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Old June 24th, 2008, 08:43 PM   #1
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understanding exposure

can someone explain to me how to manually set exposure on moving shots. I am using the glidecam and don't understand exposure. Using the zebras at 100% I can see what is overexposed but how do you tell what is underexposed? How would you use the zebras to the best extent. Especially indoors during the preps and outdoors for the photos.

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Old June 24th, 2008, 10:59 PM   #2
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Jason:

I only use the zebra as a guide and to use judgement on how the overall image looks to you. My experience has been that it is easier to work the slightly over exposed in post versus under exposed shots. Not sure if you are shooting HDV or SD but for me if I am shooting HDV I will always keep the image right on the edge in terms of letting as much light in as possible, iris wide open to give you a better shallow DOF. Sometimes its just a matter of trial and error.
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Old June 25th, 2008, 02:28 AM   #3
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With a glidecam it can be hard, especially if your going from outside to inside. Deffinatly, never ever use auto. as you move around it wont be able to keep up and it all goes wrong.

Agree with over exposed, the camera will always suggest to take it down a notch but its easier to lower brightness in post than boost. If its under exposed then the parts of the picture you want just arnt there on tape so you cant make the invisible appear. but if its over exposed its all there, just need toning down.
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Old June 25th, 2008, 03:13 AM   #4
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People set their zebras on all sorts of levels, so it's hard to say what you "should" do. Personally, I have my zebras on 95, that way I know that anything with a zebra on it is either overexposed or just about overexposed. I can then adjust my exposure to see how close the various areas are to 100, or overexposed.

My goal is always to keep the vital part of the shot exposed properly. So if I'm shooting a person's face indoors and there is a window behind them then I will up the exposure so that their face looks right even if it means (and it usually will) overexposing the window.

As for glidecamming, it's just hard. Originally I experimented on auto, then on what you could call semi-auto. Semi-auto is where I would locked down one element (like shutter, or iris) and let the others compensate. This seems to work okay if you need to move a shot from a bright area to a dark area or whatever. If I'm shooting all of my shots in an area where the exposure won't be changing, then I'll go full manual on the camera for that. I've even gotten to where I set the focus manually sometimes and just watch my distance to the subject to ensure I get a good shot without the autofocus screwing it up.

Hope that helps!
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Old June 25th, 2008, 04:01 AM   #5
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I don't really know that it is better to overexpose then to underexpose? I did some shoots the last weeks with a dvx100 and noticed that overexposed shots, which are indicated by the zebra 100% setting don't have any detail in it afterwards, no way to correct it in post.
I also always try to stay in the F4 to F11 range as that appears to be the best setting for the sharpest picture with DV, not sure if that is an issue with HDV?
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Old June 25th, 2008, 07:33 AM   #6
 
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My experience with HDV:
1-if it's blown out(over-exposed) there's absolutely nothing there to recover. it's a done deal
2-if it's underexposed, there is still a lot in the shadows that can be recovered, however, you stand a vry good chance of making all kinds of noise, mostly in the shadows, when you bring them up. Long form GOP compression isn't very robust.
3-perfect exposure with the dynamic range withing the camera's capability is just right. if there's too much dynamic range, use fill light to reduce it.
4-some people jump on the CINE mode in their cams to deal with excessive dynamic range. Unfortunately, CINE modes compress the gamma curve so that when you adjust the exposure in post, you will experience more noise and more banding.
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Old June 25th, 2008, 07:36 AM   #7
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thanks for the replies,

I am shooting HDV at 24p. How can you tell if the shot is underexposed? If you remove the zebras are you underexposed or do you just judge from the lcd? Especially faces and hands.
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Old June 25th, 2008, 08:07 AM   #8
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Quote:
Originally Posted by Jason Bowers View Post
thanks for the replies,

I am shooting HDV at 24p. How can you tell if the shot is underexposed? If you remove the zebras are you underexposed or do you just judge from the lcd? Especially faces and hands.
For me it's a matter of experience, after you use a camera for a while you can judge based on what you see on your viewfinder if it's good or not and with the help of the zebra's you can avoid overexposure on parts that are important, like faces. This I base on the end result when I see the footage on a regular or lcd tv. Only then I know if the information I get from my camera corresponds with what I see on tv. f.i. for the vdx100 you can be sure that when the 100% zebra appear on that area it still might look ok in your viewfinder but afterwards you notice that almost all detail is gone in that part and not recoverable. When I think it's right visually I tend to underexpose a little bit.
Also i noticed that some tv's display the image different, my demo footage may look perfect in exposure with still some detail in a bit overexposed parts on some tv's and other (cheap ones like thompson) will completely wash out all detail in those parts.
Instead of asking us when it's underexposed you need to go out and start shooting, as much as possible in all type of circumstances and then judge the end result on a tv, only then you can be sure :)
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Old June 25th, 2008, 08:41 AM   #9
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Originally Posted by Jason Bowers View Post
How would you use the zebras to the best extent. Especially indoors during the preps and outdoors for the photos.
If you're talking about shooting people then you're exposing for skin. Set your zebras to 70% and adjust till you see a little zebra on the skin. Again, this if if you're exposing for people, not objects. If your main subject is a person, then expose them properly and let the highlights (like a window) go. If you don't like the idea of having anything blowing out in your shot, then re-frame your subject to where they are the brightest object in your shot. If this isn't possible, then your only other options are to gel the windows, or bring in additional lighting.

My personal not by the book method if I'm exposing in this manor is that I tend to set my exposure for the skin using the 70% zebras and then dial it back a little. For some reason I tend to prefer my skin tones to be exposed at around 60%, but that's just me.
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Old June 25th, 2008, 08:52 AM   #10
 
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I was wondering when this would come up. I agree, it seems skin tones set for 60% works much better for me, as well.

Last edited by Bill Ravens; June 25th, 2008 at 08:52 AM. Reason: spell check
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Old June 25th, 2008, 09:02 AM   #11
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Got something else for you Bill.

About losing all values over 100%, this doesn't appear to be the case. It would seem that there is some image data recorded up to about 110%. Sony use to call this extra exposing area "Super White" in the VX2000 days. I don't know if it was an official DV term or just Sony's own marketing speak, but it existed.
I've tested this in HDV by shooting a landscape with a bright sky and exposing the sky past the 100% histogram marker on my FX7 but not allowing it to touch the end line which I'm guessing is 110%. I am able to bring the highlights down to under 100% in post (using the waveform monitor as my guide) and reveal some cloud detail that seemed to be blown out indicating that there is a little head room in HDV. I'm not sure how much detail is there, but there definitely is something.
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Old June 25th, 2008, 09:06 AM   #12
 
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I've noticed the same thing, Ethan. Same, same with the JVC HD110. I make extensive use of the WFM and curves to bring things back to legal, add a bit of knee to the color grading to increase contrast. Generally yields pleasing results. There is some detail info in that >100% IRE signal, but very, very little. Most zebras seem to indicate up to 100%. So, for me, anyway, setting zebra at 100% gives me 10% headroom.
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Old June 25th, 2008, 09:12 AM   #13
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Bill - I see you got your technical merit badge at video sumer camp too.
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Old June 25th, 2008, 12:35 PM   #14
 
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umm...did I miss something?
r u referring to my wee bit o' sarcasm?
summer camp is still going...we're moving into production/cuts...director's cut
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Old June 25th, 2008, 01:18 PM   #15
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Bill - sorry for the confusion. I was just trying to say in my own odd little way that you've got some decent technical knowledge for a wedding guy. It was meant as a strange little compliment.

Next time I'll keep it simple and say, "hey Bill, you seem to know your stuff".
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