Grain focuser recommendation

AgX said:

So far no one mentioned that there are two kinds of grain-focusers:

-) with a ground screen

-) with an eyepiece focussed on the aerial image

The former is most easy to view, the latter gives brighter image with higher resolution

Click to expand...

This has the makings of a long esoteric discussion about why aerial image focusing is so bad for SLR cameras, yet the most expensive enlarger grain focusers use an aerial image.
My take on it is that it is about magnification. When you magnify the ground glass image it becomes too coarse to use and the ground portion is also not a single plane. It is microscopic hills and valleys with ambiguous depth. Aerial image solves those issues, in exchange for a host of other issues.

The ground screens in grain-focusers are for direct vision, the ground screens in most SLRs are to by viewed by eyepiece (as with the aerial image).

From Bill Burk

https://www.largeformatphotography....092-Looking-for-Peak-Micromega-Model-1-Manual