cleaner to gain down -3db? 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 July 31st, 2007, 04:57 PM   #1
Major Player
 
Join Date: Jun 2007
Location: Great Neck, NY
Posts: 291
cleaner to gain down -3db?

Is it potentially cleaner to gain down -3db when shooting with this camera? I have some footage and I am sure the camera was set to 0db gain and auto gain was off (I was not shooting, I was being shot) and while most was very clean, some in relatively bright lighting conditions outdoors bright day, there are scenes that are very noisy, so I am curious if shooting -3db is a way to keep it a bit cleaner in shooting, assuming enough light natural or artificial of course.

Whats the downside to this?

Stephen Eastwood
http://www.StephenEastwood.com
Stephen Eastwood is offline   Reply With Quote
Old July 31st, 2007, 05:02 PM   #2
Major Player
 
Join Date: Mar 2007
Location: Philly,PA
Posts: 360
i've run into this too and -3db didn't help. i don't think the exposure meter is very accurate. i've been "over exposing" by a notch or three and have gotten cleaner results. please try it and let me know if that's the case..or if it's just me.

i also import with an hv20 and monitor the source footage via hdmi/1080i/32"

the a1 is capable of some really clean images in bright and dark settings..so i'm sure the odd grain issues are exposure issues.
Eric Weiss is offline   Reply With Quote
Old July 31st, 2007, 07:17 PM   #3
Major Player
 
Join Date: Feb 2007
Location: Bruce Pennisula, Canada
Posts: 316
I'm usually shooting using Steve Dempsey's VIVGRB preset and -3db gain. I have only once come across video noise in almost all daylight recording situations be them full sun or cloudy. In particular I was filming elephants at a zoo with a painted brown post behind the animals. Everything about the shot is perfect except for sparkling pixels on the brown post. I don't have an explantion for it, but I don't think it is necessarily noise caused by any sort of gain influence.

Whenever I can get away with -3db I use it. I have seen extremely subtle sparkling on some thing I shot at +0db although rare and more like film grain....mostly on large flat coloured surfaces not unlike the brown post in the above example.
James Hooey is offline   Reply With Quote
Old July 31st, 2007, 07:41 PM   #4
Regular Crew
 
Join Date: Mar 2007
Location: New Prague, MN
Posts: 112
When using Steve Dempsey's VIVGRB Preset and 0 or -3 gain I found that there was a considerable abount of grain in the grean and red channel. I have not had the grain show up at -3 in any other Preset that I have used.
__________________
Kevin | www.kraentertainment.com
A picture is worth 1,000 words | A 2 hour film at 24fps is worth 172,800,000 words
Kevin Amundson is offline   Reply With Quote
Old July 31st, 2007, 07:55 PM   #5
Major Player
 
Join Date: Jan 2007
Location: Portland, OR
Posts: 949
The only downides to -3db is the (obvious) loss of light, and the potentially less dynamic range. I don't know anyone who has measured the dynamic range of each gain setting independantly, and I suspect that 0db has very slightly greater lattitude.

Noise can be caused by a warm sensor (30+ minutes of shooting), narrow spectrum light (tungsten), or dark scenes (low key).
Daniel Browning is offline   Reply With Quote
Old July 31st, 2007, 08:11 PM   #6
Major Player
 
Join Date: Mar 2007
Location: Philly,PA
Posts: 360
James, YES! What I'm speaking of is more like a film grain...and I really don't like it.
Eric Weiss is offline   Reply With Quote
Old August 1st, 2007, 08:02 AM   #7
Wrangler
 
Join Date: Sep 2001
Location: Northern VA
Posts: 4,294
The 0 dB gain setting was probably arrived at based on using the optimal portion of the light sensitivity range of the CCD. The sweet range in the CCD transfer function of converting light to electricity. Using -3 dB gain effectively pushes the noise floor of the CCD down 3 dB. That is generally good. But in the process it also cuts 3 dB off the high end (bright light) headroom of the light-to-electricity conversion curve of the CCD, which might introduce other artifacts under certain scene conditions; e.g., possibly more susceptibility to vertical smear from bright point sources of light and other non-linear behaviors. You have to judge whether or not -3 dB works for you.
__________________
dpalomaki@dspalomaki.com
Don Palomaki is offline   Reply With Quote
Old August 1st, 2007, 11:32 AM   #8
Regular Crew
 
Join Date: Apr 2007
Location: Copenhagen, Denmark
Posts: 49
Could the noise using VIVIDRGB be caused by the +25 Color Gain setting?
Rene Roslev is offline   Reply With Quote
Old August 2nd, 2007, 02:14 AM   #9
Major Player
 
Join Date: Feb 2007
Location: Bruce Pennisula, Canada
Posts: 316
Quote:
Originally Posted by Rene Roslev View Post
Could the noise using VIVIDRGB be caused by the +25 Color Gain setting?
Certainly might play a role....in particular the worst (and really only) time I have noticed any problems with the -3/VIVIDRGB combo is the one brown painted post I mentioned earlier. Being brown it may have hyped up the red CCD on the camera a bit and acted up. Generally -3 works very cleanly for me.

Quote:
Originally Posted by Eric Weiss View Post
James, YES! What I'm speaking of is more like a film grain...and I really don't like it.
So your seeing noise/grain, but is it very often? Or just in some very unique situtations. I don't see the corelation between exposure and noise. Can you explain your thoughts on this?
James Hooey is offline   Reply With Quote
Old August 2nd, 2007, 08:47 AM   #10
Major Player
 
Join Date: Mar 2007
Location: Philly,PA
Posts: 360
It’s not very often.

I wish I could explain it. At least then I could identify the issue and solve it.

Frankly, it’s no worse than what can be seen on any HD broadcast…. and I am a bit OCD when it comes to a “clean” image
Eric Weiss is offline   Reply With Quote
Old August 2nd, 2007, 01:12 PM   #11
Wrangler
 
Join Date: Sep 2001
Location: Northern VA
Posts: 4,294
Slower shutter speeds can result in more visible grain thanks to the longer integration time for the dark current of the individual pixels.
__________________
dpalomaki@dspalomaki.com
Don Palomaki is offline   Reply With Quote
Old August 2nd, 2007, 10:42 PM   #12
New Boot
 
Join Date: Jul 2007
Location: Los Angeles
Posts: 16
James - How is the overall brightness of your video at -3?

I tried using the VIVIDRGB preset earlier today, the image was really bright. I tried using the nd filter which darkened the image and really brought out the colors, but there was considerable noise.

Perhaps not using nd and instead lowering the gain to -3 might improve things. So far with this camera, whether day, night, auto, manual, I have some degree of noise. I love my camera, but I'll love it more if I can get rid of the noise.
Scott Becker is offline   Reply With Quote
Old August 3rd, 2007, 01:00 AM   #13
Major Player
 
Join Date: Feb 2007
Location: Bruce Pennisula, Canada
Posts: 316
[QUOTE=Scott Becker;722638]James - How is the overall brightness of your video at -3? [QUOTE]

In daylight situations I have no issues with the brightness of the video. Generally I'm trying to stay in the sweet spot of the lens aperture at around f4-5 and shutter speeds of 60fps. Depending on the amount of available daylight this may need none, one or both ND filters with a gain of -3 to achieve a suitable exposure.

IMO the XHA1 has very low noise levels and I certainly don't have any issue with the camera.

Last edited by James Hooey; August 3rd, 2007 at 01:04 AM. Reason: added content
James Hooey is offline   Reply With Quote
Old August 3rd, 2007, 01:36 PM   #14
Inner Circle
 
Join Date: Dec 2005
Location: Rhode Island
Posts: 3,865
I shoot in bright light on the water and found that the camera ND is much better then ND add on filters. I purchased a .6 and 1.2 Formatt ND filters and Hoya Pro1Digital filters ND x4 and NDx8 and did not like the results. Also when I have both ND camera filters on and still have too much light to have the iris in the 3-5 range I put the shutter to 120 with excellent results.

As for the VIVID with grain I found cutting down the color gain to 15 helped and lowering the red gain also.

Now no grain unless I under expose trusing the camera meter. I all most always go one to two stops more open then the meter recommends and always use -3 gain while shooting outdoors.

Hope this helps.
__________________
Paul Cronin
www.paulcroninstudios.com

Last edited by Paul Cronin; August 3rd, 2007 at 03:00 PM.
Paul Cronin 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 09:59 PM.


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