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


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Old September 5th, 2002, 01:52 PM   #1
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Gain settings and grain patterns

Hey all,
Have had my GL2 since yesterday so I have been busy testing it.
There is an annoying thing I have found. I saw it mentioned in one other post but not referenced again so I'd like to know if this is with everyone.
I was under the impression that if I just lower the gain to 0, then I would get NO grain. This isn't true. In fact it looks like I get a more annoying grain.
It doesn't become just a less overall pattern from the grain max'd at 18, but a MOVING set of patterns. Rows of "dots" quite noticeable, sweeping across the screen at a diaganol. Sometimes there are less rows, sometimes there are elongated dots, sometimes they move fast, slow, up down.
Do ya'll know what I am talking about??
And what is going on here??
Let me say I come from a film background and this is my first experience with video and I have an overly suspicious eye on picture quality and some may not see this unless pointed out...I don't know. This may be how video is?
In the VERY low light I was just expecting a black screen if I gave no gain and my aperture and shutterspeeds could not be opened or slowed enough.

Ok...any advice here?

Michael
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Old September 5th, 2002, 02:28 PM   #2
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Hello Michael,
Well for starters let's make sure that we're all on the same page.

First, are you sure that you are adjusting image gain versus COLOR GAIN? Image gain is reached only through MANUAL mode and will be displayed in Decibels (dB) in the viewfinder. Color gain is a slider under presets.

Second, are you sure you're shooting in MANUAL mode? When the camera is in one of the program modes (Tv, Av) it will automatically boost gain when it reaches the limits of that program.
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Old September 5th, 2002, 03:11 PM   #3
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Yes and yes.

The camera set up is very easy and not a problem for me to figure out.

Peterbutler described the same thing I am seeing(I think) in a recent post as:
"As for gain I noticed how it got grainy and have been experimenting with what Barry said in changing the sharpness in custom. This works although you do get a slight weird affect in the very slight grain remaining seems to move with the picture. It's hard to explain it's like having a pane of glass in front of the lens and on the glass a small grain material. So the fuzz isn't within in the scene more fixed on the lens, still it's not that noticable so I'm not complaining."

Only it moves independently of camera and image movement. Like video noise.

It is dark and rainy here today. If I plug my camera into the TV, or not mind you it records on the tape the same effect, and point it towards the dark areas of the room, set the gain to 0db, set the aperture(anything will do since it is already very low in here), set the shutter to whatever. I do not get a clean picture. There is movement in the image. Like the problem is with your TV only it is not. Like bad reception only at a minute scale. And if I pan the camera around past the various window light sources, I can make the movement of the noise change patterns to diaganol and such. At one point there were dots spaced about a half inch apart, in a grid, moving through the dark areas of the screen. Now these dots are grain sized so don't think there was a checkerboard on the screen. But they are also lighter in color so seen.

When you point your camera into a dark room and set your gain to 0db and record it, then watch it on your TV, and get close to the screen, that is when you see it. And then once you see it, you can't miss it. Sometimes the pattern is ridiculous as described above.

So do you get a perfectly black smooth screen?

Michael
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Old September 5th, 2002, 04:04 PM   #4
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Michael

I think I know what you are seeing...I've seen it in otherwise normal frames where a dark area seams to have more (chunkier) noise than the rest of the picture, it's almost as if the camera is applying gain just to the shadows even when you are on manual. My experience is that the gl2 doesn't necessarily produce more noise than other camera's, just that it sharpens it more.

Have you tried lowering the sharpness a bit...one or two notches (make sure you hit the custom preset button after you make the adjustment (cp will appear on display).

Actually here is the custom preset I use alot. I haven't noticed a problem since I started using it.

+2 color gain
-2 sharpness
+1 setup

Also viewing a television in a dark room can often reveal a lot of noise in sources (like broadcast) that isn't visible typically...perhaps this is part of the issue as well. (also, I don't know if there is any such thing as a smooth black in video, just the stuff you see, and the stuff you dont see)

Let us know if this works.

Barry
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Old September 5th, 2002, 04:48 PM   #5
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Hey,

Yes...I have read many of your posts Barry and gotten a lot of info on those presets. Thanks to you it was one of the first things I tried.
I suppose what I am looking at is just residue of the technology that makes for the electronic gain in the first place. What?
Well, if I am at 18db, and you really look at what's going on there, you see the whole screen looks like a bunch of ants moving around. Appears to be a criss cross of layers of data all intersecting and reevaluating.
When I drop down to 12db, it appears as though there is less grain by taking away some of these layers.
Down to 6db even less layers.
And down to 0db there are a few left over.

Now after reading what I just said, No I have not taken any hallucinogens
lately. Maybe it is because it is my first whole day with the camera and I am couped up inside with this rainy low light. I work at home.

As it is though, I am liking the image with 18db more and more. It is at least consistant throughout.

As for the broadcast in THIS particular occasion, when recorded onto DV and watched a couple times over, the same particularly annoying and unique patch of noise shows up at the same place on the tape. I think, therefore, this is how it was recorded onto the tape.
And speaking of tape, am I correct to assume that the quality of tapes among various brands should be consistant? I have only used this one Sony tape. Since it is recording just digital information, it is not likely to be a quality of tape issue eh?

In the meantime, looks like I need to read up on my video technology.

And Barry, when I download your GL2 sample footage, it starts off fine in the garden for like 4 secs then jumps ahead to quick stuttered glimpse of your model, then stutters to another quick glimpse, then ends.

Thanks for your responses,
Michael
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Old September 5th, 2002, 05:41 PM   #6
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Ok...It's over.

I found the problem...or lack of one.

It WAS the broadcast. It was my TV.

I can't quite understand HOW it was my TV but it was.
Hooked up to another TV and it looked beautiful. I mean it looked PERFECT.
The original TV looks great playing tapes and watching TV but for some reason when you run the DV through it looks imcompatible. Exactly what it was.

Maybe this post can serve as a try all avenues post.

Thanks for the help,
Michael
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Old September 5th, 2002, 11:33 PM   #7
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Barry's preset

<<<-- Originally posted by barrygoyette : Michael


Actually here is the custom preset I use alot. I haven't noticed a problem since I started using it.

+2 color gain
-2 sharpness
+1 setup

------

Barry do you use this preset with frame mode on or in normal? I shot a commercial with -2 sharpness in frame mode and found it a touch on the soft side.

Jim
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Old September 6th, 2002, 07:37 AM   #8
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There is noise and there is grain. The grain pattern tends to be fixed and is based on variations in individual pixels. Noise tends to be random. Higher gain settings tend to bring these out by raising the noise floor above the setup level of the TV, and by amplifying the individual variations. They can be most apparent in darker saturated color areas like reds and blues

Many consumer TV sets include internal signal processing to "improve the image" and these circuits may behave differently in different sets, especially among different makes and models.

Which make/model gave the good image and which gave the not so good image?
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Old September 6th, 2002, 08:28 AM   #9
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A common problem is watching the footage on home TV sets. The vast majority are not any where near being set up properly. One of the most common problems (and possibly Michael's problem) is the sets Sharpness Control. Most people see the control when they cruise through the on screen video menu and crank it all the way up. After all who wouldn't want a sharp image? Wrong. Turn it all the way down. Yes, down. This is a standard procedure in all manuals for adjusting TVs to produce optimum results. It may take a day or two for your eyes to adjust, but you'll be amazed at how much better your DV, DVD and broadcast TV will look. You may want to apply just a little sharpness to VHS tapes.

Jeff
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Old September 6th, 2002, 08:31 AM   #10
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Jim

I typically set the sharpness to neutral on wider shots, and down as low as -2 for closeups on people.The preset I mentioned works well to keep gain noise at bay when necessary.

I shoot everything in frame mode...my stock preset works pretty well for me in most situations...frame mode is by nature a little less sharp than movie mode, so depending on your taste or subject matter, maybe -1 (or 0) works better. Additionally, there may be variables within the cameras themselves which might give us differing results with the same settings.

Barry
---------------------------------------------

as always, actual mileage may vary
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Old September 6th, 2002, 09:43 AM   #11
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The TV that gave the bad signal was a 10 yr old 19" Sharp 19C-M100. It's old but it has had an amazing picture on it. Best TV I have ever owned. I have seen deterioration in a lot of aspects though and been thinking of a new one. The sharpness is set to the midway point. Interesting point on the sharpness Jeff. I just picked the midway point because when I moved it I couldn't see any difference happening in my set.
Tried to set the TV with the color bars but it really turned out looking terrible.
The TV it looked great on was a 13" Phillips Magnavox PR1302-C12. A cheap TV I picked up for the bedroom.
The camera's video was connected with the included stereo video cable through a Sony vcr.

All I did was bring the other TV in and just plugged it in with the exact configuration and it gave a whole different result.

The "noise" or interference I was talking about I determined could not have been with the camera just before I switched TVs. It was just the look of it. You see I was having a hard time explaining it as grain. At one point I took the image with a couple of lamps in the picture and I blurred it completely out. The "noise" I was seeing was still there, riding above what was the image. Blurring it out kind of seperated what the camera was and what had to be like electrical interference. The camera was not plugged into the wall.

And I have never seen that noise while watching the TV with any other source. VCR or Digital Cable. Can't get my mind around it.

The custom settings on the camera are the best and one of the main reasons I bought this one.

Michael
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Old September 6th, 2002, 02:47 PM   #12
 
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All television sets generate RF (radio frequency) noise. The cheaper television sets, and especially older sets, generated a lot more RF and weren't as well shielded as the newer sets. It sounds like your old TV and new GL were transmitting and receiving RF interference. The CCD circuits are incredible low amperage and the circuitry was probably picking up the RF from your TV's oscillator.
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Old September 6th, 2002, 05:23 PM   #13
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Michael,

You had the Camera hooked up to a VCR and the output of the VCR hooked up to the TV? Where you using the F connector (threaded, with a thin wire center, used for cable TV) on the VCR and TV? Or was the VCR and TV hooked up using RCA connectors? If you were using the Cable connection, F, then you were altering the signal. It was being converted from line level (sometimes called base band) to RF (radio frequency). This can cause a lot of trouble and is a poor way to view video.

Jeff
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Old September 6th, 2002, 09:54 PM   #14
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Nope...just RCA and just the video.
Remember the second TV had the same set up and worked right.
I am pretty sure what I was seeing is explained in billravens' reply.
Sounds like what I was experiencing.

Thanks for the posts,
Michael
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