Cleaning Scans and Prepping for Print
Cleaning up scans! Originally published in EMG-Zine.
2006-11-01
Getting a file from that first virgin scan into something that you can actually turn in to your printer or publisher can be a real nightmare. In the best case, your scan is perfect and all you have to do is size it correctly and save it. Usually, we're not so lucky. Let's identify the problems individually, and solve them all. I will be using Photoshop for these examples, but most high-end art programs will have similar commands and tools.

Problem: Scanner burn

Scanner burn is an unsightly darkening that haunts corners, edges, and anywhere that the paper may be warped. It can be accompanied by blur, especially in areas where the paper wasn't held tight to the glass.

The most important thing to remember—for not just this, but all of these solutions—is that you don't want to make hard-edged changes to your piece. If you select an area, and lighten or darken only that area, you'll have this very distinct line that will immediately draw attention.

Select an area with a burn. We'll want to do each area
separately, since each burn will be a different severity! Next, you want to feather the selection. How much you want to feather depends on your file size. If it's a large file for print, 25-50 pixels is a good feather range. Now you can adjust the Brightness/Contrast (Image >> Adjustments >> Brightness/Contrast). Remember that your entire piece is likely to need adjustment - you want to match this section to the rest, not get it perfect and still have to adjust the rest. Just tweak the bars until you get something that matches the rest.

Problem: Muddy contrast

Contrast is how dark and light everything is. This is most easily adjusted through Image >> Adjustments >> Brightness/Contrast. Increasing brightness makes the entire thing lighter, while increasing contrast will change the darks to be darker and the lights to be lighter. If you are finding that this control panel isn't capturing some of the mid-ranges you want, you may have more luck adjusting levels (Image >> Adjustments >> Levels...). This control allows you to set what the program considers a midrange, as well as how dark the darks are and how light the lights are. Play with sliding the three bars around until you get something that shows what you want it to. Auto levels are an option, but you may find that they won't give you quite the level of control that adjusting levels manually will. Remember that whatever you do cannot be undone with a step later. If you increase contrast to the point that you can't see some light pencil lines, you cannot later decrease the contrast and expect them to pop back up. They are gone forever!

Problem: Color shift

Ah, color shift. How we hate it. There is little to be done when a scanner ''eats'' a color and it isn't present at all, but we can adjust a bit to compensate. Before you get over the top making adjustments, remember the cardinal rule: What you see is not what someone else sees. If you are printing your own work, do print tests before you get carried away making adjustments. Remember that both monitors and printers vary widely in output. Particularly, I've got my CRT monitor pretty well calibrated to my printers, but my laptop screen and my husband's flat screen both wash out and tint image significantly. I've found that generally, customers with flat screens and laptops find my prints darker and richer than expected, and customers with CRTs find them a perfect match, or close. This isn't gospel, but has rung true for me. Your mileage may vary. Calibration of monitors and printers is its own wide topic!

The major thing to note: The Image >> Adjustments >> Hue/Saturation control panel is much more powerful than you might guess at first. Make sure you have your preview box checked, so that you can see what you're doing, and then play with the channels! Sometimes a scanner will only mess with a particular set of the colors, and adjusting the master hue results in gross skewing of all the other ones. My habit is to adjust the master channel until it's as good as it will get. Then, I skip down through each color channel and see if I can't adjust it a little more, specifically, adding saturation to washed out blues, and lowering their brightness, for example.

It will take a little bit of playing to get the colors to look perfect, and the only recipe I've found for really getting the hang of them is to experiment. If you're continually using the same monitor and printer, you'll probably find particular settings that work for just about all of your work, give or take a little specific tweaking.

Problem: Background haze

Is that background supposed to be white? Sure... but is it really white?

Frequently, what looks white on your monitor isn't really white. The best way to check for this is to set your foreground color to white—make sure it's really white by resetting the pallet colors to black and white and then reversing them. Then, paint a blob into your background. Don't see anything? Great! But wait - don’t trust your eyes yet! First, use Image >> Adjustments >> Brightness/Contrast to darken the full image. If you still can't see where you painted, you're safe, cancel out and continue with an easy heart. But if your brushstroke suddenly pops out, you didn't have a pure white background to start from! Go back and adjust the brightness/contrast until you can do the same thing again and not show any brushstroke.

Problem: Deleting specks and goobers

Sure, a white background is easy! You can just erase any stray specks or hairs or smudges that show up. But what about a background that shows texture and paint strokes? What happens when you get a goober over that?

The cloning tool is your friend! The icon is a little rubber stamp, and you assign it a paintbrush shape, just as if you were painting with it. The only difference is, with the cloning tool, you select a piece of your painting as a ''source'' using the alt key and clicking. The cloning tool doesn't paint with new paint, but copies that source as if it were stamping a new piece of your painting right over the old. If you aren't sure how this will look, make a new layer in your piece and stamp over the old layer until you're happy with it. Selecting the right paintbrush for this operation is important! A too-fuzzy-edged paintbrush will look blurry at the edges, instead of capturing the texture of your painting. A paintbrush that is too small won't cover the goober. A paintbrush that is too hard-edged will have abrupt edges and look alarming. Experiment to find what's going to work best with the texture you've got in your particular piece.

Problem: Crooked lines that aren't really crooked, I swear!

This problem is worse with photographed artwork, because of lens distortion, but even scanners can make lines that were perfectly straight and perpendicular suddenly look off. Again, don't trust just your eyes. Turn on a grid and check any lines that are important. Sometimes, just rotating the entire image will fix the problem, but sometimes, you'll find your piece is out of square, and rotating just doesn't take care of the error.

Don't worry, this is fixable, too. Select the whole painting, and hit ctrl-T. This activates the transform command you should already be fairly comfortable with. But wait, this command is much more powerful than you might already know! Right-click, and you'll get a new menu. Select ''skew'' and you'll be able to drag each corner independently in the vertical and horizontal direction, pulling your piece back into square.

Problem: Lurking Edges

Have you got lurking edges? This is the most common print-file error I run into. You just don't notice that at the very, very edge of a file, there's a teensy bit of scanner burn. This isn't so bad if your piece is dark, but if you've got one of those backgrounds that is supposed to be white, your lurking edge is going to stick out like a sore thumb against the margins of the print. Check for these very nasty little critters by enlarging your canvas with a white background and then zooming in to inspect every edge and corner. You might be surprised by what shows up! You can use scanner burn techniques on these bits, but generally your best bet is to just crop out that very edge of the file or delete the offenders.

Problem: My printer wants to bleed?

If you're sending off a file for a specific product (book covers, for example), your printer may give you very particular size specifications. They may also say they want a trim size of so-and-so, and a bleed size of so-and-so. You should know what this is before you actually do your artwork, because it's pretty important. The trim size is where your image will be trimmed to - the very edge of the product. Naturally, anything important should not be larger than this! If you have text in your image, make sure it doesn't run right up against this specification or it will look crowded. Sometimes trim isn't exact, and you don't want vital things to get cut off. They often give you a 'gutter size,' which is the margin of error for trim. A printer gets close to the trim, but they want to have a little room for wiggle. The gutter goes inside the trim, and borders the 'safe zone' for important things like text and design elements.

Bleed, on the other hand, is what you want if you want an image - your background texture, for example—to run off the edge. You want that to extend a little ways off, in case your trim isn't exact. Otherwise, you might get an ugly white sliver showing up at the edge of your product. A standard bleed is 1/4 inch.

So, you want to resize your image (Image >> Image size) to the size of the trim plus the bleed, at the requested resolution (usually 300 dpi) and make sure that none of your important parts fall outside of the gutter. (If you have a white background, your bleed is white, and you don't have to worry so much!)


Problem: My printer wants my format in a what who?

Your printer or publisher wants something very specific. Be sure that's what you give them. Once everything is cleaned up, flatten your image, save it for yourself in your program-specific format (I keep a Photoshop copy of every file that's important to me!), and then save-as whatever format they require. If they require an RGB file, make sure it's in that mode, or in CMYK if they request that. You can adjust the mode in Image >> Mode.

You may wish to adjust the color after you've put it into CMYK, as there can be a color shift at that stage!

Problem: My file's HUGE!

This should not cause much stress, actually. A print file at an appropriate resolution (300 dpi is pretty common) is going to be large. If it isn't at least 10 Megs (I frequently get 50 Meg files), you should re-examine your image size, because something is probably wrong. If you are saving as a jpg (some printers will accept this format – I generally do not), make sure your compression is not high. High compression = low quality in terms of jpgs.

If you need to upload your file and you are concerned that your connection is not equal to the task, consider zipping the file. It won't save much on a .tif file, but it can make a difference. You may also be able to split the file into parts and send them individually, but make sure your printer is okay with that, as they will have to put
your files back together.

You can run into a lot of problems cleaning up your scans for final print files, but it's worth the time and effort to take care of them all. It will show your artwork to its best advantage, and keep your hard-working printer from tearing her hair out!


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