Half tone screens and half tone negative reproduction

[senderoaburrido]

I do some screen printing on t-shirts from time to time. recently I decided I wanted to try making some shirt prints of my photography. I figured the new 4x5 material would be a great source for that. After a bit of reading, I've learned that the way that they used to convert negatives into half tones for printing in newspapers involved copying the negative using a special screen. Does anyone know if those screens are still produced, and where I could find them? evilBay doesn't have any right now, at least not under the keywords "half tone screen".

Additionally, is anyone familiar with this process? I'd like some advice/pointers going in, if anyone has any to offer.

I know I could just digitize the negative, use PS to change it to half tones, and then print on acetate, but where's the fun in that?

[Drew Wiley]

T shirt shops just scan whatever and make relatively crude halftone screens, typically for silkscreen frames. Some might still use old stat cameras, basically cheap
versions of graphics art copy cameras. It's still an active industry with its own supply chain, some of which do advertise on EvilBay. I had a co-worker here that
got into making custom sports uniforms that way, got rich too. Kinda boring otherwise. But you can take silkscreen technique as far as you wish, clear into a highly
collectible fine art medium if you're good enough at it. Halftone just semi-automates the process at a more casual level.

[mdarnton]

Photoshop will do it for you easily. You'll need to scan the neg, then print another neg on transparency material from the halftoned result, but that would permit you to enlarge it to any size your printer could handle.

The other alternative of using a screen is equally or more laborious, so you might consider the scanning method.

[senderoaburrido]

I want to do it the analogue way, though. I've done a little reading since I made the thread, and I have refined my question: you need a halftone screen through which you project a negative in order to make the halftone copy. Can I just print my own acetate halftone screen for projection, or does it need to have special material properties? Those that I saw on evilBay are only for polaroid cameras.

edit: http://www.ebay.ca/itm/Lot-of-5-Vintage-Kodak-Contact-Screens-4-11x14-1-14x17-Misc-Types-/272183134950? Found these. Expensive. Anyone know how to properly value old contact screens?

[mdarnton]

However you do it, the screen needs to be in very good contact with your print, not the neg, and the print is made on lith film (high contrast). For making a silk screen you need a negative, which means the origin piece for the lith negative needs to be a positive, which means you first have to make your neg into a positive, then use that to make the halftone. This is getting more complex than you thought it would be, or do you have another plan?

Before you buy any screens, you need to find out what the right size is for silk screening. The coarsest one in that pile is 100, and I suspect that this is way too fine for silk. I am betting you want something around 40 or so---just a guess. Do you know? If not, you need to find out before spending a lot of bucks.

[senderoaburrido]

No, I don't know. I appreciate this information you're sharing. I'm going to look into the elements which you have described. That resolution issue sounds like it might be a big one. I'll have to figure this out. Either way, I don't intend on spending a lot of money.

Have you used the halftoning contact sheets before? What exactly do they look like? Could I not jury rig my own, if they're simply opaque plastic with holes?

As for the positive/negative problem, can you reversal-process c41 B&W?

[koraks]

You can print the halftone screen on an inkjet printer; I'd recommend that route. The UV sensitive dyes used for silkscreen are pretty high contrast, so you should be able to get by with an inkjet printed screen just fine.

[Jim C.]

A millenia ago when I worked in motion graphics I used half tone screens for moiré animation effects,
they're lith film with clear dots corresponding to the dot pitch.

Like others have said you could use PS to generate your halftone screen and find a prepress service bureau
that can print out a imagesetter negative.

The screens that you found on eBay have a make an offer option, make an offer !
Worse that can happen is they say no or counter offer.

[Jim Jones]

Improvising and printing a quality halftone screen on a laser or inkjet printer may be deceptively difficult. As I recall from working in graphic arts long ago, halftone screens were not pure black and white, but dots graduating from black through grey to white. Another way of achieving similar results is printing with a screen that is all pure black and white, but separating it slightly from the light sensitive material so the out-of-focus dot edges provide the halftone effect. The size, distance, and shape of the light source all affect the quality of the halftone image made with this technique. Early halftone screens sometimes consisted of crossed Ronchi rulings used thus.

[Jac@stafford.net]

Another solid gold post from mdarton. I would ask the Kodak screen seller for specifics and make him an offer.

[blindpig]

I suspect you'd be way ahead printing your photos on some iron on material as the halftone screens aren't black and white as Jim Jones said.The soft edges the dots have won't reproduce well on a silk screen because of the nature of the gray dot pattern and conflicting silk screen lines and the halftone line arrangement of the halftone screen itself,
IMHO.

[Gary Beasley]

The resulting halftone you would produce should have hard edges to the dots. The soft edges of the screen dot used on lithographic film creates dots of different sizes to cause the visual effect of grey tone. The spacing of the dots will cause moire patterns with the silkscreen mesh if oriented wrong and/or the line ratio is not good. Experimentally I found that a 300 mesh screen works well with a 75 line screen printing on non textile flatwork.

[senderoaburrido]

I managed to find a guy who has an old industrial printing camera who has some in Ontario. He has a bunch of these screens, and he's willing to chop them down to size for 5$ a piece. I'll update once I receive them.

Just to be clear: I enlarge onto the copy negative with a slate of glass keeping the contact screen flush over it, right?

[Gary Beasley]

Right. The screen is actually photo emulsion so you will want to determine the emulsion side of it and place it emulsion to emulsion. The halftones generally require a bump exposure to bring up the shadow dot. Experimentation will find the right bump exposure, a weak diffuse light giving just enough to create a small dot without any other exposure. Then you find the required exposure to the image to get a highlight dot that is still open enough to print right.

[senderoaburrido]

What do you mean by a "bump exposure"?

[Gary Beasley]

It's a non image exposure for bringing the shadow dots up. Without it the image would be blank in the black zones and shadow detail would be lost. In practical use the smallest shadow dot that will remain open using the printing method chosen is determined and the required bump exposure to get that size dot in the shadow is used before or after the image exposure. For silkscreen that will be a bit large due to the ink flooding into the small dot detail so the positive will look a lot more gray than you want the finished print to look.

[bob carnie]

Gary or others -

I have a question slightly off topic but I think relevant
Some of the best Carbon Colour Printers and Gum Printers for that matter are using a stocastic screen pattern to create their prints.
The screen is applied at a screen printing shop that is traditionally what you all are talking about here.

I am working with continuous tone silver film or I am using pictorico overhead transparancy film and separating the the image into four negatives and making prints with some success. Using
tri colour gum over pd.

I have some knowledge of the graphic arts - film to plate - film less plates but not at a level that I would like( for example I remember the bump but could not explain.}

Here is the question.

I have a Image setter that can produce a con ton negative or print... have you ever heard of applying a screen to each file that is then sent to an image setter like mine or
an inkjet printer.. I think the end result would be a negative with the required hard dot that may hold the pigments much easier.

I am thinking that this would work as if I scan and 35mm colour negative or black and white negative- put it to my image setter and make prints- the resulting print if you take a loupe
to the print or film you will see the film grain, and not pixels as one would imagine... therefore I am taking the leap that the pixels are smaller than the input original.

If so applying a fine screen pattern would then of course be visible in somewhat the same manner. which the would work much like the Ganglers, Taylors of this world.

This application could have great benefit to rotogravure workers or colour alternative workers wanting to lay down tone without a lot of image bleed from trying to do it with contone film.
BTW the contone film works but the resulting print is somewhere between a Fresson or a dye transfer- I think by applying a hard dot at the file stage may work.

your or any thoughts on this would be appreciated.

I actually have more questions but I will see how this one plays out.

Bob





It's a non image exposure for bringing the shadow dots up. Without it the image would be blank in the black zones and shadow detail would be lost. In practical use the smallest shadow dot that will remain open using the printing method chosen is determined and the required bump exposure to get that size dot in the shadow is used before or after the image exposure. For silkscreen that will be a bit large due to the ink flooding into the small dot detail so the positive will look a lot more gray than you want the finished print to look.

[bob carnie]

Also I do apologize to the OP if this takes the topic off track.

[Gary Beasley]

I've got no experience with imagesetters but a platemaking machine is doing much the sameexcept it burns a hardedge screen pattern withe required printing angles or some will also do stochastic dot as well. Its all in the software driving it so you might want to pose that question to you imagesetter tech or manufacturer and see if the software for that particular machine will support what you want to do. I know imagesetters came a little before the laser platemakers and were making litho style negs for plateburning the old fashioned way, so it may be a case of using different film and chemistry to get what you want.

[senderoaburrido]

When you say non-image exposure, you mean that I do an initial exposure of the negative I want to copy the image to without the original transparency in the enlarger, so that there is already a lightly exposed, uniform halftone pattern across the entire negative? I feel like my reading comprehension is poor, here. Should I maybe consult a manual for this process? There must be one online.

[Struan Gray]

Bob. You sound as if you want to add gravure-style stippling to gum or carbon prints. If you are lucky enough to have some colour gravure workers whose prints you can look at, they will give you an idea of the graphical potential.

With stippled/halftoned techniques it is easy to get posterisation in the transitions to the brightest highlights and/or deepest shadows - you have to control whether and how the plate transitions to no dots or all dot. Traditional gravure has the advantage over most other dot-based processes that the holes (dots) holding the ink can be made to vary in depth as well as density. All the same, most modern gravures I have seen are more 'graphic' in their treatment of tones than a carbon print. Classic gravure for book production and the like used mask-making and/or retouching to avoid this look. High quality CYMK halftone printing also used masks for highlight and shadow protection, and general contrast control. With a digital step, all of this can be combined in one output film for each colour, but without it, things get complex fast, requiring craftsmanship and artistry, and a knowledge of your particular press, inks, and paper for best results.

The Getty Atlas of Photographic Processes has a section on halftone, which gives a good introduction to the possibilities:

http://www.getty.edu/conservation/publications_resources/pdf_publications/atlas.html

Otherwise, the best, most detailed information on halftoning I have found has come from books and research papers published in the 50s and 60s. Best of all was John A. C. Yule's 'Principles of Colour Reproduction':

https://books.google.co.uk/books?id=U_QeAQAAIAAJ

[Struan Gray]

PS: I have a set of Polaroid screens. They have metal 'wings' along the side that were meant to be inserted into slots in a special holder, which also had a slot for a Polaroid sheet film holder like the older 500 series models. I found I could just place the screen (carefully) in the opening of an international back, holding it in place with a film holder and the spring pressure from the gg.

The coarsest screen was 65 lpi, which may be a bit fine for t-shirt work.

Note that these are ruled-line screens, which need to be held at some separation from the film to work properly. Modern screens are more often contact screens, which are easier to use, but less flexible (with a ruled-line screen you can adjust contrast by varying the height of the screen).

The screens work, but limit you to 4x5, which is a tad small for a shirt print.

[senderoaburrido]

The coarsest screen was 65 lpi, which may be a bit fine for t-shirt work.

The screens work, but limit you to 4x5, which is a tad small for a shirt print.

My thinking was that I could make an 8x10 litho or heavily overexposed xray enlargement of the halftoned product. From there I could do the t-shirt prints.
The alternative I envisioned was to enlarge the original halftoned product of 4x5 litho film onto a screen. I'm not sure whether that would work, as I'm completely unfamiliar with this process.

[Struan Gray]

If you have space, and if you really want to do this the analogue way, vertical graphics arts cameras like the Agfa Repromaster series usually go for free or peanuts if you can pick up. Find one with lens and halftone screens included and away you go.

I can't help feeling that you're making life unnecessarily hard for yourself though. If your goal was fine-art four colour gravure I could understand, but the very best T-shirt is not going to be able to justify the effort you put in. I personally would concentrate on getting the photograph right, and use a digital step to get it on the shirt.

[senderoaburrido]

I live in Montreal. I know this place used to be a big textile center. Maybe there is a graphic arts camera lying in a back room somewhere. I'll investigate that, thanks.

I know it seems unnecessarily difficult, and unreasonable of me. I just have an interest in doing it how it used to be done as an adventure of sorts. To learn how prints would have been made 30 years ago while simultaneously training myself in what will soon be lost skills. Who knows? Maybe vogue-obsessed youths of the 2030's will even pay me to do it "the old fashioned way".

I run a farm project in the summer to grow crops for myself for no other reason than to farm for fun. I have a habit of taking on activities just for the hell of it.

[Struan Gray]

Excellent attitude!

Have fun.

[barnacle]

I have a habit of taking on activities just for the hell of it.

I suspect that's why many of us are here. Certainly me - what else would account for the LF photography? (Not to mention sidelines like building the camera, rebuilding old cars, paragliding, etc, etc...)

Neil

[senderoaburrido]

I've got a question for those of you who have done this before: Do you know of any books or resources to look at for instruction on this process? I know there must be plenty of manuals out there. If I have a specific title, I can look that up in the library.

[andrewch59]

Hi Senderoaburrido, I have a old process camera in my shed which is 18 x 18 inch square, I am just coming to terms with half tone printing myself. I have a bigger Hunter Penrose camera that I a picking up in December that is also a process camera. It seems the LPI (Lines Per Inch) of the screen is of importance dependant on what kind of material you are going to print on. For me the old comic book dots would be pretty awesome to try. I already dabble in xray film photography so it would seem natural that if I could get a screen made with the lines etched on them I could just expose onto xray film and then make a carbon print which could be used as a printing plate???
Fortunately I have a friend who wants to revive his printing press, so it may be an amicable process for both of us. I think like you it is a way of staying traditional.