Is the TV =Time Value no more than GAIN? at DVinfo.net

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Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


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Old November 26th, 2005, 03:48 AM   #1
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Is the TV =Time Value no more than GAIN?

In my search to squeeze out more from my XM2s, I did a low light test - this was inspired by Dale Guthormsen "The simplest way to deal with low light on the gl2 is to set it to TV mode."

here: http://www.dvinfo.net/conf/showthread.php?t=54388

Now, as we all know, by switching into Manual Mode we can "interrogate" the settings that the XM2 is then being subject to. Well, here's the thing: Having set TV mode and getting a "brighter" image, I thought I would then see what was being registered within Manual Mode. It says there 18Db. Does this "mean" that TV is in fact NOT adjusting the TV value but only upper the GAIN?

This is very odd indeed.

Please confirm or deny - thanks,

Grazie
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Old November 26th, 2005, 06:53 AM   #2
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TV mode is shutter priority exposure mode. You select the shutter speed that you want. The camcorder is still is doing auto exposure, but it holds the shutter speed fixed at your setting, and the aperture and gain are automatically adjusted to provide the hopefully proper exposure. In very poor light the aperture will open to maximum and gain will go to 18 dB.
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Old November 27th, 2005, 12:58 AM   #3
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Don thanks.

So, as I suspected, the "command" to increase GAIN becomes part of the TV mode when, as you say, light levels are low. But, more to the point, TV works in conjunction with AUTO, as part of its mode. Where does it say THIS in the manual? I would have thought that adjusting TV would ONLY have been that? I must be misunderstanding a basic premise somewhere?

Grazie
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Old November 27th, 2005, 06:23 AM   #4
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In the NTSC GL2 manual it is on page 52, in the section titled "Using the Various Recording Programs." There is a table of recording progams and available functions. With the GL2 manual gain adjustment is available only in manual mode. I expect that the XM2 is the same.
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Old November 27th, 2005, 06:33 AM   #5
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On the PAL it is on p50 of the Manual. It says that GAIN is not adjustable in this mode. It doesn't say that GAIN will automatically be adjusted for me? And having interrogated my Manual Mode and seeing 18Db - it MUST have come from somewhere. That is my point.

Well, Don, you have certainly cleared up a few points for me.

Grazie
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Old November 27th, 2005, 07:06 AM   #6
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On page 54 of the NTSC manual (might be on 52 in the pal manual if logic holds) under the "Giving Prioirty to Shutter Speed (Shuter-Priority: Tv)" heading it reads "Use this progam to select the shutter speed: Aperture and gain are adjusted automatically" Again, I can't speak to your manual.
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Old November 27th, 2005, 08:23 AM   #7
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Yup, there it is p52 - "Aperture and gain are adjusted automatically" - why? Why would I want to adjust Tv and have the GAIN and Aperture automatically adjusted too?Having "seen" GAIN pushed up - by seeing it within Manual Mode - why would I want GAIN/Aperture to be adjusted?

Anybody know why?

Grazie
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Old November 27th, 2005, 08:52 AM   #8
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Quote:
Originally Posted by Graham Bernard
Why would I want to adjust Tv and have the GAIN and Aperture automatically adjusted too?Having "seen" GAIN pushed up - by seeing it within Manual Mode - why would I want GAIN/Aperture to be adjusted?
Makes sense to me: TV mode merely implies that you want to control the shutter speed, and let the camera do whatever else it can do to get an accurate exposure. If you don't want the gain and aperture adjusted automatically, then you need to switch to full manual mode.
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Old November 27th, 2005, 11:34 AM   #9
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Kevin, can you give me an example where I could benefit from this? Having the XM2 adjust automatically?

TIA,

Grazie
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Old November 27th, 2005, 02:20 PM   #10
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Quote:
Originally Posted by Graham Bernard
can you give me an example where I could benefit from this? Having the XM2 adjust automatically?
In the case of Tv mode, the point would be to control the effect of shutter speed on your image while allowing the camera to continue to adjust automatically for changing lighting conditions. Examples of when you might want to do this would be for videotaping a TV screen (to reduce flicker), controlling motion blur for sports or other fast-action subjects, making moving water looked blurred using a slow shutter speed, etc. In other words, if you know you want a particular shutter speed but don't care about the effect of other settings, let the camera figure the correct exposure.
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Old November 27th, 2005, 05:03 PM   #11
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Kevin! Thank you .. I can NOW see where I might want to experiment with this.

Grazie
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