Controlling exposure. at DVinfo.net

Warren Eagleton · November 27th, 2011, 12:26 AM

On my HXR-NX70p camera LCD, I have displayed the ‘Iris, Gain & Shutter speed’ readout. The general rule is to aim for is 0db gain as much as I am able. However in auto I have noticed that often the shutter speed readout can go from 50 to 1000fps as the cam pans a dim to bright scene yet the iris stays at say F4.0. Why is the iris not changing also rather than just the shutter speed. Is there a setting I have inadvertently fiddled with? Maybe it uses the shutter speed to vary light transmission in leiu of the iris because it can make finer adjustments? I used to like to keep the iris mid range in summer shooting with my old camera, using an ND4 filter in bright conditions open the iris a little. Any constructive comments welcome.

Jack Markham · November 27th, 2011, 09:24 AM

Full auto works pretty well on the NX70. On a bright day, a three stop ND filter keeps the shutter speed down. On my NX70, I set Manual. I set the shutter at 60 and leave it there (for 60i). I usually have the gain set to auto. I adjust the exposure with the iris.

I am not an video professional. I have been using video for several years and have become familiar with what works for me.

Ron Evans · November 27th, 2011, 11:58 AM

Auto is trying to keep the lens in its sweet spot. From looking at the data code in full auto on my CX700 that looks like between around F4 or a little less. I have much the same approach as Jack to leave gain in auto ( I can't control gain on the CX700 anyway ) but can control shutter speed and iris !!!! I think F4 is about it for a 1/3 sensor as detailed in some other posts. Any smaller will lead to softening of the image. So shutter speed or a ND is the solution.

Ron Evans

Warren Eagleton · November 27th, 2011, 01:28 PM

Thanks Jack & Ron for your helpful replys. My old camera was the HVR-A1p and I didn't have the luxury of Iris,Gain & Shutter speed numerical readings on screen. The NX70p is more informative in that respect. I understand your comment about the lens 'sweet spot' but have been more aware of that with my SLR equipment and often use aperature priority. As we go further into summer here in New Zealand I will experiment with my ND filters vs shutter speed in the auto setting. Good to know that at around F4 the lens tends to perform best, thanks again.

Dan Crowell · November 27th, 2011, 05:56 PM

Warren,

Get yourself a variable ND filter and that will solve your problem. Just do a google search and pick one. I find the cheap ones work as well as the more expensive one. Try the cheap one first.

Here's some footage I shoot one after attaching the ND filter that cost me $30 from Amazon.

Nice little camera.

Dan

November 27th, 2011, 12:26 AM	#1
Warren Eagleton Regular Crew Join Date: Nov 2010 Location: Auckland, New Zealand. Posts: 52	Controlling exposure. On my HXR-NX70p camera LCD, I have displayed the ‘Iris, Gain & Shutter speed’ readout. The general rule is to aim for is 0db gain as much as I am able. However in auto I have noticed that often the shutter speed readout can go from 50 to 1000fps as the cam pans a dim to bright scene yet the iris stays at say F4.0. Why is the iris not changing also rather than just the shutter speed. Is there a setting I have inadvertently fiddled with? Maybe it uses the shutter speed to vary light transmission in leiu of the iris because it can make finer adjustments? I used to like to keep the iris mid range in summer shooting with my old camera, using an ND4 filter in bright conditions open the iris a little. Any constructive comments welcome.

November 27th, 2011, 09:24 AM	#2
Jack Markham New Boot Join Date: Oct 2004 Posts: 19	Re: Controlling exposure. Full auto works pretty well on the NX70. On a bright day, a three stop ND filter keeps the shutter speed down. On my NX70, I set Manual. I set the shutter at 60 and leave it there (for 60i). I usually have the gain set to auto. I adjust the exposure with the iris. I am not an video professional. I have been using video for several years and have become familiar with what works for me.

November 27th, 2011, 11:58 AM	#3
Ron Evans Inner Circle Join Date: Mar 2003 Location: Ottawa, Ontario, Canada Posts: 4,222	Re: Controlling exposure. Auto is trying to keep the lens in its sweet spot. From looking at the data code in full auto on my CX700 that looks like between around F4 or a little less. I have much the same approach as Jack to leave gain in auto ( I can't control gain on the CX700 anyway ) but can control shutter speed and iris !!!! I think F4 is about it for a 1/3 sensor as detailed in some other posts. Any smaller will lead to softening of the image. So shutter speed or a ND is the solution. Ron Evans

November 27th, 2011, 01:28 PM	#4
Warren Eagleton Regular Crew Join Date: Nov 2010 Location: Auckland, New Zealand. Posts: 52	Re: Controlling exposure. Thanks Jack & Ron for your helpful replys. My old camera was the HVR-A1p and I didn't have the luxury of Iris,Gain & Shutter speed numerical readings on screen. The NX70p is more informative in that respect. I understand your comment about the lens 'sweet spot' but have been more aware of that with my SLR equipment and often use aperature priority. As we go further into summer here in New Zealand I will experiment with my ND filters vs shutter speed in the auto setting. Good to know that at around F4 the lens tends to perform best, thanks again.

November 27th, 2011, 05:56 PM	#5
Dan Crowell Regular Crew Join Date: Oct 2010 Location: Brick, New Jersey Posts: 47	Re: Controlling exposure. Warren, Get yourself a variable ND filter and that will solve your problem. Just do a google search and pick one. I find the cheap ones work as well as the more expensive one. Try the cheap one first. Here's some footage I shoot one after attaching the ND filter that cost me $30 from Amazon. Arabella; a day in the life on Vimeo Nice little camera. Dan