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auto iris too dark

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dan jones
auto iris too dark
on Nov 8, 2009 at 12:33:26 pm

I've shot a few things with my new EX-3 with no external monitor and all the footage has turned out too dark. Not unusably dark, but definitely under exposed.

I have been using the auto iris as a reference and then opening up from 1/2 to a full stop, and still it needs to be bumped up in post. This has all been at 1080p.

Any ideas on what I can do? Thanks.


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olof ekbergh
Re: auto iris too dark
on Nov 8, 2009 at 1:56:14 pm

Relying on auto iris is not a good idea.

There are to may situations where it will always be wrong, snow, bright beach and backlighting comes to mind for starters.

Learn how to use the histogram and zebras. And there is the percentage readout in the center of the EX cams.

Using manual exposure also keeps the shots from the dreaded iris change when moving camera or having a light or dark object pass through your scene.

There is nothing that says amateur in a shot more than auto iris.

Olof Ekbergh


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Daniel Startek
Re: auto iris too dark
on Nov 8, 2009 at 2:01:17 pm

You should experiment with the Picture Profiles. Use a waveform monitor and a DSC chart. I find that Cinegamma 1 requires 1 extra stop or more over the auto iris (Cinegamma 3 + 1/2 stop) but other settings also affect proper exposure. I used to use just the zebra in the field but find the histogram is also valuable.



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Greg Ondera
Re: auto iris too dark
on Nov 8, 2009 at 2:47:54 pm

Auto iris is at least not the end of the world if it is dark. I often use it as I have to in surgery, because I can't often reach the cameras which are on boom arms. I certainly don't do this when I can have full control of the camera. And if I shoot an open wound case, in which auto iris will flutter and adjust when white surgical gloves come into the scene, I will most certainly use manual iris.

If the footage is dark then take it into FCP and use the 3-way color corrector to raise the exposure level as you would in photoshop. What is unforgiving about digital exposure is when you shot overexposed. And in principle, only underexposed footage can be brightened, but overexposed cannot.

Greg Ondera
http://www.Plexus.tv
http://www.SurgeonToday.org


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Rafael Amador
Re: auto iris too dark
on Nov 8, 2009 at 3:26:39 pm

I absolutely agree with Olof. Learn to use all the controls in manual.
However as Greg points, in certain occasions you need to use the Auto.
I haven't got with me the camera, neither the manual, but I think in the "TLCS"> Levels, you can adjust the iris increasing or decreasing the aperture in a fixed amount.
I haven't tried it.
Rafael

http://www.nagavideo.com


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Daniel Startek
Re: auto iris too dark
on Nov 8, 2009 at 6:30:26 pm

"auto iris as a reference and then opening up from 1/2 to a full stop" = manual iris!



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Christopher Kinsman
Re: auto iris too dark
on Nov 9, 2009 at 6:19:28 am

Hi Dan
FWIW everyone's focused on the iris, but have you done a camera monitor calibration test to make sure what you see in the monitor is what you're rolling to tape/drive/card. I've had guys turn their monitors up brighter and think they're exposed properly. NOT! It may have been bumped up accidently or not set properly from factory. Just a thought.
Hope this helps and best of luck.
Kind Regards,
Chris K.



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Noah Kadner
Re: auto iris too dark
on Nov 9, 2009 at 2:54:41 pm

Yeah I'd sit down and calibrate the onboard monitor at least- that + an auto iris check should be more than enough to get you into the ballpark of a usable exposure.

Noah

Check out my book: RED: The Ultimate Guide to Using the Revolutionary Camera! Unlock the secrets of 24p, HD and Final Cut Studio.
Call Box Training now featuring the Sony EX1 Guidebook, Panasonic HVX200, Canon EOS 5D Mark II, Canon 7D, and Panasonic DVX100.


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Brent Dunn
Re: auto iris too dark
on Nov 9, 2009 at 8:13:48 pm

What also matters is your location lighting. Do you have your ND filter on, Gain off? If it is a low light situation, then maybe these bumps need to be made.

I just shot an outdoor event at sunset on the beach where I had one EX 1 unmanned. I had to leave it at autoiris, which saved my butt. Once that sun started dropping, it went dark fast. The lowlight capability of the EX 1 /3 saved the day again.

Brent Dunn
Owner / Director / Editor
DunnRight Video.com


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Bryan Donnell
Re: auto iris too dark
on Mar 8, 2010 at 8:55:33 pm

Those who have responded, take a step back and look at how you've answered the fellow: as if he were completely inexperienced, and even stupid.

The fact is that the EX3's auto-exposure IS terribly off. If I come in asking about why this is, assuming I'm even moderately experienced, having people suggest I calibrate my monitor, check to see if my ND is off, or even "learn to use the manual controls" is only going to annoy me. Patronizing and useless at best. It doesn't even make sense to say the ND might be the problem, if he's already saying that manual works.

Sorry, but with all due respect, I dislike it when one asks a question and can't get a proper answer because people assume you are a pre-schooler. It lowers the level of the forums to technically useless as well.

As a doc shooter, I can tell you that auto-exposure is often a useful reference point when you are moving quickly. In my brief experience with the EX3 the auto-exposure is useless because it's so far off -- it feels as if there were something wrong with the firmware, it's so dark, to where I'd wonder if even color correction could help without a lot of noise added.

So to cut to the question again, is there a practical reason why the auto-exposure would be so low? Are there settings in the PP, like gamma etc, that throw the auto-exposure off so radically? if so it must be a design flaw. I have, yes, tried stepping up the TLCS levels, but it doesn't seem to make it work properly.

Any insights?

Thanks in advance....


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Bryan Donnell
Re: auto iris too dark
on Mar 8, 2010 at 9:07:04 pm

Did you ever find out why the auto-exposure runs so dark on the EX3?


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