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Problem- recording video on 5D M3 where in manual, video looks like Iris is closing down then back up!

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Luis Perez
Problem- recording video on 5D M3 where in manual, video looks like Iris is closing down then back up!
on Mar 24, 2013 at 12:09:38 am

I'm fairly new to canon 5d Mark 3 but I was Doing an interview for a client indoors, well lit with some outdoor light coming from window. Had camera in manual mode set using canon 70 to 200 lens. Had iris wide open 2.8. Had 1080p 30. Had ND filter on lens to get widest aperture. ISO was around 250 shutter 30, 4800 K. LCD brightness manual. First few interviews looked ok. Only noticed on third interview while watching on my small HD monitor that the video would all of a sudden start gradually stopping Down what looked to be a stop or two, hang for 10-15 seconds or though and then come back up to the original setting. I unplugged the monitor and it was also doing it in the LCD of the camera. Checked the video later on my computer and it was there! Seems like every 4, 5 or 6 minutes it would do this! Anybody else have this happen? Am I missing something? Thanks for all input!


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Thomas Alexander
Re: Problem- recording video on 5D M3 where in manual, video looks like Iris is closing down then back up!
on Mar 24, 2013 at 6:53:18 am

My advise is that for 30p you should use 1/60 shutter. And for indoors tungsten lighting setup i personally use 3200K. Though the problem you came across is not because of shutter or frame rates and stuff like that. Your lens probably was set on auto-iris or auto-focus. Or maybe there was movement from your subject and the lens tried to focus. While it did that due to the long barrel of the lens once you had your aperture wide-open the lens took it two f/stops down to compensate.

Thomas Alexander | Independent Cinematographer
Soulman Films | Nicosia Cyprus | +357-97697640


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Luis Perez
Re: Problem- recording video on 5D M3 where in manual, video looks like Iris is closing down then back up!
on Mar 26, 2013 at 4:28:32 pm

Hi Thomas thanks for the input! I had put the IS on off but I noticed that the auto focus switch was in the on position on the lens. Though looking at the video it doesn't look like its trying to find focus just getting darker then ramping back up. So even though the camera is in total manual mode, If the lens auto focus is switched on, then what your saying is that the lens has the ability to compensate the fstop?


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Thomas Alexander
Re: Problem- recording video on 5D M3 where in manual, video looks like Iris is closing down then back up!
on Mar 27, 2013 at 8:29:05 am

Because your lens has a long cylinder due to the high range of mm. of focal length means that the barrel of the lens is long. The longer the lens cylinder the more difficult is for the light to reach the sensor. When your lens was on auto-focus there was probably some movement from your subject. From that movement the lens attempt to zoom-in and focus better and while the lens cylinder extends when zooming in the f/stops drop.

Thomas Alexander | Independent Cinematographer
Soulman Films | Nicosia Cyprus | +357-97697640


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