Question about the gain at DVinfo.net

Josh Frye · July 27th, 2003, 04:05 AM

Greetings. I shoot on a Canon XL-1, and would like to know more about the electronic in camera gain feature. I only shoot in manual mode, and try not to let the camera do anything. I run the white balance on locked manual, and take the gain off of auto. Here is my question; the other day, I was shooting outside, and I had forgotten that I had locked the gain at +12 db. When I watched the footage, the colors seemed washed out. The scene wasn’t particularly over exposed, and the colors just did not seem extremely vibrant. Could using the electronic gain be responsible for this sacrifice in color saturation? I have decided to use the gain only for shots in low light conditions, and on a case-by-case basis from now on.

Thanks.

Bill Ravens · July 28th, 2003, 07:19 AM

sounds like you saturated the CCD. Too much light..too much gain and the camera was unable to compensate.

BJ Thomas · July 28th, 2003, 12:14 PM

Avoid using auto DB. This has caused me more headache then anything else. I try to keep the XL1s at zero DB and I make sure that I only use extra DB if absolutly necessary. When you add extra db it can introduce artifacting or a unclean looking image. So best to use external lighting versus using the DB.

Josh Bass · July 28th, 2003, 12:41 PM

-3 is even better.

Don Palomaki · July 28th, 2003, 07:40 PM

Runing at +12 dB gain will force you to set the aperture and shutter to provide what is effective low light to the CCD, causing all the kinds of limitations found with low light situations such as increased grain, potentially low saturation in some colors, less effective white balance, poor autofocus response, and perhaps a funny grayscale curve.

Josh Frye · July 29th, 2003, 02:14 AM

Yeah. I have been getting much better results with setting the dB levels on a case by case, and as-needed basis. I never use the automatic setting. Thanks for the replies.

Dan Uneken · August 1st, 2003, 09:45 AM

Don: that's interesting! Why should the grayscale curve differ at +12 Db (if you compensate for exposure in other ways, such as ND filter)? Does the circuitry of the gain settings do anything else but simply amplify the signal? Do you know of any characteristical curves for the XL-1(s) / at various gain settings?

Thanks!

Dan.

Don Palomaki · August 4th, 2003, 07:53 PM

Because when the light reaching the CCD gets very low the output may not be linear.

I've not seen any curves specifically for the XL1.

Rob Lohman · August 11th, 2003, 06:06 AM

I'll shoot at -3 or 0 db. If I need more I start looking at other
settings or add light [if possible]. If you start to add gain you'll
notice it very quickly in the resulting image [in my opinion].

Dan Uneken · August 11th, 2003, 01:04 PM

In my opinion it all depends.
It's like a grainy b & w photo: it can even add to the atmosphere. Also, if shooting a unique event, in my opinion content goes over form and I'll watch a lower image quality + great content video over a great image quality + poor content video any time. Of course the best is to have both optimal.
I've often cranked up to +12 and have not yet been sorry I did.

July 27th, 2003, 04:05 AM	#1
Josh Frye Regular Crew Join Date: Jul 2003 Location: Berlin Germany Posts: 46	Question about the gain Greetings. I shoot on a Canon XL-1, and would like to know more about the electronic in camera gain feature. I only shoot in manual mode, and try not to let the camera do anything. I run the white balance on locked manual, and take the gain off of auto. Here is my question; the other day, I was shooting outside, and I had forgotten that I had locked the gain at +12 db. When I watched the footage, the colors seemed washed out. The scene wasn’t particularly over exposed, and the colors just did not seem extremely vibrant. Could using the electronic gain be responsible for this sacrifice in color saturation? I have decided to use the gain only for shots in low light conditions, and on a case-by-case basis from now on. Thanks. __________________ Cheers

July 28th, 2003, 12:41 PM	#4
Josh Bass Slash Rules! Join Date: Apr 2002 Location: Houston, Texas Posts: 5,472	-3 is even better. __________________ The Bass' camerawork The Bass on IMDB

July 28th, 2003, 07:40 PM	#5
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	Runing at +12 dB gain will force you to set the aperture and shutter to provide what is effective low light to the CCD, causing all the kinds of limitations found with low light situations such as increased grain, potentially low saturation in some colors, less effective white balance, poor autofocus response, and perhaps a funny grayscale curve. __________________ dpalomaki@dspalomaki.com

July 29th, 2003, 02:14 AM	#6
Josh Frye Regular Crew Join Date: Jul 2003 Location: Berlin Germany Posts: 46	Yeah. I have been getting much better results with setting the dB levels on a case by case, and as-needed basis. I never use the automatic setting. Thanks for the replies. __________________ Cheers

August 1st, 2003, 09:45 AM	#7
Dan Uneken Major Player Join Date: Sep 2001 Location: Andalucia, Spain Posts: 301	About that grayscale curve... Don: that's interesting! Why should the grayscale curve differ at +12 Db (if you compensate for exposure in other ways, such as ND filter)? Does the circuitry of the gain settings do anything else but simply amplify the signal? Do you know of any characteristical curves for the XL-1(s) / at various gain settings? Thanks! Dan. __________________ Film & TV locations & production Spain http://www.fotofilmvideo.com/

July 28th, 2003, 07:19 AM	#2
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	sounds like you saturated the CCD. Too much light..too much gain and the camera was unable to compensate.

July 28th, 2003, 12:14 PM	#3
BJ Thomas Regular Crew Join Date: Jul 2003 Posts: 39	Avoid using auto DB. This has caused me more headache then anything else. I try to keep the XL1s at zero DB and I make sure that I only use extra DB if absolutly necessary. When you add extra db it can introduce artifacting or a unclean looking image. So best to use external lighting versus using the DB.

August 4th, 2003, 07:53 PM	#8
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	Because when the light reaching the CCD gets very low the output may not be linear. I've not seen any curves specifically for the XL1. __________________ dpalomaki@dspalomaki.com

August 11th, 2003, 06:06 AM	#9
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	I'll shoot at -3 or 0 db. If I need more I start looking at other settings or add light [if possible]. If you start to add gain you'll notice it very quickly in the resulting image [in my opinion]. __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

August 11th, 2003, 01:04 PM	#10
Dan Uneken Major Player Join Date: Sep 2001 Location: Andalucia, Spain Posts: 301	In my opinion it all depends. It's like a grainy b & w photo: it can even add to the atmosphere. Also, if shooting a unique event, in my opinion content goes over form and I'll watch a lower image quality + great content video over a great image quality + poor content video any time. Of course the best is to have both optimal. I've often cranked up to +12 and have not yet been sorry I did. __________________ Film & TV locations & production Spain http://www.fotofilmvideo.com/