Grain Focuser/Magnifier

bobwysiwyg

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I did a search and found many references to grain magnifiers, but nothing mentioning my question. I've never used one before and this may seem like a silly question. I'm assuming their design compensates for the difference in height between the print surface and the mirror stage platform? It seems to, but hard to be sure.:confused:
 

bdial

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Yes, they compensate for that difference in height.
Lot's of folks contend that you should always use the magnifier on a sheet of the paper you're printing on so that the plane of focus is the same as the print's will be. In practice it shouldn't matter much, if any, assuming you are stopped down a few stops. This has always been my method, but I've never tested it rigorously to see if it really matters.
The only silly questions are the ones unasked that keep you from learning.
 

pentaxuser

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It's worth getting one. Even with good eyesight and max aperture I find that after getting the neg as sharp as poss by eye I can still do a lot better with the grain magnifier. In the U.K the Paterson magnifier goes quite cheaply on e-bay. Hopefully it is the same in the U.S. It doesn't require you to use glasses even if you normally wear them as there is a guideline in the scope which you set to sharp focus with your unaided eyesight and this gets focusiing on the grain spot on.

pentaxuser
 

Phillip P. Dimor

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I'll second the patterson. It is good and cheap used. I would not buy it new.
I've used a Micromega/Peak Grain focuser (the expensive one) and it was outstanding, but honestly my prints are just as sharp. The difference is that the Patterson must be directly underneath the enlarging lens for you to focus the image adequately. The Peak/Micromega can focus the image from all four corners of your easel which is nice for checking the focus there.

I use a 6x7 negative carrier for 645 and 6x6 negatives. If the image I am enlarging is on the end of the roll, I place the negative right against the edge of the frame and move the easel to 'compensate' if that makes any sense. It's a pain to focus with the patterson in this case. I end up focusing on an edge of the image because that is directly where the enlarging lens 'falls'.

I guess what i'm trying to say is that if you have $100-200 and want a precision focusing instrument for the rest of your days with a good option to sell and still get back most of your investment, go for the peak/micromega. If you want something reasonably priced used and works with a few quirks that can be overcome, don't fear purchasing a patterson or even a microsight which work just as well.

You do stick a piece of enlarging paper, a 4x4 square or a test-strip to account for the thickness of the paper. With fiber paper I feel this is a bit more important as it is usually thicker but I do it with everything.

Read Ctein's Post Exposure. Heavy reading but it is probably the definitive source.
 
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bobwysiwyg

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Thank you all for the replies. When I was doing enlarging and printing 25+ years ago, I could eyeball it, or maybe use a magnifying glass. Sigh.. the eyes are a bit older and more fatiqued, hense the switch to a grain magnifier. Thanks Phil for the reading reference.
 

Phillip P. Dimor

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The Kaiser is _probably_ similiar to the unicolor mitchel focuser in that it focuses an aerial image. The Unicolor one can be found for $2 to $8 on E* bay. Pretty cheap. No one seems to want it.

I agree about the eyes. Mine definitely aren't the same and I _need_ a grain focuser. I can get there about 80% of the way without a grain focuser. The 20% really does make a difference, atleast to me.

Post Exposure is a good read, i've never read more than 3 chapters but then again I haven't had the pleasure of owning the book. I'm probably close to saying that any grain magnifier is better than no magnifier.

Ctein would tell you that a grain magnifier that focuses the blue spectrum of light is better than none. I can't tell the difference as i've never used a blue filter. The Peak/Micromega supplies a blue filter for this very purpose.
 

jd callow

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I use the peak because it lets me check the corners of the print.
 

sly

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Glasses with focuser?

pentaxuser said:
It doesn't require you to use glasses even if you normally wear them as there is a guideline in the scope which you set to sharp focus with your unaided eyesight and this gets focusiing on the grain spot on.

pentaxuser
Click to expand...

I have noticed that there is a difference between grain focusing with my naked eye and with my glasses. Should I be doing it without glasses? I've been focusing with the glasses on, figuring they are correcting the toll nature has taken. I'm myopic, astigmatic, aging, and have had laser surgery to spot weld numerous tears in my retinas. My glasses are progressives. I'm glad I can still see well enough to use a camera.
I do focus my 4x5 by taking my glasses off under the focusing cloth and getting my nose up against the GG.
 

youngrichard

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Testing grain focussers

I have Paterson Major, Paterson Minor, Peak, and Focoblitz grain focussers. The latter has a lens which focuses grain on a sensor which produces an image on a cathode ray tube - much easier to see than squinting into an eye-piece. I put the enlarger head up to the top with a 35mm HP5 grainy neg ie equivalent to 20x16" enlargement and printed the centre at full aperture onto 7x5" paper with sharp focus as indicated by each of the grain focussers. The focoblitz gave prints in which the grain was much more sharply focussed than each of the other three. That is not to say that the other three are necessarily inaccurate but when you think of the tolerances required in the manufacture of these devices, I imagine that even a tiny knock could affect the accuracy. So I recommend this simple test to ensure that your grain focusser is as accurate as you think. Of course simple stopping down of the lens may eliminate any error.
 

Jim Jones

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Phillip P. Dimor said:
The Kaiser is _probably_ similiar to the unicolor mitchel focuser in that it focuses an aerial image. The Unicolor one can be found for $2 to $8 on E* bay. Pretty cheap. No one seems to want it.
. . .
Click to expand...


These focusing aids that can be used anywhere on the image are also great for checking enlarger alignment. The Unicolor Mitchell works well with great enlarger heights. The eye doesn't have to be close to the eyepiece.
 

MattKing

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pentaxuser

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Interesting question to which I haven't a definitive answer except to say that with corrective lenses i.e. a pair of glasses the "sharp black line in the Paterson is probably at a different point than it would be without glasses. So yes if you were to remove your glasses you should alter the movable section on the Paterson to get the line into sharp focus again. You have then simply compensated for your less than 100% eyesight.

What I don't know is how accurate your focussing can be with glasses in that the lens of the glasses means that your eye is further away from the entrance lens of the Paterson.

As long as you can focus on the grain with glasses, I'd stick with glasses. Thar way you can also see everything else in sharp focus instead of whipping your glasses on and off.

The test would be to get the line in focus with your glasses on and then move the enlarger lens to "pop" the grain. Then remove them and alter the Paterson magnifier via the screw until the black line grain comes back into focus. At this point the grain should also be in focus without your glasses. If it isn't and it requires you to move the enlarger bellows to bring the grain back into focus it suggests that focussing with glasses isn't as accurate as with glasses off.

I think this is a good test unless I am missing something. If so maybe someone else will chime in.

pentaxuser
 

dancqu

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In my opinion the rational for use of a grain
magnifier has no basis. I've a grain magnifier
which I quit using.

With it's use a 4 diameter enlargement on the
baseboard becomes a 40 diameter enlargement.
Also, a lens wide open has least depth of field.
An exposure stop is usually a minimum of one
stop less.

I use a pair of reading glasses for close
viewing with both eyes open. Dan
 

fschifano

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I don't know if you want to call this rigorous testing, but I have checked under my enlarger. There is a very slight difference between having/not having a sheet of paper in the easel when the lens aperture is wide open. In my case, the focal length was 50mm, the max aperture f/2.8, and the magnification ratio about 8 - 9x. Stop down to f/5.6 and for all practical purposes, the difference disappears. I still use a sheet in the easel for focusing - the same sheet I have marked off in a grid pattern to help align the image.
 

bdial

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Seems rigorous enough to me.
I've always done it that way, because it makes sense, and habit/learning. My new easel is black so a sheet of paper on it for focusing and composing is automatic.
 

michael9793

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don't go cheap!!!!!!!
E-bay has ones that are top of the line. I find that your print isn't worth crap if it is out of focus.

ma
 
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dancqu

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Your enlarging lens may be at fault. It may suffer from
linear chromatic abberation. There may have been some
reference this thread to that abberation. To be brief, wave
lengths by which one focuses and wave lengths to which the
paper responds are not the same. To compound the problem
papers can be sensitive to wave lengths not visible; the very
deep blue and UV.

If the lens is very well corrected so that all wave lengths
come to a common focus, no problem. Perhaps the Focoblitz
is 'seeing' in a portion of the spectrum which coincides with
the paper's spectral sensitivity. The VISIBLE focus is not in
the same plane due to chromatic abberation.

Three visible light focusers gave much less sharply focused
images. So, IMO your lens is suspect. The Patersons and
Peak may be OK. Dan
 

Larry Bullis

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I suspect that you will just get really tired of putting glasses on and taking off. You will need them on to size and crop. I have progressives, too, and I don't have any problem with it. You will set it up so the line is sharp, and then when focusing, you will naturally find the place in your glasses where the line is sharp without even thinking about it. Try it.

I got one of those fancy Peak ones at a thrift store. Unfortunately, the instructions are in Japanese, so I can't read them!
 

df cardwell

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If your focuser has a reticle, crosshairs or a frame superimposed in your view of the image,
you adjust the eyepiece by holding the focuser to your eye, as if it were a telescope,
with both eyes open. Focus you vision on an object as far away as possible.
Adjust the eyepiece until - with your eye focused on a distant object - you can see the reticle clearly.

If you wear glasses, do this with your glasses. Do this at the end of the day, when your eyes are tired
otherwise they will accommodate instead of focus.
This is exactly the same as adjusting a microscope's eyepiece.

You focus the the reticle while looking at a distant object because our eyes relax at distance,
and are stressed when seeing close. Which is why your high school teacher yelled at you for
looking out the window instead of your lesson in front of you. But I digress.

When you use the focuser, work quickly. If you labor, your eye will 'pull the image' into focus,
and you will wonder why it isn't sharp ! This is the biggest problem have with reticle focusers.
If your prints aren't sharp, you haven't adjusted the eyepiece properly.

If you are working with low magnificaton images and low granularity images,
you're better off with reading glasses !
 

dancqu

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df cardwell said:
If you are working with low magnificaton images
and low granularity images, you're better off with
reading glasses !
Click to expand...

First off, as I've mentioned this thread, I do use reading
glasses though I'll admit I've never made a case such
as you've made against the use of a grain magnifier.

A couple of not so fine points: First, who is concerned
that the grain, it be possible to discern, be sharp at a 40
to 100 diameter? Likely most grain magnifiers allow 10 or
more diameter enlargement of the projected image. So
a 4 to 10 diameter enlargement on the easel is seen
as a 40 to 100 diameter image viewed through the
magnifier.

Second, visual focus does not take into account
the spectral sensitivity of the paper or linear chromatic
correction of the lens. This I've mentioned this thread.
The problem is exacerbate when using VC papers due
to their extended deep blue and UV sensitivity.

I appreciate the fact that the use of a grain magnifier
introduces complications. So, two pair of reading glasses,
one most powerful. Although the Graded paper I use has
a spectral sensitivity into the deep blue and I focus with
the white of the enlargers light I do obtain sharp results.
How so? Likely the color correction of the lens is good
and the lens is stoped down. The last, IMO, a major
factor in sharp image production. Dan
 

df cardwell

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"I've never made a case such as you've made against the use of a grain magnifier."
I didn't argue against a grain magnifier. If you can't see the grain, you can't focus with a grain magnifier. There ARE no complications in the use of a magnifier, unless one hasn't focussed on the reticle.

..."not so fine points: First, who is concerned that the grain, it be possible to discern, be sharp at a 40 to 100 diameter?" This is a rhetorical argument; practice overwhelmingly supports a correctly adjusted grain magnifier yields quick, consistent and accurate focus.

Second, visual focus does not take into account the spectral sensitivity of the paper or linear chromatic correction of the lens. This is speculative; it has no effect.

Unless you are using an unusual lens, like the Apo El Nikkor, which is diffraction limited wide open, stopping down 1 /2 to 2 stops equalizes the edge and center performance and creates a sweet spot which is necessary to good prints. Another way to optimize the aperture is to check the vignetting of the lens at the corner of the print: lay a mirror at the corner of the cropped print and stop the lens until you see a clear round diaphragm, but go no further.

There has been an argument for ages about the complications caused by visual focus, paper sensitivity, source light, and so on. I've never seen it in practice, nor have I EVER met a printer who had.

I didn't join the thread to argue with you, instead to offer a good way to set up a grain magnifier. If you are getting great results without one, fine. I'm not here to make a case for or against, just to help use one. But you've introduced technical issues which - to my limited experience - aren't really a practical concern.
 
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