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Consistent exposure and lighting


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#1 Lukeo

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Posted 19 December 2005 - 05:49 PM

Hey,

I understand a bit about photography exposure, depth of field and a bit of lighting, I am wondering how i can get consistent exposures with my mini dv cam since it has no f stop numbers. All it has is a dial that allows you to darken the image, or over expose it. Instead of numbers there are dots. So would the best thing to do is record how many dots are there for each take, and keep it consistant like that? Because a video I did a while ago, i changed the exposure level each time, and ended up with bad lighting continuity. Also I've been setting up lights for experimentation and although everything is really blasted with light, I can decrease the exposure on the dial and get an ok image, is this acceptable to do or will it give me too muddy of a picture, because it's slightly like that.

Lighting- I can't afford a light meter presently, so many costs are bringing me down- recording sound gear etc. I was wondering if anybody uses a tape measure to measure the distance the lights are from the performers and also make a sketch of the lighting diagram and how the lights are angled and diffusion/gels etc. Do you think a set up and routine like this could work for my low budget needs?

Thanks for taking the time to read

Luke O
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#2 Michael Collier

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Posted 19 December 2005 - 07:01 PM

Without a meter you have to trust your eyes. A while back i found a trick to use the CCDs as a light meter. You set the iris to get a reading on one point(using zebra lines). then iris up or down to get the reading for the second part (again getting the zebras to appear where the second reading is to be taken) then note how many stops it took to get there. Unfortunatley without proper markings this will be impossible on your camera.

I have done ratios by measuring. It works well with matched light. put a light x distance away and put the fill 2x away and you get predictable results. In the end video lighting tends to be a lot by eye. get the ratio correct by eye and keep a copy of that ready to playback when you are setting up the next shot, so you can compare. you can even bring a laptop to the set and see how one shot intercuts with the other if you need too. Also check out DVrack by Serious magic. It costs almost as much as a light meter, but for video has a million useful features. If at all possible I always have one rigged up.
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#3 Lukeo

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Posted 23 December 2005 - 04:29 PM

Does anybody else have any advice or solutions?
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#4 David Mullen ASC

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Posted 23 December 2005 - 06:49 PM

Does anybody else have any advice or solutions?


Doesn't your camera allow zebras in the viewfinder? If not, you're basically using a camera designed for amateurs who tend to use auto-expose.

Zebras and/or waveform monitors are the only way to know exactly how the camera is exposing a scene, but that doesn't mean you can't expose without them.
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#5 Lukeo

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Posted 23 December 2005 - 06:57 PM

Yeah,

My camcorder does not have zebra patterns, it's a decent camcorder for starting out I think, it at least has a manual focus ring which is a bonus. the model is DCR-TRV27, i will definitely be upgrading to a better cam in the future. But I'm just wondering is it worthwhile to play with the exposure dial to darken or lighten the image, and do some measurments of how many notches on the dial it's darkened, and measure distances from lights to actors, I want to learn as much as i can on this cheaper cam, so I'm ready when I step up to better ones. Thanks for the replies thus far.
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#6 David Mullen ASC

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Posted 23 December 2005 - 07:46 PM

For practice, you could first expose by zooming into an 18% gray card, use auto-exposure, and then lock it off -- although you'll probably find that the "right" exposure is often a stop darker than that. Or find a lighter gray card or paper that gives you the right scene exposure when you first zoom into it, lock off the exposure, and zoom out. Make sure you are looking at a properly set-up monitor (although I assume your camera doesn't generate color bars either!)

The distance between the actors and the lights doesn't really need to be measured, but you may try using a light meter to start to get an idea of the light levels being used. Does your camera even tell you what f-stop / shutter speed is being used?

Without zebras, f-stop info, etc. you might as well just play with the thumbwheel and set things by eye. If you really want to learn about exposing, you need basic scene information.

Edited by David Mullen, 23 December 2005 - 07:50 PM.

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#7 Peter J DeCrescenzo

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Posted 23 December 2005 - 08:57 PM

If your cam doesn't generate standard SMPTE colorbars -- commonly used to calibrate a TV monitor so it can be used to properly evaluate video exposure and color -- as an alternative you can adjust a TV monitor fairly close to correct calibration by using the THX set-up feature available on some DVD movie releases.

There are quite a few popular movie titles available on DVD which include this feature. If you don't already own a DVD movie disc which has the THX set-up feature, your local DVD rental store may have such titles.

If your camcorder _does_ generate SMPTE colorbars (which I doubt, but just in case), instructions on how to use them can be found here:
http://videouniversity.com/tvbars2.htm

The above steps are necessary because the small LCD screens built-into most camcorders are no-where near as accurate as a properly calibrated "CRT" (tube-type) TV monitor. After you've worked with a calibrated CRT monitor for a while, your eyes and brain get "calibrated" so you can learn to mentally compenstate somewhat for the deficiencies of a cam's LCD screen. After that, you can usually judge exposure semi-accurately using the little LCD screen. But it takes practice, and you should periodically do a reality check against a calibrated CRT monitor.

Edited by Peter DeCrescenzo, 23 December 2005 - 09:00 PM.

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#8 Lukeo

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Posted 23 December 2005 - 09:59 PM

Hey thanks very much guys, that helps me a lot, one more question tho, how do you "lock off" exposure on a camcorder?
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#9 David Mullen ASC

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Posted 23 December 2005 - 11:18 PM

Hey thanks very much guys, that helps me a lot, one more question tho, how do you "lock off" exposure on a camcorder?


Your camera doesn't even have an exposure lock? It only does auto exposure? Many cameras have an exposure lock so that when you pan past a bright window, the camera doesn't compensate by closing down the iris suddenly.
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#10 Peter J DeCrescenzo

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Posted 24 December 2005 - 02:12 PM

Hey thanks very much guys, that helps me a lot, one more question tho, how do you "lock off" exposure on a camcorder?

You may wish to refer to Sony's user manual for your camcorder for info on how to use its features.
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Aerial Filmworks

Rig Wheels Passport

Gamma Ray Digital Inc

Broadcast Solutions Inc

Ritter Battery

Technodolly

FJS International, LLC

Wooden Camera

CineTape

CineLab

Metropolis Post

Visual Products

Glidecam

Abel Cine

Tai Audio

Willys Widgets