Projects to aid 50" panoramic prints and darkroom nic nacs

[resurgance]

Great to get up to date on all sorts of new thread on all sorts of topics....
Have been absent for a year or so with life being life, and am rekindling the darkroom 'fire'....

Was investigating making a vacuum easel to suck flat what I would call large prints (600 x 1200mm, or 2ft x 4ft) and am now confident that I have come up with an OK plan, involving alloy plate with 1mm holes at 10mm centers, and an alloy ribbed system internally to hold 'platter' dead flat but keep weight down so my Devere base does not sag. Looking like I may be able to get it around 10kg which is probably not far off the current base which I will remove. It is not magnetic, so nice magnetic strips are out, but I think as I will always have a factory edge as my paper roll dimensions match the sides i should be able to use clamps and an RHS extrusion to get same end result and keep it square.

Another project is to be a roller that goes in custom made SMALL trays to automatically scroll the print. Have now a pretty decent mental image of what this thing is going to look like, and have located all of the materials. Will be constructed from Acetal, with acetal gears on one end, a paper holding method, and a DC gear motor with a built in encoder so I teach it different lengths and have a simple high speed counter to reverse the paper before it strains. The trays can then hold easily less than 3L of chems and have a small footprint - maybe even match the contours of the rollers.

The roll of paper is an Ilford 50"x90ft roll of that 'new' FB Glossy emulsion, I have not printed on it yet, apparently the grains are smaller etc etc. I plan to make the rollers 50mm diameter and have the 1200mm long print go its length through the chems in about 8 seconds per pass.

Just wondering if anyone had attempted this, or used a similar setup, as I have seen photos of an italian or french contraption that looked like it did just this.

Would like to hear please about any potential pitfalls, and things like - would i be best to pre-wet the paper prior to putting through the developer to let it 'settle' and things like that that I may not have considered? Open to any suggestions or experiences.

[ic-racer]

I was going to make some troughs like shown in this video. I'm still thinking about it, but currently only doing 16x20" in regular trays.

https://youtu.be/J0VPCHDqg7M

[bob carnie]

I was going to make some troughs like shown in this video. I'm still thinking about it, but currently only doing 16x20" in regular trays.

https://youtu.be/J0VPCHDqg7M

This is exactly how I do large lambda fibres and prints bigger than my 30 x40 trays... doing some 6 footers this month this way for a new show coming to Toronto.

[jon.oman]

In the 70's, I made prints like this that were 50" x 120", while working for Ford Motor Co. We had SS sinks that were trough like in a line. We rolled the paper stock just like the video.

[resurgance]

Thats the way I'll do it to start with for sure, I understand now what is meant by 'scrolling'. I would be keen with the larger prints especially with wash-aid, and prep for selenium as well as selenium to automate the scrolling of the print? Essentially I will be doing as per the youtube clip but with a mechanical aid. Well I'll see if it works without pre-wetting the paper, I guess the only real way to figure it all out is to do it.
Previously I have only processed using trays, and only done 16x20 max as you say IC-Racer.

6ft. Bob that is a decent print! I have only just started getting an idea of just how much detail is contained in a decent neg, and I have not even gone past the print size where it becomes obvious/noticeable. I am really looking forward to enlarging a 4x10" neg onto a 2ftx4ft print! Provided obviously that I do my job with the loupe properly on the ground glass when making the neg to start with.... Am really fond of using the view camera to produce angled focal planes; its uncanny how it affects the print, and such a nice thing to look at - also watching a photographer who has always had his focal planes parallel try and figure it out is a treat haha!

Great to get excited again about this great art, and the wet process.

[resurgance]

Is there a calculation for actual depth of field with enlargers? For example, tonight I cut a 600mm bit from my 1250mm wide roll (or 24" x 50") and taped it onto my baseboard. It was almost flat, but using my eyecrometer I detected very scientifically using my index finger that in certain parts that fought the natural curl, the paper was around about 2mm off the baseboard.
I am using an 8x10 enlarger and 300mm lens, I always stop down 2 stops. Also the baseboard is accurately aligned with the film plane via a precision level etc.
With any luck I can postpone making a vacuum easel for a while, and just get to some printing, until I free up some spare time.

[resurgance]

Hey! IC-Racer I just saw a post you wrote in 2010 about enlarging lenses;
quote
"Isn't stopping down an enlarger lens also helping to overcome the curving of some types of FB paper?

Perhaps in some settings. Here are some numbers (based on CoC 0.15mm):
The focal depth on the baseobard side at f5.6 with a 5x enlargement is 2.5mm. When stopping down for a print (f22) the focal depth at the baseboard is 43mm."

Thats gold - so tell me, do you happen to know where you got this info from? or is it done with your eyeball? I just tried to tape a piece of FB 2ft x 4ft paper from a roll onto my baseboard and I could see it was mostly flat with a chance of rain; I am using a 300mm lens, 8x10 enlarger, roughly 2 - 3ft enlarger height, stopped down two stops.
What this means to me is that I will be able to produce some decent prints WITHOUT a vacuum easel! Keen to hear your thoughts.

[Nodda Duma]

Hi resurgance,

I'm jumping in as a lens designer to reinforce your conclusion that you will probably not need a vacuum easel.

Math discussions are typically pretty boring, but I think the depth of field calculation is really useful for your current endeavor. The tolerance in "sheet curl" or focus accuracy required is the depth of focus. This can be calculated from basic parameters of the optical setup.

Probably the most useful form of the depth of focus equation is based on the enlargement of the print (magnification):

t = 2*f/#*c*(1+m)

where

t is depth of focus
f/# is the enlarging lens f/# setting
c is the acceptable blur spot size (Circle of confusion in optics jargon)
m is the enlargement magnification.

Circle of confusion is usually the point of contention, and I'll just say that it's a deep discussion beyond the scope of this thread. A common circle of confusion "rule of thumb" for a negative is d/1500, where d is the diagonal size of the negative. That value would be magnified by the enlarger magnification for a print-sized circle of confusion (for 35mm, it gets close to commonly used value of 0.2mm for viewing an 8x10 print at comfortable reading distance) IC-racer's value of 0.15mm is just fine for enlarging a 35mm negative.

So as an example calculation, if I were to enlarge a 35mm negative to an 8x10:

magnification m = (8*25.4)/24 = ~8.5x
acceptable blur size c = 0.15mm (I use IC-racer's value mentioned above)
enlarging lens f/# = 8.0

t = 2 * 8 * 0.15 * 8.5 = 20.4mm, or 0.803".

There are a couple of caveats to keep in mind:

1) Be aware of what height the grain focuser is showing you the image relative to where the paper will lay (usually a paper's thickness above the surface that the grain focuser's base is sitting on).
2) The equation assumes your enlarger is perfectly aligned.

For these reasons, I would add a "safety factor" of, say, 4x. So I would want the print in the example above to lay flat to within 20.4 / 4 = 5.1mm, or 0.200"...easily accomplished on an easel.



For your goal of enlarging a 4 x 10" negative to a 2ft x 4ft, or 24" x 48" print, the circle of confusion for the final print will probably be more like 0.91mm (negative diagonal divided by 1500, then multiplied by the magnification determined below). This is just an example .. so define the acceptable blur size based on your assumption / experience / intuition about the viewing distance of the final print.

magnification = 24" / 4" = 6x
acceptable blur size, c = 0.91 mm
enlarging lens f/# = 11.0

t = 2 * 11 * 0.91 * 6 = 120 mm

With a 4x "safety factor", the paper would still only need to lay flat to within 30mm, or 1.18". So I agree, you probably do not need a vacuum easel.


Hope this helps,
Jason

[bob carnie]

Regarding paper on walls for murals.. I have done both magnets to metal wall no Vacuum , and as well have worked with huge Vacuum Walls for murals... I prefer no Vacuum wall just a laser aligned metal wall and a very good set of handled magnets . You will be fine.

[resurgance]

Thanks guys, this is a revelation for me! I think as i have heard over and over that enlarger alignment is critical and to get the sweet grain everything must be dead flat, I just resigned myself to the fact that I was going to build a vacuum easel. And its not that easy to do it properly. I tend to over-engineer things, so it had to be light-weight (to not bend my enlarger subframe as I moved it up and down for bigger prints) dead flat, and not big holes, the right vacuum pump, blah blah. I worked out on my milling machine I was staring down the barrel of between 3000 - 7000 holes.... Humbug.
But now I'm off the hook and I can get on with taking photos and printing. *happy*

[bob carnie]

I remember working at a very large Mural Printing house and though the vacuum walls were present none of the printers used them, Yes a result of zealous in-house Mechanics wanting more toys than really needed. These walls were huge as some of the rooms were to handle 72 in roll b 100ft paper stock from Kodak , you can imagine the cost of these units .

I used a series of 3 ft magnets with handles, not sure where the hell we got them, the basic idea was to set a corner angle from the top left corner if you were right handed.. you would but the paper into this corner and with a second magnet you would put on the paper in the butt... this would mean that you set the starting position 1-2 inches on the width to hold the paper and you would then use the top magnet to guide you along and placing magnets along the top as you go , you would be tipping the magnet slightly onto the paper to hold which means you would be hard pressed to make a full image bleed. Once you got the paper across the width of the image you would anchor with magnets the complete sheet top bottom and sides.

This sounds quite complicated but actually after a few trys quite easy, In a good day we could go through 5-7 hundred of feet of paper making 4ft x 8 ft prints. We had econo-rolls to give exact paper cuts but I also did work with paper directly from the box on the floor and cut with blade using a point on your body for measurement when you pull the paper up. This method was actually quite accurate after time, but for sure I preferred the auto cutters. We worked in individual rooms connected to the dark hall which had three different processors for whatever size or product you were using .. one machine for the 72 inch paper , one machine for Duratrans , one for smaller paper runs , and one machine for Black and White RC.

Taking the paper from the wall was just reversing your magnet removal and believe me after time it gets real easy. Once off the wall run to the processor in dark put on machine and back to the enlarger for the next print.

Enlarger needs glass carrier and much effort must be made in advance to lock the enlarger on rails in at different magnifications and critical level.. This is actually the really hard part and without this you are screwed IMHO . I never did this job as it is above my pay grade, the floor quality the leveling of the rails that will over time not move and the ability to level the Metal wall is crucial.
I have seen some poor lab technicians working in sub standard labs trying to compete with no leveled rails and in my worst nightmare I would never attempt to do this. The only exception is if 1. you can set the enlarger up and never again move it . This would be a situation where all the negs are exactly the same and one never does a second size.(this sounds quite Impractical) the other is to do a set up where the wall moves to the enlarger ... I have actually scene this setup where a photographer cut a hole through his floor and projected to a drop table in the basement below, this was an incredibly efficient idea for this fellow, and in my 40 years of professional printing the only time I ever saw this vertical setup.

[resurgance]

WOW. I can only imagine looking at one of these enormous prints in person! There is something very different about a proper silver gelatine print, and made with a decent negative it would be a thing to behold. And the rooms with enormous paper rolls~! far out.
The vertical setup into the basement is a brilliant idea! I'm not a fan of safety but the idea of a hole in the floor in a darkened room sounded pretty exciting :)

I'm sure some would disagree but I am a fan of glass carriers - I am wrapt to discover about depth of focus on the paper side of the enlarger, but the negative plane looks pretty critical.
I dry my negatives with a positively pressured and filtered drying cabinet that I built, so the negatives are hung a dry without ANY dust settling into the emulsion. Then I bought a cheap airbrush setup and simply blow both sides of the negative, and all glass surfaces prior to inserting the carrier into the enlarger. Have not had ANY dust spots yet!! By the way this is also after the fact that I have gone to great lengths to paint every bare wood surface, and clean down every horizontal surface periodically with a damp rag, clean the floor regularly with a damp mop, and never wear synthetic clothing into the darkroom. I have an antistatic gun but never really needed it.
I bought a precision level with an adjustable long bubble which is perfect, as my enlarger itself is not perfectly level, but as the level is adjustable I can set it, and simply ensure that at the different heights I set my baseboard to, it is parallel to the baseboard.
At least I know my negative is dead flat and I don't have an issue with dust.

Funny for me 2x4ft is massive!

[Joshua Dunn]

I finished my thesis this year and printed it on my Canon PF9400 printer (60" wide). So they were not darkroom prints but what I am going to describe could be used in a digital or wet environment. If I am understanding you correctly you need to keep large paper flat for exposure. I needed to be able to keep large prints (some 5'x8') flat on a wall for viewing. What I did was paint one entire wall with a metallic primer (I have no idea if this is available in New Zealand) and then one coat of paint in an 18% grey color. When I want to view/display a print I roll it onto onto the wall and hold it in place with rare earth magnets. I wrapped the magnets in archival hinging tape so that they will not damage the surface of the paper. It holds 300+ gsm paper with no problem. If you go the blog section of my website www.joshuadunnphotography.com or Instagram @JoshuaDunn_Phot you can see some photos of the prints to give you a sense of scale. You might be able to do this on a large easel to help keep things in place.

Hope this helps!

-Joshua

[Kirk Gittings]

Regarding paper on walls for murals.. I have done both magnets to metal wall no Vacuum , and as well have worked with huge Vacuum Walls for murals... I prefer no Vacuum wall just a laser aligned metal wall and a very good set of handled magnets . You will be fine.

Have you tried magnetic paint to adhere to? Not cheap but works very well.

[resurgance]

Joshua and Kirk, GREAT idea. To tell you the truth I had never heard of magnetic paint!
Actually at first I thought that it was in the same category/ isle as striped and chequered paint :)
I wonder if I could simply add iron filings to some existing paint? I have been keeping grinding metal/dust in a container to demonstrate the magnetic field shape to my son, so I could try some of that, I don't see why it wouldn't have the same effect with some trial and error.

Brilliant idea. So I do not have a horizontal enlarger, just a Devere 5108 so I can put the baseboard down to the floor and raise my head up to the ceiling (actually I need to cut a hole in the ceiling there so I can lift it a little bit higher) but even holding the prints onto the baseboard with magnets would be beneficial.

One thing Joshua is that the fibre based paper I am using is a double weight and quite curly product that comes off a roll like the digital stuff, however because of the small roll size, when I unroll it and hold it flat by each side the centre is on the baseboard, and the edges, but the 25% and 75% on each side if you will sort of pops up in defiance. This fortunately is only by 2-3mm so based on what I now know about depth of focus especially stopped down a few, I am quite safe here.

Magnets and magnetic paint are a brilliant idea thanks. I am not keen on using adhesive stuff in the darkroom. And the proper low tack stuff is expensive, and I really don't like the idea of pulling tape off a print and creasing the print.

[Joshua Dunn]

I have the same experience with roll paper curling, especially at the end of the roll. What I would suggest is leaving the paper unrolled on the easel for as long as you can, preferably with some weight on it. If you use an old print on top it will protect the emulsion side of the paper. If you use the same size you can pre-cut several and flatten them all at once. Obviously you would have to either turn the darkroom light off (to make sure it doesn't fog) and leave it for at least an hour or so so it will flatten.

[resurgance]

Thats a good idea; I can leave it in the early evening when overcast or no moon/new moon so I can vacate and reenter the darkroom....

Actually on a similar theme - there is no reason why I could not simply cut 5 - 10 of the size that I will be using, (roughly the same), make a custom drawer/light trap, box thing with a weight on top, to leave long term? Brilliant.

Next wee mission is coming up with an elegant solution for a new wider baseboard for the Devere; the baseboard moves up and down, and is on a reasonable chassis, but means that the board itself can't be hugely heavy. I would like it to be decently flat, and am also probably going to incorporate metal strips top and bottom that are flush with the top surface for magnetic hold downs. I will probably laminate 2 layers of something pretty flat, and maybe even machine channels internally to lower mass but keep overall flatness....

[resurgance]

Well I made my first 2x4ft print last night, and uncovered another wee issue that I probably should of anticipated; well thats hoping that the roll of paper was not x-ray damaged when it got accidentally scanned and semi opened by baggage scanners...
I have my floor standing Devere enlarger in between 2 white cupboards and I am pretty sure light is reflecting off the cupboards and onto the print to fog it.

Was still pretty exciting making something that big. Am not convinced that I have so much depth of field on the baseboard though, I stopped down 3 stops to print as my baseboard is not completely flat, and the results were a little average; although it could also be that my negative is not sharp, as I was using a Seitz Roundshot and stopped that down as I was inside the 7 meter optimum range. (I was shooting at f22 and at 3m subject distance)

Fun and games

[ic-racer]

The size of Airy disks and circles of confusion can be optimized for any depth of field required as represented in this slight modification of the view camera focusing equation based on the method of Paul Hansma (equation #38 in http://www.largeformatphotography.in...DoFinDepth.pdf):

N_max ~ 20 / (1 + m) sqrt(dv)

N-max = F number
m = magnification
dv = focusing leeway on the baseboard, represented as the distance on the enlarger column between good focus on the highest and lowest positions (without touching the focus knob).
20 = constant for circle of confusion about 0.15mm on the print

[resurgance]

Thanks ic-racer, I need to digest that, but from what I can roughly figure out I should have at least 5mm. I have my enlarger raised to top height, and my baseboard on the floor. Funny what you find when you start looking though; I replaced my baseboard and found at least 4 significant issues with enlarger setup; (Scheimpflug was not on my side)
1) lens stage was not parallel with negative stage despite being a solid and well built unit - have found adjustment screws.
2) Lens board was made from some kind of epoxy resin or cast plastic, and was of BAD build quality - off centre, and was NOT parallel with lens stage!
3) Lens stage on Devere is separate from film stage and whole unit on slide was loose on the bearing surfaces.
4) Baseboard was way off I think as my new one was a lot lighter being Birch core HPL, and not using the beastly 20x24" Saunders easel with roll paper.

Plus after painting the sides of the cabinetry flat black I then discovered that the little TFT touchscreen I have controlling my grades/time was the source of the fogging!