Is your grain focuser correct?

[matti]

I mean:
- Did you check it against another one?
- Did they both focus at the same point?
- Am I just too nervous?

/matti

 

[Ray Heath]

g'day matti

why dontcha just make a print with it and see how it looks?

 

[Ole]

I mean:
- Did you check it against another one?
- Did they both focus at the same point?
- Am I just too nervous?

/matti

Mine isn't.

I've checked it against prints, and against prints made after focussing with a loupe directly on the paper, and against prints made after focusing with the "crossed slit" which the negative carriers have on both my enlargers.

The grain focuser is off enough to make soft prints. The neg carriers are spot on...

 

[Whiteymorange]

I work in a school darkroom (when I get in there) and I've found quite a bit of difference from one grain focuser to the next, even when they are all the same brand and all new. Check your own and adjust until you get it right. I don't trust any one of them until I'm happy with a print that that particular one gives me. Most have some way of adjusting the lens.

Problem is... I can't seem to keep them assigned to individual enlargers ( see the "school" comment.) Shouldn't be a problem if you're the only one using it.

 

[Stephen Frizza]

I have a generic 30 dollar Grain Focuser and it isn't accurate! So I invested in a PEAK Professor Z.Koana model #2000 system Enlarging focuser
and having compared 3 of them with one another they are all the same accuracy. Totally accurate!!! I love these focuses the are the best design Ive ever encountered.
they have 30 degree angle of coverage. I will be honest though I don't quite see an advantage of the Blue filter. im told because the paper is sensitive to blue light the blue filter lets u focus the blue wave lenghts more accurately. Who else uses this focuser and can anyone tell me where this may come into play for me.

~Steve

 

[rst]

Mine seems to be correct. I checked this with a magnifier on a final print. The good thing, it is in sync with my eyes. I always first focus by not using a grain focuser on the back of an old working print of the same paper. Then I only check with the grain focuser and in 95% the print is already in focus. When I then stop down by two stops ...

ciao
-- Ruediger

 

[walter23]

I have two cheap plastic ones and both work perfectly. I use a scrap of paper of the same thickness as my printing paper on the easel when I print.

 

[Dietmar Wolf]

I use my eyes. Printing at stop 5.6 I never had any problems with sharpness. I have never used a focuser.

 

[youngrichard]

Testing

Testing and adjusting the autofocus on my enlarger I noticed that my Paterson Minor and Major focuscopes did not agree. I got a Peak 111 and that didn't agree with either. I picked up a Focoblitz which focuses the image onto a sensor and then displays it on a small cathode ray tube - great as you don't have to do contortions as you do when using an eyepiece with the head at the top of its column. Expensive, though. This didn't agree with any of them either. So I put the enlarger head at the top of the column and printed the centre of a grainy negative onto 5x7 paper at maximum aperture with the focus set to show the grain according to each of the 4 grain focussers. The focoblitz was easily the most accurate, as well as the most expensive, showing sharpest grain. Whether the inaccuracy of the others matters when you have closed down a stop or two I have not tested; probably not. Certainly I relied on the Paterson Minor with non-autofocus enlargers and also for setting up a Focomat V35 (which has perfect auto-focus) for 30 years, and never felt there was a problem. It was only when I acquired a Durst DA 900 with non-original lenses last year, and tinkered with the autofocus set-up that I realised that grain focussers are not super-accurate.
PS Tim Rudman in his book says he does not think using spare paper under the focus-scope makes any difference

 

[walter23]

I use my eyes. Printing at stop 5.6 I never had any problems with sharpness. I have never used a focuser.

Yeah, there's no point in worrying about it if you have to go in on your printswith a high-powered loupe to even notice it. If it looks razor sharp in hand or mounted on the wall, who cares?

 

[matti]

It seems like getting another one will just cause confusion (if I don't get me five new ones). Maybe it would be best to make some test prints wide open and focus under or over the point where the focuser says. If the under and over focused prints don't look better, then I might stop worrying.

/matti

 

[Lee Shively]

When I bought a grain focuser sometime back, it was an eye-opening experience. I proceeded to get rid of the old and cloudy 50/2.8 El Nikkor lens I had been using in favor of a 50/2.8 Rodenstock Rodagon. I also bought a glass negative carrier and did a little adjusting on the enlarger. I compare my recent prints with older ones and the difference in sharpness is astounding.

 

[srs5694]

I will be honest though I don't quite see an advantage of the Blue filter. im told because the paper is sensitive to blue light the blue filter lets u focus the blue wave lenghts more accurately.

The problem with this theory is that the human eye is a rather poor device, optically speaking, and focus in the human eye varies with color. Pat Gainer wrote a piece for Photo Techniques a while back called "Hazards of the Grain Focuser" or something similar. (I don't have the issue in front of me at the moment, so this is from memory.) He related some theory and the results of some tests he did. He found that he achieved the best focus when using white or green light. I've done some even simpler tests myself and I've found that the apparent best focus does vary with the color of the light, so I'm willing to accept Gainer's conclusions, at least tentatively. I now use green light for focusing. (My enlarger is an additive color model, so I've got separate red, green, and blue lights.)

 

[rwyoung]

Ctein has a section in his book on this topic. He also mentions Gainer's article.

 

[Stephen Frizza]

im so glad to have heard this I will look at gainers article now. I don't use the blue filter its just been an added accessory sitting here in the lab. I don't have a choice with my enlarger i either focus under green or I focus under green.

 

[Jim Jones]

In my 30s a focusing aid wasn't needed. Ten or twenty years later they were useful. Now nothing insures sharp prints. Could it be , , , ?