sensor size

"Scott W" wrote:
"Philip Homburg" wrote:
In article ,
rafe b rafebATspeakeasy.net wrote:
As photographers, we're gatherers of light.
Big cameras gather more light than small ones,
and it almost always shows in the end, if you
care enough to look closely. This applies in a
totally fair, just, equitable and non-discriminatory
manner to both film and digital cameras.

Except that if you fix subject distance, field of view, and depth of
field,
the total amount of light across the frame tends to be more or constant
(independent of the frame size).
This is true

Right. It also means that the claim that smaller formats have more DOF is
false.

Larger formats can 'store' more light. But once you find a system that is
big enough to handle the amount of light you've got, there is no point of
selecting even bigger systems.

This is not complete true. If you fix the subject distance, field of view
and depth of field then a larger sensor will be using a lens at a higher f
number, this can either reduce the cost of the lens or if you keep the
cost the same improve the quality. There is a limit to this of course
since the lens can get pretty large, but not as large as you might think
since the aperture of the lens would stay the same.

In real life if you actually take pictures, one either has enough DOF or not
enough, and linear changes in DOF tend to be relatively small compared to
the size of what that "enough" is. The experience here is that up to 645,
lack of DOF isn't really a problem, and only becomes an issue at 6x7.

In the end there is a trade off between the cost of larger sensors and the
cost of the lenses that are used. As the number of pixels increase the
need for a larger sensor is going to also increase, not just for capturing
more light but also to keep the cost of the lens within reason.

Another thing here is that the amount of charge you can store is
proportional to the area of the individual pixel, so the best SNR and
dynamic range you can get from a sensor is limited by the size of the pixel.
I've seen comments from D2x users to the effect that it requires correct
exposure and has very little room for boosting shadows without noise, and
even the 20D has worse noise at ISO 100 than the 10D/300D.

David J. Littleboy
Tokyo, Japan

"John" writes:

What is the main difference between a full size sensor (EOS 5d) and
a smaller sensor size (Nikon D200). Is a smaller sensor worse in
getting light/resolution compared to a full size sensor? Why is a full
size sensor more preferable?

For any given resolution, a larger sensor is prefereable (larger pixel
wells on the sensor are less noisy).

For people with a full set of 35mm lenses, a full-frame sensor leaves
all the lenses doing what the person is used to them doing, and lots
of people really like that idea.

For people working with extreme wide-angle lenses in 35mm( beyond
15mm) (or, until fairly recently, beyond 18mm), there's no solution in
the small-sensor world (nobody has yet built an 8mm rectilinear lens
for cropped-sensor DSLRs). (There are a number of 14mm and 12mm
rectilinear wideangle lenses out there for 35mm cameras.)

In addition, many people seem to have taken on a political position
that "full frame" is somehow "right" and anything less is somehow,
well, less. This adds considerable heat to the discussion.
--
David Dyer-Bennet, , http://www.dd-b.net/dd-b/
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