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

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Old July 21st, 2009, 08:46 PM   #1
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Has anybody noticed the EX1 produces much cleaner images under blue light?

It seems the camera produces much cleaner images under blue light. I have been shooting with the EX1 almost exclusively under tungsten light. But I had to gel all my tungsten light with CTB for a shot recently and I was like, whoa!... when I looked at the monitor. It looked very clean, way cleaner than it has ever looked. Has anybody noticed that?
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Old July 22nd, 2009, 06:45 AM   #2
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This is a very well known fact for nearly all video cameras. Panavision did a nice education series some time ago, maybe a year or more, on why this happens and I posted it here. Others have posted it at other forums. If you're interested in digging into the why, I'll post the link to the videos here so you can see them.
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Old July 22nd, 2009, 07:20 AM   #3
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Hi Perrone. It would be certainly interesting to see the videos. I don't think I have seen them yet.
I was aware about the blue channel problem in a similar way that the RED ONE has a problem. But I was under the impression it worked differently. In the shot I mentioned the light was blue. We had tungsten with full CTB, but the intention was not to match daylight. So we didn't have the white balance set to daylight. We kept the white balance set for tungsten (3200K for the shot) so the lights came off really blue. But it looked the cleanest I ever seen from the EX1. I was under the impression that the advice was to shoot with HMIs or use full CTB for tungsten but the WB should also be daylight.
Unless the equation goes like this:

*Tungsten+CTO at 5600k = The worst ( I have used this for an extreme Mars red effect)
*Tungsten+CTO at 3200K= still noisy but better than the above.( I have used this for sunset effects)
*Tungsten at 3200k= acceptable (many people will say it looks as good as any other)
*Tungsten +CTB or HMI lights at 5600k = Clean
*Tungsten + CTB or HMI lights at 3200k= The cleanest.

I guess I just misunderstood how it works. I thought when using daylight sources you should white balance for day light if you want the cleanest image.
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Old July 22nd, 2009, 09:04 AM   #4
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Hmmmm...this is VERY interesting. I've been wanting to ditch our tungsten hot lights for a while now for some Kino's. Do Kino's qualify as "blue lights"? I assume any daylight balanced light source would qualify.
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Old July 22nd, 2009, 09:12 AM   #5
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Blue, in our visible light, is poorly represented. Our cameras are STARVED for blue. The more blue light you can feed the cameras, regardless of white balance, the cleaner they will be. The white balance merely increases gain in the blue circuit (hence the noise) so that it roughly equals out to the red and green channels.

You can see this effect easily if you have a program that can show you each of the RGB channels as grayscales. You'll note that green is lovely, red is decent, and blue is awful. Especially under tungsten lighting.

I'd shoot with 6500k lights if I could get them.
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Old July 22nd, 2009, 09:24 AM   #6
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Have a gander at this...

Demystifying Digital Camera Specifications Part 7: Single Sensor Cameras Continued
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Old July 22nd, 2009, 09:26 AM   #7
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Regardless of white balance? How can that be?
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Old July 22nd, 2009, 09:29 AM   #8
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Quote:
Originally Posted by Michael Maier View Post
Regardless of white balance?
The amount of blue light hitting the sensors does not change whatsoever with a white balance. That happens AFTER the sensors convert the light to digital data. Which is why on cameras like the RED and Viper, that give you the RAW data, you can change white balance and ISO after the fact.
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Old July 22nd, 2009, 09:31 AM   #9
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Yes, but if the white balance increases gain in the blue circuit to match the red and green channels, the white balance should make a difference. What am I missing?

Downloading the video now. Thanks!
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Old July 22nd, 2009, 10:39 AM   #10
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Originally Posted by Michael Maier View Post
Yes, but if the white balance increases gain in the blue circuit to match the red and green channels, the white balance should make a difference. What am I missing?

Downloading the video now. Thanks!
The white balance is trying to make up for the fact that there isn't enough blue light. So it's faking it. When there is ample, or nearly ample light, the white balance circuit adds FAR less gain, making the image appear cleaner. So yes, the white balance matters, but not nearly as much as actually having adequate blue light.
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Old July 22nd, 2009, 12:01 PM   #11
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This is why white balancing with filters is superior - the filters provide the sensor with an image which is colour balanced with the same gain on all three channels. The only time electronic white balance is better is if the light levels are so low that the gain has to be increased to compensate for the light lost in the filters.

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Old July 22nd, 2009, 12:08 PM   #12
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This is why white balancing with filters is superior - the filters provide the sensor with an image which is colour balanced with the same gain on all three channels. The only time electronic white balance is better is if the light levels are so low that the gain has to be increased to compensate for the light lost in the filters.

N
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.

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.
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Old July 22nd, 2009, 12:15 PM   #13
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Just finished the video. Very informative. It cracked me up when he said the JVC 4k camera prototype was a 12K camera using the "new math". What a dig at RED.
About the blue channel, it's a bit more clear now. But so if you have daylight, and you white balance for daylight or use a 5600k preset you add gain to the red channel, but it is a very little amount and way less than would be needed for the blue channel under tungsten. But if you have daylight and use a 3200k WB preset, wouldn't the WB be boosting the blue channel still? Wouldn't that still add noise? If not, because we would already have enough blue to begin with and the red channel is what need to be boosted but it won't be boosted, it means not extra red noise would be in the image. So although the image would look blue it would also technically have less noise than if you had white balanced to daylight and the red channel had to be boosted, even if just a little, causing noise in the red channel. If this is correct it could explain why I noticed the image was extra clean in my shot where I used blue light and a 3200k WB.
But starting from this same theory, if you use tungsten light but use a preset of 5600k, although your image will be orange, it should be cleaner than if you WB it to tungsten because at 5600k the WB won't be boosting the blue channel. So in both cases it would be interesting if shooting that way, with a blue or orange image and then correcting the color shift in post would be any better than white balancing on the set in order to avoid noise.
Also would mean that blue moon light scenes and sunset orange scenes would always look clean.
This would also show why one should NEVER use tungsten lights and white balance to them with the EX1.
Or my whole theory is wrong?
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Old July 22nd, 2009, 12:58 PM   #14
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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. 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.

When I shoot at -3db on the EX1, and ensure I have enough light to record at F4, the blue channel is clean enough for nearly any purpose I can imagine. Note that this is not unique to digital filmmaking. Celluloid based film has exactly the same issues because they have to deal with the same light spectrum. HID or other light with a strong blue component improves matters for them too.
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Old July 22nd, 2009, 01:25 PM   #15
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Quote:
Originally Posted by Perrone Ford View Post
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.

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