if you have a 500mm focal length lens, if your subject is at 500mm from this objective, parallel ray will go out from the other side of the lens. Yes, parallel ray, that means, if your camera lens will focus at infinity, it will accept parallel ray! In that case, if my lens would focus as close as 1 meter, if I add this f=500mm lens in front of it, it will focus as close as, at least, 500mm now.

To do that, I will only need to buy a suitable threaded ring and stick it in the lens cell like the following:



So now I can put it on and take it off easily, and the result:



Not bad, right?