Low light problem

[Carla Schroeder]

Hi all,

Recently got the DVX 100a as an upgrade for our temple camera. We're a Buddhist temple, and record live teachings both audio and video. Our goal is eventually to edit them for distribution on DVD.

The situation does not allow for much equipment however, as the environment must critically remain teaching focused, the camera allowed only so long as it does not distract. As a result, I've had great difficulty with the lighting. Two situations:

1. During the day, large windows allow large amounts of light in, creating a backlight situation. I've viewed tape recorded in this situation, and although some shots are so overexposed in the backround I can't use them, this is the less troublesome of the two problems.

2. Teachings which occur at night are even worse. The lighting in the room is insufficient it appears. The result is a dark image, with a very golden brown tone. I tried turning the gain up to M, having been cautioned to avoid a high gain setting for fear of creating too much noise.

I'm new to this whole process, but am sincerely interested in learning to create high quality output. I was wondering if anyone had any suggestions as to other settings I could tweak to enhance the low light performance.

Thanks!
Sonam (Carla)

[John Hudson]

Can you start by supplying a few grabs of the location and your results?

[Carla Schroeder]

Here's a link to two shots which I think embody the issues I refer to.

http://www.dvinfo.net/media/carlas/

Thanks to Chris for hosting the images.

Sonam

[John Hudson]

Are you shooting 24p or 60i?

What is your shutter speed set to and are you under manual or auto conditions?

Do you have the IRIS set to Default (-) Underexpose?

The reality just might be that you need more light.

[Carla Schroeder]

I was shooting 60i (I heard it's better in low light...is this true?). I adjusted my iris setting to (0), no underexposure (it was turning out underexposed anyway.

It is possibly I need more light. I am working on that (but it is a more complicated process than changing settings). Have to get permission to place lights, and find a place where they won't be in the way, or hang lights that remain in place.

I was just wondering if there was more I could do with the camera. If not, that's a starting point.

How about increasing gain? I did go to the 6db gain setting, but noticed it can go as high as 12. I've read that high a gain setting can lead to a lot of noise.

Thanks for your attention and reply!
Sonam

[John Hudson]

Shooting 60i will be better for low light and using 'O' (Zero) for IRIS compensation is reccomended for this purpose (I use -3 for 24p).

I do not reccomend raising the GAIN as it can bring unwanted noise into your picture; but that is up to you and the end product goal.

[Barry Green]

John's 100% right. 60i gives you about a full stop more light sensitivity, and using zero for iris will avoid the underexposure that you usually want when using cinegamma.

Gain does increase brightness, but it also increases noise. You can actually go to +18db of gain, but you have to assign 18db to one of the user buttons in order to get access to that feature. I don't recommend 18db unless it's the only way to get the shot.

Another way to get more low-light response is to use a slower shutter speed. With the original DVX100 that's not possible in 60i, but with the DVX100A you can choose 1/15 or 1/30 shutter speeds. 1/30 will give you twice as much light on your subject, but will affect motion rendition -- you'll have to try it to see if you like it. 1/15 will give you four times as much light, but the motion will be very blurry/streaky.

[Matt Rickman]

probably too late for this, but I think a Sony PD170 would be a better choice of camera for your situation.

matt rickman

[Carla Schroeder]

Thanks for all the great replies! This support is awesome.

I've already gone with 60i and 0 iris settings. I think working with shutter speed will work, since for the most part, shots do not involve much panning or motion. In fact, I think that might be the temporary solution to the issue, I'll try it tomorrow night (Wednesday is the next evening teaching).

Just to be clear, when shooting at 1/30, it still records to tape in a manner that directly imports to Adobe Premier (I know Premier has a 24p setting). Maybe this needs to be posted elsewhere, but just wondering how it will affect how I work with the footage later (if it has any).

Regarding the camera, I think maybe the PD170 would have been better, but my goal is to also create some shorts for our website (interviews, chornicals of our projects) all of which will allow for much better control over light, and which I thought the ability to adjust the various settings to achieve different "looks" with the DVX100A made it worth the trade offs. At this point I am committed.

Thanks again for all the support!
Sonam

[Barry Green]

Shooting at 1/30 won't change anything about how the footage is recorded; it'll still be recorded as 60i, directly importable and editable by Premiere or any other NLE.

[Carla Schroeder]

Then it sounds like the solution! I'm glad I tried this forum out. : )

I'll post Thursday or Friday after I've had a chance to try this out and view the result.

Thanks!
Sonam

[Barry Green]

Don't know if I said this before, but it should be clarified: shooting 1/30 on interlaced material will result in a loss of vertical resolution. On progressive-scan the camera can still record the full frame, but when shooting interlaced, if you shoot with a shutter speed slower than the field capture rate, it'll result in lower vertical resolution.

So definitely try it out and see if you like the results before committing to it!

[John Hudson]

Thanks for that Barry; I had no idea about 60i and a slower shutter speed. Of course now it makes sense now that you just said it.