One point I didn't notice mentioned exactly (but touched on by PeterL) is that "pro" models (usually) have fewer Camera Modes.
That is to say most, if not all Pro bodies have few if any "Automatic Modes": these Modes are the ones usually with nice titles like "Action" "Portrait" "Night scene" . . .”Full Auto” etc.
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For example on 20D you get: Portrait / Landscape / Close up / Sports / Night Portrait / Flash Off / Full Auto / Auto Depth of Field. (and the expected “P” Program, “Tv” Shutter Priority, “Av” Aperture Priority, “M” Manual)
On a 5D you get: only get “Full Auto” . . . and then “P”, “Tv”, “Av”, “M” but you get a bonus “B” Bulb.
On a 1DsMkIV you get: “P”, “Tv”, “Av”, “M” and “B”
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Now the tongue in cheek stuff:
So I guess the 20D “just above entry level shooters” don’t have enough experience to use Bulb, and need Auto assistance with Depth of Field.
When we “graduate” to a 5D we are allowed to use Bulb – but still have the “safety net” of Full Auto, just in case if we wet our pants.
But shooting big time with a 1 Series we can ditch the safety net of Full Auto . . .
at least that’s what the salesman might tell you and also the camera owner who doesn’t know his gear and simply bought a status symbol rather than a tool or a toy to give him pleasure or an income or both.
There is a lot of big boy toy comparisons with all this I think – one method I use to sort that out at gigs, when the Guests Start playing that game with their Big Boy Toy and start to make comparisons is to look blankly at them (distracting their focus) whilst clicking the mode dial three clicks counter clockwise (putting me in “P”) then I bring the camera up and say something like – “doesn’t matter what gear you got - so long as you know how use it in P mode . . . P for Professional . . .
WW