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


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Old December 22nd, 2003, 09:56 AM   #1
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Setup? What is actually hapenning?

Okay . . after a year playing with my XM2, I've at last come to "Setup", in the menu. When I use this inconjunction with Custom Preset I can, when I slelect CP, well, "lift" the light levels. What is actually hapenning that I can't get with exposure? Is the quality of the footage - this is my terminlology - made more grainy? Is there something digital going on? Well obviously. I will say that the actual image is quite a bit more brighter. I've also experimented with frame rates, and yes there is the "strobing" - as I'd guessed. But this Setup - wonderful as it is, what is actually happenning? Sorry if this is a dumb question, but I'd really like to know. My VidPro chum says it's the Sony version of increased Gain - is this so?

Regards,

Grazie
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Old December 22nd, 2003, 11:31 AM   #2
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North American analogue NTSC has what is called "setup". Setup raises the voltage level of black 7.5 IRE units above zero. This was introduced because early TV circuitry found it difficult to distinguish black from video control signals, or something like that.

Digital video, no matter where it is in the world, doesn't have setup - remember it's a purely analogue phenonema.

However, to try and integrate DV with old analogue environments, some cameras allow DV to be recorded with setup added, even though this means that the recorded DV video no longer meets the DV spec, and will not work correctly with other correctly recorded DV. It can be useful to have the setup added if you're taking the analogue s-video directly out of the camera and are working in a multi-camera environment back to a switcher, when you're using non-Digital cameras along with your DV.

Graeme
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Old December 22nd, 2003, 01:13 PM   #3
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So . . . why does it brighten the picture? Why does the Manual say to use this if the picture I'm attempting to record is too dark? As I say, it's as if I've openned up the iris further than it will go.

I experimented with this as a result of an old thread thread here that suggested that in "low-light" to increase "Setup" to achieve better capture.

I thought I was getting what you were saying until you said,"Digital video, no matter where it is in the world, doesn't have setup - remember it's a purely analogue phenonema." But Setup is there. It is in the Menu of the XM2 . . arrrgghh . . . but then you explained this with your last para. So, is Setup=Gain of any description?

I'm still lost . . ..

Grazie
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Old December 22nd, 2003, 01:26 PM   #4
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Everything gets brighter because what was black at 0, is now at 7.5, and white remains at 100%, so everything in between gets a bit brighter.

I don't know exactly how it works on the Canon, but just raising the black level will make things brighter, but shouldn't really produce any different result to brightening the end result in your NLE - it's not gain, where all brightness values get multiplied - it's sort of an add and stretch, so that all values get 7.5 added to them, but then scaled back so that they don't go over 100%. I doubt you'd get any more detail with this method.

Setup is a nasty and complex issue, so I hope this helps.

Graeme
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Old December 22nd, 2003, 01:27 PM   #5
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Grazie, there were a lot of posts about this sometime ago, but unfortunately I can't remember where they are at the moment. I think, if you add setup you're changing what's recorded as black. Normally this is 0 on miniDV cameras, but it get's raised to some other value. This makes your blacks look greyish, but keeps it in line with the analogue stuff.

Look here

http://www.adamwilt.com/DV.html

and here

http://pro.jvc.com/prof/Attributes/i...&feature_id=19

The latter has a link on it pointing to a flash tutorial on what black setup is.


Good luck
Aaron
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Old December 22nd, 2003, 01:41 PM   #6
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Ah . . pennies dropping . . .

Graeme and Aaron thanks. NOW I truly understand. Graeme in my NLE - Vegas - there is a markedly greater brightneing, or should I call it a greying of Black, now that I've been educated to it - hah!

Aaron, yes, it was that thread I pulled out of my hardcopy file system that made me start experimenting with all this.

So, Guys 'n Gals, should I leave it alone? Are we also saying that when I should ever bring this out to VHS something "nasty" would happen? Or is it another way of achieving a bit more from low light? I guess you'll saying - "No don't do it!" The prime reason for filming ios to get the best WITH the best of ambient light. If THAT aint avvailable then use a 3, 10, 20 >> 30 watt on cammie light - yeah?

Thanks again Pals - Grazie
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Old December 22nd, 2003, 01:46 PM   #7
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If your DV deck doesn't output at 7.5 or remove the 7.5 when inputting analogue video, you can either use a filter to bring the levels in line in your NLE (not the best solution, but it works at a push) or use a proc amp on your border between the analogue and digital worlds. That's a great JVC video BTW - really enjoyed it!

Graeme
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Old December 22nd, 2003, 02:57 PM   #8
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First - I am not a setup expert ;) There, disclaimer done..

I'm not sure that the XM2 setup works like other pro camera setups as it adjusts the digital data stored on your tape and that's NOT what you want if you're wanting "real" setup. As Adam Wilt says - digital is digital. You want blacks at 16 (digital) and whites at (235) (Why those values are used I have no damned idea!)

Of course, if you don't want "real" setup and just want to see into the shadows some more it'll probably work.

I'm so glad I live in PAL land ;)


Aaron

Graeme - Yeah I stumbled across that when looking for a SVHS deck. It's a great tutorial.
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Old December 23rd, 2003, 10:09 AM   #9
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I am also very puzzled by this SETUP thing. I was very mistaken that it would give some gamma adjustment, or histogram thing when I read the online brochure. But it isn't; it simply gives you either overall brighter images or darker images to please personal perference.
To me, this feature is redundant unless someone tell me they find it useful in certain occasion.
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Old December 23rd, 2003, 10:14 AM   #10
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It's not to please personal preference, it to make sure video technically interfaces correctly with other video gear. Did you watch the JVC link below that explains it all? Also read about it at www.adamwilt.com

The only use that I can think of is when you're not recording to DV tape, but using the camera at a live event, tied by a cable to a switcher. In any other situation, like recordin to tape with the switch set to add setup will produce a non-standard DV signal with incompatible black levels.

Graeme
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Old December 23rd, 2003, 10:53 AM   #11
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Graeme, I am not sure if this SETUP preset on my XM2 does the job you described. If it is for blacklevel adjustment in matching any digital to analogue media conversion, it should not affect the those area reaching 100IRE or 235 RGB, should it? What happens on XM2 is when you pull the index to the right (plus side) on SETUP preset, you bring up more detail in the shadow, but more white area will be clipped. Is it the way it works? And why it gives you the options of 6 or 7 clicks before you reach the SETUP limit?
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Old December 23rd, 2003, 11:06 AM   #12
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That shure sounds like it just adding a number to any brightness. That's not setup, but a brightness control! If it were a setup control, white should be un-effected as you rightly point out.

Graeme
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Old December 24th, 2003, 12:26 AM   #13
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Okay, folks it appears we have come full circle. This is what I was asking at the head of this post.

"When I use this inconjunction with Custom Preset I can, when I select CP, well, "lift" the light levels. What is actually happening that I can't get with exposure?"

. . . and now with Graeme saying, "That shure sounds like it just adding a number to any brightness!" - I'm even more convinced this is what is happening. PLUS the Manual does say that if you are finding the thing you are capturing is too dark, knock up the Setup . . .So Friends, what is actually happening . .hmmm...

Thanks for all your technical information, Graeme, but now I really need to know what on Earth is happening when I use Setup. The manual aint that . . transparent!?!

Colin thanks you for reiterating what I've been stumbling around . . much appreciated . . .

Happy hols

Grazie
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Old December 24th, 2003, 12:47 AM   #14
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Grazie, what NLE do you use? Capture some footage with controlled light that won't vary and as you're capturing, change the setup. Then load into an NLE and view the waveform. If, as you view the footage changing setup the highs and lows move, then you've just got a luma control and not a real setup If only the black levels change, you have setup.

Aaron

Edit: Ok, just tried it myself, and yes it's a simple luminance adjust. The whole waveform moved up as I increased setup.

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Old December 24th, 2003, 12:55 AM   #15
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Ah! - Thanks Aaron . . .

Neat Aaron! - I use Sony-Vegas 4.0d. It's got waveforms and all that stuff for viewing - yeah?

I have noticed that the capture into S-V I can see a markedly lighter look to the footage. But yes, I'll try your suggestion.

Perhaps others would like to have a go . ..

Grazie
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