Focusing on the grain when printing on wall

[envy]

I recently added a wall-projection-setup to my darkroom, so that I can go for prints up to 1m side length.
The problem now is focusing the negative on the projection wall. :)
I have to focus whith my hand on the wheel at the enlarger head and of course this way I am standing to far away for using my standard focusing loupe.
Maybe someone here faced the same problem already and has some tips for a loupe Setup or a DIY solution?

154445

[LabRat]

Put a strip of black tape across lens so the lens forms two halves... As you focus it, the image will be slightly out of register (like in a rangefinder focusing unit on a camera), but when in focus, the image will combine perfectly... Try different sized tape over lens until you find the right size, then you can make a tube that slides over the lens (like a lens cap) with the tape, so that it can easily be added and removed for the focusing step... Try It!!!!!

Steve K

[Jim Jones]

A small telescope that focuses close enough should be more accurate than Steve's "rangefinder". Such a telescope can be improvised from lenses that many photographers accumulate over the years. If it gives an inverted image, no problem in this application.

[ic-racer]

Depending on how big you enlarge in one step without an internegative, the grain may not be resolved. A 45X enlargement will make your f2.8 enlarging lens over f120 when wide open.

[bob carnie]

Most horizontal enlargers have remote control focus so you can stand at the wall and focus on the grain.


Here is the simplest way of doing this... You need two people unfortunately.. one at the wall with the grain scope and another at the enlarger.

take the image in and out of focus so you are in the ballpark , you can see this on the wall, delibertly go out of focus slightly.

then slowly move the focus towards critical sharpness, the person at the wall will slow you down until you get exact grain , if you go to far the person at the wall
says back slowly and you move back even slower and stop when the person at the wall sees sharp grain and yells stop.


This absolutely works as I do this all the time with my vertical setup, my arms are not long enough.

[Jac@stafford.net]

First, not all enlarging lenses are designed for great enlargements. Choose carefully.

As it concerns manipulating the bellows focus knob, consider finding a large diameter replacement (Ace Hardware), and glue or fasten an offset clip on the surface that can slip-fit a long wooden or aluminum dowel. (Gads, I have a ton of those). Then using that as an extension use a grain magnifier. Once focused remove the extension. Recheck. I can make a drawing if you wish.

The telescope is a good idea, however my experience is with short-range micro-measurement models. I would like to see alternatives.

[LabRat]

But don't forget that it's not hard to get focus when the image is large... (You know, like it's not too hard to focus a projector, right!?!!) The image is in focus or not... Grain is about as big as it's going to get, and should not be too hard to see, even at a distance... (And you can walk up to the enlarged image, and look right at it...) If someone has made murals on a mural enlarger, handling the paper is the tough part, but focus is straightforward...(Unless the enlarger is REALLY dim!!!!)

Steve K

[bob carnie]

I am just saying , finished murals jobs just last week , finding a second pair of hands for about 1minute is not all that hard.

[Jim Jones]

When Kodachrome was king, precise focusing on the screen from near the projector was difficult. The audience could tell better than I if the image was sharp.

[envy]

Thanks a lot for the Responses. There are some nice ideas which I have to try.
The only method I can tell as non-working is the "rangefinder" solution with the tape.
The rest will probably be testet this Weekend. I will Report...