Using grains focuser with or without paper on the easel

Read what I just posted at apparently almost the same time, Wilt. Sometimes, it DOES make a real difference. Quite often in my case. In film to film applications (rather than paper) tolerances need to be kept within .002 inches for acceptable results. Furthermore, the film itself ideally needs to be dimensionally stable polyester base rather than triacetate, which is dimensionally susceptible. And there are even certain alt paper processes where swelling must be taken into account. And not all paper is "paper". I frequently make color prints themselves using a polyester-base medium rather than FB or RC.

Now about magnification factors. Let's say I enlarge a 6X7 cm original onto 8x10 film. That's roughly a 4X magnification. But that in turn might be magnified 4 times more, hypothetically. So now you're dealing with a substantial degree of enlargment where the slightest focus error becomes dramatically compounded. (More often I enlarge a 4X5 original onto 8X10 film, so the difference is not that much dramatic, but still substantial, since I'm after something that can be printed fairly large).

Well, you might ask, why not just stop the lens down more for sake of more depth of field? It's because I deliberately want a very shallow precise depth of field, so that the grain structure of any attached film mask, or any little flaws in the negative carrier glass either side, or any tiny bits of dust I failed to remove, don't themselves become visible in the enlarged duplicate.

Greg Davis said:

How about everyone send me their grain focusers and I’ll compare them all for accuracy.

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But when you compare multipe samples and they disagree, which one is right?

DREW WILEY said:

Read what I just posted at apparently almost the same time, Wilt. Sometimes, it DOES make a real difference. Quite often in my case. In film to film applications (rather than paper) tolerances need to be kept within .002 inches for acceptable results. Furthermore, the film itself ideally needs to be dimensionally stable polyester base rather than triacetate, which is dimensionally susceptible. And there are even certain alt paper processes where swelling must be taken into account. And not all paper is "paper". I frequently make color prints themselves using a polyester-base medium rather than FB or RC.

Now about magnification factors. Let's say I enlarge a 6X7 cm original onto 8x10 film. That's roughly a 4X magnification. But that in turn might be magnified 4 times more, hypothetically. So now you're dealing with a substantial degree of enlargment where the slightest focus error becomes dramatically compounded. (More often I enlarge a 4X5 original onto 8X10 film, so the difference is not that much dramatic, but still substantial, since I'm after something that can be printed fairly large).

Well, you might ask, why not just stop the lens down more for sake of more depth of field? It's because I deliberately want a very shallow precise depth of field, so that the grain structure of any attached film mask, or any little flaws in the negative carrier glass either side, or any tiny bits of dust I failed to remove, don't themselves become visible in the enlarged duplicate.

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I read your post, very thoroughly and more than once, Drew. Why does 5mm DOF at the enlargring easel mean it 'does not matter', but 5mm DOF for the 8x transparency dupe it does matter? Curious minds cannot figure out 'Why the difference?'.

I didn't say 5 mm, that would be atrociously off ! I wouldn't tolerate anything that sloppy even using paper. Note I stated for film purposes, the tolerance level is two one-thousandths of an inch! Five mm is nearly a quarter of an inch.

DREW WILEY said:

I didn't say 5 mm, that would be atrociously off ! I wouldn't tolerate anything that sloppy even using paper. Note I stated for film purposes, the tolerance level is two one-thousandths of an inch! Five mm is nearly a quarter of an inch.

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Drew, I am not playing games in my sincere inquiry...Why is an 8x duplication of a slide so much less tolerant of any deviation from perfect point replication (no blur circle tolerated) than an 8x enlargement? In both cases, the starting point is a 24 x 36mm image, and the end point is roughly 8x enlargement of that starting point.

Greg Davis said:

How about everyone send me their grain focusers and I’ll compare them all for accuracy.

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But then we'd have to debate which parcel carrier was least likely to bang them around and mess up the calibration, lol.

bdial said:

Given how far this thread has devolved into minutia;
Has everyone calibrated their grain focuser to determine that its focus point is actually even with the base, and not 0.000001 mm too high or too low? Is the base of the focuser actually flat and square? Is a $30 Patterson equal to a $100 peak in accuracy? Is there any debris trapped between the base of the focuser and the paper, or between the paper and the easel? Does one check this for every print? Do you place the focuser in exactly the same spot under the lens each time it's used?
If you focus and defocus, say, 5 times, do you get exactly the same lens extension each time. If not, then what is the variance? Is that variance larger or smaller than the thickness of a sheet of Multigrade?

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Good point!
And are we focussing for/in the same light our paper is sensitive to?

Best
Jens

Luckless said:

An enlarger is just kind of an inside out camera, with the subject and light in a smaller box that is positioned inside the bigger light tight box that the recording medium is setup in, so what exactly is the difference between 'depth of field' and 'depth of focus'?

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depth of focus is always on the film side, were depth of field is always on the object side.

Anyone posting here should wear this one : https://vedostuu.creator-spring.com/listing/grainfocus?product=373

vedostuu said:

Anyone posting here should wear this one : https://vedostuu.creator-spring.com/listing/grainfocus?product=373

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I am surprised to hear you pushing this. I always assumed that you would need optics to scale down the size of your grain to manageable levels

In a different, but related matter, did any of you considered a small camera and a screen (a cell phone?) to focus your enlarger directly on paper?

bdial said:

Has everyone calibrated their grain focuser to determine that its focus point is actually even with the base,

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There's no calibration of accuracy available on the Paterson one - or another, older one I have. The only adjustment is for your own vision.

bdial said:

Has everyone calibrated their grain focuser to determine that its focus point is actually even with the base, and not 0.000001 mm too high or too low? Is the base of the focuser actually flat and square? Is a $30 Paterson equal to a $100 Peak.

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I accept 13mm as a possible discussion point. In this regard we are talking close is good enough.
I have had both and they both work.
The Peak lets you focus on different places. The Paterson sticks you in the middle. But they are both a joy to use

The other really valuable feature of the Peak Critical is the ability to focus way out in the corners of the easel due to the tilting front-surface mirror and related superior optics. That not only allows one to check for plane accuracy and overall focus (rather than just central focus), but is a convenient way to compare lens performance center to edge too at respective stops, or between different potential enlarging lenses.

Regarding viewing according to the specific light wavelength involved in printing, that's why a strong blue filter is included with certain of the Peak magnifiers. But that's basically a holdover from way back - half a century or more ago - when enlarging lenses were not anywhere near as well apo corrected as today, and when b&w printing papers were graded blue-sensitive.
Now we're mostly dealing with VC papers which respond primarily to blue and green light. A deep blue filter just make things hard to see. But I've sometimes found it useful for interpreting the effect under magnification of yellowish pyro stain in the neg.

RalphLambrecht said:

depth of focus is always on the film side, were depth of field is always on the object side.

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And therein lies the question
(note: I use > < simply to indicate the image converging at the lens nodel point and then diverging again, it is not intended to indicate 'greater than' or 'less than'

1. OBJECT (Depth of Field) > lens < FILM in camera (Depth of Focus)
2. NEG > lens < PAPER

#1 has object 'in front of the lens' and film as 'behind the lens'
#2 has neg 'in front the the lens' and paper 'behind the lens

So so depth of Field applies to the object while depth of Focus applies to camera film, but what about in the enlarger equation? The 'object' is the neg in the enlarger, so Depth of Focus should pertain to the Paper, not the neg?!

Wilt - I rarely print 35mm color slides, but have done a few 4X5 enlarged dupes from them in order to sustain hue saturation at bigger print scale. This might not be the ideal thread to discuss it in detail. A grain magnifier is just what makes visual focus check possible. Degree of necessary precision in all the rest of the system is a further topic. But I think you're getting off on the wrong foot if you are thinking of this in terms of "circle of confusion" issues. Film potentially holds far more detail than printing paper, and there is a complex inter-relationship between "grain" per se and the printing characteristics of film dye clouds. And in this case we've got em all - film to film dye clouds, true silver grain in any attached masks, perhaps anti-Newton texture if the incidence of light isn't correct, etc. So keeping a shallow but very precise plane of focus is critical for best results.

I also use very precise true apo lenses for this kind of applications, especially Apo Nikkor process lenses for large format applications, which are significantly better corrected apo-wise and per retail retention than any official enlarging lenses, including at short range. Combine that with a top-end grain magnifier like a front-surface mirror Peak, and the qualitative result and true plane of focus tolerance can be visually detected under magnification. It's easier done than explained. But one likewise needs an equally precise enlarger and precision negative carrier with optical glass on both sides of the original.

I need to get back to other projects, but if you have even more specific questions, I'll try to get back to them later in the day. Among other things, I need to make sure any dry grass remaining in back yard is removed before the 4th. Almost 40 homes have already caught fire in this county alone due to fireworks idiocy, with 13 families now outright homeless. I'll be up late on the 4th with a water hose nearby. Last year, the official city SF, Berkeley, Richmond, and Emeryville fireworks shot over the Bay paled compared to what was going on right in the neighborhood. A lot of bored kids and stupid adults out there due to the pandemic, wanting something exciting to do.

Good luck with avoiding fireworks...the TV news shots over San Jose and Oakland in past years of illegal displays is unbelievable in quantity and sophistication of fireworks. It is so tragic that brainless folks' pursuit of thrills during dry years surmounts their fear of starting big fires.

My mention of 15mm DOF with enlarging paper was due to others' statements about DOF at f/8 permitting lots of elevation error for paper print, so 0.015" double weight paper was immaterial in focus accuracy. One report was -5mm focus error might not even be discernable vs perfect focus. So I was trying to understand why paper print resulted in laksadaisical practices ('paper thickness did not affect grain focuser results enough to matter'), yet slide duplication was exacting...yet both are 8x projections from neg/slide. APO lens might give sharper results in projection, but for so many, lack of focus precision does not bother print makers...why the difference in tolerance to imprecision?! You mention grain and dye cloud density, maybe that is the cause...paper with lower density, duplicating film with higher density.

I got the back well cleaned up. The afternoon of the 4th I'll simply hose water into the gutter where cedar twigs fall. The .002" I mentioned goes back a long ways as a kind of common-denominator standard in the graphics industry and with respect to those who made specialized related equipment. I don't intend to make a religion out of that, but it makes a lot of sense in that context. Elevation errors perhaps tolerable for some practitioners making prints sound atrocious to me, and especially in the context of essentially "printing" onto film rather than paper, and trying to retain all the detail of the original even in projected fashion. That is an unforgiving task. Likewise, printing onto Cibachrome, itself a polyester rather than paper medium, taught me how to be routinely precise. It could capture extreme detail just like film. The current equivalent is Fujiflex Supergloss.

Large format originals can contain a lot of information. I'm won't get into arguments over extreme detail versus softie looks; but when actually needed in a big enlargement, every step of the process has to be tightly handled. And people do tend to get nose-up to my displayed prints. An old 4X5 or 8x10 chrome might be retrieved from my pile and converted into a master printing dupe using multiple masks for sake of Ciba printing. But that being gone, the adjusted master chrome might get turned into an internegative instead for sake of RA4 chromogenic printing. Every step of the sequence has to be spot on. Fooling around with something like 15mm alleged depth of field would be like shooting at a duck a hundred yards away with the gun 15 degrees off. Errors compound.

Commercial slide duplication, and even large format chrome duplication, tended to be awful. There was simply no way to do that on a commercial clock-in / clock-out assembly line basis and do it well. What was a LF dupe back then? - fifteen bucks apiece, and a couple dollars for a 35mm slide. I'd charge $500 dollars per chrome to do it the slow right way, and even that wasn't all that expensive because people holding laser film-recorders back then could potentially charge a thousand bucks for an enlarged dupe. And yes, the right lenses make a huge difference. The kind I use, even though a bargain today on the used market, were once quite expensive when new, four or five times as expensive as top-end enlarging lenses. The very very best for 35mm repro would easily cost you a couple thousand dollars today, if you can even find one.

So, I'd sum this up by stating, not all printmakers are the same by any means. Depends both one's priorities and specific equipment. Much of my equipment has been specially made by myself, saving me a lot of money. Other items came from specialty graphics sources no longer around, true machinists who knew how to routinely work within the very tight standards I mentioned, and were counted on to predictably do so over several generations.

And what is "discernable" or not, well, that too is related to one's specific standards. I'll walk into our local camera store (or did so in pre-pandemic days), and one of the employees would proudly show me a slide on the light box and hand me a loupe, and brag how sharp their shot is; but to me it looked like sheer mush. The preponderance of the web and inkjet printing just seems to keep lowering and lowering the standard of what is acceptable. It's all nice in that it has democratized and simplified the process of personal imagery, but people seem to have laid aside the fact that there are much higher quality alternatives, or more likely, they've never seen quality work to begin with.

So much for the depth of field (focus) calculation Matt did. I guess. Maybe. Scratches head while looking at the gears on the focus assembly of his enlarger and thinking they may more closely resemble those used to raise and lower a portcullis than those driving the second hand on a Patek Philippe.

DREW WILEY said:

Large format originals can contain a lot of information....

And what is "discernable" or not, well, that too is related to one's specific standards. I'll walk into our local camera store (or did so in pre-pandemic days), and one of the employees would proudly show me a slide on the light box and hand me a loupe, and brag how sharp their shot is; but to me it looked like sheer mush. The preponderance of the web and inkjet printing just seems to keep lowering and lowering the standard of what is acceptable. It's all nice in that it has democratized and simplified the process of personal imagery, but people seem to have laid aside the fact that there are much higher quality alternatives, or more likely, they've never seen quality work to begin with.

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My take on your elaboration is, "Some folks are fussy and some are very laksadaisical about precision in processes....some folks see differences and some folks do not, resulting in their attitudes."
I will relate a similar circumstance: My uncle had a TV/stereo store and did electronics repairs many decades ago. Someone would come in, having learned about my uncle from someone else, and complain about something that was scarcely detectable to my uncle. The customer complained that he had taken the unit elsewhere, and gotten no satisfaction from them. My uncle put the oscilloscope on the unit, and the very tiny amount of distortion the customer complained about would be visible. He would then try to remove what had been visible, to get the perfect oscilloscope trace.
IOW, some folks simply cannot see something while someone else is acuately aware of imperfection.

None of this changes the fact that there is a minute range of elevation over which there is no discernible difference in grain appearance through a grain focuser. That range exceeds the thickness of the paper. Be as precise as you wish with your process - you cannot change the basic fact of physical nature - unless your lens has an aperture that opens enough to give a dof thinner than twice the thickness of the paper.

Don, it's YOU claiming "no discernable difference" - not me !!!! Have you ever worked with pin-registered systems where multiples had to be in complete agreement? But you said it yourself - UNLESS one is working at a wide enough apertures - that is part of the whole point - ideally achieving precise focus ONLY on the original emulsion surface itself, and not even one film thickness behind it. That applies to the negative carrier, but in principle, nearly equal precision is needed at the vacuum repro position below too. I already explained why. What you claim is "none of this" amounts to saying a baseball itself has no relation to a baseball game. It is the game.

One man's "good enough" is another man's nightmare. I recognize the distinction between necessarily nitpicky applications and general black and white paper printing. However, if I get lazy, that inevitably becomes a habit drifting over onto something else where I'll regret it. I have very precise darkroom equipment for a reason, because it makes it relatively easy and routine to do fussy things. Things which to other people might seem like overkill are just second nature to me. I don't even think about them anymore, just do them. But the proof is in the pudding. All those little details cumulatively add up.

Don Heisz said:

None of this changes the fact that there is a minute range of elevation over which there is no discernible difference in grain appearance through a grain focuser.

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Emphasis added

DREW WILEY said:

Don, it's YOU claiming "no discernable difference" - not me !!!!

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Drew:
Note the emphasis I've added.
The combination of the visual acuity of the user and the capability of the grain focuser is the limiting factor.
And that combination results in the "no discernable difference" - at the time you are setting the focus.
I expect that with additional techniques and equipment you can detect a difference - at the time you are setting the focus - and with complex pin registration systems that difference will definitely matter in the result.

DREW WILEY said:

One man's "good enough" is another man's nightmare

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It's not a matter of "good enough" or "perfect" - simply because you can't actually tell the difference between one and the other with at least the vast majority of grain focusers and enlarging lenses. There is clearly an exact elevation of the lens that is perfect focus. But, as @MattKing said:

MattKing said:

The combination of the visual acuity of the user and the capability of the grain focuser is the limiting factor. And that combination results in the "no discernable difference" - at the time you are setting the focus.

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There is no question that, the more techniques you employ, the more likely you are to get it "as good as possible". But even that can't be confused with "perfect" when "perfect" is an ideal point the exact location of which is only approachable given technical limitations.

Suppose that your enlarger has an elevator or crank so that you raise and lower the head of the enlarger as you grain focus.

Hypothetically you may find a discrepancy between the elevation at which one stops if focusing on the way up, versus focusing on the way down. A few iterations can rule out user mistakes.

And I would say that discrepancy may indicate a critical range within which all planes will produce a sharp print.

Anyone willing to try this and share their results?