Images print oddly

[Michael J B]

This morning I scanned a photo, taken in 1904, I found in a magazine that shows a relative. The image size in the magazine is 4x3 and it is very grainy. I understood that I was not going to get a crisp image but scanned at 1200 dpi to get what I could.

When I scanned it, on an HP Laserjet Pro MFP 4301dw, I did not notice that the Preset setting was "Document" which yielded a PDF - see 01.jpeg attached (jpeg because I photographed it on my computer screen using my cell phone, as is the case for all 3 attached images).

I placed the pdf in an InDesign document and printed it using the HP Laserjet Pro MFP 4301dw; it was dark as I expected - see cell phone image 02.jpeg.

I then rescanned at 1200 dpi with Preset "Photo" which produced a jpeg and, on screen, a somewhat better image - see cell phone image 03.jpeg attached.

I then imported both 01 and 02 into Photoshop and modified the brightness/contrast. However, when I went to print the modified images out of InDesign they came out with an odd pattern. - the same pattern as described below re 04.jpeg.

I then removed the images modified in Photoshop from the InDesign document and replaced them with the original pdf and jpeg - and again got the odd pattern shown in cell phone image 04.jpeg.

Could someone explain what is happening

With thanks in advance.

[James Gifford—NitroPress]

It looks as if you're getting moiré patterns from the interaction of the source's half-toning, the scan and ID's processing of the image.

I'd take your best scan, straighten and crop it in Photoshop, (optional: convert to Grayscale, or use the Black and White feature to do an optimized color conversion), adjust the tonal balance as best you can using Curves (keeping in mind it will always print a little darker than you see it on the screen), apply a very slight blur to blend the halftone dots (I've had a lot of success with a Median-blur-then-sharpen cycle, but you may have to go through a dozen iterations to find the optimal one)... and then scale it down to no more than 600ppi for your intended print size. 300ppi is probably more than enough. Try different scaling modes, but I'd say a blur mode will work best. You'll lose some detail but get a "better" illustration overall.

What you want to do is (1) remove the halftone screening as much as you can and (2) pre-scale the doc to something reasonable so that InDesign doesn't have to do all the heavy work.

If you're going to reproduce in color, I've found it best to work in grayscale, via a Black and White conversion, and then re-apply a sepia tint.

[BobLevine]

I've found that with images like that, you can get sometimes get better results by taking a picture of the picture and bringing that into Photoshop and cleaning them up using the neural filters. 

[James Gifford—NitroPress]

Some scanners, especially the SOHO all-in-ones, often have a halftone mode where they interpolate and blur halftoning right at the start. Nothing I use, but I have seen it work in "office" situations.

[Michael J B]

Thanks James, I tried this but when I got to the enlargement in the Median blur operation i could see that the dot pattern is such that even a slight twitch of the blur sider throws the whole thing into black. I fiddled a lot but keep getting the moiré pattern in all cases. I own the copy of the magazine - the image is of my maternal grandfather at a western outpost of the Royal Northwest Mounted Police, later the Royal Canadian Mounted Police (RCMP) in 1904. The magazine itself has no great value to me so I am going to simply cut out the image and frame it.

[James Gifford—NitroPress]

This is where numeric entry is your friend. There are many sliders in Adobe apps that can have far too much effect in the tiniest nudges.

It is possible to get a good, usable digital image of almost any photo, no matter how it's presented — it's just not always easy. 🙂

[Conrad_C]

To expand on what James Gifford said, look in the scanning software to see if it has an option labeled something like “Halftone removal” or “Descreen”. The image below is what it looks like in the scanning software I use:

Basically, the print of the image has no actual gray shades because it was printed with fully black ink, so the only way to simulate gray shades was to render it with a halftone screen applied, which is a pattern of larger and smaller black dots. It’s that pattern that interferes with the pixel grid of a digital image and causes the moiré pattern.

This is a very common problem when scanning old images printed on a press, so if you do web research using terms like “descreen halftone scan” you’ll find a long list of techniques and plug-ins; some work better than others and it isn’t always possible to remove it completely. Whatever is used must match as closely as possible the frequency, angle, and dot shape of the halftone screen that was applied to the image when it was prepared for the press, and then undo that back into gray shades.

[Brad @ Roaring Mouse]

For shots like this, your first best approach is to use Median filter in Photoshop to eliminate as much of the halftone pattern in the scan as possible. You are going to lose some detail no matter what you do, especially in the shadows. I would avoid using Blur as it will soften the picture and lose more detail. In this example, I scanned a halftone photo at 1200, and started increasing the Median setting ONLY as much a it takes to eliminate the haftone. Try one and print it out. I'm sure you will be satisfied.

[Michael J B]

Thanks Brad - see the reply above I made to James re the blur.

[Brad @ Roaring Mouse]

If you have a lot of these pictures to scan, you might look at purchasing a decsreen plug-in for Photoshop. I've used one from Sattva which is pretty darn good, and maintains details in the shadows.