why only 3 fps on 5d?

Lacks_focus wrote in post #4112749
All 1 series bodies have a "full size" mirror, even the 1.3 crops. Film bodies, like the 1N and 1V series, were capable of 6 and 10 FPS respectively with a booster grip mounted. They, of course, also have a "full size" mirror. The mirror size is not an issue. Processing speed, buffer size (and speed), and amount of data to process = max FPS available.

I agree that it's totally possible to make a FF camera do 10fps, but I do believe that there are some durability issues with going to a higher frame rate. Check out this video from the 1D MKIII launch--Chuck points out that the mirror box is now magnesium which allows for the 10fps rate:
http://www.youtube.com​/watch?v=Bb3yuh_0E9s

I don't know if Canon would need to beef up the 5D to allow for a fps increase, but its possible. That is a big mirror moving around in there.

And an expensive one that people wouldn't pay for.

LOL I just saw your new tagline Jason. That's fitting

timnosenzo wrote in post #4112889
Chuck points out that the mirror box is now magnesium which allows for the 10fps rate:
http://www.youtube.com​/watch?v=Bb3yuh_0E9s

I don't know if Canon would need to beef up the 5D to allow for a fps increase, but its possible. That is a big mirror moving around in there.

Well, I don't know... As far as I know the box on the other 1 series cams are aluminum? Anyway, they’re not plastic. I doubt that magnesium dose much more than reduce weight in this case. I know that magnesium is lighter than "most" aluminum alloys, at least this is the case in the world of motorcycle rims, but I don't believe it's any more durable. In fact, again in the world of racing rims, it's more susceptible to cracking over the aluminum alloy counterparts... Not sure what the 5Ds mirror box is made out of, but again, I doubt that is what's keeping the fame rate at 3-4 FPS!

BTW, I didn't watch the vid, so ignore me if the video makes it obvious, and if Chuck is anyone other than some guy with an opinion (like me!)...

EDIT!!! OK, watched the vid... Chuck is cool (not like me), but I still don't think making the box mag alone did the trick for 10FPS!

Rule #1: Good, fast, cheap; pick any two. Move on.

Observation #1: Even with noise reduction off, my buffer counter and CF card indicator show fewer shots with higher ISO. Perhaps there's something to be said for _processing_ the images, and perhaps the 5D simply does more processing than other comparably-processed cameras for better IQ.

Why only 10FPS on the 1D Mark III?

Canon artificially limits it's features on the different cameras to create feature separation in their lineup. You want high speed, get a 1D camera. You want good fast autofocus, get a 1D camera. You want weather proofing, get a 1D camera. Nikon with it's D3 and D300 cameras is going to change this game in a hurry.

my friends 35mm EOS 55 does 4FPS...