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Canon XL and GL Series DV Camcorders
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Old August 11th, 2005, 07:03 PM   #1
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Coring, Noise Reduction, and Gain

I used the XL2 for the first time last weekend. It was a very low light shoot for a dramatic short, at night, mostly on residential streets, using street lights as our only light source. We also shot in a subway terminal and subway train. My settings were 24p advanced pulldown, 1/48 shutter speed, 16:9, and I had the 3x wide angle lens open to f/1.8 with a black pro mist 1/2 filter on it. Coring and sharpness were set to zero. I switched back and forth from 0 gain for the subway scenes to +12db gain for the outdoor scenes. Noise reduction was set to Medium and I shot everything in Manual mode.

Now that the shoot is over, I've been second guessing my decisions. I think that in order to make the shots match and have a consistent look throughout the film, I should have used the same gain settings throughout. What do you think of this?

If I could do it over again, I would leave the gain on +12db the whole time, keep noise reduction at Medium, and bump up the coring all the way to limit the noise.

Would bumping up the coring give me a cleaner look? and do you guys think the pro mist filter will also help with hiding excessive noise?

I haven't seen any of the footage yet but I'm worried that things will come out noisy and too soft.
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Old August 11th, 2005, 11:51 PM   #2
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Anybody?

I'll be viewing the raw footage this weekend. If anyone's interested I'll post the outcome.
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Old August 12th, 2005, 12:35 AM   #3
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I wouldnt worry about it being soft... coring is really for fine detail and turning it down can help with noise. You may also want to turn down the sharpness. The difference in gain shouldnt be a killer. Turning the blacks to press can help reduce noise in shadowy areas and turning down the master pedestal and setup level can help to, however, those will make the image darker.


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Old August 12th, 2005, 02:48 AM   #4
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I thought turning the coring up, not down, was supposed to reduce noise. Thanks for the advice. Overall I think it will look good. I'm just a little worried that shooting at +12db of gain will have a distracting effect, since the rest of the movie is clean.
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Old August 12th, 2005, 12:39 PM   #5
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LOL... sorry, I meant UP... to make the noise go DOWN...




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Old August 12th, 2005, 01:31 PM   #6
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Adding noise reduction is also supposed to help when shooting at higher gain settings in low light. But, the trade off is that you don't want a lot of motion in the frame or you'll get some ghosting effects.

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Old August 12th, 2005, 02:33 PM   #7
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Quote:
Originally Posted by Javier Urena

Would bumping up the coring give me a cleaner look? and do you guys think the pro mist filter will also help with hiding excessive noise?
I'd venture to guess that the majority of noise is generated well after the image has passed through this filter. So in my opinion, the pro mist probably won't have a positive or negative affect on noise.

I am curious how the 3x wide worked out for you. In a dark environment you are likely using a wide open iris which means a really shallow depth of field. I am wondering how you set critical focus....with a field monitor? Sometimes in dark shoots you think you are in focus in the EVF but you might be just a little off.

Let us know how it turns out!
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Old August 13th, 2005, 11:56 PM   #8
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Today we used a TV to watch the raw footage from a DV deck. There were a couple of shots that I'm proud of, but I'd say about 1/4 of the footage was too dark and is unusable. The strange thing is that all of these shots that are too dark now looked acceptable to me when looking through the viewfinder and/or the field monitor.

The Pro-mist filter gave a very subtle effect and I like it. The noise was not excessive at 12db with the noise reduction set to Medium. It looks like we'll be doing some reshoots to get the dark footage.

Do you guys think there is a way of salvaging the dark images during the editing process? Do editing programs have exposure tweaks?

My editor says that it is easier to fix an over-exposed image than it is to fix an under-exposed one. I know this is true with film, however, I've heard that in video this is not the case.
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Old August 14th, 2005, 12:03 AM   #9
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Quote:
Originally Posted by Marty Hudzik
I am curious how the 3x wide worked out for you. In a dark environment you are likely using a wide open iris which means a really shallow depth of field. I am wondering how you set critical focus....with a field monitor?
Marty,
I had it at the widest angle most of the time, so focussing was really easy. With wider angles, you have lots of depth of field even at larger apertures.

I didn't use a field monitor on the subway or on the streets. When necessary, I zoomed in tight and made sure the eyes were crisp, then I zoomed out again.
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Old August 15th, 2005, 08:28 AM   #10
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Quote:
Originally Posted by Javier Urena
Marty,
I had it at the widest angle most of the time, so focussing was really easy. With wider angles, you have lots of depth of field even at larger apertures.

I didn't use a field monitor on the subway or on the streets. When necessary, I zoomed in tight and made sure the eyes were crisp, then I zoomed out again.
Correct me if I am wrong about this. I only used the 3x for a weekend and had poor results so I sent it back. What I can't remember for sure is if it has a focus that is for infinity when you turn the ring as far as it will go. Does this make sense? let me explain.

On the 16x manual there is a hard stop on the focus ring that is essentially the infinity setting. When in doubt, I can pull the zoom full wide, and crank the focus all the way to infinity and I know that everything in the frame will be in sharp focus.

In contradiction to this is the auto lenses which don't have a hard stop. So when you turn it all the way to focus on inifinity, the focus travels past that point and can easily go into Macro Mode. I know technically this doesn't exist on the 20x lens but it is that point of focus where objects just a few inches in front of the lens are in sharp focus but background is not. On the 16x manual this is a seperate ring that you turn to focus in that area. If you don't engage the macro ring then you are certain that everything is in focus when wide. On the auto lenses this is not the case. The focus ring just transitions from the "normal" focusing range into the "macro" area without any notification. It is possible to think you are at the infinity point and actually be focused ever so slightly in the macro area and end up with an extremely soft focus on you subject who are further away than 1-2 feet.

This, for me, makes it so hard to tell when you are at infinite focus, especially on the small EVF of the XL2. With the manual 16x lens I can just "trust" the marking on the barrel and know that I am at the infinite setting. The only problem is that it is not wide enough.

So I ask this now after that extensive diatribe. Does the 3x behave like the 20x and 16x auto lenses? Can you turn the focus in the direction of infinity and actually go past it and have the focus be in the macro range and have the background be out of focus (bad thing)? Or is there a point where you have turned the servo so far and everything is in focus and I don't have to concern myself with worrying about focus being to close to the lens?? Am I making any sense at all?
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Old August 15th, 2005, 03:43 PM   #11
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The 3X acts the same as the other servo lenses. I have NEVER had any problems with any lens. I do sometimes use a wide adapter on my 16X manual though, gives a little different look than the 3X.




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Old August 15th, 2005, 03:58 PM   #12
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Quote:
Originally Posted by Ash Greyson
The 3X acts the same as the other servo lenses. I have NEVER had any problems with any lens. I do sometimes use a wide adapter on my 16X manual though, gives a little different look than the 3X.




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Ash,
So you feel you can just whip the focus all the way to the "wide end" and everything is always in focus? The lens doesn't go into that super up close "macro" focus if you go too far? I appreciate your response but it is vague. Are the issues I am describing not there for you or are you saying that you have learned to work around them?

Because even the DVX100 has an infinity button you can hit and know 100% that you are at that mark. With no barrel markings or on screen displays I find it hard to know exactly where the perfect focus is for the widest setting without going into the super close-up focus area. Again, on the manual lens I rely on the barrel markings and the hard stop. Especially for run and gun where I can't always setup shots or even predict where subjects will be.

I want to like the 3x but the servo behavior is driving me nuts! If I felt comfortable that I could consistently be at the widest setting and set the focus for infinity I"d be happy with it.
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Old August 16th, 2005, 10:13 PM   #13
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There is no infinity in servo world... you always have to adjust on the fly. I have learned to work around the auto lenses "faults" If you are in an environment that focus is tricky, try a B&W pre-set...



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Old August 18th, 2005, 11:54 AM   #14
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Quote:
Originally Posted by Javier Urena
My editor says that it is easier to fix an over-exposed image than it is to fix an under-exposed one. I know this is true with film, however, I've heard that in video this is not the case.
I'm not sure about that; I read an article once where a guy had a camera aimed at a chip chart and intentionally over/underexposed while noting the vectorscope (?).
I wish I had the article handy but what it boiled down to was that a degree of color information is irrecoverably lost when things are overexposed. If it's underexposed you can brighten it up in post, you will get some gain effect if you brighten too much but the color will still be there.
That's why if I get confused in the field I underexpose, in hopes of it brightening it up later.

(oops, I thought you meant video is better shot overexposed, my bad)

Last edited by Jeff Miller; August 18th, 2005 at 11:57 AM. Reason: wish I could delete this
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Old August 18th, 2005, 01:12 PM   #15
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[QUOTE=Javier Urena]Do you guys think there is a way of salvaging the dark images during the editing process? Do editing programs have exposure tweaks?[/QUOTE[

Javier, you can decrease the gamma to brighten dark images. You'd be surprised how much information is there. You can adjust it a little and get away with it. Too much and you will start to get nasty artifacts.

When decreasing gamma, you may want to also add a little contrast. You'll see the image will look a little washed out without it.

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