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Improve Resolution on Low Resolution Images Okay, let's suppose you
forgot to change your digital camera's image resolution or used a low
quality .jpg compression and now your client wants a large print. So
what's the best method for obtaining a quality print?
Start by understanding that the image resolution and the physical size of an
image are interchangeable values. For example, an image that is 4"x5" at 72 ppi has the same amount of information as an image that is 2"x2.5" at 144
ppi. Therefore you can enlarge the physical size of an image if you
reduce its resolution. Of course this really doesn't help your current
dilemma since you haven't actually increased the number of pixels in the
image.
However all is not lost. Photoshop's (CS version or higher)
resampling techniques have been significantly improved in the latest
versions. To resample, choose: Image>Image Size. Click the
Resample check box and pick one of the five predefined interpolation
algorithms.
In previous versions of Photoshop, the first three algorithms -
Nearest Neighbor, Bilinear, or Bicubic - produced a loss of sharpness
and dulling of color when an image was enlarged by resampling up. In
the newer versions of Photoshop, two new interpolation algorithms -Bicubic
Smoother and Bicubic Sharper - have been added to the
Image Size - dialog box that help reduce the diminished quality of
enlargements.
Bicubic Smoother is a new algorithm that slightly blurs the
edges of areas to produce the most contrast when it adds pixels for a more
sublimated continuous-tone look.
Bicubic Sharper is another new interpolation algorithm that
does a better job of increasing the size and enhancing edge contrast.
Both of these new methods require much less time than most available third
party plug-ins that basically perform the same task.
To resize your low resolution image, make a copy of your original image
first, then resize the image copy up to the at least half the size of the
final print at 300 ppi using either the Bicubic Smoother or Bicubic
Sharper interpolation. For example, if you're largest print needed
is 20x24, resize the image up to at least 10x12 at 300 ppi. Once the
image is resized, enlarge it on your screen and compare to the original
image with the same enlargement.
It is nearly impossible to determine how your final photograph will look
and if your client will be satisfied until an actual photograph as been
printed. We recommend ordering a Bullock 30x40 DigiCam Test Print
and reviewing how large your new interpolated image will go before ordering
your final prints.
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