Question about HC VX870 at DVinfo.net

Steve Siegel · September 17th, 2015, 06:40 PM

I just bought a little 870 to see what I could do in 4K. It is nice that the unit has a manual iris, but is it really an iris? The settings seem to change the exposure by increasing the gain (in dB, that's gain, not exposure). Is there a way to adjust the exposure while keeping the gain at a sensible 0 dB?

Emmanuel Asset · September 20th, 2015, 01:00 AM

In page 67, the user manual says : "When the iris value is adjusted to brighter than OPEN, it changes to the gain value"
It sounds like Gain is at 0db until you go beyond full open Iris value...

Benoit Matthys · February 5th, 2016, 10:29 AM

When changing the iris value, the displayed iris/gain value is changed only for every other step up or down, while the actual brightness of the picture changes for every step up or down.
So, I guess there are intermediate iris and/or gain values that are used but not displayed.
And I have no clue which one of each step in a "pair" actually matches the displayed value.
The question is: when do I actually have iris fully OPEN and NO gain ? When does gain actually kick in ?
If I increase brightness from some larger iris value step by step until OPEN/0dB is displayed, I can go one step further (brighter) and still see OPEN/0dB...is the latter now the real 0dB or did I just start adding 1.5 dB gain ???? Or was the "first" OPEN/0dB more "something between f 1.8 and OPEN=F2.0 / 0 dB" and the second one really OPEN/0dB ?

September 17th, 2015, 06:40 PM	#1
Steve Siegel Major Player Join Date: Nov 2001 Location: Albuquerque, New Mexico, USA Posts: 839	Question about HC VX870 I just bought a little 870 to see what I could do in 4K. It is nice that the unit has a manual iris, but is it really an iris? The settings seem to change the exposure by increasing the gain (in dB, that's gain, not exposure). Is there a way to adjust the exposure while keeping the gain at a sensible 0 dB?

September 20th, 2015, 01:00 AM	#2
Emmanuel Asset Tourist Join Date: Nov 2014 Location: France Posts: 2	Re: Question about HC VX870 In page 67, the user manual says : "When the iris value is adjusted to brighter than OPEN, it changes to the gain value" It sounds like Gain is at 0db until you go beyond full open Iris value...

February 5th, 2016, 10:29 AM	#3
Benoit Matthys New Boot Join Date: Jun 2010 Location: Brussels, Belgium Posts: 15	Re: Question about HC VX870 When changing the iris value, the displayed iris/gain value is changed only for every other step up or down, while the actual brightness of the picture changes for every step up or down. So, I guess there are intermediate iris and/or gain values that are used but not displayed. And I have no clue which one of each step in a "pair" actually matches the displayed value. The question is: when do I actually have iris fully OPEN and NO gain ? When does gain actually kick in ? If I increase brightness from some larger iris value step by step until OPEN/0dB is displayed, I can go one step further (brighter) and still see OPEN/0dB...is the latter now the real 0dB or did I just start adding 1.5 dB gain ???? Or was the "first" OPEN/0dB more "something between f 1.8 and OPEN=F2.0 / 0 dB" and the second one really OPEN/0dB ?