1dmkIV varying FPS with different lenses

I cant say i have noticed this before with other cameras, chime in if you have , but today i noticed that with the 300mm f4 lens, with apertures smaller than 6.3 , the FPS was reduced from 10 to about 8. Clicking through various apertures you could clearly hear the FPS changing. I tried various other lenses and the results werent quite the same. No noticeable difference until stopped down to about f14 with the 70-200 and 17-40.

So is it just the aged design of the 300mm f4IS aperture that is taking it longer to close down? Nothing that would ever make a huge difference, just curious to know if people have found this with other lenses?

Long shot: Maybe the decreased aperture is slowing your shutter speed down to a point where it's the limiting factor?

Yes certainly, not a long shot at all, i'm sure that is what is happening. So im wandering if there are other older lenses out there that maybe have similar inferior aperture mechanisms.

I had never imagined that stopping down the aperture would be the limiting factor in increasing FPS.

dandig wrote in post #9451714
I had never imagined that stopping down the aperture would be the limiting factor in increasing FPS.

It's not stopping down that's the limiting factor. Stopping down is creating less light so the shutter speed is not fast enough. Canon's manuals usually state that their tests (when seeing if the FPS is as advertised) is done with a shutter speed faster than 1/500". Since you're just testing FPS, put the camera in M and change it to 1/1000" for the shutter speed and wide open on the lenses you've got. Make sure it's on high speed drive, 10FPS, and then just shoot. Forget about exposure for now. Repeat for all your lenses, wide open, and then try f/16 for the apertures without changing the shutter speed away from 1/1000". If there is a real slow down, maybe something is wrong. But I think you're just confusing a slow shutter speed for a nonexistent problem.

Thanks Tim,

That is the first thing i tried. I put it in manual at 1/1600 of a second and the same results happened. Shutter speed is not the limiting factor.

I don't have your camera or your lens (but do drool when thinking about it!), but I asked a similar question not long back regards to my camera going slow in AI servo (I know not exactly the same issue) but in the thread I was pointed to a site that explained it as basically what you are saying, some lenses do take longer to open and close between shots. I'll see if I can find the link.

Yes it happens on my MKIII and my friends as well with the 100-400 shooting at 1/1000 or 1/1250 sec at 10fps, I don't know what it drops down to but you can tell the difference in the sound of the shutter firing, for us it hasn't been a problem, shooting AV and around 100 or 200 ISO. I was generally at around 300mm. I've also noticed it will do that with other lenses if the shutter speed is lower than 1/500th sec., this happens when using AV and pan into a darker part of a landscape and the shutter speed drops.

Just a suggestion. Read the Canon white paper on the Mk IV. There is a lot of data which might explain the difference in frame rate.

Is the performance any different if you change the lens to MF?

Well, every time you take a shot, the aperture ring thingy physically moves from wide open to the aperture you set F4 --> F 6.3, and then goes wide open again. Perhaps this is taking too much time and so youre loosing fps?

This is totally normal. The train of thought is that if you need the utmost highest frame rate, you are generally shooting action which coincidentally uses (most of the time) higher SS IE: more light and the in turn would normally use the widest aperture. Obviously there are times when you would like to stop down and the frame rate will slow as a result of the lag of the Ap ring.