While I was looking for an upgrade from my G3, I first examined the new set of 8mp prosumer offerings. I was not quite happy with either of the five brands though. Then I discovered the cheapest SLR class digicams are similarly priced and quite attractive. Here, it was a choice between the nikon d70 and the canon 300d as the lowest priced. I chose the canon because of canon's reputed image processing algorithms, and the lower price.
The 300D was supposed to be the planned upgrade from my G3, and I kept considering the drawbacks of the transition to a SLR camera. The most important thing to consider is the lack of the G3's famous flippable screen. I'd have to do with the limited viewing angle flexibility of a viewfinder. I found myself get used to the viewfinder's constraints quite easily though, with the main drawback being the risk of getting a pain in the back or neck when shooting in certain situations. A flippable screen does have the edge when it comes to working conditions however.
Secondly, I kept wondering if the viewfinder would give me enough resolution to precisely focus manually. I was used to the Praktica series, which you can focus precisely, by a special optical tool found in the middle of the viewfinder, which translates focus of the image to alignment of two halves of the image. By aligning the two halves precisely, a very accurate focus is guaranteed.
As it turns out, the 300D's viewfinder's resolution is quite fine. It really is quite a relief from the rather limited TFT screen image of non-SLR cameras. The resolution is similar to the picture's actual resolution. There won't be TFT screens like that for a long while. Even if we manage to compress the pixels of the most expensive 21" TFT onto an area about 2 inches across, it will still have less resolution than the viewfinder.
Manual focus also turned out to be easy. The viewfinder is almost enough to focus with pinpoint accuracy. But if you need to focus precisely, the AF points flash as soon as they are in focus, and the "focus ok" light in the status line lights up. With the viewfinder it is much easier to get a good focus on difficult subjects, such as insects, than with a TFT.
There is some trouble with autofocus though. It functions very well in low light conditions, as compared to the G3. Sometimes though, it fails to lock on to a focus point with very low contrast (such as a blank wall, even if the wall has some texture). This happens even in some well lighted conditions, which I find disturbing. It happens little in multi-AF-point focus, as it can usually find at least one AF point that focuses well, but I usually use the center point only. I wonder if this is normal, or whether there is some fault with my camera or lens. I tried two lenses, and it really looks like the af system cannot determine focus in those cases, it fails to indicate the in-focus signal when in manual focus too.
The pictures shot in the slowest mode, 100 asa, are reputedly smooth. You see very little noise indeed, yet subtle textures are visible. But sometimes the picture looks a bit "too" smooth, as if they overdone the noise reduction a bit. Nevertheless, it is obvious the camera has great resolving power. I estimate it about 1.5 stop more sensitive than the G3, and about 2-2.5 stops more sensitive than the 8 mp compacts. This means the camera has increased exposure latitude as compared to compact cameras.
I am a little troubled by the jpeg compression settings. You only have two: normal and high. In the normal mode however, jpeg artifacts are regularly visible as they surpass the noise level in the 100 asa images. The high mode, however, results in large jpegs, about 3.5-4 megs a piece, twice the size of the normal jpegs. I need to upgrade some of my stuff to enable such large pictures, so now I shoot in normal most of the time.
I recently bought a second lens second-hand, a sigma 100-300mm f/4.5-6.7, translating to 160-480 mm. That's pretty long, and this kind of lens takes some getting used to. It's a good lens (beside some bad bokeh), and very cheap for what it offers. The increased length due to the crop factor is good news for telephoto lovers. There may be a second advantage next to the increased length: less corner distortion. With the smaller ccd just covering the center of the image, the corners are simply cropped off. Someone suggested that diopter screw-on lenses, which have strong corner distortion, would be more acceptable too. I wonder how this corner distortion story works out theoretically.
Swapping lenses took some practice, as I am not used to the lens mount. There is another problem with swapping lenses: dust. It gets into the body, and settle on the pentamirror, or on the ccd. In case of the ccd, you will see the dust prominently visible on your pictures. Then it's time to clean the ccd, which most say is tricky. The camera has a "ccd clean" mode in which the mirror flips up. Then you can have a go at the ccd with lens blower, brush, and cloth. Not sure what is best here cause i haven't needed to clean it. Someone also warned against cleaning the mirror system with a cloth: it will leave tissue on the mirror.
The battery life of the 300D may vary according to your shooting habits. When shooting, the DSLR turns into a rather ordinary SLR, as the photosensor and TFT screen are not used, instead, only the traditional SLR stuff is in operation. According to the docs, you can take some 600 pics on one charged battery. However, in practice it will be less. I use the TFT screen to check some pictures for exposure and sharpness, and using the screen seems to be very power consuming, more so than on the G3, and usually my battery is empty after 50-100 pictures.