Pt/pd Printing - Making a test strip

[Alan9940]

Though I've been printing pt/pd sporadically for several years, I've decided to get more serious about it. I'd like to make a test strip to determine a Standard Printing Time, but it seems that the 4-ply matboard I normally use for making test prints under the enlarger for silver printing is not heavy enough or not UV blocking enough to work. Rather than nice clean strips across the print for each exposure increment, I get more of an overall exposure with, maybe, faint strips.

I use an Edwards Engineered Product UV exposure unit where the printing frame is placed inside the box with a door that flips down to close it. Therefore, I can't make a test strip exactly the way I do it for silver printing. I'm thinking I need some kind of UV blocking material, perhaps a few different sizes, whereby I could place a piece on top of the frame, carefully slide the frame into the exposure unit, expose, rinse-n-repeat for, at least, a few exposures across the paper?

Anyway, how do you alt process printers using UV exposure handle test strips?

Thank you for any insight provided.

Alan

[cowanw]

A small Stouffer 21 Step inserted along side your negative will help you know exactly how many stops of time you need to alter to change a particular density to another.

[tgtaylor]

Alan - I haven't yet printed a Pt/Pd but have printed a few dozen Kallitypes which are very similar. I use the sun which is plentiful here in sunny California rather than an exposure unit and what I have found is that each negative is different. For example the last negative required 6 minutes is the open shade and 45 seconds direct sun and another 4 minutes is the shade and 25 seconds in the sun. So you have to know what it should look like when you pull it and to check. I usually start checking at the 4 minute mark.

Thomas

[peter schrager]

Although I'm not answering your question I strongly advise taking a class...tillmsn crane is a great instructor get in touch with him

[jim10219]

I just use black construction paper. You can also use a manila envelope. Lots of things will block UV light really well. You don't need to get fancy with it. I just cut them into strips of the appropriate width and place a few coins on the edges to keep them down, then expose for whatever desired time increment, pull the UV blocking sheet over a row, and repeat. I usually start off with a 15x15 negative that has 15 rows of 15 steps each. I just slide the UV blocker over 1 row at a time to get a rough idea of how it will look at different intervals. I usually have a pretty good idea ahead of time of how long it should take, but if I don't, I'll do it twice. Once for a rough figure, say pulling the sheet after every minute, and the second to fine tune it pulling the sheet over every 10 seconds or whatever is appropriate depending on how long the first test suggested. Then I have a 10x10 negative with 100 boxes that increase density by 1% each. I print that at the time I determined from the first test, and I get my curves. I just scan that final print into PS and measure each square with the eye dropper (after converting to B&W and adjusting levels for max and minimum possible tones) looking for an example that gives me the desired output density (say 25%), and it's location on the chart tells me what the input was needed on the negative to create that. So if the box that has 25% density is number 31, I'll set the curve's input to 25 and output to 31. Therefore I can get a really reliable procedure down for just about any process with just two exposures, saving time and money. Although, if you change anything in your setup, like the type of paper or coating procedure, you can expect to have to redo this whole process for optimum results.

[Alan9940]

@cowanw - When printing analog negatives, I do usually include a Stouffer Step strip just as a double check that tones are falling where I expect. With digital negs, I have a step strip that prints out right alongside the negative. However, neither of those will tell me what minimum exposure time is needed to produce dMax through the film. One simple test strip using blank film will tell me all I need to know.

@jim10219 - if you use something as simple as black construction paper, then I'd think my black 4-ply matboard should work. Perhaps I wasn't holding my mouth right or didn't have on my lucky underwear when I tried making a test strip the first time. ;) I will try, again, using a technique very similar to what you describe. Thank you.

[bob carnie]

I use a thick black lexan material for step offs when making Pt Pd prints . Very opaque.

[cowanw]

Not to want you to change anything, but if you lay down a blank film, a stouffer negative and your paper, and exposing over time, won't the first step of unchanging black be your minimum exposure time (Calculated from actual time)? Or am I out to lunch?

[tgtaylor]

I use test strips in silver printing to put the general exposure in the ball park and make adjustments to it from there. There is no substitute for not knowing what to look for in the work print. The advantage of the alt print is that you can open up the printing frame and see where the exposure is at, that is, if you know what you are looking for. If after development the print is a little too dark/light, then you know where to go with the next one. But maybe you can find an app in the store that will tell you all that.

Thomas

[Vaughn]

The thick 4-ply might be throwing a shadow, thus no sharp line...especially separated from the paper by the glass of the contact print frame. I use strips of rubylith.

[Alan9940]

Not to want you to change anything, but if you lay down a blank film, a stouffer negative and your paper, and exposing over time, won't the first step of unchanging black be your minimum exposure time (Calculated from actual time)? Or am I out to lunch?

Not sure exactly what this setup would look like, but, basically, when determining a Standard Printing Time you want the first exposure (that is, minimum time) needed to render black through film the same as uncovered paper. Therefore, the way I try to do this with pt/pd is to coat my paper, lay a piece of unexposed film along the coating at about the halfway point, then run a series of test strips across the paper. If it all works correctly, you should have a series of increasing density strips along the film next to paper black (well...as black as pt/pd can render.) The strip on the film side that matches the uncovered paper side is your SPT. Going forward, all negs will begin with the SPT exposure, then adjusted from there as needed.

Sure is a lot harder to describe this than it is to do it. :)

[Alan9940]

The thick 4-ply might be throwing a shadow, thus no sharp line...especially separated from the paper by the glass of the contact print frame. I use strips of rubylith.

Yeah, I thought of that. Do you mean standard red rubylith?

[koraks]

I used rubylith before I figured out that simple tinfoil works great as well.

[Vaughn]

Yeah, I thought of that. Do you mean standard red rubylith?

Red or amber both work. Tin foil, as suggested would also work, tho might throw a lot of reflected light around (but might not be significant). The rubylith is nice to use since one can see thru it for easy placement.

[koraks]

I see no problem with light scattering when using tinfoil, but I only use it for masking, so it's in direct contact with the negative. I glue a piece of tinfoil to a sheet of paper and rhen cut to size. The paper base probably helps with scattering if the foil is placed on top of the glass of the contact frame, particularly if you use a non-reflective paper base (matte black).
For exposure step tests I've used corrugated cardboard in the past, works like a charm as well. I think a plastic film bag should do the trick also.

[Christopher Barrett]

I use Cinefoil quite a bit on set for lighting. It's basically a roll of matte black aluminum foil. Could have a ton of darkroom uses.

25 bucks at B&H (https://www.bhphotovideo.com/c/product/44690-REG/Rosco_RS100113_Matte_Black_Cinefoil.html) or your favorite photo/cine supply house

[Alan9940]

Thank you all for your help. I think I'm going to try black matboard (hopefully, this will eliminate light scattering and reflections) and, if that doesn't work, I may give the Cinefoil a try. Thanks, Christopher, for the link.

[Colin Graham]

I had this problem with my vacuum frame, so I cut sensitized paper into strips and spaced them far-enough apart in the frame to eliminate shadow bleed from the card.


The thick 4-ply might be throwing a shadow, thus no sharp line...especially separated from the paper by the glass of the contact print frame. I use strips of rubylith.

[jim10219]

Not sure exactly what this setup would look like, but, basically, when determining a Standard Printing Time you want the first exposure (that is, minimum time) needed to render black through film the same as uncovered paper. Therefore, the way I try to do this with pt/pd is to coat my paper, lay a piece of unexposed film along the coating at about the halfway point, then run a series of test strips across the paper. If it all works correctly, you should have a series of increasing density strips along the film next to paper black (well...as black as pt/pd can render.) The strip on the film side that matches the uncovered paper side is your SPT. Going forward, all negs will begin with the SPT exposure, then adjusted from there as needed.

Sure is a lot harder to describe this than it is to do it. :)

I've tried this before, but I ran into a problem with this method. However, my problem was with Cyanotypes, not Pt/Pd printing, and I was using digital negatives.

Basically, I found out I could get 100% density at around 10 minutes with my UV light source. The problem was, that exposure was so long that I couldn't get any midtones. My only options were pretty much all exposed, or all unexposed. I tried using various colors of ink for UV blocking on my digital negatives, but unfortunately the ones that blocked enough UV light to leave areas unexposed after 10 minutes didn't allow me to create smooth transitions from 0-100%. I couldn't figure out a way for Photoshop and my printer to keep the proportions of the max density ink the same throughout it's curve. So for example, it might start off at 100c, 100m, 100y, 100k. But by what should have been 50% density (and read as 50c, 50m, 50y, 50k), I was getting outputs like 30c, 8m, 15y,70k. And then my printer was imparting it's own curve over that because I have several different tanks for each of those colors Photoshop was recognizing (magenta, light magenta, etc.), none of which seem to block UV the same. So in order to get the smoothest curves with the most usable midtones, I had to switch to using black ink only, and to considerably shorten my exposure time. Now I'm exposing around 4 minutes and getting about 97% of the max density, but am able to achieve a much smoother and more usable curve while only sacrificing the last few % points of density.

Obviously with a different setup, you'll get different results. And maybe with film negatives it wouldn't be an issue. But that is why I have to use a step wedge when determining my max exposure times with my equipment.

[tgtaylor]

The bulk of my alt printing these days is in the shade with a short hit of sunlight at the end. I find that although it takes a little longer it gives a much better result than all sun. It would be difficult if not impossible to achieve the same result with a UV light box.

Thomas

[Alan9940]

I had this problem with my vacuum frame, so I cut sensitized paper into strips and spaced them far-enough apart in the frame to eliminate shadow bleed from the card.

Wow, I really like this idea! I don't think it would have ever occurred to me...thanks Colin.

[Alan9940]

@jim10219 - thank you for the detailed response. Out of curiosity and your issues with ink colors that are most efficient at blocking UV light, have you ever looked at:

https://www.precisiondigitalnegatives.com/

Mark's process of testing to generate a digital negative is quite involved, but once you've locked it down the family of general curves and the option to build hybrid curves is quite extraordinary and powerful. Maybe you don't need all this, but thought I'd point it out for interests sake.

[jim10219]

@jim10219 - thank you for the detailed response. Out of curiosity and your issues with ink colors that are most efficient at blocking UV light, have you ever looked at:

https://www.precisiondigitalnegatives.com/

Mark's process of testing to generate a digital negative is quite involved, but once you've locked it down the family of general curves and the option to build hybrid curves is quite extraordinary and powerful. Maybe you don't need all this, but thought I'd point it out for interests sake.

That's interesting. Thanks for the link! I can't seem to find much info on what exactly it is and how it varies from what I'm currently doing, but it does seem to have some big names associated with it. I might just stick with what I've been using for now, as that is kind of pricey. But I'll keep that idea on the back burner in case things change.

[Alan9940]

@jim10219 - what I've always found fascinating about Mark's process is that it allows me to tailor my digital negative to a specific printing process; in my case, pt/pd. It's quite a bit of work and it takes some futzing around to understand the software (Mark is quite accessible and helpful here), but once you've dialed it in it will never change unless you change inkset. I'll admit...it's kind of weird seeing green or orange negatives, but they print beautifully! A very useful additional benefit is that I can build what Mark calls a hybrid curve. For example, I can apply a less steep curve in the upper region of the paper curve to maintain delicate high values while, at the same time, apply a steeper curve to the shadow end of the paper curve to maintain contrast in shadows. Some time ago, I built a template in PS that allows me to apply a series of individual curves to large thumbnail sized duplicates of my image and print several versions all on one single sheet. This enables me to see the effect of each basic curve which allows me to zero in on a very good starting point quickly. Anyway, not trying to "sell ya" rather as you said "food for thought."

[Jim Andrada]

Mark Nelson runs a great workshop on this. I took it last year, and aside from coming down with Pneumonia and barely remembering half of what he said, it was outstanding.

[Alan9940]

Mark Nelson runs a great workshop on this. I took it last year, and aside from coming down with Pneumonia and barely remembering half of what he said, it was outstanding.

Yes he does! I attended his workshop years ago with Mark & Dick Artenz in Flagstaff. Great fun! Highly recommended!!

[Jim Andrada]

Dick told me he's no longer doing the workshops - too bad.

[Cor]

I print pure Pt too infrequently too work systematically..I coat a small strip (2.5*10 cm) and expose using previous "experience", process and dry, and go from there to a full print..

good luck,

Cor

[Vaughn]

Cor -- actually, I cannot remember when I last made a test strip for Pt/pd (or carbon). I just make a full size print (up to 8x10), and make any corrections on the next print. (using in-camera negatives)

[Colin Graham]

Well no, it's not something that you 'd want to do for every print, it's more useful for finding the minimum exposure time for maximum black when starting a new process or calibrating a process for digital negatives. That's what I took from the OP anyway.


I'd like to make a test strip to determine a Standard Printing Time [snip]

[Vaughn]

I just happen to be a hopeless optimist (what a strange pairing of words!) I always hope the first one nails it.

[Alan9940]

Well no, it's not something that you 'd want to do for every print, it's more useful for finding the minimum exposure time for maximum black when starting a new process or calibrating a process for digital negatives. That's what I took from the OP anyway.

That's exactly what I was doing...calibrating for digital negatives. I suppose I don't always express myself properly and completely. My bad.