Using grains focuser with or without paper on the easel

[MattKing]

If I try to paraphrase what I think you're asking, "If you put the grain focuser on the top layer, as you removed each of the layers of double-weight paper, would you be able to detect increase/decrease in focus accuracy as you passed thru the ideal focus plane?" (finding out if the 25X grain focuser would reveal what the naked eye would be fooled as 'in focus')

The first part is a correct description of what I've been posting about throughout this thread.
The part in parentheses assumes that we can use magnification to correct the deficiencies of the naked eye. I'm not convinced of that, but it may be true. It also may be true that the entire system would need to be able to resolve to a much greater extent than it does (and in particular, a much greater extent than photographic paper can) before we could "see" a one paper sheet difference at the easel.

 

[wiltw]

The first part is a correct description of what I've been posting about throughout this thread.
The part in parentheses assumes that we can use magnification to correct the deficiencies of the naked eye. I'm not convinced of that, but it may be true. It also may be true that the entire system would need to be able to resolve to a much greater extent than it does (and in particular, a much greater extent than photographic paper can) before we could "see" a one paper sheet difference at the easel.

Matt,
We have to remember the limitation of human visual acuity, or about one-half second of arc. Where resolution of the photo exceeds the ability to detect the detail, mangnification blows up everything, perhaps to a point the eye CAN begin to detect what it could not previously!
At a viewing distance of 10", the eye detects down to 0.00145". Under an 8x loupe (area magnification) the eye only needs to detect 0.0041" (2.8X linear magnification)

 

[Pieter12]

Well perhaps Bill should test using single weight paper?

Is single-weight even available any more?

 

[MattKing]

Matt,
We have to remember the limitation of human visual acuity, or about one-half second of arc. Where resolution of the photo exceeds the ability to detect the detail, mangnification blows up everything, perhaps to a point the eye CAN begin to detect what it could not previously!
At a viewing distance of 10", the eye detects down to 0.00145". Under an 8x loupe (area magnification) the eye only needs to see 0.0058" (linear magnification)

I'm just saying that it isn't only the naked eye that provides a limitation. It is the entire optical system, including the eye, the grain focuser and the enlarging lens.

 

[cliveh]

Is single-weight even available any more?

Are all papers now double weight? What is Ilford multigrade? Single or double?

 

[MattKing]

Are all papers now double weight?

Medium weight is probably a better description.

 

[Pieter12]

Are all papers now double weight? What is Ilford multigrade? Single or double?

Ilford describes the fiber-based MG as double weight. RC seems a bi thinner, but not single-weight.

 

[Don_ih]

Medium weight is probably a better description.

I'd agree. Single weight is much thinner than modern rc paper. Fibre paper is pretty much double weight and also thicker than modern rc paper.

This thread is really devolving into serious hair-splitting.

 

[MattKing]

This thread is really devolving into serious hair-splitting.

Was this intended as a pun?

 

[Don_ih]

Was this intended as a pun?

Sort of. I was going to mention that you brought up a good point - that moving the lens has a much greater impact than moving the easel - but I guess people would argue about that, too - since, if you agree, you also agree that having or not having paper under the focuser probably has no impact.

 

[DREW WILEY]

You just place the thicker paper into a sweat chamber and starve it for a week before the matchup. Or else you swell the thin paper in fatty grease just like a Sumo wrestler, and then have them both compete in the thicker division. There's an answer to everything. Just don't place bets on any of this, however.

 

[wiltw]

I don't think anyone disputes that vertical movement of easel is less impactful than a change of distance between lens node and negative. Anyone who has tried to reduce convergence during shot by easel angle during enlargement is aware of the tolerance of easel tilt.

The point of Bill's test, IMHO, was to try to quantify the claims about easel/paper height, so that the amount of 'height makes no difference' subjective statement could be objectively quanitifed (or not), when lens is wide open.

 

[DREW WILEY]

As far as grain "snapping into place" when at precisely the correct focus, it's easier to do with certain kinds of film-developer combinations than others, being easier with more conspicuous grain shape. And in fact you arrive at a more precise position than focussing on very fine grain. For those of you with Durst commercial enlargers, accessories like the Nega 138 carrier come with a precisely adjustable focus target made from such a film. Once the film crosshair of this is calibrated to the exact height of the inner surface of the bottom carrier glass itself, then you can use this target in advance, and every negative used at that same spacing afterwards, easel to baseboard, will be in correct focus. This is particularly useful when needing to bring into precise focus harder to see fine detail, like the dye clouds in low-contrast orange-masked color neg film.

Those of us who know what these special enlarger features were designed to do in the first place, and appreciate that kind of precision, naturally trend toward different opinions that those who place their easel atop a decaying hay bale and use an empty Coke bottle for the enlarging lens. To each his own.

 

[Andrew O'Neill]

I always stick a piece of paper in under the grain focuser when using fibre-based. It's a habit.

 

[Pieter12]

I'd agree. Single weight is much thinner than modern rc paper. Fibre paper is pretty much double weight and also thicker than modern rc paper.

This thread is really devolving into serious hair-splitting.

But that is what it is about!

 

[DREW WILEY]

Michael - It doesn't sound like you've ever even seen one of these Durst carriers, or else you sure as heck don't know how to use one. You bring into focus an actual film crosshair target factory-mounted toward the front of the carrier. There are two different registered positions where the carrier locks into the head. Halfway-in, the crosshair lies directly over the center position of the baseboard (everything is fine-tunable). Pushed all the way in, your own film image (up to 5X7 format) is centered over the baseboard on axis. Therefore if you just focus on the film crosshair (much like a reticle), you attain the same focus usable for your sheet of film sandwiched in the carrier. Film plane A (crosshair) and Film B (you negative) are exactly the same distance from the easel, centered on exactly the same spot. In both instances, you are focusing on the respective EMULSION GRAIN ITSELF. Get it?

Junk?... Damn expensive "junk". Yes, they made even more expensive carriers; I have some of them, as well as their 8x10 enlarger equivalents. No one can afford that kind of true machinist quality production or die-casting for an enlarger model anymore. Every recent enlarger model is aluminum extrusion, CNC shaping, plastic parts etc. But you must think a Ferrari is junk too. Unless they're old and all beat up, or you are exceptionally lucky (it happens), these particular carriers by themselves often cost more on the used market than nearly all complete production 4X5 enlargers from other manufacturers, even brand new.

What kind of enlarger do you use? - a VW van with one of the headlamps inverted through the top as the enlarging light source, and the amount of pressure in the rear tire constituting the focus mechanism? Something you learned from the hippies who fled to Canada in the 70's? Either way, keep it - tie-dyed enlarger curtains will soon be back in fashion.

 

[Bill Burk]

I’ve got a machine shop at my disposal, all I have to do is ask. But whenever I go there, my stepfather and I just talk about the old days.

He works in tolerances of millionths and likes to talk about his two hundred year old grinding wheel that doesn’t have tolerances because it’s perfect.

That is kind of what got us here. If you can get perfect focus by dropping a piece of paper on the easel why not? The answer “because it doesn’t matter” holds true by theory and experiment for certain applications.

I focused my attention on an application which has great tolerance at the paper plane; 35mm enlargements about 10 diameters. I chose f/2.8, although most people stop down a bit.

Here is the video, enjoy:

https://youtube.com/shorts/VfFs6YqKwU8?feature=share

 

[Don_ih]

Bill, that video reminded me of A Clockwork Orange.

 

[DREW WILEY]

Of course I understood what you were up to all along, Michael. But what fun would it be if I didn't respond as you hoped? And it did give the opportunity to explain this in a little more detail for sake of others. But otherwise, no ... you wouldn't need different kinds of crosshairs on different kinds of film. Just the emulsion plane itself is involved, regardless. I almost never use that crosshair device personally, except for precise centering purposes. For example, my excellent projection densitometer correctly reads only on-axis.

 

[wiltw]

Bill, that video reminded me of A Clockwork Orange.

At least you got that out of the Youtube...I watched it three times, and all I got from it was,

"I see see a series of 19 images which are 14cm x 14cm on my monitor, so smaller than they were printed and occupying only 39% of the vertical pixels of the monitor, amd therefore it is impossible for me to conclude anything from seeing any of the images at smaller than lifesize, and at about 560 x 560 monitor pixels each pixel is 0.5mm real size on the print but my vision is better than that."​

...I guess I have gotten stupid as the years advance. At least it did not start an epileptic seizure.

 

[Bill Burk]

At least you got that out of the Youtube...I watched it three times, and all I got from it was,

"I see see a series of 19 images which are 14cm x 14cm on my monitor, so smaller than they were printed and occupying only 39% of the vertical pixels of the monitor, amd therefore it is impossible for me to conclude anything from seeing any of the images at smaller than lifesize, and at about 560 x 560 monitor pixels each pixel is 0.5mm real size on the print but my vision is better than that."​

...I guess I have gotten stupid as the years advance. At least it did not start an epileptic seizure.

Actually you saw all there is to see. Prints are 7cm square. In a quarter inch of range there is no discernible difference. I can’t see it under a microscope either.

 

[wiltw]

Actually you saw all there is to see. Prints are 7cm square. In a quarter inch of range there is no discernible difference. I can’t see it under a microscope either.

And that is the key summary statement, to answer the issue of detectability under magnification vs. by naked eye! Thx for advising there was not much to be gained in seeing the Youtube segment. I was starting to think my IQ had dropped over the years, undetected until now.

 

[DREW WILEY]

Hi, Michael. Well, given that this is all about grain-magnifier levels of hypothetical resolution, and not about what can be achieved by slicing off sub-micron layers using some kind of super-microtome for sake of electron microscope viewing, once again for all PRACTICAL PURPOSES, discernible grain simply lies on the surface of the emulsion side. But anything like a quarter inch of range is like a football field of distance in comparison. I don't buy into that either.

 

[Danner]

On YouTube, The Naked Photographer recently posted a video testing whether a sheet of paper under the grain focuser made any difference in print sharpness.

It didn't.

 

[Danner]

LOL see post #1 of this thread

Consider that my confirmation of the OP