Control Your Density - ADJUST LEVELS

The first thing I do after making a scan is crop to the image, leaving no border, and take a look at the Histogram (a graphic mapping of scanís density) in the ADJUST LEVELS window under the Image menu. Although scanning software has built-in abilities to place the highlights and shadows at specific densities, scans usually need some density fine tuning. Various methods of printing require specific maximum and minimum densities and a prediction for dot gain when printing. For instance, a quality offset press, when printing a halftone on a glossy stock, may require a 97% maximum density for shadows and 3% minimum density for highlights and a midtone adjustment for gain of 15% in the midtones. This is because the printer wants to hold a dot in the shadows and highlights - any densities darker than 97% may go to solid black and any densities lighter than 3% may go to pure (white) paper. Middle greys will get darker, the amount depending on type of stock, line screen and ink coverage (and knowledge of the press operator). Letís work with a black and white photograph for simplicityís sake, like the before and after example to the right. The original scan of snow, ice and water photographed on a grey day came out kind of flat - a distinct lack of contrast. Initially there was one overall Levels adjustment. With the Adjust Levels and Info Windows open, the Input Levels highlight slider (on the far right) was moved in (to 250 from 255) to make the highlights a little brighter. Placing the cursor over the highlight areas in the scan and looking at the Info window shows that 5% areas are now 3% areas. The midtone slider (in the middle) was moved over to the left (to 1.10 from 1.00) to brighten the middle greys a little. With the cursor over a 50% grey area the Info window states that what was 50% grey is now 45% grey. When checking the darkest shadow of the original scan I find that what was 98% is now 97% with the two adjustments I have already made (or just where I want the darkest shadow to be). Now that Iíve brightened up the scan overall (and have increased its contrast range), I still have a pretty grey photo. Time to do some Levels adjustments to specific sections of the image by selecting them first. In order to make the ice more contrasty to show more detail, a lasso selection was made with lots of feathering (see ďSeamless SelectionĒ Tip for more information). Both the shadow and highlight sliders of the Input Levels where moved in to snap up the contrast range so that what was 75% in the shadows moved to 90% and what was 12% in the highlights moved to 4%, again, checking the changes with the cursor and Info window while doing this,

Photoshop Tips and Related Links

Photoshop Tip of the Week: This Week's Featured Tip, image samples and related Links
Photoshop Tip: Seamless Selection & Transitional Masks
Photoshop Tip: Control Your Density - Adjust Levels
Photoshop Tip: Sharpening Scans
Photoshop Tip: Digital Spot Tone - The Rubber Stamp Tool
Getting Digital with Your Images: Article about scanning and digital imaging devices, my Digital Services, the "Digitized Nude" photograph and related Links
Fine Art Photography by Carl Volk: Black and White and Color Landscapes, Street Portraits, Still Life and figure studies, all finished out in Photoshop
Commercial & Architectural Photographs: Some of my commercial work including retouching and compositing in Photoshop
More Photoshop Sites: Link list of other Photoshop Sites well worth visiting plus a nude abstraction created in Photoshop utilizing transitional masks

relying on the actual numbers, not the monitor, to state the changes taking place. (Of course, you should have the Preview button checked on to see these changes.) Other Levels adjustments were made to specific areas of the scan to expand the contrast, bringing out detail even more and the Finished Scan is the result (after re-sampling down and sharpening). The Output Levels sliders rarely need to be touched. If your scan has 100% or 0% in any areas, which means you probably lost detail in these areas because of a poor scan, you can give these areas some dot by moving in the Output Levels sliders. Going from 0 to 10 in the shadows slider will change 100% black to 96% nearly black and going from 255 to 245 in the highlights slider will change 0% white to 4% almost white, so that your printer will have some dot to work with (but this will not add detail). Once you have finalized a Levels Adjustment, you have the choice to save it and load it to adjust another scan (which is nice if you have a number of consistently made scans from a number of consistently made photographs). Adjusting Levels does cause a little posterization to occur so it is wise to scan at a higher resolution than needed, perform Adjust Levels, then re-size (re-sample) down, which dissolves the posterization, then perform an Unsharp Mask (see Sharpening Scans Tip Link above).


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