taking away the grain? at DVinfo.net

Ian Weston · June 7th, 2004, 11:12 AM

Hello,

I'm in the process of planning my first short film, but have have run into a little problem where my camera is concerned.

Basically, the whole vid will be shot in very low light conditions, and unfortunatly for me with my panasonic gs-30, that means i get a very grainy picture. My question is:

Is there a way of either compensating for this problem in post-prod. or is there a way of eliminating the problem in the fist place.

Thanks

Ian.

btw, my film takes place in a field, about 50Meters from an illuminated street. through experimentation, i have found 2 x 20Watt lamps seem to provide a convincing street lamp hue?

Ken Tanaka · June 7th, 2004, 11:34 AM

Welcome, Ian.

As you might imagine, this topic surfaces relatively frequently here. So if you Search on "grain" you'll see quite a few threads.

But, unfortunately, the short answer is that there's very little you can do to mitigate grainy footage. Some try to add blur to gritty clips hoping to make it less obtrusive, but generally to little avail and almost always to the detriment of the clip.

Making matters worse, if you plan to compress your final movie (ex: for Web viewing) the grain will quickly become an even greater nightmare. Not only will it probably become even more prominent as compression artifacts magnify it, but this false random detail will greatly hamper your ability to compress clips to a more manageable size (for online viewing).

The best advice I can offer is to take every possible measure to avoid the problem. Change your shots. Add some light. Change the time of day. If you're doing a dramatic piece, remember that you can shoot in daylight and manipulate the footage to look like night.

Good luck.

Norm Couture · June 7th, 2004, 01:50 PM

Ian,
I'm afraid removing grain from a noisy video picture is something close to impossible. But you can avoid getting a noisy picture when you shoot.
Noise - or grain - is caused by excessive electronic gain applied by the cam in Automatic Aperture (Auto-Iris) when shooting in low light.
The obvious answer to your question would be «Use more light»!
But if you want to preserve night ambiance, you must first switch to MANUAL Iris, and avoid setting the aperture at anything over «OP +6», which means «open iris plus 6dB of gain».
At this aperture, if your scene is still too dark for your taste, think of adding lights instead of pushing gain over +9.

Remember, night scenes can be understood correctly even if just a few highlights are visible. Auto-Iris will ruin your footage by pushing the gain to +18dB or until night resembles daylight!

John Jay · June 7th, 2004, 03:53 PM

Hello Ian

There is a way of duplicating the Dual Pixel readout found in Hi End Sony Gear

You will need After FX:-

Create a composition with two copies of your footage on the timeline - one on top of the other

Choose blend mode -screen- for the topmost footage

the next step is most critical - you must horizontally displace the topmost footage by exactly one pixel

the result is an improvement of Signal/Noise ratio of +12db at a minor loss of resolution

Emre Safak · June 7th, 2004, 04:11 PM

My approach is to import the video into VirtualDubMod so I have access to the excellent array of free Avisynth noise cancellation plug-ins. Visit http://forum.doom9.org/ for more information, but be warned: there is a lot to learn.

Frank Ladner · June 8th, 2004, 10:52 AM

Ian: There's been a lot of excellent information posted already, but I wanted to just throw in that if you were to go with something along the route of blur filters, etc. then you may want to experiment with the Median filter. This would keep the appearance of sharpness better than a blur filter.

,Frank

Ian Weston · June 8th, 2004, 01:00 PM

Thanks for your help guys, I did'nt expect such a response.

There is alot for me to learn and experiment with here, and as has already been sugested, i shall take a look around the forum for other related topics. I'll give it a go and see what happens (hopfully a film).

Once again, thanks.

Ian.

EDIT: Err.. just as an after thought, if it turns that i cant satisfacturaly get a good image, would it help if i hired a XL1s (or similar) for a couple of days. or would this still suffer from the same syndrome?

June 7th, 2004, 11:12 AM	#1
Ian Weston Tourist Join Date: Jun 2004 Location: Harrogate, England Posts: 2	taking away the grain? Hello, I'm in the process of planning my first short film, but have have run into a little problem where my camera is concerned. Basically, the whole vid will be shot in very low light conditions, and unfortunatly for me with my panasonic gs-30, that means i get a very grainy picture. My question is: Is there a way of either compensating for this problem in post-prod. or is there a way of eliminating the problem in the fist place. Thanks Ian. btw, my film takes place in a field, about 50Meters from an illuminated street. through experimentation, i have found 2 x 20Watt lamps seem to provide a convincing street lamp hue?

June 7th, 2004, 11:34 AM	#2
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Welcome, Ian. As you might imagine, this topic surfaces relatively frequently here. So if you Search on "grain" you'll see quite a few threads. But, unfortunately, the short answer is that there's very little you can do to mitigate grainy footage. Some try to add blur to gritty clips hoping to make it less obtrusive, but generally to little avail and almost always to the detriment of the clip. Making matters worse, if you plan to compress your final movie (ex: for Web viewing) the grain will quickly become an even greater nightmare. Not only will it probably become even more prominent as compression artifacts magnify it, but this false random detail will greatly hamper your ability to compress clips to a more manageable size (for online viewing). The best advice I can offer is to take every possible measure to avoid the problem. Change your shots. Add some light. Change the time of day. If you're doing a dramatic piece, remember that you can shoot in daylight and manipulate the footage to look like night. Good luck. __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

June 7th, 2004, 01:50 PM	#3
Norm Couture Regular Crew Join Date: Sep 2003 Location: Quebec, QC, Canada Posts: 123	Avoiding grain (video noise) Ian, I'm afraid removing grain from a noisy video picture is something close to impossible. But you can avoid getting a noisy picture when you shoot. Noise - or grain - is caused by excessive electronic gain applied by the cam in Automatic Aperture (Auto-Iris) when shooting in low light. The obvious answer to your question would be «Use more light»! But if you want to preserve night ambiance, you must first switch to MANUAL Iris, and avoid setting the aperture at anything over «OP +6», which means «open iris plus 6dB of gain». At this aperture, if your scene is still too dark for your taste, think of adding lights instead of pushing gain over +9. Remember, night scenes can be understood correctly even if just a few highlights are visible. Auto-Iris will ruin your footage by pushing the gain to +18dB or until night resembles daylight! __________________ Norm :)

June 7th, 2004, 03:53 PM	#4
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	Hello Ian There is a way of duplicating the Dual Pixel readout found in Hi End Sony Gear You will need After FX:- Create a composition with two copies of your footage on the timeline - one on top of the other Choose blend mode -screen- for the topmost footage the next step is most critical - you must horizontally displace the topmost footage by exactly one pixel the result is an improvement of Signal/Noise ratio of +12db at a minor loss of resolution __________________ John Jay Beware *PLUGGER-BYTES*

June 7th, 2004, 04:11 PM	#5
Emre Safak Trustee Join Date: Feb 2004 Location: Brookline, MA Posts: 1,447	My approach is to import the video into VirtualDubMod so I have access to the excellent array of free Avisynth noise cancellation plug-ins. Visit http://forum.doom9.org/ for more information, but be warned: there is a lot to learn.

June 8th, 2004, 10:52 AM	#6
Frank Ladner Major Player Join Date: Aug 2003 Location: Poplarville, MS Posts: 453	Ian: There's been a lot of excellent information posted already, but I wanted to just throw in that if you were to go with something along the route of blur filters, etc. then you may want to experiment with the Median filter. This would keep the appearance of sharpness better than a blur filter. ,Frank

June 8th, 2004, 01:00 PM	#7
Ian Weston Tourist Join Date: Jun 2004 Location: Harrogate, England Posts: 2	Thanks for your help guys, I did'nt expect such a response. There is alot for me to learn and experiment with here, and as has already been sugested, i shall take a look around the forum for other related topics. I'll give it a go and see what happens (hopfully a film). Once again, thanks. Ian. EDIT: Err.. just as an after thought, if it turns that i cant satisfacturaly get a good image, would it help if i hired a XL1s (or similar) for a couple of days. or would this still suffer from the same syndrome?