creating image with aquatint screen pattern

DF
Posted By
David_Freed
Feb 5, 2007
Views
816
Replies
5
Status
Closed
I am working with ImagOn, a photopolymer film, to make etching plates from my photos. To do this you expose this film twice: once with an aquatint screen and then again with a transparency positive of your image. (the screen creates a necessary grain on the film that when developed will hold the etching ink for printing).

So, I’m trying to create inkjet transparencies with the screen pattern "built in" instead of making a pre-exposure with an aquatint screen first.

Does anyone one know how to do this, and what DPI or LPI is needed (and other settings) to emulate an aquatint screen?

I’m playing with this method: converting my image to grayscale, then converting to Bitmap using one of these methods:

– diffusion dither (which seems to create a random pattern of dots/specs on the image, but doesn’t call for me to make any decisions about the pattern or ‘dot’ size),

or

– halftone screen, which does require some choices on my part such as frequency (lines per inch), angle in degrees, and shape (such as diamond, elipse, line, etc). I tried this at 720 LPI, 180 degrees and diamond shape, but I’m not sure what is correct.

Best, David.

MacBook Pro 16” Mockups 🔥

– in 4 materials (clay versions included)

– 12 scenes

– 48 MacBook Pro 16″ mockups

– 6000 x 4500 px

B
Bernie
Feb 5, 2007
720 LPI

Yikes!

At what resolutions?

Be aware that the number of apparent shades of grey available on a screened image depends on the resolution of the bitmap and the number of lines per inch according to the following formula:

(Resolution in PPI/LPI)^2 +1

As for what is correct, my guess would be it’s up to you to decide what pleases you.
DF
David_Freed
Feb 5, 2007
I used 720 PPI only as a starting place. For inkjet printing I usually try to size my images with output resolution of 360 PPI. Since my post, I’ve read that aquatint screens are about 200 LPI, so I may be going overboard with resolution.

Another method would be to apply the Grain filter, only I don’t know how to interpret the intensity and contrast sliders to mimic an aquatint.

Best, d.
B
Bernie
Feb 5, 2007
DPI (dots per inch) and LPI (lines per inch) are two very different things.

Printers have a resolution measured in DPIs

Files have a resolution measured in PPIs (Pixel per inch)

Halftone screens are measured in LPIs
DF
David_Freed
Feb 5, 2007
Exactly, that’s why I noted my images in pixels per inch and halftone screen in LPI.

David.
B
Bernie
Feb 6, 2007
Yes, but in your original post, you mention 720 LPI and in post No. 2 you mention 720 PPI as a starting place.

If you want the optimum number of shades of grey (256) and a using a traditional linescreen, you will want a resolution of 3200.

I’ve not yet found a mathematical relationship between file resolution, pattern ditter and shades for stochastic screens, not that I’ve looked all that hard.

Master Retouching Hair

Learn how to rescue details, remove flyaways, add volume, and enhance the definition of hair in any photo. We break down every tool and technique in Photoshop to get picture-perfect hair, every time.

Related Discussion Topics

Nice and short text about related topics in discussion sections