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Tutorials

How to fix a bad scan

Oct 18th 2005
Correcting Scans With The Levels Command:
1.
Bad Scanner!
A long time ago in galaxy far, far away...

It was back in 1999 actually. I owned a bad scanner. I had gotten rid of an old gigantic dinosaur of a scanner (which was really expensive in its day) and gotten one of those new incredibly sli9m models. They looked so cool. And the price was right; under $100. Well, folks, you get what you pay for,; and from the very start I was experiencing a feeling bewilderment after scanning my photos.
Take this one of Mr. Photoshop and his son celebrating Halloween here. I was preparing to possibly do a tutorial a viewer had requested on making a light saber effect in Photoshop. I opened this old file and thought, well, that just won't do. The darks are way too much. There's huge flat near-black areas where we can see almost no detail. This is a bad scan. To paraphrase Bob the Builder, Can we fix it?
Yes we can!

 2.
Levels

Meet The Levels Command. This is a good place to come for what we need to do to correct the tonal problems with this scan. It's going to give you a ton more control than the Brightness/Contrast dialog, and it's not as hard to understand as the Curves command.
This is going to be a short, easy tutorial designed to help you fix bad scans with minimal effort. There's a lot more to know about Levels than what we'll cover. If you'd like to know the whole story, check out part one: Adjusting Levels of my seven-step tutorial, Retouching and Color Correcting.

So let's get to it. Choose Image: Adjust: Levels. That black spiky, wavy thing is called a histogram. It represents the range of values in your image. It should be now surprise to us to see the tallest spikes on the left side, indicating some pretty strong darks in the image. A good histogram should slope off at either end. If yours has empty space on either side, you can slide over either the white or black triangle (found under the histogram.) Doing so would re-establish what the lightest or darkest areas of you image are. Slide these around and you'll understand it quickly by seeing results in your image. An alternative to this is to use the eyedroppers to set the white and black points. I might click on the white eyedropper tool and then click on the lightest part of my image, say the flash reflection on the light saber handle. I might use the black eyedropper to click on the darkest part found in my boot in the background.

 3.
Before & After

You may need to do those things, but in this case I do not. My tonal range fills the whole histogram area and tapers of at either end (aside from a slight wave near the right edge, caused by the harsh light of the camera's flash.) No, what I really need to change for this image are the middle values.
Check out that middle (gray) triangle under the histogram. Compare it's position now as opposed to step 2 above. With just a few seconds work I've cured most the ills of my bad scan just by sliding that toward the left. This has lightened the middle values.

If we had tried this with the Brightness/Contrast command, all the values would have been lightened and that would be bad, because the shirts and faces can't take it. They'd be flat, white areas.

Check out the close-up images to the left to see how my image looked before, and after I made this mid-tone adjustment. What once were dark, confusing areas in the original, now have variety and detail.

Here are some tips:
-Scanner settings: I don't know how true this is, but I was told long ago not to try and correct what's going on within your scanner plug-in dialog box. The software that controls the scanner is nowhere near as sophisticated as Photoshop, was the reasoning. (The few times I've ignored this advice out of curiosity yielded poor results.) Just scan badly and make any corrections needed in Photoshop.
-Channel: Though all I showed you was an adjustment to the RGB Channel, you can select another from the pop-up menu and adjust colors here, too. In truth, compared to the photo, my scanner gave me a little too much red, so I chose the Red Channel in the Levels Dialog and slid the gray triangle slider toward the right. That fixed my red problem.
-Contour: affects the shape of your shadow, rather than sharp corners, in my example, I can change it to have curved edges.
-Noise: can add random-valued pixels to the shadow, which may add to its realism depending on the smoothness of your background.


 4.
Good Scan.. Finally

Hey.... Now that looks a lot better. Scroll back up to step 1 and you'll see what a world of difference that Levels adjustment made.

Now, for those of you who were worried about the quality of my hardware, rest assured that I soon found the money to purchase an equally cool and slim, but higher-priced scanner. I was curious to see how it fared compared to the old one. It took me only 20 minutes of rummaging through the box of old photos in my basement, but I found the original print and re-scanned it. I was pleased that the scanner gave me something very like the image you see at left.

Here's another tip:
Use an Adjustment Layer to fix the image. Choose Layer: New Adjustment Layer: Levels. This will get you the same results, without permanently altering the image.


 5.
Save & Load

Before we go, I want to show you how to save some time. If you've got a number of images that were shot in the same environment (all you indoor photos, perhaps) and they're scanning in with the same types of problems, you can quickly apply the same levels adjustments to each one by saving your settings.



Take some time on the first image. Have your photo handy for comparison. When you're sure everything is just as you want it, click the Save... button in the Levels Dialog. Give the settings a name and remember where you put them. I did this and for the image at left, all I had to do was hit the Load... button and select my saved settings. I clicked OK and quickly corrected another image.
If you really had a lot of images in need of the same settings, you could create an action to run the levels adjustment, then batch process them all in a few seconds (File: Automate: Batch...).
You see, with Photoshop, it's okay to have a bad scanner. .