are a few tips for getting a good balance between quality and file size
when scanning prints or slides for the web. These are based on my own
experience, supplemented by advice from www.scantips.com
, a place for excellent (but long winded) advice on scanning. These notes
can only summarise a subject that can, and has, filled books.
photograph can be scanned successfully, no matter how old and faded. Image
processing software can improve the quality of the most damaged photo,
hiding tears, spots of mildew, increasing contrast and even sharpening the
Basic Principles of Web Images
are many cheap scanners around, and they can all scan well enough for
use on the web. Unless you plan to make high resolution scans, don't pay
more than you need to. I get perfectly adequate results from prints with a £45
scanner. (Canoscan 3000F)
slides require a specialised slide scanner. I now use an Epson
Perfection V700, which scans both prints and slides, and this is hoovering through 40 years of slides, and is definitely
worth the extra money.
can be ignored! This
may seem counter-intuitive, given that scanners advertise how high a
resolution they can achieve. Resolution on the web is set by the userís
monitor. For example, if you have it set to display 640 x 480 pixels,
resolution will be low and the image grainy, but the image will be big.
Conversely, if you set your monitor to 1024 x 768 pixels, then
resolution will be high, but the image small.
what counts is the number of pixels in the image. For web
use I resize
my images to 800 pixels across for landscape format, or 600 pixels high
for portrait format. This will just fill the screen on 800x600 monitors,
and three quarters of the screen on 1024 x 768 . Of course, the number
of pixels in the image depends on the scanner resolution you set during
the scanning process. Read on for details.
scanners are different, so I can only offer general advice. The
principles are identical, the means of achieving them may vary.
- Switch on the
scanner, start the image processing software, or the scannerís own
software. (It is usually better to scan from within an image
processing package, if you have one, but this is not essential.)
- Place material
to be scanned face down on the scanner, squared off as much as
"preview", to obtain a small low resolution image in
scanner's software control panel.
- use the
controls to crop the image, as required. Be sure to leave space around
the main subject so the image can be adjusted later.
- set the
resolution to 150 dots per inch (dpi). For a small image, set this to
a higher resolution, say 250 or 400, to allow the image to be
expanded. All other controls should be at their default setting.
"scan" to (surprise!) scan the image.
Save to disc
- save it to disc
as a "jpeg" file, with a ".jpg" extension, giving it
a meaningful name so you can find it again. Jpeg compresses files,
throwing away information as it does so. The more you compress, the more
it throws away. However massive reductions in file size can be achieved
without compromising quality.
- I used to recommend
saving the file in an uncompressed format (eg .tif or .png), but I have
found through experience that saving as a .jpg with low compression
saves a massive amount of disc space without sacrificing quality. Note,
however, that if you continually work on a jpg, and keep saving it to
the same file, quality drops and file sizes increase.
Email it to me
to put on the website
email it me as
the image is very small, much higher resolution is required to obtain a
reasonable size of image on the screen. I now use these settings:
- resolution - 2400 dpi,
Scan quality - best, all other controls set to
- From this
point, the scanning process is the same as for prints. A scan of the
full slide will give a similar sized image to a 6 megapixel
You will find that a
resolution of 150 dpi is entirely adequate. Higher resolution cannot be
seen by the eye, results in bigger file sizes, slower printing, and
wasted ink. In my experience, it is difficult to better the value for
money and quality you get from taking a CD or memory stick into Jessops.
So an image that is 1500 pixels X 800 pixels will happily produce a
10"X8" print. (I.e. 150 dpi*10"=1500 pixels.)
document is intended as a quick guide, to help anyone to produce an
adequate scan. I have avoided a whole raft of complicating detail which a
purist would reckon essential. If you have any queries, email me & I
will try to assist (but no promises).
Photo Editing Software
you are planning to scan and keep a number of pictures, or have taken up
digital photography, then good image processing software is invaluable. I
use Photoshop Elements, which I find entirely adequate, and is compatible
with Photoshop itself, a heavyweight professional (and expensive) software
Newton, www.hmssirius.info; www.hmsbacchante.co.uk,