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Q: IMAGE ENLARGEMENT: HOW LARGE CAN I "BLOW UP" THE IMAGE? CAN I DO POSTERS?
BILLBOARDS?
A: The short answer is: Yes, our images are used for everything from posters to billboards all the time...
But please consult the technical specifications of each of the various
image brands we carry, and use common sense.
For example, with many of the images in our royalty-free division, the largest file
size available is 28MB optimized at 8" X 12". Can you blow that up to poster size?
Maybe (see below). Many of our newer royalty-free images, and all of
our premium royalty-free images, are now available in an even
larger files size: 56MB optimized at 12" x 18". Is THAT big enough? Maybe.
Again, in depends on the factors described below.
ENLARGEMENT: FACTORS TO CONSIDER
Yes, our images can be used larger than their "optimized" size, and, indeed, our clients
do that frequently, But doing so successfully can be tricky and technical (see below).
This is true with our images, or anyone's images...
We'll give you a basic foundation here: The things you need to be aware of, consider and
attend to if you are enlarging an image beyond it's "optimized" size. But if you are
intending to use one of our images very large, be sure to consult with your service
bureau, printer or digital imaging specialist.
Factor #1: Image Aesthetics
Generally speaking, an image can be enlarged to approximately 125% of its original size
without significant loss of quality. However, with some images that are highly "atmospheric",
where there is a photographic style overlaying it that lends itself to creative interpretation,
enlargement can often safely exceed 125%.
On the other hand, with an image whose aesthetic underpinning requires crispness and extreme
detail, anything over 100% might be a problem, unless you apply the technical correctives
described below.
Factor #2: Your Output Device
Presses and printers are improving all the time and incorporating some magical ability to
enlarge images from relatively small amounts of underlying data. Find out exactly what
hardware will be used to produce your project and consult with the expert on it to determine
whether the file we provide you will be adequate to achieve your goal on that particular device.
Factor #3: LPI to PPI Ratio
Okay, this is technical, not suitable viewing for children or the faint of heart...
Our 28MB and 56MB images are scanned using image resolution of 300 pixels per inch (ppi),
and a screen frequency of 150 lines per inch (lpi). You'll notice that the ratio between
those two things is 2 to 1, which is ideal. If you enlarge an image beyond it's "optimized"
size, you want to maintain that ratio.
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THAT MEANS YOU CAN TRY THE FOLLOWING TO INCREASE THE SIZE OF THE IMAGE
Lower the screen frequency
Try going down to 130 lpi on your screen frequency (or even lower if the image
aesthetics allow it: see factor #1, above). As you do so, lower the ppi accordingly,
always maintaining the 2 to 1 ratio. So, for example, if you lower lpi to 130, you can
lower the ppi to 260, and the image size will now be approximately 15% larger. You can
experiment with lower and lower ppi/lpi settings which produce larger and larger images--
until the image quality begins to suffer, at which point you know you've gone a bridge
to far...
Break the rule
Some images will not suffer in quality if you "break the rule" on the 2:1 ppi to lpi
ratio. Try going to 1.8 to 1 or 1.5 to 1. Experiment. A lot will depend on the
aesthetics of the underlying image, and no two images will react identically.
Resample, then sharpen
Those great people who create image editing programs haven't been sitting on their hands.
They know you want to enlarge images and "resampling" is the tool they've given you to do
it. Almost all good image editing programs have this feature these days, and the process
involves a kind of "recipe" for adding data to your image so that you can enlarge it.
Essentially what happens when you "resample" an image is that it takes a look at what you've
got and then interpolates it to a greater density, allowing you to use the image larger.
Quite often the process causes a slight blurring of the image, which, equally often, can be
corrected by then "sharpening" the image. Try it. This technique can often allow you to
use an image much larger than its "optimized" size.
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In the end, it's subjective...
Are the results of the enlargement acceptable? That, in the final analysis, is a subjective
judgment you need to make. It might depend on how far away from the image the viewer is
expected to be (Billboards). It might depend on the creative effect you want to achieve and
the degree to which the particular aesthetics of the original image lend themselves to that
effect. You need to make that judgment, and no one can make it for you.
Consult your printer, service bureau, expert
Once again, we need to stress that the amount you can enlarge an image is
determined by a great number of factors, many of which are outside our control. Yes, our
images are used in a great variety of ways, often very large. But, we strongly recommend
that you consult with whomever will be doing the final output of your project about the ways
in which the particular image you are interested in will behave under the parameters you set.
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