Understand Exposure Control on the A1 at DVinfo.net

David Ziegelheim · July 10th, 2006, 04:57 PM

This is just a question to see if I understand this correctly. It is my understanding that you can adjust the shutter speed in the touch screen. But beyond that all control over iris and gain joined together, with no report of what the iris or the gain is and no way to observe the result until post processing? This is somewhat important since 1) gain can add lots of noise to the image; and 2) aperture affects depth of field.

Thanks,

David

Stu Holmes · July 10th, 2006, 05:20 PM

Yes its tricky to separate iris from gain on A1.
But you dont have to wait til post. - on playback, enable this function :
DAta Code, Camera Data. and that will show on playback, the shutter speed used, iris, gain, white balance setting, Exposure mode (auto /manual) etc.
In Manual exposure mode, also, you can tell what gain is being used by the position of the small marker on the exposure bar. If its fully to the right the cams using +18db gain (f1.8), one click left is 15db, then 12db, 9db, 6db, 3db, 0db. There is a little sticky tag that you can stick on the LCd screen that shows the settings for each marker position. Someone posted a link to that little sticky thing a few days ago.

Also, heres an other post with the run down on iris and gain settings from "max.exposure" at the top.

And heres another view of the same sort of table for HC1 (same for A1).:
http://hdvforever.com/hdv/exposure/

David Ziegelheim · July 11th, 2006, 08:50 PM

Interesting...but it also means that under F4 the camera starts loosing dynamic range rather than waiting until the iris was wide open. The sensor is large enough that opening the iris wide could give you some DOF control. But it is only available with a loss of dynamic range.

Evan Donn · July 12th, 2006, 01:10 AM

Quote:

Originally Posted by David Ziegelheim

Interesting...but it also means that under F4 the camera starts loosing dynamic range rather than waiting until the iris was wide open. The sensor is large enough that opening the iris wide could give you some DOF control. But it is only available with a loss of dynamic range.

Actually I don't believe the author's theory about the sliding bit range is true - what he doesn't seem to be aware of is the internal ND filters which slide into place to maintain f.4 across 8 exposure positions. So my guess is the same dynamic range is available across all f stops, although considering the trouble they went to to hold at f.4 whenever possible I'm guessing that's where you'll get your sharpest image.

July 10th, 2006, 04:57 PM	#1
David Ziegelheim Major Player Join Date: Jul 2003 Location: Warren, NJ Posts: 398	Understanding Exposure Control on the A1 This is just a question to see if I understand this correctly. It is my understanding that you can adjust the shutter speed in the touch screen. But beyond that all control over iris and gain joined together, with no report of what the iris or the gain is and no way to observe the result until post processing? This is somewhat important since 1) gain can add lots of noise to the image; and 2) aperture affects depth of field. Thanks, David Last edited by David Ziegelheim; July 10th, 2006 at 07:51 PM.

July 10th, 2006, 05:20 PM	#2
Stu Holmes Major Player Join Date: May 2005 Location: Europe Posts: 844	Yes its tricky to separate iris from gain on A1. But you dont have to wait til post. - on playback, enable this function : DAta Code, Camera Data. and that will show on playback, the shutter speed used, iris, gain, white balance setting, Exposure mode (auto /manual) etc. In Manual exposure mode, also, you can tell what gain is being used by the position of the small marker on the exposure bar. If its fully to the right the cams using +18db gain (f1.8), one click left is 15db, then 12db, 9db, 6db, 3db, 0db. There is a little sticky tag that you can stick on the LCd screen that shows the settings for each marker position. Someone posted a link to that little sticky thing a few days ago. Also, heres an other post with the run down on iris and gain settings from "max.exposure" at the top. And heres another view of the same sort of table for HC1 (same for A1).: http://hdvforever.com/hdv/exposure/

July 11th, 2006, 08:50 PM	#3
David Ziegelheim Major Player Join Date: Jul 2003 Location: Warren, NJ Posts: 398	Interesting...but it also means that under F4 the camera starts loosing dynamic range rather than waiting until the iris was wide open. The sensor is large enough that opening the iris wide could give you some DOF control. But it is only available with a loss of dynamic range.