Has anybody noticed the EX1 produces much cleaner images under blue light? - Page 2 at DVinfo.net

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Old July 22nd, 2009, 02:12 PM   #16
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Originally Posted by Nick Wilson View Post
What is important is that the sensor gets sufficient blue (and green and red, for that matter) and that the amounts are in balance so it doesn't have to compensate by increasing the blue channel gain (and noise).



The answer is to give the camera more blue relative to red and green. HMI is close to daylight in colour temperature (ie, mix of the primaries) but the intensity is usually far lower. CTB adds nothing; it just reduces red and green.

N
Lets see if I can state this another way.

Let's assume that I want to record with my EX1. And for the settings I have in the camera, I need 100 lumens of light. If I provide 100 lumens with nothing but Tungsten, the blue channel is going to be starved, and the video will be more noisy than ideal because of the gain applied to blue IF I white balance and add the gain to blue.

If I could reduce amount of red and green light, and boost the blue so that the light going to the sensors was more proportional (like using HMI) then I would still have the 100 lumens I wanted, and I would have to add less gain to the blue channel.

If I had tungsten lights that could give me 200 lumens, and I used CTB on them and reduced their output to 100 lumens with a strong blue component, I have the light level I want, and the light color I want. But I have to use more powerful fixtures to get there because I am knocking down so much red and green.

There are a number of ways to skin this cat. But they all come down to the same thing. Reducing the gain that needs to be added to the blue channel, whether that be in post or in the camera.
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Old July 22nd, 2009, 02:59 PM   #17
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I use Gyoury 56K florescent lights almost exclusively these days except when I need hard light then I use HMI's.

I find that the EX3 has a really good responce to the Gyoury's.

Lighting for film, video, photography by Gyoury Evolved

I have also noticed that it really helps on the IR problem people are talking about with the EX cams.

I still have a bunch of tungsten's but they stay in the cases most of the time. I do use a couple Arri 650 fresnels at times with dichroic filters and I carry blue bulbs for light fixtures on location, when I include table lamps or whatever in the shot.

It is just so much easier to have everything be daylight, no blue spill from windows.

The only exception is sunset shots with fill light, then I use my Arri 650's bare bulb or even with slight orange gels.

So my answer is yes the EX's and most other cams love lots of blue.
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Old July 22nd, 2009, 03:03 PM   #18
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Can you explain how shooting tungstun at -3DB also solves this problem. Is that because the increased amount of light neccessary for -3DB insures an adequate level of blue light without needing to increase gain on the blue channel? If so that would imply that the -3DB may only actually be applied to the red and green channels. That's an interesting idea if I understood you correctly.

I wonder how this differs from the Red where its recommended to shoot with a blue filter in order to drop the red and green channels. In the Red of course you don't really white balance so the issue of overexposing red channels is critical when shooting under tungstun.

In the EX or any other "normal camera" when white balancing (esp under -3DB) might you really be reducing the amount of exposure on the Red and Green channels before it gets to later processing?
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Old July 22nd, 2009, 03:10 PM   #19
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Can you explain how shooting tungstun at -3DB also solves this problem. Is that because the increased amount of light neccessary for -3DB insures an adequate level of blue light without needing to increase gain on the blue channel? If so that would imply that the -3DB may only actually be applied to the red and green channels. That's an interesting idea if I understood you correctly.
No, that's not where I was going.

My point was that -3db reduces the noise so much in ALL channels, that it is just less of a problem to deal with. The proportions of light off the sensor are still the same. Or at least I believe them to be.
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Old July 22nd, 2009, 03:12 PM   #20
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I wonder how this differs from the Red where its recommended to shoot with a blue filter in order to drop the red and green channels. In the Red of course you don't really white balance so the issue of overexposing red channels is critical when shooting under tungstun.
Remember that the RED only has one sensor. It is not prism split like in most video cameras. Different rules, and the Panavision video speaks to that.
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Old July 22nd, 2009, 05:45 PM   #21
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Well doesn't it stand to reason that if under tungstun, at 0DB it needs to add gain to the blue channel, then at -3DB it is probably still pushing the blue channel perhaps up to 0DB while pulling back only on the green and red channels?
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Old July 22nd, 2009, 08:26 PM   #22
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Originally Posted by Perrone Ford View Post
You're theory isn't necessarily wrong, but you are going to have to add that gain SOMEWHERE if you are going to get a usable picture. Whether it happens in the camera, or in post, you're going to have to boost the blues or the reds. And when you do that, you are GOING to get noise.
Yeah, you're right. I'm glad the shot I mentioned in my original post was to be kept blue.

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Originally Posted by Perrone Ford View Post
The only way around the problem is to ensure that the camera is getting enough light in each channel. Hence white balance to tungsten if you are using tungsten, and then if you are willing to live with recording a "blue" image, gel the lights. I generally don't bother with this.
If you don't bother with this, then how do you do? Sorry, you lost me there in the end.
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Old July 22nd, 2009, 09:39 PM   #23
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If you don't bother with this, then how do you do? Sorry, you lost me there in the end.
I generally don't bother because I am normally shooting in an environment where the blue channel is "clean enough" for me at -3db. When I do my color corrections in post, it's just a minor correction here or there, and then I am delivering web based video, or DVDs. I simply don't NEED the extra clean video the additional blue would give me.

Now, I did a shoot a couple weeks ago. Outdoors, existing light. I shot that very much like I'd shoot a movie. Light meter on the talent, working out the blocking, etc. And even with a 5600K pre-set, the image was VERY blue/cyan. I let it go because I knew it would help me later. The people with me were VERY worried about the colors, but I assured them everything would be just fine. :)

Very clean images. I've attached one for you to look at.
Attached Thumbnails
Has anybody noticed the EX1 produces much cleaner images under blue light?-as_shot.png   Has anybody noticed the EX1 produces much cleaner images under blue light?-with_correction.png  

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Old July 22nd, 2009, 10:00 PM   #24
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Thanks. Nice images.

But it's indoors that things get ugly. :)

What I didn't understand was this:
Quote:
Originally Posted by Perrone Ford View Post
The only way around the problem is to ensure that the camera is getting enough light in each channel. Hence white balance to tungsten if you are using tungsten, and then if you are willing to live with recording a "blue" image, gel the lights.
You white balance to tungsten and the put the CTB on? Shouldn't you be doing the WB after you put the CTB to avoid the noise?
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Old July 22nd, 2009, 10:12 PM   #25
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You white balance to tungsten and the put the CTB on? Shouldn't you be doing the WB after you put the CTB to avoid the noise?
This is why I need to stop thinking about RAW. Yes, you're right. In a RAW workflow, my comments are right. but in the EX1, it would raise the gain (and noise) even though we are adding more blue light.

I have a corporate shoot tomorrow, and we did a walk-through today. Mostly a podium delivery, live audience. I tested tungsten pre-set, with mostly 4500k fluo top-light and I added a Lowel DP light with diffusion. Didn't bother with CTB. I'll post an uncorrected still tomorrow night.
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Old July 22nd, 2009, 11:44 PM   #26
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Perrone,

Was the corrected shot the final version you were going for? I still see a lot of blue. My concern is when allowing that much blue during the shoot whether you can correct to a balance that would be the same as if WB in camera.

Quote:
Originally Posted by Nick Wilson View Post

Quote:
Originally Posted by Perrone Ford
The filters merely reduce the amount of red and green reaching the sensors. They do nothing to help increase the blue. This is akin to asserting that if you get a flat tire on the road, you should flatten the other three so the car will ride level.

What is important is that the sensor gets sufficient blue (and green and red, for that matter) and that the amounts are in balance so it doesn't have to compensate by increasing the blue channel gain (and noise).


Quote:
Originally Posted by Perrone Ford View Post
The answer is to give the camera what it wants, which is MORE blue light. And no filter is going to do that. Going to HMI lighting will do that. Adding CTB to existing lights will do that.
The answer is to give the camera more blue relative to red and green. HMI is close to daylight in colour temperature (ie, mix of the primaries) but the intensity is usually far lower. CTB adds nothing; it just reduces red and green.

N
So do you agree with Nick's last post on filter use?

I'm adding this to a list of tests to perform when I have some time.
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Old July 23rd, 2009, 06:36 AM   #27
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Perrone,

Was the corrected shot the final version you were going for? I still see a lot of blue. My concern is when allowing that much blue during the shoot whether you can correct to a balance that would be the same as if WB in camera.



So do you agree with Nick's last post on filter use?

I'm adding this to a list of tests to perform when I have some time.
The corrected shot was "corrected", not color graded. It is an accurate depiction of the scene as seen with our eyes. I typically work that way. I will do a color correction if necessary, and then let the director make choices on how to grade the material for effect.

As for Nick's post, technically, he is correct. No filter can ADD anything. And that is not their job. Their job is to remove things. And CTB's job is primarily to remove red light. That said, increasing overall light, while shifting color temps using filters is helpful.

But to be sure, when the scene is examined with the naked eye, it is going to look VERY blue. Hence tho pictures I posted. One that shows accurately how blue the scene was, and one that shows how much blue I let the camera record. They are not the same.
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Old July 25th, 2009, 09:12 PM   #28
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Now, I did a shoot a couple weeks ago. Outdoors, existing light. I shot that very much like I'd shoot a movie. Light meter on the talent, working out the blocking, etc. And even with a 5600K pre-set, the image was VERY blue/cyan. I let it go because I knew it would help me later.
Your images look very clean and reflect the care you put into your work. What you're describing is Uniform White Balance in which all three components are equal, although the 5600K preset is probably very close. While this helps with metering, I don't see how this helps as much with noise in correct exposures. It can help with clipping since that information can be warped down before clipping, but the cost of protecting the highlights is loss of protection of the shadows.

An inaccurate white balance means that needed information is attenuated during video recording and amplified during color balancing in post processing. Such an exposure method makes more sense with equipment that records lossless information with more bits than the final output, such as Nikon D3/D700 DSLR's with their RAW format and nearly 12 bits/color channel of information that is usually distributed in a JPG file with 8 bits/color channel.
Does this method really work for you, or is it slightly better in situations because you typically color balance anyway?

Last edited by Gints Klimanis; July 26th, 2009 at 07:18 PM.
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Old July 26th, 2009, 01:41 PM   #29
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Perrone,

I get what you are saying about putting the blue filters on the lights, but how are you handling things like stage lighting where you have no control over what they dish out?

How are you compensating for it? The EX1 seems much worse at handling that type of lighting than my Sony VX2000. Or don't you typically shoot stage work?

John
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Old July 26th, 2009, 02:58 PM   #30
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Perrone,

I get what you are saying about putting the blue filters on the lights, but how are you handling things like stage lighting where you have no control over what they dish out?

How are you compensating for it? The EX1 seems much worse at handling that type of lighting than my Sony VX2000. Or don't you typically shoot stage work?

John
I don't often shoot "stage" work, but I do shoot conferences and other things where I hae little to no control over light color.

In my shoot last week, I had mostly fluo toplight which was at 4500k approximately. I added some tungsten with full CTB to try to get more blue light on the subject. I would have put a LOT more blue light on the subject because the shot needed it, but he was uncomfortable with the lighting. Consequently, the footage is very noisy. Probably as noisy as anything I've shot recently. I was on the -3db preset and I was at F4 - F3.4 so I wasn't starving the camera for light overall.

Sometimes there's just not a lot you can do.
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