Photoshop Elements 3 Solutions, Pt. 2 | 4
Photoshop Elements 3 Solutions, Pt. 2.
One of the secrets of success in digital imaging is matching the size of your digital image to the requirements of your output. This means that if your digital image is destined for print, you'll need more resolution than you would if it were destined for a monitor (Chapter 12). Most likely, the original image that you are working with is larger or smaller than needed, and you'll have to resize. Keep in mind that resizing, up or down, always involves some loss of image quality. It is also the next-to-last step that you want to perform, just before sharpening.
Figure 2.28 shows a 720 Ã 480 at 72dpi video frame grab from filmmaker/producer Micha X. Peled's acclaimed PBS film, Store Wars: When Wal-Mart Comes to Town. Micha wanted to use the frame for a publicity shot, but it didn't have enough resolution for the higher demands of print.
Figure 2.28: A low-resolution frame from a video grab contains obvious scan lines.
Here is what I had him do to boost the resolution and make the image more acceptable:
1. I had him apply the De-Interlace filter (Filter > Video > De-Interlace), keeping the default settings: Odd Fields and Interpolation. This removed the odd interlaced lines and, by interpolation, replaced the lines with adjacent pixels, which made the video grab appear smoother. Just from this simple move, the picture quality greatly improved. See Figure 2.29.
Figure 2.29: The De-Interlace filter dialog box. With its scan lines removed and its resolution increased, the video grab is now a perfectly acceptable still image.
2. I had him choose Image > Resize > Image Size to open the Image Size dialog box (see Figure 2.30). I made sure that the Constrain Proportions and Resample Image options were selected. I had him change the resample image interpolation method from BicubicÂthe default settingÂto Bicubic Smoother. (Bicubic Smoother is the preferred interpolation method when enlarging imagesÂBicubic Sharper is often preferred when reducing images, but more on that shortly).
Figure 2.30: The Image Size dialog box.
3. I had Micha enter 300 pixels/inch in the Resolution box, and voila! He had a digital image that would look great in a magazine as long as it wasn't published much larger than 4 Ã 6 inches.
What about going the other wayÂmaking a large image small? This is a common task when you are resizing digital images for the Web or for e-mail transmission to many people. You'd think all you'd have to do is enter the values into the Image Size dialog box and leave it at that. That's fine if you are reducing the image to, say, only 50 percent and you use the Bicubic Sharper resample image interpolation methodÂbut it's a big mistake if you need to shrink it more than that.
Take the image shown in Figure 2.31. It is 2700 Ã 1932 pixels at 288 pixels/inch. Now look at the image on the left in Figure 2.32. I've reduced it to 675 Ã 624 pixels at 72 pixels/inch in one swoop. The image looks mushy and soft. It's best to reduce your file size in increments of no more than 50 percent at a time and to apply the Unsharp Mask after each step. It takes a little longer to resize this way, but the results make it worthwhile, as you can see on the right in Figure 2.32.
Figure 2.31: The original image started at 2700 Ã 1932 pixels. (Photo by Monica Lee)
Figure 2.32: Resizing in one step to 675 Ã 624 pixels at 72 pixels/inch creates this mushy looking image (left). Resizing incrementally, with an Unsharp Mask filter applied between each step, results in a sharper-looking resized image (right).
If you have a digital image that appears soft or blurry, Photoshop Elements gives you several options for sharpening it. The Sharpen filter globally increases the contrast of adjacent pixels, whereas the Sharpen Edges filter sharpens only the areas of a major brightness change and leaves smooth areas untouched. The toolbox also has a Sharpen tool, which sharpens specific areas of an image. Quick Fix's Sharpen command has an auto-sharpen feature plus amount controls.
But the tool I consistently use is the Unsharp Mask filter, which can be accessed from either Standard Edit or Quick Fix. This filter is based on a traditional film compositing technique that creates a blurred negative version of the image. It then averages this copy with the original, and through three controlsÂAmount (percentage), Threshold, and RadiusÂgives you precise control over the amount of sharpening and the way the sharpening is applied. (Quick Fix's Sharpen command utilizes the Unsharp Mask filter, albeit without Threshold and Radius controls. When you adjust the Sharpen Amount slider, Commit and Cancel icons appear next to the word Sharpen. Select Commit when you are satisfied with the amount of sharpening. Select Cancel if you are not. Until you select either the Commit or Cancel icon, the Reset button located above the After version of your image is dimmed and inoperable).
Here is how I used the Unsharp Mask filter to improve the photo (1700 Ã 1680 pixels, 72 pixels/inch) shown on the left in Figure 2.33.
Figure 2.33: The original image (left) is lacking sharpness. The Unsharp Mask dialog box (right). Your settings will vary depending on the size and content of the image.
1. I chose Filter > Sharpen > Unsharp Mask and made sure the Preview check box was selected.
2. I then dragged the Amount slider until it reached 100 percent.
3. I set the Threshold at 12. (Setting the Threshold slider at a higher value forces the Unsharp Mask filter to leave the flesh tones, or other areas containing contiguous pixels of similar tonal values, relatively alone. Leaving the Threshold set at 0 forces the filter to sharpen all the pixels in the image equally and may introduce unwanted artifacts in flat-colored areas such as the skin).
4. I then slid the Radius slider until I was visually happy with the amount of sharpening. In the case of this image, a value of 4.2 was just about right.
|Note : If the Preview check box is selected, you can see the effects of the Unsharp Mask on the image in the document window. Selecting and deselecting the Preview option gives you a way to toggle back and forth between a sharpened and unsharpened version of your image. You can also view the effect of the Unsharp Mask in the dialog box's small preview window. If you click the image in the preview window, you'll see how the image looks without the effect of the Unsharp Mask. In the preview window, you can also drag to see different parts of the image and click the plus sign (+) or the minus sign (Â) to zoom in or out. To see a particular spot in your image in the preview, just click on it in the image window. You may have to move the Unsharp Mask window out of the way to do this.|
5. I then clicked OK. Figure 2.34 shows the resulting image.
Figure 2.34: Image sharpened with the Unsharp Mask filter.
The values that you use for your image will vary depending on such factors as the image's content, size, and final destination. For an average-sized image that contains a lot of detailÂsay an architectural shot at 1600 Ã 1800 pixelsÂtry setting your percentage at 150 percent and your Radius at 2. For these kinds of images, I generally leave the Threshold setting at 0, which forces the Unsharp Mask filter to sharpen all the pixels equally.
For an image of the same size that contains expanses of color and tone, such as a face, I recommend setting your Amount at 100 percent, your Radius between 0.5 and 1, and your Threshold between 2 and 15. Playing with your Threshold setting will help you avoid introducing noise in the flat areas of color. Increase these numbers if you are working with larger images. Decrease them for smaller images.
|Note : On the enclosed CD is a trial version of nik Sharpener Pro, a Photoshop Elements plug-in. Using the plug-in takes the guesswork out of using the Unsharp Mask filter. It also automatically optimizes sharpening for different display outputs.|
Grabbing Digital: Which File Format Should You Choose?
Many popular video frame grabbers give you the option of saving your image in various file formats, such as JPEG, TIFF, PICT, or PSD. Which one should you select? For the best quality, choose TIFF or PSD, which is Photoshop Elements' native file format. If you do this, your file won't be as small as it would be if you saved it as a JPEG, but the TIFF and PSD file formats are lossless, which means no data is thrown away during the conversion. PICT is a Mac-only file format and is therefore inherently limited.
Created: March 27, 2003
Revised: December 6, 2004