![]() ![]() When you print a grayscale image on a printing press, those 256 levels of gray often get reduced to 100 or so because of the limitations of the press. You can save 16-bit grayscale images in a number of formats, but if you add layers, your choices are limited to Photoshop, Large Document Format, PNG, PDF, and Photoshop Raw, and TIFF. But that redundancy translates into editing headroom, so if your camera or scanner can capture 12 or more bits per pixel, it's often worthwhile bringing the high-bit data into Photoshop.Įight-bit grayscale images are pretty generic, so you can save them in almost any format this side of MacPaint. With 16-bit grayscale, each pixel has a value from 0 (black) to 32,768 (white), for a theoretical maximum of 32,769 possible gray shades.įew capture devices can actually deliver all those gray shades, so 16-bit files usually have rather a lot of redundancy. With 8-bit grayscale, each pixel has a value from 0 (black) to 255 (white), so there are a maximum of 256 levels of gray possible. Eight-bit is still more common, although most scanners now allow you to bring more than 8 bits into Photoshop. Grayscale files in Photoshop are always either 8- or 16-bit images: Anything less than 8-bit gets converted to 8-bit anything more than 8-bit gets converted to 16-bit. For instance, you can't use any filters, and because there's no such thing as anti-aliasing in 1-bit images, you just cannot use tools that require this, such as the Smudge tool, the Blur tool, or the Dodge/Burn tool.īilevel bitmaps are the most generic of images, so you can save them in almost any file format. The other major difference between the other image modes and Bitmap mode is that you're much more limited in the sorts of image editing you can do. ![]() Ordinarily, images are opaque, except for the occasional white silhouetted background made with clipping paths (see "Silhouettes" in Chapter 12, Essential Image Techniques). One-bit pictures have a particular difference from other images when it comes to PostScript printing: the white areas throughout the image can appear transparent, showing through to whatever the image is printing over. He insists that all images in Photoshop are bitmapped, but only "flat" black-and-white images, in which each pixel is defined using one bit of data (a zero or a one), are bitmaps. Bitmapĭavid really wishes that Adobe had picked a different word for this image mode. ![]() We'll talk more about this in Chapter 13, Image Storage and Output. For instance, you can't save as JPEG if the file is in Lab mode. Note that the mode your image is in determines the file formats you can save in. Each of the following image modes appears on Photoshop's Mode menu. Fortunately, they're the most important of the bunch, at least for those in the world of graphic arts. Photoshop reads and writes only a handful of the many different color modes they came up with. So color scientists created a whole mess of ways for us to describe colors with some precision-to each other and to a computer. However, even Bruce and David can't agree on what navy blue looks like, much less you and your printer. In a perfect world, you could say to a printer, "I'd like this box to be navy blue," and they'd know exactly what you were talking about. Ultimately, an image mode is simply a method of organizing the bits to describe a color. Fortunately, Photoshop makes it easy to see what image mode an image is in, as well as to convert it to a different mode, if you want. That 165 could represent a level of gray, or a particular color, or it might be only one member of a set of three or four other 8-bit values. As we said earlier, a pixel can have a value of 165, but that doesn't mean anything until you know what image mode the image lives in. ![]()
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