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gain or pushing in post.


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#1 ben jones

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Posted 29 March 2006 - 07:52 AM

hey all,

just a quick thought - which method produces more video noise.

1 - using the gain on camera
2 - pushing the image to the equivilant gain value in post using a program such as FCP.

Can anyone recomend which of the more accesable programs are better at dealing with this?

thanks Benjamin.
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#2 Laurent Andrieux

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Posted 29 March 2006 - 11:25 AM

Do you mean you want noise or are you trying to see what causes the less noise ?
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#3 Brian Drysdale

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Posted 29 March 2006 - 12:00 PM

I suppose it depends if you're applying gain to improve the sensitivity of the camera or applying gain to apply noise.

Applying gain in post won't get the image details that you didn't capture in the first place, it'll just lift the levels of you've managed to capture on tape plus the noise in the chain.
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#4 Laurent Andrieux

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Posted 29 March 2006 - 12:48 PM

And it will light your image. If you add gain et the shooting, you can close the iris so that your image is not overexposed
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#5 ben jones

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Posted 30 March 2006 - 04:09 AM

Hi guys thanks for the replies.

my aim is to obtain the least amout of gain. Im shooting a short this weekend, and the director wants to use only candle light in one area of the room (this is to be the only source within the room) The charactor will be moving all around the room, so im not entirely sure if 5 normal 6 inch candles will be sufficient. I just want to be prepared for certain comments like "why cant I see anything" etc.

I'll be using an XL1 for the shoot, but ive been doing tests with an XM2 and monitoring the image using a standard television. It is suprising to see how much more information is presented on the t.v compared with the on board TFT. I shot with 0db gain, wide open (f1.6 at the lenses widest) and 1/50th shutter. the results were ok near the candles - up to about 3 feet away) then things start to look grim.

some advise would be most appreciated!

regards, Benjamin.
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#6 Jay Gladwell

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Posted 30 March 2006 - 06:52 AM

Ben, it all depends on what "look" is wanted.

Do you want the area 3-feet away from the candles to be black? If not, you have to light your set for the look you want to see. Remember, what your eyes see and what the camera's chips see are two entirely different things.

If you want some detail in the "dark" areas, you'll have to add some light (at the same color temperature as the candles) to bring up the detail in these "unlit" areas. Use a monitor (or television) so you can see what you're actually getting.

Using the gain WILL add noise. Too, it's easier to salvage some detail from dark areas (if there's any there at all, i.e., it's not totally black) than it is to salvage detail from over exposed areas, 'cause there simply isn't any detail there to recover!

Edited by Jay Gladwell, 30 March 2006 - 06:53 AM.

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#7 ben jones

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Posted 30 March 2006 - 08:42 AM

Thanks Jay.

I will just have to persuade my director that using additional light is neccessary. As I said, the character is moving around the whole space and to tell this story, we will need to see what is actually going on.

Ben.
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#8 Michael Nash

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Posted 31 March 2006 - 02:20 AM

Can you do a test? That will tell you which method looks the least objectionable.

The amount of noise differs from camera to camera. I can't speak for the XL2. And noise created in post depends on the noise present in the signal, and the method used to boost the image (you can futz with things endlessly in post if you really want to).

But I think you're on the right track by wanting to supplement the candle light. Even if you want it to realistically appear as though the candle is the only light source in the room, it's not exactly unheard of to add light to a candle-lit scene!
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#9 ben jones

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Posted 31 March 2006 - 03:34 AM

Hi michael.

Yeh ive done tests in camera, but as yet I haven't been able to play around in post. I guess like most things its a case of trial and error. I have an interesting army of small practicals that should bring the candle light to other areas of the room including an ostrich egg with small stars drilled all over.

there has been no budget for any professional lamps so it should be a healthy challenge. In fact I cant wait!

thanks for the posts everyone.

regards, Ben.
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#10 Brian Drysdale

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Posted 31 March 2006 - 08:16 AM

You could try using Chinese lanterns with the bulb on a dimmer (to reduce the colour temperature and you can also give a slight flicker effect with the dimmer) or put CTO onto the lantern to give a soft fill. You can hang them over the set, or put one on a boom pole so that it moves around with the character. These work extremely well and have been used for lifting candle light scenes on a number of feature films.

Another method is to rig a small light inside the candle powered by a battery that the actor carries around..

For a drama you don't want to be putting large amounts of gain. Avoid over exposing the highlights, you'll never get those back in post.
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