Basic Digital FAQ
What's a Pixel?
PIXEL is short for PIcture Element
and it's the smallest component of a digital image. Digital images are
in fact a mosaic of pixels, just like the tiles on your bathroom wall for
example. Each pixel is a small square of uniform color. They can be light
or dark, red, green, pink, brown, black , white or any one of millions
of other colors. When seen from a distance you don't see the individual
color dots and they blend together to form an continuous tone image.
How many Pixels do I need?
That depends on what you want to do with
the image. If you want to view it on a computer monitor you only need as
many pixels as your monitor can display. So for example if you have an
800x600 video display, the maximum image you can fit on the screen would
be 480,000 pixels.
How many pixels do I need to print the
As a rule of thumb, when printing a digital
image you need at least 200 pixels per inch for the image to look good.
More is better and for the best image quality you may need 300 pixels per
inch. So if you want a 4"x6" print you'd need an image of at least 800x1200
pixels, i.e. 960,000 pixels. So a 1 megapixel camera (1 megapixel = 1 million
pixels) should give you decent 4"x6" prints. The following table gives
you a very rough idea of image size in pixels vs. maximum print size for
high quality. With high quality digital images it may be possible to go
to slightly larger print sizes than indicated in the table
Printed at 200dpi
Printed at 300dpi
Are all pixels equal?
No, not really. A 3 megapixel image from
a high end digital SLR like a Canon D30 may be of significantly better
quality than a 3 megapixel image from a $300 "point and shoot" digital
camera. For one thing the lens may be better and the image sharper. There
may be less "digital noise", so the image may be smoother and can be enlarged
more while still keeping good quality.
What are the advantages/disadvantages of
The advantage of more pixels is the ability
to make larger prints, or to crop the image significantly and still make
reasonable size prints. The disadvantage is that the digital files are
larger and so you can store less of them in any given size camera memory.
Images are usually stored as JPEG files. These are compressed files and
a 3 megapixel image typically takes up about 1 megabyte of memory. So on
a typical 32 Megabyte memory card you could store 96 1-megapixel images,
32 3-megapixel images or 16 6-megapixel images.
What are the practical disadvantages of
This really comes down to two things. Power
and storage. Digital cameras are typically power hungry, so you need a
lot of battery power. In a studio or at home this isn't a problem, but
out in the field it can be. You need storage capacity for all those digital
files. Once you have filled up the camera memory card you have to download
the data to some sort of storage device, either the hard drive on your
PC or a portable hard disk - and don't forget the portable hard disk needs
power too! There is a third disadvantage if you want slides, basically
you can't get them. You can have digital files printed as slides but the
cost is high and the quality lower than slide film images. You can project
digital images with a digital projector, but they are expensive and the
quality is much lower than a slide projector projecting an original slide.
Though not an intrinsic disadvantage, many of the "P&S" style digital
cameras have a significant lag between the shutter being pressed and the
image being taken and some require several seconds between shots. High
end digital SLR bodies don't suffer from these limitations.
What are the advantages of digital cameras?
First the film is free (once you've bought
the memory). No film or processing costs. Second you can erase any bad
shots, so you don't waste film/memory space. Third you can see what you
get immediately. This means you can reshoot anything that doesn't look
quite right on the spot, no waiting for film to be processed before a reshoot.
Fourth, if you are going to print digitally, you don't have to scan your
Why are digital cameras so expensive?
Because they are new technology. When VCRs
first came out a basic model might cost you $1000. Today that same VCR
would cost under $100. In 1980 the Apple II computer (with 64K of memory
and a 350Kbyte disk drive) cost over $1000. Today you can get a much more
powerful PC for under $300. 15 years ago a 10MB hard drive was expensive,
today a 20GB drive is cheaper than the 10MB drive was! Not too many years ago a 1
megapixel camera cost $1000. Today you can get a 3 megapixel camera for under $100 or
a 6.3MP digital SLR for under $800. Prices
are dropping rapidly while the camera capabilities are getting better and
better. The technology isn't fully mature yet, but then it probably never
will be. When to jump in is a question only you can answer. The longer
you wait, the more you will get for your money - but you won't have the
use of a digital camera while you are waiting!
What about digital printing?
Digital printing can be excellent. Quite
a few professional photographers are now doing all their printing digitally.
Digital printer prices have dropped dramatically over the last few years
and quality has gone up. One of the problems has been that some digital
prints have shown fairly rapid fading. I think this problem has been pretty
much solved now with better inks and papers but you do need to choose both
carefully if you want archival prints. High quality digital printing isn't
as easy as just hitting the "print" button though. There are issues with
color matching which can be problematic and getting good B&W prints
may require the use of special inks so you might want separate printers
for advanced B&W and color work. For most users though, one printer
can do both jobs. Be aware that the major cost in digital printing (assuming
you regularly make prints) isn't the printer itself (they almost give them
away now), it's the cost of the ink and paper supplies.
What about scanning negatives and slides?
Certainly a good option, though not as convenient
as shooting directly in digital. Film scanners which will give you 10 megapixel
images can be bought for under $500 and scanners which can give you 24
megapixel images can be bought for under $800. The problems are that you
have to pay for and develop the film and you have problems, or at least
issues, with grain. A scanned pixel may not be quite as good as a pixel
captured directly because it's a second generation image (a picture of
a picture) and there are the grain issues (grain
aliasing for example). Still scanning is an option, not least because
it also enables you to digitize all your old slides and negatives as well
as new ones. Scanning a slide or negative at high resolution can be slow.
For the best possible image quality a full frame scan could take anything
from 2 or 3 minutes to over 15 minutes depending on the scanner and the
software. Obviously a lot slower than shooting a digital image in the first
What should I buy?
Anything you want to and can afford! There's
such a huge range of stuff out there that it's impossible to give recommendations,
plus the market is changing so fast that whatever I suggest would be out
of date in a few months. If you want to save money, look for closeout specials
on whatever was "king of the hill" last month but has just been replaced
by a new model.
Where should I buy it?
I've been dealing a lot with Amazon.com recently. Though you might think of them only as
a bookstore, in fact they often have great prices on electronics too and they carry most
digital cameras and lenses, scanners and printers as well as printer supplies. They have a free shipping
option and a 30 day return policy on most items
Adorama is one of the more reputable New York City discount stores.
They carry everything photographic from the most popular items to the more hard to find accessories. If Amazon
doesn't carry it, Adorama is the next place I usually look.
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