[anthoiphone]

Hi. I am new to this forum and will like your help. I was filming a demo for a Pet TV show and I encountered a terrible problem with my exposure.
I was filming outdoors with a ND and suddenly when I hit the record button, I noticed that my exposure was changing automaticly. It brighten the
image so terribly, I was very disappointed. I try to look up in the menu, but didn't had no luck. Later on I kept on moving around in the menu and
I did fixed the issue but don't know who I did it.
Does anyone knows where in the menu I activate or disactivate this function? I can't let this happen again. I did looked on the 5d manual, but I am
not clear with this issue.
thanks for your help,
Anthony

[AmilaC]

Look in to Exposure - Then set to manual. Dont use auto exposure in video mode.

[planetMitch]

The other thing to look for is auto ISO - letting the camera pick ISO even when exposure is locked will cause the effect reported above.

[anthoiphone]

Amila C Kumarasinghe, on 02 November 2010 - 04:30 PM, said:

Look in to Exposure - Then set to manual. Dont use auto exposure in video mode.

Hi Amila. Where in the menu do I navigate to disable the auto exposure?
thanks for your help

[AmilaC]

anthoiphone, Im not Sure about 5Dmk 2. i think planetMitch is a 5D Guy. its better to ask him about whare that place exactly. I'm working with 60D and 7D.

Its better, search in all the menus for name "Exposure". then select it and change that to Manual.

as planet Mitch says, Dont use Auto ISO. use manual ISOs. to Disable auto ISO, click the ISO button on top LCD on 5Dmk2 and change it to manual nomber. that desables the auto ISO.

Ask from planetMitch about where the exposure controller in 5D. or search it from everywhere in your menu. (its better because you can learn about your camera's menu things)

Cheers . . .

[anthoiphone]

Amila C Kumarasinghe, on 02 November 2010 - 05:24 PM, said:

anthoiphone, Im not Sure about 5Dmk 2. i think planetMitch is a 5D Guy. its better to ask him about whare that place exactly. I'm working with 60D and 7D.

Its better, search in all the menus for name "Exposure". then select it and change that to Manual.

as planet Mitch says, Dont use Auto ISO. use manual ISOs. to Disable auto ISO, click the ISO button on top LCD on 5Dmk2 and change it to manual nomber. that desables the auto ISO.

Ask from planetMitch about where the exposure controller in 5D. or search it from everywhere in your menu. (its better because you can learn about your camera's menu things)

Cheers . . .

Great. Thanks

[anthoiphone]

planetMitch, on 02 November 2010 - 05:08 PM, said:

The other thing to look for is auto ISO - letting the camera pick ISO even when exposure is locked will cause the effect reported above.

Hi planetMitch, I was shooting at 160 iso with and ND filter. I was outdoors in Old San Juan, PR. We cannot live here without an ND.
So I think the iso was not the problem. I just went over the menu again moving here and there, and I got the problem again.
The exposure is auto adjusting. I move the camera from a dark area to my monitor and it adjusts.

It only does it when recording. When viewing the LCD on standby, it doesn't happens. Only when I hit the record button.

Any help?
thanks,
Anthony

[anthoiphone]

Thanks for your help. I found the setting concerning to this auto exposure issue.
It is under Live View/Movie func. / Stills+Movies and then be sure to be set to Movie Display. If
it is set to Exposure Simulation, the camera, after hitting the record button, will go to auto exposure.

thanks guys,
anthoiphone

[planetMitch]

wow - I don't think I would have solved that one... I was stumped

besides, I don't think I've ever turned on that exposure simulation.

[anthoiphone]

planetMitch, on 02 November 2010 - 06:09 PM, said:

wow - I don't think I would have solved that one... I was stumped

besides, I don't think I've ever turned on that exposure simulation.

I don't use either. For some strange reason it changed. I do know that this settings comes as default
when you get the camera.
The only issue I could speculate on is that my camera when battery dead when turned on... maybe
this reset the settings to default. I really don't know... just speculating...

but life is good. Problem resolved.

thanks

[planetMitch]

Is this a sample of the original question?



Or is this something else?

[GrownUpBoy]

planetMitch, on 17 December 2010 - 12:31 PM, said:

Is this a sample of the original question?



Or is this something else?

thanks for the reply, mitch!

in my case everything is set to manual and auto iso is off. exposure simulation is off - the camera is locked down manual.

we've been able to reproduce the above problem using 2 different 7D's and a 5d mk ii (all set to full manual).

i thought that there might be some deeply buried menu setting that affects "auto gain (video)" in video mode? but if it was an auto-exposure thing then you'd expect the opposite result to happen. auto exposure would try to darken the scene when "zoomed out" becuase there's so much white in the scene. the video darkens when zoomed in in this case. either way i've been through the manual top to bottom and have found nothing there...

does it look to you like the highlights are being compressed or do you think like the exposure is being affected? ie: the part in the middle of this video with the lamp almost looks like the tone curve is being affected?

what's really odd is that this only happens in video mode. same camera settings / modes - switch camera to stills mode live view and the darkening affect disappears. this is what leads me to believe it's not an auto-exposre toggle somewhere...

karl

[planetMitch]

GrownUpBoy, on 17 December 2010 - 12:56 PM, said:

thanks for the reply - this is not a sample of the original question. in the above case everything is set to manual and auto iso is off. exposure simulation is off - the camera is locked down manual.

we've been able to reproduce the above problem using 2 different 7D's and a 5d mk ii (all set to full manual).

give this a try with your own canon dslr and a fixed aperture zoom. seems to happen on every canon cam i've tried in video mode. the problem doesn't happen in live view (stills mode) and only occurs when in video mode.

I posted again on twitter this morning and got these replies:


@GregNuspel Greg Nuspel
@planetMitch I suspect that the lens diaphram does not adjust during live video, mathmatically this equates to an appature change.

@GregNuspel Greg Nuspel
@planetMitch this maybe useful info http://www.cambridge...mera-lenses.htm

@coffeephoto Coffee Photography
@planetMitch Does the metering mode have any impact on that video issue?

@p_chaves Pedro Chaves
@planetMitch it's a zoom lens. the more you zoom in the more light you lose.

Not sure any of them help... but passing along

I don't see this issue on my 24-105L as far as I can tell unless I have the >>movie mode>>screen settings set to Stills Display

[GrownUpBoy]

"@GregNuspel Greg Nuspel
@planetMitch I suspect that the lens diaphram does not adjust during live video, mathmatically this equates to an appature change."


thanks mitch - i wonder if this might just be the answer!

correct me if i'm wrong - the effective size of the diaphram at a given aperture value is different at different focal lengths. this is how lens manufacturers account for the light falloff in longer focal length lenses. f4 is still f4 in terms of the amount of light that aperture lets in but on a 400mm zoom an aperture of f4 would need to be much larger than the a little 28mm. this might also explain why fixed aperture zooms are so damn expensive!

it's really likely that canon's lenses are locked down in video mode cannont "scale" the aperture as the zoom moves through its range. hmm..

i'm going to do another test today and see if that's it. basically it means you'll need to start and stop your video every time you switch focal length to let the lens re-adjust it's aperture to be true at that focal length. exposure doesn't change but the lens needs to re-cajigger itself so the aperture is the aperture.

this has been excellent insight! i wonder why this doesn't happen in true video cameras... maybe it's the constantly variable aperture of video cameras. canons are limited to 1/3 or 1/2 stop increments whereas a true video camera can get it just right?

never encountered this problem before so i'm taking a stab in the dark. i'll post another sample later today to see if setting up new shots on the same scene at different focal lengths solves the problem or if it's something else.

thanks a ton for your help on this - been a ton of help!

karl

[GrownUpBoy]

quick update.

looks like starting and stopping the shot doesn't "re-cajigger" the aperture back to it's correct size depending on the position of the zoom in video mode. the correct aperture value at any other point in the zoom's range must be tied to the shutter on canon dslrs. my tests have shown that exposure definitely isn't affected by zooming when shooting photos.

what i have discovered is that the issue ISN'T PRESENT when the lens is wide open. this would explain why you don't see it in live view in photo mode (it's always wide open until the shutter is triggered). weird that it only happens when stopped down but could have something to do with the mechanics of the lens.

THE BAD NEWS:

unfortunately this seems to mean that you'll need to adjust your exposure every time you change your focal length with a canon zoom lens in video mode on canon hdslrs. my tests showed approx. 2/3 stop from 17 mm to 40 mm on my 17-40 f4 L lens. haven't tested any other lenses to find the exact exposure difference.

the other issue seems to be that this change in exposure isn't regular and has an odd spherical shape to the decrease in exposure. you can see this shape in the posted video - almost resembles the way the 17-40 elements move inside the lens barrel... i could just be making that part up but it looks that way to my drunken eyes.

it's too bad - the versatility of having mulitiple focal lengths available (i don't zoom during video... hate that!) during a single shot is really handy. especially for run and gun shooting where you might want to keep the clip running as you quickly change angle perspective and sort the shots out in post.

THE GOOD NEWS:

hdslr video has its own character and produces undeniably beautiful images quality if handled correctly. the entire hdslr revolution seems to be about working around the fact that these damn things weren't really meant to shoot video but the happen to do it really well. just another example i guess!

time to get some primes!

k

p.s. i've seen this problem on a 24-70 f2.8 to a much lesser degree than the 17-40 f4. i think mitch said he doesn't see it on his 24-105 - can you confirm that mitch? maybe point the camera at a white wall and do a quick shot with zooms from one end of the lens to the other? if there's an L series lens that doesn't do this it would be great to know!

[GrownUpBoy]

after further review this sounds like a known issue affecting a number of canon zoom lenses. check this video:



he's talking about the crap-ass kit lens in this video but does specifically mention the 17-40 f4 L as having a known issue of darkening while zooming during video recording. you can see what he's talking about around 1:06

interesting but good to know it's not something limited to my particular rig!

k

[Shaz J. Ahmed]

That looks annoying as hell. I couldn't imagine a worst case when out on a shoot and that exposure pop happens. I'd go insane! Stick to prime lenses dude. Faster and no pop!

[GrownUpBoy]

well, the 17-40 doesn't pop but definitely has the issue as described in that video and in my test vid earlier in this thread. ya, primes!

problem with primes is... they don't zoom. for run and gun it would be nice to have a little more versatility. but what are ya gonna do?

k

[planetMitch]

GrownUpBoy, on 21 December 2010 - 07:01 PM, said:

after further review this sounds like a known issue affecting a number of canon zoom lenses. check this video:

k

Thanks for keeping us up to date on your research!

[GrownUpBoy]

planetMitch, on 22 December 2010 - 01:27 AM, said:

Thanks for keeping us up to date on your research!

glad to do it mitch, this has been a weird problem that most people chalked up to being related to auto-exposure. it's frustrating to find out that its mired in canon's zoom lens design.

to their credit these lenses were never designed for live video but it's still interesting to see what's happening and why.

i'm heading to the store later today to check out the 16-35 f2.8 to see if it has the same issue. i really like the 17-40 as a general purpose lens for my 7d but i'd love to be able to zoom again!

thanks for keeping a great and informative site!
k