Depends on what you plan to do with the scanned picture. If you are sending via email or posting on a website then 800x600 would be fine. If you plan on editing then as high as you can without killing your machine. The higher the resolution the bigger the file and some PCs really chew on those large files for a while
Scan & print.
A good quality high resolution scanner (600-1200 dpi) will almost always reproduce a film or printed image better than any camera could.
A satellite photograph is a photograph or image taken by earth orbiting satellite with special high resolution cameras. The GeoEye-1 satellite has the highest resolution of any commercial imaging system and is able to collect images of the Earth with a ground resolution of 0.41 meters (or 16 inches) in the panchromatic or black and white mode.
To scan a photo on a computer, you would need to choose the appropriate format, like jpeg. Then the resolution needs to be doubled or at least increase. Put the photo on the scanner, and let the computer scan the photo.
resolution is the number of pixels in a photograph- for example 10 MP means 10 million pixels (picture elements)
If possible, the easiest and safest way is to scan the photograph, remove the spots digitally, and print a new version - there's no danger of damaging the original photograph that way. If that is impractical, for example the photograph might be too big to scan, then you will have to remove the spots from the original image. You can get specialist inks from photo suppliers which are designed to "de-spot" images. Obviously, follow the instructions on the inks, but you will need a fine brush, a good light, a magnifier and lots of patience! I'd strongly recommend that you practise with a photograph where it doesn't matter if it is damaged.
scan
No. Progressive scan DVD players display about twice the resolution that regular ones do. Today however even the cheapest DVD player will have progressive scan. Also not all TVs can display full DVD resolution.
Many smartphones have the ability to download apps from a marketplace. You will need to download an app that will allow you to scan, or photograph, a barcode. There are several apps that have this ability.
For a photograph you need a camera for a sketch you need a pad and pencil
It helps to scan or take a picture of a document
to show that it not HD