Scanning

Scanning

Q1:	How do I scan from within Photoshop? I have installed a scanner but have to use a separate application to scan. I thought there was a way to scan from within Photoshop, but I can't find it.
A1:	The way in which you set this up depends on your platform. Macintosh : Most scanners come with a piece of software called a plug-in. This software needs to be put in this location: Photoshop CS2 application folder>Plug-ins>Import/Export. The next time you launch Photoshop, look under File>Import and your scanning software (plug-in) should appear. Windows : Go to the File menu and choose Import>TWAIN Select Source. Navigate to your scanning application and select it. (You only have to do this once.) To scan, go to File>Import>TWAIN Acquire (or choose WIA Support) and your scanning software should launch.
Q2:	Is it possible to scan negatives using Photoshop?
A2:	Whether you can scan negatives or not is based on your scanner, not Photoshop. Some scanners have adapters to scan film and negs, others don't. If you don't have an adapter, chances are your results will not be very good. You need a light source shining through the negative (from above) as opposed to from underneath, as the scanner normally does. If you have an adapter, scan and then Invert the image (Command-I [PC: Control-I]) in Photoshop.
Q3:	Is it possible to scan three-dimensional objects? I've heard people say that they have scanned actual objects like cell phones and paper clips. How do I do that to get the best results?
A3:	In general, just place the object on the glass and give it a try. You may want to use a large sheet of white paper to cover the object if the lid won't close. Note: Depending on what you are scanning, you may want to protect your glass with some clear plastic (e.g., cookie crumbs).
Q4:	What is lpi? Photoshop uses pixels per inch (ppi), but my print shop mentions a figure in lpi. What does that mean and how does it relate to ppi?
A4:	When you scan an image, you end up with a continuous tone image, but that cannot be printed on a printing press. A press needs a halftonea series of small dots, as opposed to shades of tones. To convert your contone to a halftone, the printer needs to apply a line screen and uses a figure of X lines per inch (lpi). The number used for line screens depends on several factors, but mostly on the paper being used. Check with your printer to determine what lpi they will use for a particular print job. In general, take the lpi and double it to determine ppi.
Q5:	How can I scan a photo that's already a halftone? When I am scanning a photograph that is already a halftone (i.e., from a brochure, book, etc.), is there a way to convert the photo back into a non-halftone image?
A5:	First of all, let's quickly agree that we are not going to scan anything unless we have the copyright approval to do so. Assuming we do, there are a couple of ways to deal with the problems you get when scanning a halftone. First, if your scanner has a Descreen function in its scanning software, try that. It will often remove all or most of the pattern that appears. If not, try scanning at a higher resolution than you need, resampling the resolution down (by going to Image>Image Size), applying a very slight blur (try Filter>Blur>Gaussian Blur), and then Unsharp Mask (Filter>Sharpen). Another possible approach is to scan the image at an angle and then rotate it (Image>Rotate Canvas) so it's even in Photoshop. This will remove the lines. Note: Neither of these approaches work as well, of course, as scanning an original photo.
Q6:	What is a moir pattern? My service bureau refers to a moir pattern, but I'm not sure what they're talking about. Can you explain it to me?
A6:	Without going into all kinds of technical details, moir patterns appear when you scan an image that has already been printed. During the printing process, inks are printed at different angles, and all the inks together create a pattern that the eye can't see, but the scanner will pick up. This is a moir pattern.