Omega Grain Focuser Problem... Am I missing something?

[TheTrailTog]

I'm in the finishing stages of setting up my new darkroom space. I set up my enlarger today and was testing things out when I noticed that my Omega grain focuser seems to be out of whack. I did a mock set-up of a 35mm negative to be printed at 8x10. I brought the negative into rough focus on the easel and went to fine tune with the grain focuser. Now years ago when I was printing before I was using a microsight. When I would do my rough focus then, I could at least generally see the grain when I went to fine tune. This time around, nothing. So I start focusing with the enlarger and finally the grain comes into focus. However, when I stand back to look at the projection, the image is now completely out of focus on the easel. I looked online to find the instructions for the focuser and it said to adjust the eyepiece so that you can see the double rings. Unfortunately, the double rings never become visible, let alone in focus for me. If I pull back, I can clearly see the circles, but getting up close like you would if focusing, they never come into focus for me. I tried both with and without my glasses. I'm assuming this explains the negative focusing issues I was having. I bought this about a year ago and just set it aside without really testing it. Am I doing something wrong or is my focuser a dud? I included a pic so you can see which model I have. Thanks in advance for any help!

 

[bsdunek]

Dumb question, I'm sure, but, is that a cover over the mirror? The one that says "omega" on it? I'm sure you're opening/removing that to use the focuser. I would assume the double rings are to focus your eye on. My focuser has a squiggle line for that. You keep focused on that and notice the grain that way. Otherwise, I can't see why it shouldn't work. Certainly Omega is a good brand.

 

[TheTrailTog]

Hi Bruce,

Thanks for chiming in. Yes, lens cap and mirror cover were opened/removed for focusing. I was testing with 35mm Tri-X enlarged to 8x10, so seeing grain is no issue. I am using a Durst M605 with a 50mm Componon-S stopped to f/4. The directions state that you should adjust the eye piece until the double rings come into focus. The eyepiece moves up and down easily, but the rings never come into focus. The eyepiece top ring can be removed exposing the top element in the lens assembly, which is loose. The top element is concave on both sides, with one side being more concave than the other. I tried flipping the element just in case a previous owner had tampered with it, but that didn't help, I still couldn't focus on the double rings and it didn't change the focusing issue at the enlarger. At the enlarger with the lens opened up to f/4, the difference in focusing between focused with the scope and focused with the naked eye is quite stark. Stopping down all the way brings the image into range, but it's still slightly off. Can't think of anything else to try. There are two screws under the mirror on the focuser, which I tried removing to see if it released the mirror for adjustment, but that did nothing. The mirror doesn't budge.

 

[Ian C]

I removed the retaining ring at the top of my Omega Enlarging Focuser (Peak Model II or model 2020 in some literature) eyepiece and examined it. The two elements at the top of the barrel are:


1. The top element is a biconvex lens. The top surface facing the user’s eye is a small male spherical radius (bulges outward noticeably). The bottom surface is a larger male spherical radius (bulges outward much less than the top surface).


2. The second element is biconcave of two different radii. The top surface is a mirror image of and perfectly matches the bottom surface of the top element. In fact, these two elements mate at this common joint when assembled.


If you try to install element 2 with the wrong surface facing up, their vertices touch and won’t fit together (since the radii are different). Should you try to mismatch them in this way, tightening the retaining ring would likely damage them where they meet at the vertices.


Putting them together gently at the common spherical radius forms a perfect joint. When they are assembled correctly as noted and I view through the eyepiece, the reticle “snaps” into focus when the loupe is adjusted to suit my eyesight.


The remaining elements are farther down inside the barrel and not readily accessible.


I suspect that the top biconvex element in your eyepiece has been removed and it was assembled minus this part. When the retaining ring is snugged all clearance is eliminated, so there should be no "rattling" of the parts.


Without this biconvex lens the magnifier is useless. The top lens is too large in diameter to fit down inside the barrel, so there is no possibility that it could have been misplaced deeper inside the barrel. I believe the Peak Model II has been discontinued.



http://www.peakoptics.com/index.php..._id=63&zenid=2a52fc4a605a6fe90b1f2de14c093f60

 

[TheTrailTog]

I think that solves the mystery. I only have one element in the top and with the eyepiece tightened all the way down there is a bit of play. You can rattle the element. Well, that sucks. Bought it a while ago as I was slowly accumulating pieces for my darkroom. I never tested it. Took it out of the box and gave it a cursory glance and stored it away. Sigh, lesson learned.