Is -6dB gain actually 0dB gain, in disguise? at DVinfo.net

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Sony HVR-Z7 / HVR-S270
Handheld and shoulder mount versions of this Sony 3-CMOS HDV camcorder.


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Old July 22nd, 2008, 09:18 AM   #1
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Is -6dB gain actually 0dB gain, in disguise?

Setting the Z7 to -6dB just produces a cleaner, less noisy image, over 0db. Have sony just sneeked in 6dB calling it 0dB on the Z7, to improve the low light performance?

-6db HDV Progressive (not 25pscan) produces really quite good image :)
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Old July 22nd, 2008, 09:57 AM   #2
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0db simply means "default". Every other setting is just relative to the default.
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Old July 22nd, 2008, 04:53 PM   #3
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It's a sneaky way to appear to have improved low light performance at 0db. Poor, cynical behaviour by Sony. I find the noise at 0db unacceptably high and shoot at -6db whenever possible.
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Old July 22nd, 2008, 08:50 PM   #4
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It's a sneaky way to appear to have improved low light performance at 0db. Poor, cynical behaviour by Sony. I find the noise at 0db unacceptably high and shoot at -6db whenever possible.
Hi Mike - so you reckon, lock the gain at -6db, lock shutter speed at 50 (or 60) then adjust the iris manually to get correct exposure?
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Old July 23rd, 2008, 03:50 AM   #5
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yeah could set all gain settings to -6dB, also use zebras to get a, say, 75% reading for faces
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Old July 23rd, 2008, 04:33 AM   #6
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I set gain settings to -6, 0 & 6, which I feel equates to 0, 6, & 12 as I understand it. Don't get me wrong - the image is great at -6db - I just feel it's a really cheap trick that Sony have pulled here.
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Old July 23rd, 2008, 04:22 PM   #7
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I set gain settings to -6, 0 & 6, which I feel equates to 0, 6, & 12 as I understand it. Don't get me wrong - the image is great at -6db - I just feel it's a really cheap trick that Sony have pulled here.
Mike have you actually shot at -6 in low lighting? This issue has come up before and part of me did doubt it, but I have since had grain at 0 and +3 and 6, so I think there might be something to this. Just curious if you have seen the results of shooting at -6?

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Old July 24th, 2008, 05:04 PM   #8
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Hi Bruce - I'm not sure what you mean. I shoot a lot with available light and I'm shooting everything at -6db unless forced to increase the gain because there's not enough light. I won't go above +6db on the Z7 as personally find the image too noisy to be acceptable above this level. If there's enough light you should shoot at -6db as this will produce the cleanest image (if this is what you want). Sony simply labelled the lowest gain level -6db instead of 0db for marketing reasons.
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Old July 24th, 2008, 05:54 PM   #9
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Hi Bruce - I'm not sure what you mean. I shoot a lot with available light and I'm shooting everything at -6db unless forced to increase the gain because there's not enough light. I won't go above +6db on the Z7 as personally find the image too noisy to be acceptable above this level. If there's enough light you should shoot at -6db as this will produce the cleanest image (if this is what you want). Sony simply labelled the lowest gain level -6db instead of 0db for marketing reasons.
I'm not sure about that. Gain should be amplification to the signal. Zero should be no amplification and -6db should be trim. If it is Sony's marketing then they may be lying about the numbers.
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Old July 24th, 2008, 05:59 PM   #10
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Well -6dB is just a much cleaner image (less noise), compared to 0dB, so maybe they are lying...?
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Old July 24th, 2008, 06:15 PM   #11
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Well -6dB is just a much cleaner image (less noise), compared to 0dB, so maybe they are lying...?
Keen to test this - how do you measure "less noise" - what am I looking for in the image??
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Old July 25th, 2008, 02:09 AM   #12
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Keen to test this - how do you measure "less noise" - what am I looking for in the image??
Hi John,

Look for mosquito like speckles dancing around the image as you increase gain. At 9db or greater you can't miss them, especially in the shadow areas / underexposed areas of the image, and where there are large areas of uniform colour (blue is often a contender).

As you decrease gain (electronic amplification of the image to increase brightness), you will see the image become "cleaner". In most cases, it's desirable to shoot at -6db if at all possible, only applying gain as your environs necessitate (eg: in a dim room when your iris is already open and your shutter is as slow as you're prepared to go).

I haven't used a Z7 myself, but I'm renting one soon as I need a second camera for a shoot. I'm going to compare it to my XHA1, and if the difference is significant, look to transfer. Noise is a big deal for me - that is, achieving a clean image. It sounds like Sony is fudging things a bit here by calling 0db what should perhaps be +3db or even +6db, but maybe someone has a solid technical explanation for this.

I was a little puzzled with my XHA1 having a -3db setting after my previous cameras only went as low as 0.
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