# Canon 5D MK3 malfunction with 24-105 f4 while zooming when shooting video!!!



## orfeas (May 16, 2013)

hey,
i have really unusual problem with my new canon 5d mk3.

i was shooting video, using 24-105mm f4 canon lens, no filters, manual settings both lens and camera, at an aperture f9 shutter 60 at 24mm. when i zoomed to 105mm i noticed that overall amount of light changed as if it was stopped down one and a half stops while the setting remained at f9?! so i had to adjust aperture to get the proper exposure. i checked the recorded material and the change in light was also recorded, thus eliminating monitor preview. i went through all settings and double checked that everything is set to manual. i went to a friend and tried my lens on his 5d mk2 and everything was in order. i tried his lens canon 24-105mm on my camera and it did the same mistake. then we tried canon 70-200 f2.8 and it worked properly. i also tried installing new firmware and everything was the same. i tried different combinations of apertures and shutter speeds and it was still there. here is a link to youtube video that shows the malfunction.

https://www.youtube.com/watch?v=xvC1A2BsGms


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## msowsun (Jun 13, 2013)

I have noticed the same thing with my 24-105, but it also did it on my 5D Mk II before I got the Mk III. You can actually see it in the exposure meter.


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## orfeas (Aug 21, 2013)

yes!
sorry for taking me so long to reply. i didn't previously own mk2 but borrowed it from a friend and it did the same thing. i sent the footage to cps in frankfurt and they ran some tests with other models, and noticed the same thing with d1x! they have no idea what might be the problem and they said that they will get back to me after they send everything to japan. for me this is major problem, especially because i am shooting a lot of video with mk3. it is strange that i haven't seen anything about this problem anywhere.


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## neuroanatomist (Aug 21, 2013)

I wonder if this occurs with other zoom lenses? It should be correctable with a firmware update, as it seems to be an electronic control issue. While we think of a lens like the 24-105 f/4L as a 'constant aperture zoom' it's really a _constant f-number_ zoom. Since f-number is a ratio of focal length to aperture (iris diaphragm diameter), as the focal length is changed, the physical aperture must also change to maintain constant exposure. Sounds like that's not happening in this case...


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## orfeas (Sep 21, 2013)

hey, again late reply...yes that is right what you said about f number. i tried 70-200 f2.8 and there is no such problem, you can see it in the link i posted. i tried latest firmware and the same thing happens. funny thing is that i send all the description of this issue to cps in frankfurt and they ran tests with their 5dmk3 and d1x and noticed the same problem, also not with all the lenses. and they have no idea what it is or they say so. namely they sent this to canon in japan so they say and got no reply.
for me this is really big issue because sometimes when i do news or documentary while i shoot i change focal lens without stopping recording, and it is annoying to keep adjusting aperture non stop.
also i wonder why is this not a bigger issue on forums, hmmm...


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## Camerajah (Sep 21, 2013)

did you check the box in Canon EOS Utility for that lens when you linked the camera up to your computer?

Just wondering if that would help


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## orfeas (Sep 21, 2013)

i think that is only for lens aberration correction, right?


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