Richard,
I've been using a 1D MkIIn for the past year or so, compared to the 450D
it has fewer MP, much higher frame rate a much much nicer viewfinder,
much quicker autofocus and the images are generally less noisy. All
this applies to the 1D MkIV which has a higher still frame rate and more
MP. The 7D also has a similar frame rate. The 450D uses a pentamirror
rather than a pentaprism, to relay the image from the focus screen to
the viewfinder the result is a rather dim viewfinder, the 7D and 1D
cameras us a pentaprism. The 1D series have excellent focus screens and
are a joy to use and you can easily manuallly focus if desired. The
cheaper cameras can be quite difficult to manual focus as the screen is
designed for brightness rather than focusing snap.
The 1D series use a 1.3x crop factor sensor, which is 28.7 x 19mm, the
7D and 450D have a 22.2 x 14.8 mm sensor with a 1.6x crop factor. The
difference besides having a wider field of view with the bigger sensor
is that bigger sensor gathers more photons of light and generates give
or take the same amount of electronic noise per pixel. So the big
sensor has better signal to noise than the small sensor. What I find is
this translates to being able to casual about exposure and being able to
correct the files more readily in RAW before noise intrudes. The 7D and
also the 50D have have a bit of a reputation for being noisy unless you
expose the image well, generally this means exposing to get the
histogram all the way to the right without blowing highlights then
correcting the image in the raw converter. This link explains it further:
http://en.wikipedia.org/wiki/Image_sensor_format
The other thing the 1 series cameras give is complete weather sealing
and the provision of two card slots and a much more robust body overall,
along with great long battery life and a built in vertical grip and
shutter button. Another addition is the ability to autofocus at f8 on
the centre sensor, all other non 1 series canon give up beyond f5.6,
consequently they will AF in lower light and the 1 series also feature
many more AF points to choose from, the MKII has 45 AF points.
Another option to consider is the 5D MkII which has a full frame 36 x
24mm sensor, very low noise, reportedly very good auto focus and image
quality as good as it gets. What you don't get is the frame rate, f8
AF, built in vertical grip and weather sealing.
If you want to extend your $ to buy some nice long glass, you could
always check out what the cameras go for on Ebay. 1D MkIIn's go for
about $1600 and MkIII's for about $2500 or so. The MkIII has 10MP and
great image quality and low noise at high ISO, but issues with
autofocus, both for moving targets and static targets in high
temperatures. which seems to vary from body to body, you want to be able
to try out the AF before buying and preferably buy a late production
example and confirm it has had the sub mirror fix, either built with it
or has the mod done under warranty. Having said that a lot of people on
forums report they are very happy with their MkIIIs. The MkII I have is
8.2 MP and noise performance is good, I use ISO400 as a standard and
ISO800 and 1600 are both good as long as well exposed. The MKII's are
heavier as they use a Ni-MH battery rather tan the Lithium batteries in
later versions.
hope that's helpful,
Chri Ross
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