Any way to use a loupe as a grain focuser?

[click]

I have an autofocus enlarger and I just set it up by eye and it seems to work well. I would like to dial it in and have wondered if I can successfully use a loupe (somehow) to focus it, rather than buy a loupe that I'll probably only use once.

Thank you

 

[farlymac]

I wouldn't think that will work. For one thing, your head will be in the light path. There is a reason that grain maginfiers are designed the way they are. And don't think your autofocusing head will stay in tune once you check it. I would use the grain magnifier at the start of every session to make sure, then put it away till next time.

PF

 

[Steve M.]

You'll need the grain focuser, and you might want to use it to ck the focus on every print. When you get one you'll see why. They are built, and work, very differently from a loupe.

 

[Rob-F]

You should be able to find a grain magnifier on ebay for almost nothing.

 

[Darkhorse]

I've tried and failed to do this.

 

[Tom A]

If you are using an autofocus enlarger (Leica Focomat ?) - and Variable Contrast filters, you are better off doing a test run. Set it up and focus as well as you can (by eye) and then do a print. Check it for sharpness and do two more prints, one with the focus slightly off in one direction (very small focus adjustment) and the 2nd the same way in the other direction. Again, process and check focus and if you are satisfied lock in the autofocus at the best setting. You have to compensate for paper thickness too. Double Weight Fiber paper tends to be thicker than RC paper.
The whole idea of autofocus is not having to check and double check focus all the time - particularly if you are cropping on the easel.
Most auto focus enlargers have an optimum "band of focus" - a Focomat 1C usually between 5x7 inches to 11x14 inches. Smaller or larger than that, you often need to correct and check - and this is where the grain focuser comes in handy.
I use a Focomat 1C and a IIC - with the IC I usually never bother to check the focus as most prints are either 8x10" or "full frame" on 11x14 paper and the focus stays pretty well constant. With the IIC I do check focus - at least with 120 film as those prints are usually either larger than 11x14 or cropped.
You can also take a piece of exposed film (black) an scratch a pattern in it with a needle (emulsion side obviously) and use that as a test negative. I keep making them (and loosing them) - just use a straight edge or a ruler and make a grid-pattern (1-2 mm "squares"). This will also tell you at which f-stop your enlarging lens performs the best - or if your enlarger is properly aligned or if the film is kept flat in the negative carrier.

 

[click]

I've been wondering exactly how to test the alignment of my enlarger for some time so this is a great piece of information, thank you! I'd stumbled upon the idea of scratching a line in a blank negative but I forgot about doing that. so thanks again! Wow Tom you got two exclamation marks in one paragraph! Oh no, now three...

For now I am just working on getting back into making prints so I'm only making 8x10 contact sheets and 5x7 prints, trying to work out how to make split grade decisions. I've no clue as to what I'm doing but it sure is fun.

So far I think eyeballing the focus works pretty well but then I've nothing to really compare it to because the new enlarger is far superior in quality and I think even at it's worst outperforms my old one.

I always assumed that 5.6 would be the best F stop but I should actually test it to be certain.

I have bid on a few grain focusers but because I'm not actively staring at the computer when these things end people keep outbidding me by a quarter or whatever, I find eBay somewhat frustrating. When I was thinking of the possibility of using my loupe I was thinking maybe I could tilt and focus it because my loupe has the capability to manually focus, though I have no idea why the loupe is built this way, when I use it for negatives the focus is all the way down.

Thank you all for your replies,

Click

 

[RichL]

Any decent quality magnifying glass that can be used at around 2" or more works just fine. The only difference between that and a grain focuser is that the grain focuser being a hands free device is easier for some to use.