Excessive JPEG compression
With most digital cameras, the default level for image
quality is fairly low, adequate for a 4 x 6-inch print, perhaps.
Many camera owners use this quality level, which produces a
fairly small image file due to high compression, for one
reason—they can fit a lot of images into their memory cards.
That makes sense, but it's a mistake for anyone who plans to
make larger prints. Before we talk about how to avoid the
mistake of excessive compression, here's a little refresher on
the connection between photo quality and file size.
Image quality The better the quality, the higher the resolution,
and the more pixels each image will contain. With more pixels,
you get superior definition of detail. A low-quality image has a
lower resolution and is composed of very few pixels. Many
digital cameras offer several image quality options, from low to
super fine.
File size
In addition to choosing image quality, you can usually choose
the image-file size, from small to large. The larger the file,
the lower the compression, and the higher the image quality. A
small file is extensively compressed with internal software,
which produces a major loss of important image data and results
in poor image quality.
These two features, image quality and file size, work
together. When selecting a JPEG-capture mode, you can choose a
combination that will make high resolution/large files (for the
very finest quality), medium resolution/small files, low
resolution/large files, and so on.
Each camera manufacturer uses its own terminology for image
quality options and for image file-size levels. Some cameras
offer only basic quality options such as normal, better, and
best. Read your instruction manual closely to determine what
options your camera provides and their actual designations.
The mistake It's tempting to use the camera's default
setting, which provides medium-level quality and a fairly small
image file. Some people, trying to maximize the number of images
their 16 MB memory card will hold, even select the lowest image
quality option and the smallest file size. Unfortunately,
neither combination produces images that will make for excellent
prints.
The fix
Buy a high-capacity memory card and you'll be less tempted to
use the low-quality setting or a high-compression option. A 128
MB or a 256 MB card can save many large/high-resolution image
files. Regardless of the card, you should frequently review your
pictures and delete unsuccessful images. This makes space for
new, better pictures.
With a 2- to 4-megapixel camera, use the large/super fine
combination if you plan to make 5 x 7-inch or larger prints. If
you rarely make prints larger than 4 x 6-inches, you can get by
with the medium/fine setting. This will still produce an image
file with an adequate number of pixels and a medium level of
JPEG compression that should maintain decent image quality.
For the best results, always use the highest image quality
option, ideally with a large file size setting. But what should
you do if your memory cards are almost full? Select the "Small
File/Super Fine" combination. The JPEG image will be extensively
compressed but the high pixel count should still assure
acceptable quality in a 5 x 7-inch print. |