Micromega Critical Focuser

[Dmitri Zorkau]

Bought a Micromega Critical Focuser with blue filter. Did first printing and so far very happy. The only concern is to how the blue filter works. My focuser has integrated switch-blade-filter. From what I found it is recommended to use filter for a better tuning to get sharpest grain. I've read the book by Gene Nocon where he says about Omega focuser being exceptionally good but there is no specification on how to get it work. I don't really see the grain through the blue filter but rather different light tone which in my case doesn't make any difference. Grain comes from using the focuser without a filter. I will really appreciate any given information.

 

[Dwig]

...I don't really see the grain through the blue filter but rather different light tone ...

Sounds like the filter is fogged. If you are using a decent enlarging lens don't bother with the filter.

The blue filter shouldn't be necessary with high quality modern lenses. The idea behind the filter is that B&W enlarging paper is primarily blue sensitive while the enlarger's lamp puts out mostly red light. If the lens is poorly corrected, red light may focus at a different distance than blue. Long ago and far away it was common for enlarging lenses to act this way. If you focus without the filter you are focusing with the dominant red end of the spectrum while the print will be made with the blue end resulting in poor focus. Using the filter lets you focus using only the blue light that will be used for the exposure. Modern well corrected lenses won't have significant focus differential across the spectrum and thus don't need to be focused with the filter in place.

 

[Tom A]

I have the Micromega focussing device ( i bought it n 1975) and I admit that the only time I use the blue filter is to set the auto focus on my Focomat 1c and IIc. Once set it stays in place.
If you are printing large prints (16x20 or 20x24) it is handy for critical focus - and also to check corner quality of the lens on the easel. It is a bit one of those darkroom appliances that you take for granted when you have it.