Canon A1 Problem - Help judge this footage at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XH Series HDV Camcorders

Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


Reply
 
Thread Tools Search this Thread
Old May 7th, 2007, 08:46 PM   #1
New Boot
 
Join Date: Dec 2005
Posts: 15
Canon A1 Problem - Help judge this footage

Hello there,

I just got my Canon A1 a couple months ago and had the chance to use in a shoot. I rented a second one for that shoot from the same store I bought mine.

At the shooting day, my DOP and I looked at both and thought the image to be a bit weird when indoors. I have placed here screenshots of the high res images of the footage both indoors and outdoors.

The settings are all original from manufactory. Only one image has Steven's preset which helps a bit but you will notice the grain is still there.

Should I bring my camera back to Canon? Is anyone experience this same problem or am I doing something really wrong?

Thanks for the help!
Paulo
Attached Thumbnails
Canon A1 Problem - Help judge this footage-01_normalexposure.tiff   Canon A1 Problem - Help judge this footage-02_normalexposure.tiff  

Canon A1 Problem - Help judge this footage-03_overexposed.tiff   Canon A1 Problem - Help judge this footage-04_steven_preset.tiff  

Canon A1 Problem - Help judge this footage-05_outsideshot.tiff  
Paulo Salomao is offline   Reply With Quote
Old May 7th, 2007, 08:56 PM   #2
Major Player
 
Join Date: Nov 2004
Location: Dallas
Posts: 747
Turn off the freaking auto gain.
__________________
Khoi Pham
www.proeditproductions.com
Khoi Pham is offline   Reply With Quote
Old May 7th, 2007, 09:06 PM   #3
Inner Circle
 
Join Date: Nov 2005
Location: Elk Grove CA
Posts: 6,838
Agreed. Turn of auto gain. It only took me about six months to realize my FX1 was pumping autogain, when I thought it was off. I think A1 works the same way, you have to select a gain level with one of the switches, and make sure that gain level is set at 0. Otherwise, the camera adds gain even though you think you are adjusting without it... grain shows.
__________________
Chris J. Barcellos
Chris Barcellos is offline   Reply With Quote
Old May 7th, 2007, 09:07 PM   #4
Major Player
 
Join Date: Dec 2006
Location: Los Angeles, CA
Posts: 959
Yea, what Khoi said.
Bill Busby is offline   Reply With Quote
Old May 7th, 2007, 09:09 PM   #5
New Boot
 
Join Date: Dec 2005
Posts: 15
Indeed. I can't believe I didn't figure that out.

So I believe in very dark situations its worth it to have the gain on?
Paulo Salomao is offline   Reply With Quote
Old May 7th, 2007, 09:30 PM   #6
Regular Crew
 
Join Date: Apr 2005
Location: Fairbanks, Alaska
Posts: 138
I have mine set to: L-0, M-+3, H-+6.

Experiment. You may prefer L-0, M-+6, H-+12. However, +12 isn't great.
__________________
After years of lurking, I finally made the mistake of opening my mouth.
Doug Lange is offline   Reply With Quote
Old May 7th, 2007, 09:45 PM   #7
Major Player
 
Join Date: Nov 2004
Location: Dallas
Posts: 747
Quote:
Originally Posted by Paulo Salomao View Post
Indeed. I can't believe I didn't figure that out.

So I believe in very dark situations its worth it to have the gain on?
It does not matter if you have your preset on 0db or what, the auto gain switch must be off, now if the light level is low, the first thing you want to adjust is your apperture, open that all the way, if it is still too dark then add 3 db gain, if it is still too dark then go to 6db and so on, gain should be the last thing you want to use because more gain=more grain, now if you don't mind about smooth video then you can also take your shutter speed down to 30th of a seconds or lower to gain more light. A1 is a manual camera, it is not a good auto camera.
__________________
Khoi Pham
www.proeditproductions.com
Khoi Pham is offline   Reply With Quote
Old May 7th, 2007, 10:45 PM   #8
Regular Crew
 
Join Date: Apr 2007
Location: San Francisco, CA
Posts: 114
Yep, gain is artificially increasing sensitivity of the sensors by applying higher currents/voltages. Gain is "digital". In a way, gain to the sensor is what digital zoom is to the range - it tries to create more out of less. Aperture is what optical zoom is to the range - it increases the amount of light that is hitting the sensor. Open up the aperture (use lower F-number), or slow down the shutter speed - that comes with the price of motion artifacts, but you can lower the shutter speed from the usual 1/60 (if you are shooting 60i) without introducing much artifacts by setting your shutter speed to 1/48 and shooting in 24f mode.

Quote:
Originally Posted by Khoi Pham View Post
It does not matter if you have your preset on 0db or what, the auto gain switch must be off, now if the light level is low, the first thing you want to adjust is your apperture, open that all the way, if it is still too dark then add 3 db gain, if it is still too dark then go to 6db and so on, gain should be the last thing you want to use because more gain=more grain, now if you don't mind about smooth video then you can also take your shutter speed down to 30th of a seconds or lower to gain more light. A1 is a manual camera, it is not a good auto camera.
Maksim Yankovskiy is offline   Reply With Quote
Old May 8th, 2007, 09:58 AM   #9
Wrangler
 
Join Date: Sep 2001
Location: Northern VA
Posts: 4,294
An arguably better analogy is gain is to video is like push processing is to film. Push process film and you see higher effective film speed and more grain, and perhaps other artifacts.

The signal read from the CCD is analog, a voltage based on the light intensity raching the CCD, the exposure time, and the (normally small) self-noise componets in the CCD pixels such as leakage and dark currents. Gain is analog amplification of the signal read from the CCD, and any variations in individual pixel sensitivity and leakage and dark current appears as a grain in the image. Increasing gain amplifies the differences between pixels making them more apparent in the image.

Note that slow shutter speeds also may increase certain aspects of this grain - the part attributed to the pixel leakage and dark current, but the effect may not be as pronounces as using equivalent amount of gain.

The best answer is to shoot with adequate light to keep the CCD operating in its optimum range. If light is a problem, you can improve the images with judicious use of gain, slower shutter speed, and custom presets in addition to aperture. Arriving at the best setting for a given shooting situation is a bit of an art.
__________________
dpalomaki@dspalomaki.com
Don Palomaki is offline   Reply With Quote
Old May 8th, 2007, 01:16 PM   #10
Regular Crew
 
Join Date: Apr 2007
Location: San Francisco, CA
Posts: 114
Gain

Don,

As I remember from my days of exposure at hardware designs of a high-end ultrasound system, there are two types of gain: analog and digital. The difference is at what stage the gain scheme gets applied to the signal. The analog is applied at the signal after is read from a sensor, but before the signal passes through ADCs.

It sounds that what you describe above is the analog gain. The manufacturers usually apply both types of gain - analog and digital - but for the purpouse of knobs and switches call the same - gain. It's quite often that the digital gain is the bigger component, as analog aplifiers are much more expensive.
Maksim Yankovskiy is offline   Reply With Quote
Old May 8th, 2007, 08:03 PM   #11
Wrangler
 
Join Date: Sep 2001
Location: Northern VA
Posts: 4,294
The XL1 and GL1 both use analog gain for both image gain and white balance. I suspect that the A1 does also. Does anyone know for sure?

6 dB of gain is a one-bit shift, but 3 dB (1/2 bit?) would not be as easy digitally. Digital is likely used for many of the presets.
__________________
dpalomaki@dspalomaki.com
Don Palomaki is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XH Series HDV Camcorders

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 02:53 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network