Absolute Beginner's Guide to Digital Photography

One term that cannot be used with digital cameras is
pixels per inch. The reason is that CCD sensors come in
different sizes. A 2.1-megapixel sensor might be
twice the size of a 4-megapixel sensor, for example.
This why you only hear about cameras
in terms of total pixels (megapixels) or output reso-
lution (1600×1200 pixels, for example).

Every type of digital camera—from a low-end
phone camera to the latest Nikon or Canon—out-
puts at 72 pixels per inch.

When you import an image from a digital camera
to your computer, it is notready to print. Why? It
comes in at a screen resolution (72 ppi) that would
generate an enormous print. To print it, you need
to change its resolution from 72 ppi to something
useful on your printer—300 ppi, for example. If
you try to print a photo immediately after import-
ing it, either your image editor will state that the
image is larger than the paper size, or you will
print only a portion of the image on paper.

Today’s newer technologies, such as EXIF printing
and print scaling in software, enable digital pictures
to be printed correctly without changes. (You can read about EXIF printing in
Chapter 2, “Advantages and Disadvantages of Digital Cameras.”) For example, you
can connect an HP camera directly to an HP photo printer and print a picture at the
highest resolution possible.

If you are more interested in editing images, however, you will need to change the
resolution of your images after you’ve imported them. This is pretty simple:

1. Connect your digital camera to your computer and import the images.


2. Once they are on the hard drive, open Photoshop or your favorite image edi-
   tor and open the first image.


3. Change the resolution. In Photoshop for example, choose Image, Image Size
   and then change Resolution to 200, 300, or 600 depending on the quality of
   your printer. Click OK when finished. Photo printers with high-quality glossy
   photo paper can accommodate 300–600 ppi. Traditional color inkjet printers
   can accommodate 200–300 ppi.


4. Put glossy or matte photo paper in your printer, make sure you have the cor-
   rect physical size of the image (use Image, Image Size again if necessary),
   and print your photo.

CHAPTER 12 THE IMPORTANCE OF RESOLUTION 177

The difference in size

of CCD sensors versus film

actually leads to other annoy-

ances, such as the ”focal length

multiplier.” On digital SLRs (sin-

gle-lens reflex cameras), the focal

length of a lens must be multi-

plied by a number to determine

the actual focal length. On a Fuji

S3 SLR, for example, the focal

length multiplier is 1.5×. A 50mm

lens actually is working at 75mm,

for example.