Hi Tom,
I am new to this newsgroup, so I hope I am not stepping on any toes in
my replying to your posting.
How many MP are enough is somewhat a question like how much money is
enough, or how large a house is enough. It depends upon what quality
you are after and what you plan to do with it.
In general you will get a better quality image for emailing from
downsampling a higher resolution picture (taken on a higher resolution
sensor) than you will from a jpegged small resolution sensor.
However, there is no reason for overkill either. As someone already
mentioned, cramming more sensors on the same size image sensor means
each one has to be smaller, and that means they will be less sensitive
to light individually, and therefore nosier (more randomized artifacts).
So, then it comes down to either a larger sensor, or finding the sweet
point for your needs. Larger sensors cost a lot more, and are mainly
put in much more costly cameras, so that's probably not what you are
after. A three to four MP image sensor will allow you to not only make
email images which will be of good quality, but also produce a very good
4 x 6 snapshot, and an OK 5 x 7" print. For an 8 x 10, I suggest at
least a 4 (it will be somewhat soft) but moreso a 5-6 MP sensor.
Digital cameras are still evolving. New designs in terms of sensor
shape and size, as well as new color matrixes are being introduced. New
compression methods are being developed, and certainly more light
sensitivity is being worked on. Sony, for instance, has added a second
green to the standard RGB Bayer matrix, because greens tend to be harder
to capture accurately. Fuji has gone with a hexagonal sensor shape to
try to eliminate some of the diagonal line artifacting and on some of
their cameras gone to two sensor sizes per location to help avoid the
common problem of burn out of the image area in high lighting
situations. This has improved the overall contrast range of the images.
There are other features to consider as well. How high res is the LCD
screen, and how large is it, is the screen articulated so you can move
it to avoid direct sun on it, which otherwise could make it difficult to
view, and also allowing you to change its angle for above head or below
waist images? What type of memory does the camera use (Fuji, Olympus and
Sony use proprietary memory that costs up to twice as much as the more
standard Compact Flash or SD/MMD? Then there are issues like lens
quality, shutter speeds, features, etc.
For me, having played with less costly digital cameras, I find a number
of considerations:
1) Optical zoom ratio is quite limited on these smaller cameras. Most
digital cameras in the mid price range have 2.5 to 3.5 X zooms built in.
Many people find this restrictive. They are often equivalent to about
35mm to 90mm in 35mm film. The wide angle is adequate, but a 90mm lens
is really not much more than portrait telephoto. If you are then going
to use additional lens, you may find they degrade the quality, may
distort or vignette the image in certain zoom positions. They may cut
some light, and they can be costly, to the point where a camera with a
larger zoom lens may be a better value.
2) Aperture is too small. To keep these camera small and inexpensive,
the manufacturers often use a lens with a small aperture. On many, the
lens aperture decreases with zooming. As mentioned earlier, small image
sensor is already at a loss due to noise. Noise is a product of low
light levels, so a smaller aperture lens means more noise. Most
digicams of the type we are speaking rely on good lighting, and when
not, a weak flash to fill in. So, try finding a camera that has a
larger aperture and that is constant throughout zoom range. A f/2.8
is good, lower still is better (2.5, 2.0).
3) Look at the minimum ISO setting the camera has. If it is 160 or 200,
chances are that sensor chip is going to be nosier than one which offers
50 or 80 iso as the lowest sensitivity. In general, higher ISO numbers
will mean nosier images. I'm not suggesting the cameras shouldn't have
higher ISO options, for taking pictures in lower light, and to decrease
camera shake, but the lower ISO available as an option is often an
indicator of an image chip wit higher sensitivity, and if you can use a
tripod with that lower ISO setting, for instance in a low lighted scenic
or night shot, you will get a less noisy result
4) Knobs are nice. One thing that keeps cost down on digital cameras is
having the buttons on the camera have many multiple functions and use
nested menus which you read off the LCD screen. Having a few knobs can
not only speed up some of the most important selections, but they make
it more like a film camera which is more comfortable for most people still.
5) Battery power is critical. I had one digital camera that used NiMH
batteries (2 AA) and sucked them dry in minutes. I had to carry around
5 sets for one light day's shooting, and was continually recharging
them. Another camera I use has a much smaller Li-Ion battery that takes
up to 4 hours to charge, but allows me nearly 200 images with 25% flash,
or so. Although NiMH are convenient in that they are relatively cheap,
available most anywhere, unless the camera designer has been careful
with power consumption, Li-Ion (which are often proprietary and costly
if you need to replace them) tend to perform better. Check reviews for
average battery use, do not rely on manufacturers statements about this
as they tend to exaggerate.
6) Look at the LCD screen for brightness in bright sunlight. One which
you can adjust brightness on is best, or it may be too bright in dark
situations. It should be easy to read, high enough resolution to
determine how good an image looks and if it is in focus (most camera
have a zoom in feature, but it can take a while to implement).
7) Some of the newer models are beginning to offer some form of image
stabilization. This technology reduces camera shake in slow shutter
speed images. I have worked with a very small digital 4 MP camera for
several months, and I was amazed in spite of steady hands and the ease
to hold such a lightweight camera, how many of my images were blurry in
lower light situations if I did not want to use the inadequate flash
provided. These new image stabilization systems are amazingly good, in
part because the lenses in digital cameras and the image platform are
small and light, so the processors can respond very rapidly with little
problem.
Speed of capture/lag time. Some cameras take too long (in my
opinion) to capture the image after the shutter is pressed. Some also
take a long time to write the picture to the memory card. It is a good
idea to get one with a burst option so you can take more than one
picture in a brief period, even while it is recording earlier images to
the memory.
9) Things like manual white balance, and less so on smaller cameras,
manual focus, are helpful. Some types of light and objects will tend to
be misinterpreted by either the auto white balance or the
focusing system, and it can put a crimp in your style if the camera
refuses to focus and take a picture because it keeps on misfocusing.
I found, for instance, that snow images using any of the preset white
balance setting did not give me clean and neutral snow color. I had to
balance it manually.
10) One feature I really liked, was a panoramic feature that allowed me
to take a series of images next to one another to create a wide sweeping
image, that could be either automatically or manually stitched together
in software.
In terms of brands, that's a hard one. In general, I think camera
manufacturers tend to make more user friendly cameras with more
film-camera like features. From what I have seen, Canon, Nikon, Fuji
and Olympus, Konica-Minolta, Pentax all have contenders in that price
and model type. But every company from camera, to film (Kodak, Polaroid)
to consumer electronics (Panasonic, Acer, Casio, etc, etc.) are making
digital cameras now. Each feel they have the right to claim it as their
territory.
To answer your question about the A70/A75, these are good cameras
overall from those I know who have owned them. Overall, Canon makes
good digital cameras. But look over the list above and it may help you
to consider some of the features that are potentially important for you.
I hope this is helpful.
Art
Tom H wrote:
> I'm planning to buy my 1st digital camera within a month. I've arrived at
> the conclusion that 3 mp is enough due to the fact that I plan to do a lot
> of emailing my pictures, and emailing large (more than a MB or 2) pics can
> be problematic.
> My question for this group is --- does anyone ever find that they need more
> megapixels? If so, what circumstances? Also, are there any reasons NOT to
> buy a Canon Powershot A70 or A75?
>
><!-- ~MESSAGE_AFTER~ -->
>> Stay informed about: megapixels --- how many is enough? 
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