Why are 'pro' DSLR's so big?

[MrPogo]

All the top end 'pro' dslrs are much bigger than the 'enthusiast' models, but why is this? Is there actually more stuff inside them filling up the extra space, or is it simply a carry over from the film days (when this space was used for stuff like multiple rolls of film), with the camera companies (and probably a lot of the buyers) thinking a bigger camera that instantly looks 'pro' is important?
I'm assuming they don't actually have much more stuff inside them (sure, the sensor is bigger in most of them, but that couldn't account for all of it, and the rest of the difference is surely just more expensive computer chips, rather than more or bigger), but obviously this is all guesswork and I could be wrong, so does anyone know for sure?

[JohnG]

As you noted there are additional and larger components.

There is also the metal body and seals

There is also the integrated vertical battery grip (usually an accessory on non-pro DSLRs).

[tmoreau]

Put a 3lb 'pro' lens on a digital rebel and you'll understand.

Big lens, big handle. Thats one reason anyway. The whole 'compact craze' is market driven, and as always the 'market' is not a rational force.

[BenjaminXYZ]

Just picture those dSLR cameras without the build in battery grip, and you would see that they are not so big anymore.

I agree BTW, that sometime if the camera is too big, or if the lens is too big as well, it can all get rather scary.

I like powerful compact models with small and bright prime lenses.

[eric s]

I've got a 20D and a 1D MkII N, so I can speak from a bit from experience here.

One reason is the battery is much larger. 3-4 times larger. That is the bulk of the larger size.

Some is the weather sealing. I'm sure that means larger and more complex seals on all joints which make it slightly larger.

The larger sensor does account for some of it, but not a lot I bet. Some of it is the extra electronics, although I bet much of that is being reduced into a few chips as time goes on. Still, not everything can be combined

It is my understanding (but I could be wrong) that the MkII N is basically the same size as the 1V HS (the high speed film camera canon makes.)

Personally, I don't know of any pro film cameras that can hold multiple rolls of film (I don't believe the Nikon F series or the Canon 1V do.) And those are all large 35mm cameras.

Eric

[Mark1616]

Ease of handling has to be the biggest thing, initially having built in vertical grip will add to the size but I would not be without that ability (for both sport and portrait) as your hand will soon get uncomfortable. As previously mentioned consumer DSLRs are still trying to be small so as not to be over intimidating to users who are used to compacts but they don't sit nearly so well in the hand. But a 300mm f2.8 lens or larger on one of these and you will find it very hard to handle. The last point is the ease of control with more 'dials' on the pro cameras to allow very quick accessto what you need.

[Bob Nichol]

Many experienced photographers feel a heavier camera is easier to keep stable than a lighter camera.

[Mark1616]

Very true Bob, and that has a basis in physics as well F=MA (force = mass x acceleration) - this is newtons 2nd law - so if the mass of the object you are holding is larger then it will take more force to give the same acceleration. Putting this into terms of the weight of a camera and the fact that all of us shake a little when trying to hold something still then if there is a great mass then these little shakes (increases/decreases in force) then the amount that the camera moves is less. There does come a point however when something gets too heavy and then ones physical strength will be the limit causing more shake but you get the 'picture' lol (I hope).