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All
about resolution (or why some digital images look awesome and some look lousy)
The pixel is the basic building block, quite
literally, of the digital image. This rectangular shaped object, when assembled with hundreds of other
pixels, creates an illusion of color, depth, line, shape, and form. Pixels can be transparent, opaque,
semi-opaque, black, gray, white, (value, from
pure black to pure white), and in a wide array of colors.
Maybe you had one of those "Lite-Brite" toys when you were a kid--it
was a toy with lots of colored pegs that you set into holes to create designs
or words. Behind the pegboard was
a light bulb that lit up the colored pegs and these made a rough drawing or
design.
http://fruitfly.files.wordpress.
com/2006/08/litebrite.gif
Simply put, resolution is the amount of pixels per inch, or
ppi. The basic resolution for digital images on the Internet is 72
pixels per inch, while large format photo prints can be created at 300
ppi. It would be fair to say that
the above image is of low resolution—there aren’t too many Lite-Brite
pegs for each inch, probably something like 4!
So let's take your digital camera and
look at the various settings you can use for shooting pictures. Most digital cameras allow the user to
set the image and file size for the pictures the camera will be taking. Typically, these are “high”, “medium”
or “low”. If you set the camera’s
file size to “high”, your picture files will be larger and the recording card
in the camera will hold fewer pictures. The camera records in the same amount of pixels per inch no
matter what file size setting it’s in. So let’s assume that your camera records at 180 pixels per inch. A picture taken in “high” would be 8 x
10 inches at full size at 180 pixels per inch. If you made a full size print of this image, the resolution
would be of high quality, sometimes known as photo quality. If on the other hand, your camera was
set on low, there would still be a resolution of 180 pixels per inch, but the
overall image would be smaller, something like 3 x 5 inches. If you wanted to
print that lower resolution 3 x 5 image at 8 x 10 inches, you’d have a
distorted, pixilated, or “jaggy” image that looks lousy:
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There is also a huge difference between what you see on a computer
screen and a print made from a digital image. Putting an image at anything higher than 72 ppi for
something like a webpage is a waste of space, because a computer monitor works
in it’s own environment of 72 ppi—it doesn’t need to go any higher than
that and images look just fine at this resolution on the screen.
But if you go to make a large scale print from a 72 ppi image, you
won’t be able to make anything much larger than 8 x 10 inches without it being
fuzzy or distorted.
So when you are setting up your digital camera to take pictures of
high, medium, or low quality, which setting should you use? I would say for the most part, you’d be
fine staying with medium. You’d be
pretty safe there provided that you didn’t want to make large scale prints of
over 8 x 10 inches and you’d be well within safe limits for your standard 4 x 5
inch ‘snapshot’ prints.
If you have a look at my photo prints or collage for sale pages,
you’ll see that each photograph or collage includes specifications on the image
size and resolution. While the
images are set on my WebPages at 72 ppi, the originals that I print from are of
a higher resolution, and that is why I can print these in a large format at
photo quality.
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The original file size for this photograph is 9 x 14 inches at
180 ppi. This means I can
provide photo quality prints up to the 9 x 14 size. If you tried to print this particular image at 9 x 14 it
would look horribly jaggy.
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The original file size for this collage is 13 x 19 inches at a
resolution of 250 ppi. So I can
print large sizes at high quality, but if you tried to
enlarge from this image (which has been scaled down
in both size and resolution for these Internet pages) it would be distorted.
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So what’s important
is knowing a bit about the quality of the images you are starting out
with. It can be an impossible task
for a designer to work from client provided images that are of low
resolution. “It looked good on my
computer, why can’t you do anything with it?” is a complaint that graphic designers
sometimes hear from clients who don’t know much about the quality of the images
that they provide. Because most
images on the Internet are at 72 ppi, it’s often the case that images that are
re-worked from Internet copies get distorted by being enlarged or altered. (Not to mention copyright concerns!)
What are some solutions? If you wish to provide your own images or digital photos for me to work
with, be sure to get me the original files. You may have original photographs that can be scanned into
the computer at high resolution. Scanners include software to compensate for image fading.
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I took this photograph as a slide in the early 1980’s—over
25 years ago. The colors in the
slide had faded considerably more than this image—one click on the
scanner software restored this image to its original color!
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Part of my initial
consult will include examining your files to see if they pose any issues of
resolution, and if I can work with the files or not.
This is a deliberately simplified explanation about the very
basics of image size and resolution. There’s a lot more to it, and the main thing to know is that what you
see on the computer screen isn’t always what you get with printing! My services are all about working out
the best solutions with the materials you provide me with and making that final
print as close in quality to what you see on the computer screen!
credits, sources and acknowledgments:
"Lite-Brite" is trademarked property of Hasboro Toys
special thanks to Ken Kimura for the idea of using Lite-Brite to explain pixels!
for more on Lite-Brite see: http://en.wikipedia.org/wiki/Lite-Brite