PDA

View Full Version : Regent Royal Hard-Dot film



senderoaburrido
6-May-2016, 19:13
I've been looking at this (http://www.bhphotovideo.com/c/product/1215033-REG/dotworks_rrf81050_regent_royal_hard_dot.html) film for my screen-printing project. (http://www.largeformatphotography.info/forum/showthread.php?129818-Half-tone-screens-and-half-tone-negative-reproduction) I had heard others mention that there are films which provide halftone results upon development. The film is marked "halftone-film". Is this the sort of film I'd need to produce negatives that could be converted to positives, and then to a screen for printing? Is anyone familiar with this film?

No lines per cm/inch are provided in the specs, so I'm not sure if it is something I could use anyways. I'm looking for film that outputs in low l p/cm. Last thread, I think someone suggested something as low as 60.

Gary Beasley
7-May-2016, 05:52
The hard dot designation is probably referring to the contrast curve, very steep. A lower contrast film shot through a halftone screen will produce "soft" dot, with fuzzy edges fading off from full density in the middle to greyed edges. This is useable making plates and screens but makes it tempermental and sensitive to exposure times while giving a lower quality halftone. The hard dot film because of the lack of gray transition between the black and clear makes a sharp edged dot that is easy to print and control. I have used both in my career in the newspaper business long ago and would much rather use this high quality film for graphic processes. As far as the dot size you will need a halftone screen with that size or use a finer screen and enlarge it to the size needed onto another sheet.
By the way there was film made at one time that had a halftone pattern in the emulsion and would make a halftoned image without a screen. I've never seen or used any of it as it was pretty uncommon and don't know if theres any still available. It would have the line spacing in the specs if that was the film you had.
Also you would need the lithographic developer to get the best results from the film, regular developers would give you softer results.

bob carnie
7-May-2016, 06:24
Gary - Is it feasible to add a stochastic screen or fine screen at PS stage to a file then print on Ortho film continuous tone and expect a hard dot negative or positive??

senderoaburrido
7-May-2016, 08:42
Gary: So this is a bit more like litho film? I'm guessing what must separate it from litho is the speed. I'll still need a contact screen for converting negatives, then, eh? Is it not worth trying the process of making half toned positives from normal film with the enlarger? I'm looking to make a very simple mesh screen for shirt printing.

Jim Andrada
8-May-2016, 17:14
I used to use the Kodak lith film with the built in dot pattern - they used an elliptical dot shape so that as you got to the mid grays all four corners of the dots didn't touch at once which could cause a bump in the curve - ie a sudden transition that could be visible. Instead, pairs of dots would touch in the long direction at about 40% and all dots would touch at about 60% so you got a musc smoother scale - but could have issues when printing multiple colors at standard angles to each other. The links show some examples of the effect of dot shape.

https://workflowhelp.kodak.com/display/PRIN75/About+dot+shapes

http://the-print-guide.blogspot.com/2009/02/am-screening-halftone-dot-shapes.html

senderoaburrido
9-May-2016, 07:37
I used to use the Kodak lith film with the built in dot pattern - they used an elliptical dot shape so that as you got to the mid grays all four corners of the dots didn't touch at once which could cause a bump in the curve - ie a sudden transition that could be visible. Instead, pairs of dots would touch in the long direction at about 40% and all dots would touch at about 60% so you got a musc smoother scale - but could have issues when printing multiple colors at standard angles to each other. The links show some examples of the effect of dot shape.

https://workflowhelp.kodak.com/display/PRIN75/About+dot+shapes

I'll look around and see if litho film like that is still produced. If not, I'd imagine that's something you can't reproduce with a contact screen over a negative, no?

http://the-print-guide.blogspot.com/2009/02/am-screening-halftone-dot-shapes.html

Gary Beasley
9-May-2016, 20:16
Gary - Is it feasible to add a stochastic screen or fine screen at PS stage to a file then print on Ortho film continuous tone and expect a hard dot negative or positive??

You would get close but the way film halos even a little you will get some softness to the edge. A little fiddling with the exposure and development will get better results, but hard dot litho film will create a black that continuous tone film can't come close to.

Gary Beasley
9-May-2016, 20:31
Gary: So this is a bit more like litho film? I'm guessing what must separate it from litho is the speed. I'll still need a contact screen for converting negatives, then, eh? Is it not worth trying the process of making half toned positives from normal film with the enlarger? I'm looking to make a very simple mesh screen for shirt printing.
If this hard dot film is what I think it is it actually is litho film, they came in many different brands and types from ortho to panchromatic for color separations and differing degrees of hardness. The film used to shoot the pasteup copy didn't need the hardness the halftone film did because the image was already high contrast. It also quite often had a texture to them so the page could be "opaqued" with a thick red or black medium or with a soft graphite pencil to remove shadow lines, dust specks and other defects. The halftone film was normally quite smooth to enhance the detail of the dots.

ic-racer
1-Nov-2016, 16:34
I saw this film today in the B&H catalog. Less than one dollar a sheet for 8x10 negative film. Has anyone tried it?

IanG
2-Nov-2016, 02:50
I saw this film today in the B&H catalog. Less than one dollar a sheet for 8x10 negative film. Has anyone tried it?

I used to buy a lot of similar film in the 70's & 80's, however this film is designed for rapid access processing, that usually means developer incorporated so it goes through an activator in a processor., the activator is essentially just hydroxide and development is seconds. I used an Ilfoprint rapid access machine in the late 70's early 80's with early lfospeed paper which few realised was developer incorporated.

With a developer incorporated paper or film development is to completion even in a dilute regular developer so there's little to no prospect of contrast control.

Ian