David J Taylor added these comments in the current discussion du
jour ...

What I have found in practice is that using the maximum
resolution with the "normal" quality setting can beat the
lower resolution with the "fine" quality setting. Of course,
this is highly camera dependant, and you should test for
yourself.

My theory behind this is that running at the maximum
resolution, you are more limited by the MTF of the lens and
other components, so there is relatively less high-frequency
component in the image, and that the JPEG algorithm does not
need to work so hard to compress the data, and can therefore
provide a higher quality image.

So my recommendation to the OP is to stick with maximum
resolution (3000 x 2250), and to make a series of test photos
at the different quality (JPEG compression) levels, and see
where you want to draw the line between file size and image
quality. Include both sharp edges and subtly coloured (or
even varying grey) areas in your test image. I have found
that the "normal" quality setting is satisfactory on the Nikon
cameras I have owned - your camera and image quality
requirements may differ.

We've talked about this before, and agreed to disagree. The think
that I DO agree - strongly - with you about is to test, test, and
test some more. It is ultimately the opinion of the OP what
constitutes "quality" or "defects", we're all here to help,
hopefully clarify, but also hopefully not confuse him.

For the records, again I do not dispute you, I find it best on my
Rebel XT to shoot at 4 rather than 8 MP because it is too much
bother to take the pains to resample down to my usual 1400 x 1050
final size. Doing it in one fell swoop is almost guaranteed to
introduce aliasing because few resampling algorithms can take out
so much data without messing up parts of the very fine detail. In
my world of car pictures, where I see it is in slightly off-
horizontal chrome moldings on the side of the car, grille, or
windshield. We each do what we fine works best for us, yes?

Nikon do seem to have the many parameters you can adjust in
the JPEG algorithm very well chosen.

I was pretty surprised that my Rebel XT can't save to TIFF but
only mildly miffed that it didn't have a 3rd, higher-compression-
thus-lower-quality image. I did my usualy testing the first day
at 2, 4, and 8 MP and both JPEG settings, made an initial eval,
then went and shot some real cars at each, came home and looked
at them.

I will say this about more MP: I like to include absolutely as
much AROUND my cars as I can fit within the confines of the space
I have, preferring to do my final crop for best composition in
the "digital darkroom" whilst also allowing enough to crop
correctly after doing something like perspective correction. So,
Since I finish at about 1.5 MP but shoot at 4, I'm more than OK.
And, if I ever decide I'd like to re-edit to, say 3 MP, I can
also do that.

Now, if an occasion arises where I do not have enough telephoto,
I will go up to 8 to get an effective increase in "focal length"
by simply cropping out my smallist image from the BIG one.

--
HP, aka Jerry