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1.2, 2.1, 3.4. Those numbers sound familiar?
They should. They're the megapixel resolution plateaus for
digital cameras over the past three years. Graph them and you
can easily guess where resolution is headed for the future.
There are photographers just drooling for higher
resolution cameras in the belief that they'll make better
pictures with them.
This column is intended to put a different slant
on resolution and pleasing images, plus solving a problem that
plagues the recipients of digital photos as email attachments.
It's all about image size.
The raw image that downloads from your memory
card to your computer is usually a monster. Somewhere between 16
and 29 inches wide at 72 pixels-per-inch (ppi). And uncompressed
from JPEG, it's also a file of whoppin' size.
From my 3.4mp camera, a raw file is 9 megabytes
in a format of 28.4 inches wide at 72ppi.
Many folks consider that the finished picture
and blithely attach it to their emails, causing great vexation
among recipients who have to use their browser scroll bars just
to get from one side of the image to the other.
Others tear out their remaining hair by trying
to print one of these brutes on an inkjet.
It's all about image size and the answer lies
within Photoshop (Menu: Image>Image Size). When you open Image
Size, you're confronted with a dialog box that has two sections.
The top one shows you the current file size and dimensions in
pixels. Multiply those pixel dimensions and you'll arrive at the
resolution of your camera.
The lower section provides current dimensions
and resolution in three controllable boxes. I prefer to uses
inches for my dimensional measurements but you can use any of a
number of measurements including percentage.
Photoshop's default has these three windows
linked together with the "resample image" checkbox turned off.
Changing the image size to something workable is
simply a matter of entering either one dimension or a new
resolution. For my travel stories, I prefer to convert my images
to a standard of 8 inches on the long dimension. So, by
selecting the width dimension and replacing 28.4 inches with 8
inches, I achieve a 6x8 image with a resolution of 256 pixels
per inch. The file size remains 9 megabytes.
This is a size and resolution that will make an
excellent bordered 8x10 print at 1440dpi (or higher) on an
inkjet printer.
But what of the web or multimedia designer or
the photographer who just wants to send email attachment images?
Certainly a 9mb file is too big to be used.
The image size procedure is exactly the same
except this time, the "resample image" feature is checked on.
Now only the image dimensions are changed with the 8 inch width
resulting in an image 576 pixels wide, just right for attaching
as an email.
The file size reduces to 729K and when saved as
a high quality JPEG (8) compresses to 108K.
Web designers will want to be even more specific
in their sizing and use Photoshop's "Save For Web" feature to
achieve the greatest resolution at lowest file size.
There's no doubt that higher resolution cameras
will capture more detail and provide greater sensitivity range.
However, I've found it very difficult to tell the difference in
1440dpi (or now 2880dpi) inkjet prints made from image sized
2.1mp images as opposed to 3.4mp images.
This will no doubt cause scoffing anguish from
the megapixel zealots. However, if you're in the market for a
digital camera and accept this premise, you'll be interested in
next week's column on holiday shopping. |