Slow shutter vs. gain

[Pietro Jona]

hi all

in a previous post I've been told that slow shutter speed cause a loss of picture quality, I still don't understand why. Anyway what would you prefer when shooting in low light conditions (with nobody/nothing moving in the frame): slow shutter or gain?
I post this question in this branch because I guess that every camera has a different quality of gain and I'm interested in nowing what people think specifically about the xm2...
(I think I prefer slow shutter, don't like the noisy blacks that gain gives)
thanks
pietro

[Ken Tanaka]

Pietro,
I would be inclined to follow this order of adjustment.

1. Shutter at 1/30 (or, in your case, 1/25 for PAL)

If image still not good:
2. Gain-up 1 step, view result for acceptability,

If image still not good:
3. Gain-up 1 more step, view for acceptability

If image still not good:
4. Shutter down 1-step, restore gain to 0 and repeat steps 2 and 3.

In summary, I'm more inclined to adjust the gain than lower the shutter speed below its native floor. While gain brings grain, low shutter speeds can bring far more distracting results.

Of course I would much prefer to add lighting, but that's not always possible.

[Rob Lohman]

I agree with Ken, but if actually NOTHING is moving as you
indicate then I'd probably go with a lower shutter speed first
since it should not add too much trouble if nothing moves at all.

[Pietro Jona]

ken, Rob,

Actually I was thinking about a situation like this: the camera on a tripod (or anything else), nobody and nothing moving, ten or fifteen seconds shoot. Many times when traveling I found myself in beautiful places, the light was beautiful but not enough.
I don't mind having large black areas in my pictures but -how to say- black has to be real black!
I have to thank you because you are the ones who always give an answer to my questions...

[Rob Lohman]

I'd say slow shutter speed would be ideal there. Keep in mind
that if it is outdoor something might be moving slowly (like leaves
on a tree) which will then look a bit out of focus. But otherwise
that should work fine for you.

Easy to try it out too. Set the camera up in your room and dim
the lights and expirement that way!

[Ken Tanaka]

If nothing is moving, why not simply take still photos?

[Pietro Jona]

Well, may be 'outdoor something might be moving slowly' as Rob said, like the smoke out of a chimney, people or a horse far away in the filelds , I don't know. 1/25 is one stop better (in a low light situation) than 1/50 and I hope that if anything is moving slowly enough it will not bother. Besides this I thought I could still have an audio ambience recorded, longer than the one of a still.
By the way, what about the audio?!

[Ken Tanaka]

Shutter speed is completely unrelated to audio. (Remember, "shutter speed" is not the same as "frame rate".)

[Cosmin Rotaru]

In 1/25 I see no diference compare to 1/50 in normal condition (I didn't try taping a running person that way) If the persons in the frame are not moving - maybe they just speak - and I can get a preaty stable position, I go another step down before using the gain. It looks good and is very helpfull for a codec (many times I'll have the video also on DivX or mpeg2) if there's no grain in the image. Actualy, I prefere to go a litle underexposed than to have grain in the image.

[Rob Lohman]

1/25 shouldn't be an issue to use, especially if nothing is (almost)
moving. Only (fast) motion will look different. I thought we were
talking lower than 1/25 speed.

[Noel Garner]

I'm new to video and still experimenting with the XM2. I was shooting a blues band in a small pub last night. A good learning experience. Like it helps not to plug your headphones into the mic socket if you want to monitor sound and adjust manual levels! Anyway light was so poor I had to use max aperture and max gain on manual and a choice of either 1/12th sec shutter or 1/25 and under-expose. My conclusion was that 1/12th and good exposure was much better than under-exposure and less blurring. It helped that the band was not the leaping-about variety. Grain is not such a bad deal when its an atmospheric kind of event. I was able to get up real close to the band - I know them so it helps, nonetheless in an informal venue like this it seems you can get away with anything if you're wielding what looks like a "proper" camera. Being really close made the most of the built in mike which I thought performed really well.

[John Lee]

I always try to avoid boosting the gain to 18db unless it is absolutely necessary. Even when the picture is underexposed at 12db, you can still tweak it a little bit in post. But there is only so much you can do. I agree that you should definitely adjust shutter speed first. But it also depends on where you'll be using the camera.

[Evan Kubota]

I try not to use above +12dB of gain. Normally, I leave it at 0 or +6. It's really not that bad to drop the shutter speed below 1/30 if you are doing static shots. Even if there is slow movement, the blur looks kind of cool.

[Patrick MCMurray]

Ken,
what distracting results were you referring to in the begining of the thread?Is it the look of a lower frame rate?< is that even distracting if nothings moving?> if so, could that be solved <only in the case of nothing moving> by shooting at 1/15 or 1/12 for twice the time and doubling speed in post? most of what i know about slow shutter speeds relates to still photos.

[Ken Tanaka]

Hello Patrick,
By "distracting results" I was referring to the ghostly stutter produced by low shutter speeds. In some respects, yes, there is similarity to low frame rates.