Mike wrote:
> can anyone ell me what the difference is.
>
> SLR seems more expensive but im not sure what SLR means
There are three important differences between digital SLRs and advanced
compact digital cameras that look a lot like SLRs ... but only the first
one is actually part of the SLR design.
SLR stands for "single-lens reflex", and describes the type of
viewfinder. An SLR uses a mirror directly in front of the shutter that
bounces light to a prism which in turn directs it to the eyepiece where
you see it. Since the mirror intercepts the light coming through the
actual picture-taking lens, you see what the film or digital image
sensor will see; when you press the shutter release the mirror flips out
of the way just before the shutter opens, and the light coming through
the lens passes through to the film or sensor. The eyepiece blacks out
until the shutter closes and the mirror returns to its original
position. Since an SLR's viewfinder is strictly optical, it doesn't
drain batteries. But because you cannot see what the camera sees during
exposure -- meaning you can't adjust focus, exposure or even aiming --
no digital SLR includes a "movie" mode.
Some advanced digital compacts use electronic viewfinders (EVFs) that
essentially use a tiny LCD display in the eyepiece and show you exactly
what the image sensor sees -- it's very SLR-like, since it also shows
exactly what the picture-taking lens sees. The EVF may or may not black
out during the time that the image sensor is recording the image into
memory. Some cameras that use EVFs can send the sensor's image-data to
the eyepiece and memory simultaneously in "movie" mode. But EVFs
require power continuously when in use, not just when you're actually
taking pictures. This may result in fewer shots per battery charge; you
may need to carry a spare battery or two, although that's usually a good
idea with any digital camera. (For obvious reasons, film cameras don't
have EVFs.)
Other compact cameras use a simple optical viewfinder that has its own
tiny separate lens mounted near the picture-taking lens. While these
viewfinders don't drain batteries, neither do they show exactly what the
picture-taking lens "sees". Most of them work well enough for casual
snapshooting, but they can't be as precise as a viewfinder that uses the
actual picture-taking lens.
The second big difference between digital SLRs and non-SLRs is that
every digital SLR I've heard of uses interchangeable lenses while nearly
all non-SLR digitals have permanently-attached lenses. If the lens that
comes with your digital SLR can't quite get that particular wide-angle
or telephoto shot you want, you can remove it from the camera body and
replace it with one that's better suited to the task; you can't do that
with a fixed lens, although some of the better digital compacts
accommodate adapter lenses that help extend the fixed lens's
capabilities a bit.
The third important difference actually has more to do with the size and
price of the camera than anything else -- and digital SLRs are generally
both larger and more expensive than digital compacts. As a rule,
digital SLRs use physically larger image sensors than compacts; the more
expensive (and usually larger) SLRs usually have larger sensors than
their less expensive kin. When everything else (including the number of
pixels) is the same, a larger sensor means less digital noise in the
captured image. This may not matter much if your primary interest is
taking snapshots that won't be printed any larger than 4x6 or 5x7, but
it's a very important consideration if you need high quality that lets
you see fine detail or make large prints.
No one camera has the perfect combination of features for every
photographic situation, which is why there are so many different cameras
to choose from. It's your job to decide just which features are most
important to you, then find the camera or cameras that best fit your
requirements.
--
Walter Luffman Medina, TN USA
Amateur curmudgeon, equal opportunity annoyer<!-- ~MESSAGE_AFTER~ -->
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