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Sony XDCAM EX Pro Handhelds
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Old May 12th, 2008, 08:27 PM   #1
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-3db

What's the deal with that setting? Why isn't -3db=0db and 18db=21db? Lower latitude? Worse highlight-handling?
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Old May 12th, 2008, 08:53 PM   #2
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gain settings are really arbitrairy but the MINUS (-) settings are generally used in outdoor work OR EXTREMELY bright indoors (never seen one like that EVER but I suppose it could be)

Like I said though, gain seetings are different for every manufacturer, Sony, Canon, JVC-there is no way that a JVC at 0 will be exactly the same as Sony at 0. When I had my JVC5000 and used it with a Sony PD150 one would think the 1/2 chip would be all over the 1/3 chip. Nope! In unscientific test, I used the 2 cameras in the same conditions right next to each other. The 150 had it all over the JVC. Now part of that was the Canon 16X lens (the 19X was a killer compared to the 16 but) IIRC the Sony was at 1/60th at f/2 and 0 gain-the jvc was at 1/60th,f/2 but I had to go to +6db of gain to get a quality image. BTW this was done with 2 properly calibrated production monitors not LCDs. When I dropped the footage into my NLE you didn't have to be a genius to see the difference.
So long story short, -3 can be a very helpful setting in a very very bright and contrasty outdoor setting.
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Old May 12th, 2008, 09:18 PM   #3
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gain settings are really arbitrairy but the MINUS (-) settings are generally used in outdoor work OR EXTREMELY bright indoors (never seen one like that EVER but I suppose it could be)
1/sqrt(2) isn't much help compared to a 1/8-ND. It's more like a water drop on a burning rock.
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there is no way that a JVC at 0 will be exactly the same as Sony at 0.
Of course, because they can have different iso-ratings. But that wasn't my assumption/question.
Again:
Why do they call it -3db instead of 0db (and hence 18db instead of 21db)? Just for fun? No drawbacks?
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Old May 12th, 2008, 09:34 PM   #4
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Who knows? I would guess that it's simply that the first set (Z1U) HDV cameras didn't even have a decent ISO 100 or ISO 200. I'd like to see an ISO setting as well as 1/3 stop shutter speed settings.

I'd also like some more metering functions such as lost highlights and lost shadows, but DSLRs don't even have them. The live histogram is great, but there are so many useful metering tools that could be added.
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Old May 12th, 2008, 09:47 PM   #5
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I would guess that it's simply that the first set (Z1U) HDV cameras didn't even have a decent ISO 100 or ISO 200.
I don't understand. Do you mean a "EX1-0db-noise = Z1-0db-noise"-idea?
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DSLRs
Apropos DSLRs: I know the Canon 5D which has a "L"-iso-setting which is a iso-50-setting with lower latitude than the other iso-settings. That's the source of one of my guesses.
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Old May 12th, 2008, 10:05 PM   #6
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The gain function increase (or decreases) sensitivity. 0dB gain means you are seeing what the image sensors are putting out, with all the other processing being done. +3dB means they have electronically increased the output with an amplifier. -3dB means they have electronically decreased the output.

Different manufacturers have different relative gain structures because of the different design of the cameras--you can't even compare cameras of the same manufacturer unless they use the exact same imaging device.

It is exactly like audio gain. Add it when you need more or subtract it when you need less. That includes the same penalty of gain--increased noise. However, audio negative gain usually doesn't decrease the noise the way video negative gain does.
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Old May 12th, 2008, 10:12 PM   #7
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The gain function increase (or decreases) sensitivity. 0dB gain means you are seeing what the image sensors are putting out, with all the other processing being done. +3dB means they have electronically increased the output with an amplifier. -3dB means they have electronically decreased the output.
The odd thing about the -3 dB setting is that it is apparently the optimal setting for low noise. A lot of DSLRs have a Base ISO (usually 100 or 200), but offer some settings below that that are digitally attenuted. We'll need a real answer from Sony for that. A -3dB digital attenuation may reduce the noise, but it would also reduce the headroom.
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Old May 12th, 2008, 10:17 PM   #8
 
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Looking at the SAW and WFM while switching from 0dB to -3dB will reveal that the latitude is slightly reduced at -3dB. Clipping happens around 93%, ILO 100%. You gain with a lower noise floor, however.
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Old May 13th, 2008, 01:31 AM   #9
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Bill,

Two acronyms I can't decypher in your post: SAW and ILO. Can you (or anyone else) shed some light on these?

George/
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Old May 13th, 2008, 07:32 AM   #10
 
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ILO...in liew of

SAW....I don't know what this stands for, however, it is a kind of standardized test image for displaying the gamma curve for a camera. In the EX1, the SAW curve is built into the "maintenance" menu. It consists of a luma only image gradient, extending from 0 to 100% IRE. Displaying this image, while looking at a WFM will give you the gamma curve used by the video camera. In the case of the EX1, at -3dB gain, the gamma curve abruptly clips around 90%.
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Old May 13th, 2008, 07:34 AM   #11
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I guess SAW is not an acronim, but it means what it means -- after the shape of the oscillo pattern.
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Old May 13th, 2008, 09:24 AM   #12
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ILO...in liew of

SAW....I don't know what this stands for, however, it is a kind of standardized test image for displaying the gamma curve for a camera. In the EX1, the SAW curve is built into the "maintenance" menu.
Hi Bill,

Thanks for pointing me to where to find the saw curve/gradient in the EX.

I think it was a case of early-morning acronym overload ;-)

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Old May 13th, 2008, 12:21 PM   #13
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Well, as long as everybody is taking their shots at this, it's "lieu" and I think SAW is an abbreviated form of "sawtooth pattern" from o'scope usage.
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Old May 13th, 2008, 12:58 PM   #14
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Looking at the SAW and WFM while switching from 0dB to -3dB will reveal that the latitude is slightly reduced at -3dB. Clipping happens around 93%, ILO 100%. You gain with a lower noise floor, however.
Thank you for the measurements. So, 0dB is the native dynamic range. Big question answered.
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Old May 13th, 2008, 09:29 PM   #15
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I shoot everything that I can at -3db. A lot of the bigger broadcast cameras had a -3 db setting.

It's like shooting with a low ISO film (back when we used to shoot film).

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