Blue Filter for Focuser?

[Leigh]

Has nothing to do with the enlarger's projected image. Works even when the device is not under the enlarger.

The function of a grain focuser is to enable the user to focus the grain in the film emulsion on the paper.

If that's not what you're doing, why would you use it at all ? ? ?

- Leigh

[Drew Wiley]

Well, you can use a blue filter to help you perceive how either graded paper or the high-contrast emulsion of VC paper sees film having a yellow-brown pyro stain. It's also easier to study the Mackie line effect of stained films. So I wouldn't throw away the optional blue filter.

[Jac@stafford.net]

Well, you can use a blue filter to help you perceive how either graded paper or [...]

And all the time I thought the blue filter was to counter-act our old eyes' amber cataracts.

[Mark Sampson]

I was never sure why this filter was supplied, and I've never used one. The Beacon enlargers (and their lenses) that I worked with for many years were designed for blue light (graded papers and blue-sensitive transparency films), and even at low magnifications the difference in focus between white light and blue light was substantial.
So it never made sense to me, to use a blue filter to focus when exposing by white light (as in the various Omegas, etc. we used for ordinary enlargements). Can't say that I ever had much trouble focusing a regular enlargement, condenser or color head. Those Peak focusers are the best, and rarely did anyone question the sharpness of the enlargements we made.

[jose angel]

I have been using these peaks for a long time, never with the blue filter.
Personally, I find it useless, especially because I find it almost impossible to focus with such a dim light.

[Doremus Scudder]

The function of a grain focuser is to enable the user to focus the grain in the film emulsion on the paper.

If that's not what you're doing, why would you use it at all ? ? ?

- Leigh

Leigh,

ic-racer was referring to using the blue filter to better focus on the reticle, thereby making it easier to adjust the eyepiece to one's eyesight. This can be done without the enlarger. After adjustment, one would have an easier time focusing on the grain in the image, with or without the blue filter.

Best,

Doremus