GH3 Shutter Speed - 24fps and 60fps

F

Finster

Well-known member
I'm coming from the 5D. Just purchased the GH3.

If I'm shooting at 24fps, then I've always heard that my shutter speed should stay at 50. Right?

Does this mean that if I shoot at 60fps I should adjust my shutter speed to 125?
 
Just clarifying - I'd be using the 60fps for slow-mo, so then my shutter speed would be 1/125.

Interesting about 60fps "live-action" being kept at 1/60. Not sure I understand why, but I'll trust your word. ;)

Thanks.
 
That's how it's always been done. 60i or 720/60p or 1080/60p footage shot for the "live" look has a default of 1/60th. 1/120th would make it look "choppier".
 
Also, when shooting at 24fps, be careful when shooting under fluorescent lights, or any lights that are a "non-continuous" source. In the US, they run on 60Hz, so a 1/60th shutter speed is best under these light sources. 1/50th can cause flickering and banding effects under these light sources.
Under daylight and tungsten sources, 1/50th works, and some DSLR users claim 1/40th to have a more pleasing motion blur that minimizes the "judder" of DSLR image capture.
Personally, I can't perceive the difference between 1/50th and 1/40th, but some do.
 
Barry_Green said:
That's how it's always been done. 60i or 720/60p or 1080/60p footage shot for the "live" look has a default of 1/60th. 1/120th would make it look "choppier".
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So for DSLRs you're saying the 180 degree shutter rule can be ignored unless you're wanting to use the footage for slow-mo?
 
I don't agree with Barry in this case

I don't agree with Barry in this case

Barry_Green said:
That's how it's always been done. 60i or 720/60p or 1080/60p footage shot for the "live" look has a default of 1/60th. 1/120th would make it look "choppier".
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That doesn't mean that 1/60th is better than 1/120th. It just means that it has been done that way in the past. You will be hard pressed to see the difference between 1/60th and 1/120th for low motion shots. In the case of faster shots played back in real time 1/120th will render a sharper image with less blurring. You may or may not like that. However, that is what it will do. It won't appear choppy it will just be more defined. 1/250th might even work well for slow motion and 60p as long as the lighting does not cause the flicker issues.

With the GH3 you can go as high as 1/120th without noticeable flicker issues with lights in NTSC countries. The flicker reduction setting can set the shutter speed to an exact 1/120th in stills/video mode.
 
I'm saying that for any video camera, if you're trying to accomplish the "live video" look, you shoot 60p or 60i at 1/60th.

If you're trying to accomplish the "film look", you'd use the 180 degree rule.

The only reason anyone shoots 60fps in film is for slow-motion, so if you're shooting 60p for slow-mo, you'd use the 180-degree rule.

If you're shooting your footage so that it will look "live", typically used for sports, news, live events etc., then you don't want to use the 180-degree rule. The 180 degree rule is only for footage that is meant to emulate a film camera.
 
A question given the 180 degree shutter rule gives less motion blur would that be the choice for green screen work as well as you'd surely get a cleaner key?
 
P13 said:
A question given the 180 degree shutter rule gives less motion blur would that be the choice for green screen work as well as you'd surely get a cleaner key?
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Less compared to what? Do you mean for 60p intended for 60p playback? Yes the higher the shutter the less motion blur which makes it easier to pull a key. With that said however you have to be careful. The whole art of compositing is to make a scene look realistic and natural. If you shoot greenscreen at a super hig shutter speed that layer in your composition is going to look weird compared to everything else in the shot. Shooting greenscreen at a really high shutter only makes sense if A. Everything is shot/rendered that way which is going to make an odd looking movie or B. use software to simulate the motion blur back into the footage after you pull a key. There is a plugin for After Effects that can do this.

Honestly if you light your screen well and take care when shooting then motion blur should not be an issue and the blur should key out naturally with a good keyer like Keylight. The harder you have to push the matte however the more funky the motion blur will look.

So shooting at a high shutter is only a mask or fix for sloppy greenscreen work.
 
I'm just clarifying confusion as this point seems to have conflicting advice on the net. I've got good keys off an XF300 but I've never tried with a GH camera yet. I have noticed blur in even relatively slow motion, like something as subtle as a hand wave creating motion blur with a 360 degress shutter i.e. filming 50fps (I'm in PAL land) with a 50 shutter speed, so I did think if ever I tried to key footage the blur might make it a little trickier. Like you say however, there are some good keyer plugins that would cope regardless.
 
This is getting a little confusing. On my GH3 ...

... when I'm shooting 30fps, then it's best to have a shutter speed of 1/60, right?

... when I'm shooting 24fps, then it's best to have a shutter speed of 1/50, right?

... when I'm shooting 60fps, then it's best of have a shutter speed of 1/125, right (for slow-mo)?
 
If attempting to emulate the look of film, then all those are correct, with one major exception:

1) if you're shooting in NTSC territories, under magnetic fluorescent or HMI lights, or sodium-vapor or mercury vapor lights, then you should never ever use 1/50 or it'll cause scrolling waves in your footage. Use 1/40 or 1/60 instead.

Also, if shooting in PAL territories and using 30fps, you'd use 1/50 shutter. and if shooting in PAL territories using 60p/60i, you'd use 1/100.
 
P13 said:
I'm just clarifying confusion as this point seems to have conflicting advice on the net. I've got good keys off an XF300 but I've never tried with a GH camera yet. I have noticed blur in even relatively slow motion, like something as subtle as a hand wave creating motion blur with a 360 degress shutter i.e. filming 50fps (I'm in PAL land) with a 50 shutter speed, so I did think if ever I tried to key footage the blur might make it a little trickier. Like you say however, there are some good keyer plugins that would cope regardless.
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If you have a shutter of 1/60th then your frames regardless if you shoot 30p or 60p will have the same amount of motion blur. The motion blur doesn't get larger just because you add in between frames. The problem is too many people think of the relation between number of frames and shutter speed as being directly linked and related to each other and they are not. Raise the number of frames and everybody thinks the shutter should also get higher but that is just not true. The shutter determines the look of the motion. The framerate determines the temporal resolution of the motion. Somewhat similar but not really and they can be independent of each other. Just because you add in between frames doesn't mean you want to change the look of the motion. By doubling the framerate you are just adding more frames for the motion at the shutter speed to look smoother.

The other thing to take into consideration is the higher you raise the shutter the darker your image becomes. This means you have to compensate with ISO for aperture. What if we started shooting at 240fps? Would that mean using a shutter at 1/480th? That would be insanely dark for even the fastest lenses in low light situations. Even if we had a camera that could shoot 240fps you would still want to use a shutter of 1/60th to maintain that motion signature. Of course I'm talking realtime playback here and not for slow motion.

The reason why we use a different shutter with slow motion is that when you convert 60p to 30p you want that 30p to look like it was shot at 1/60th. Since you are doing a half playback speed you want to to be able to cut the shutter in half as well. 60p shot with 1/120th slowed down 50% will give you 30p that looks like it was shot at 1/60th or the normal motion signature albeit in slow motion.

Personally I like the look of 1/40th for normal motion with 24p so for me if I shoot 60p for slow motion I would want a shutter of 1/100th. When I convert the 60p to 24p that will give me the same motion signature.
 
Barry_Green said:
If attempting to emulate the look of film, then all those are correct, with one major exception:

1) if you're shooting in NTSC territories, under magnetic fluorescent or HMI lights, or sodium-vapor or mercury vapor lights, then you should never ever use 1/50 or it'll cause scrolling waves in your footage. Use 1/40 or 1/60 instead.

Also, if shooting in PAL territories and using 30fps, you'd use 1/50 shutter. and if shooting in PAL territories using 60p/60i, you'd use 1/100.
Click to expand...

Good to know. I'm NTSC. Should I not even bother with 1/50? Even when I'm outdoors or tungsten ... just play it safe and keep it at 1/60 all the time (when shooting 24fps)?

Thanks.
 
Thomas Smet said:
The problem is too many people think of the relation between number of frames and shutter speed as being directly linked and related to each other and they are not. Raise the number of frames and everybody thinks the shutter should also get higher but that is just not true.
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Not sure where you're headed with this, but -- in terms of a film camera, it is absolutely true. For any given frame rate (number of frames per second), the shutter speed is a fixed speed, and if you change the frame rate, it will indeed change the shutter speed. That's what the whole "180 degree rule" is about... and so, if trying to emulate the look of film, you indeed would want to change the shutter speed to the appropriate speed for the given frame rate.



What if we started shooting at 240fps? Would that mean using a shutter at 1/480th?
Click to expand...
If trying to emulate the look of a film camera, yes.
That would be insanely dark for even the fastest lenses in low light situations.
Click to expand...
True, but that's how film works.

Even if we had a camera that could shoot 240fps you would still want to use a shutter of 1/60th to maintain that motion signature.
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Okay, that's absolutely not correct, because it's completely impossible. You cannot have a shutter speed that's of longer duration than your frame rate. It's simply not possible.


The very slowest shutter speed you can ever have, for 240 frames per second, is 1/240. It is impossible to get 1/60th. If you did somehow set the shutter speed to 1/60th, the only way the camera could accomplish that would be through frame duplication, which would mean you really wouldn't get any more than 60 distinct frames per second.
 
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