Shutter Speed thoughts
I might be wrong, but I have the feeling that if you film at over 180º you are breaking some golden rule (I got this impression after reading a lots of forums and watching video tutorials). 15 years ago it did't happen, I guess it comes when the borderline between video and film are becoming softer and softer.
I wonder why really do we want to shoot with 180º!!!. Ok, the book says you get the "most cinematographic" look. But, besides this, why?.
I mean... we should be adapting the shutter speed to our filming situations. Down there we are always claiming for more light, we die for fast lenses, we hate noisy high ISO. So, what's wrong with going 360º?.
Furthermore underwater everything moves much slower, you probably will get the same motion blur at 360 shooting a Manta swimming as shooting a turtle running on land.
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Shutter Speed thoughts
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One of the main issues for me and not sticking to a minimum of 180 degrees is that it's almost impossible to do any post stabilisation work - it ends up going very weird.
I actually prefer sub 180 so it's super crisp, we are filming nature, not cinematic movies - you can always add blur later. :-)
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There are two issues with shutter speed. The first is flickering lights if you shoot indoor for example. As the grid frequency is 50 Hz in Europe if you don't shoot a multiple it flickers. This is not a consideration under LED battery powered. The second is motion blur. If you shoot at 1/100 instead of 1/50 you freeze more motion and when you playback it looks more scatty. I am working in PAL 25p here. So if you shoot 1/50 PAL this is currently the smoothest footage you can produce. In low light this can become 1/25 and looks more blurry. Cinematic is actually not smooth and is obtained shooting 24p at speed of 1/50. There is a little difference between frame rate and shutter that creates a subtle scatty feeling which is your cinema effect. At 1/60 for NTSC this is stronger. The reason not to break the 180 degree with non multiple example 1/60 or 1/80 for 25p if that TV broadcasts are interlaced if you don't follow the rule it looks a utter mess. If you watch clips on a computer you can follow any combination you want as long as you are happy with the motion blur
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One of the main issues for me and not sticking to a minimum of 180 degrees is that it's almost impossible to do any post stabilisation work - it ends up going very weird.
I actually prefer sub 180 so it's super crisp, we are filming nature, not cinematic movies - you can always add blur later. :-)
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Right. We are not looking for cinematic movies, That's why I think the priority is image quality itself... if low light, we double its amount by going from 50 to 25 fps (PAL system).
I've never had stabilization issues in post. As I said, the motion blur created with UW movement is not very noticeable... I guess it is not for our eyes neither for computer software (I guess defined edges are better than blured ones in motion detect process).... but I'd have to do some test about it.
There are two issues with shutter speed. The first is flickering lights if you shoot indoor for example. As the grid frequency is 50 Hz in Europe if you don't shoot a multiple it flickers. This is not a consideration under LED battery powered. The second is motion blur. If you shoot at 1/100 instead of 1/50 you freeze more motion and when you playback it looks more scatty. I am working in PAL 25p here. So if you shoot 1/50 PAL this is currently the smoothest footage you can produce. In low light this can become 1/25 and looks more blurry. Cinematic is actually not smooth and is obtained shooting 24p at speed of 1/50. There is a little difference between frame rate and shutter that creates a subtle scatty feeling which is your cinema effect. At 1/60 for NTSC this is stronger. The reason not to break the 180 degree with non multiple example 1/60 or 1/80 for 25p if that TV broadcasts are interlaced if you don't follow the rule it looks a utter mess. If you watch clips on a computer you can follow any combination you want as long as you are happy with the motion blur
Hmm. A lot of stuff we are mixing here.... I've shooted many times at 1/25 with old PAL interlaced camcorders when needed (low natural light conditions, no moving objets) and also HDV 1080i downscaled to PAL for broadcasting and didn't notice any problems with the image apart form subsequent motion blur.
Now I realise that I have some 4K/25fps footage at 1/25 progressive that will be downscaled to 1080i to be broadcasted and haven't check the image on a TV output yet. I'll and I'll see if I see something wrong... hope not!!!!!!!!
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1/25 has more motion blur and if used under artificial light has issues but with ambient light just looks a bit soft. No major issue
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There's really no golden rule, only suggestions/acknowledgements around the effect that different choices will bring.
180 degree shutter angle, i.e the shutter is open for half the duration of the frame, when shooting in the 24-30p range is acknowledged as providing a generally smooth and pleasing look. There will be a certain amount of motion blur that allows each frame to blend into the next.
As you increase the shutter angle towards 360 degrees, you increase the amount of motion blur, depending on how fast moving the subjects are, this can becoming visible and cause a ghost like streaking.
If you reduce the shutter speed to below 180 degrees you'll get an increasing amount of "shutter effect" where the image starts to look staccato on playback. Again, how apparent this is depends entirely on how fast the subjects are moving.
Have a look at the following time-lapse, it will give you an idea of this in practice. The shutter speed used slowly increases from a very fast 1/800th second to a long 5 second exposure, as a result playback starts of very stop motion, gets gradually smoother and then eventually becomes streaky and blurred.
What to use? Well, as above it depends entirely on the look you want to achieve, and what you're filming. It's not unusual for a director to ask me to crank up to 1/400th and faster in the sort of stuff we often find ourselves pointing a camera at.... although in general, and most certainly when underwater (and ignoring slow mo/high frame rate filming), I'll be stuck on the 180 degree rule, using other methods i.e. iris and ND filter, to control exposure. Basically it maximises the amount of light in whilst maintaining a normal look.
Where's it come from? It's actually a throw back to proper filming days and the use of rotary shutters, when the shutter was a disk that spun over the top of the film as the film was pulled through. A portion of the disc would be open, this would determine how much light was allowed to hit the film.
https://en.wikipedia.org/wiki/Rotary_disc_shutter
The shutter angle was physically defined by the cut in the disk, a 180 degree angle would have a disc where 180 degrees of the circle, i.e half, was cut open and the remainder was left closed.
Translating that to modern cameras, 180 degrees would equate to a shutter speed equal to half the frame rate, so:
PAL, 25P = 1/50th secondNTSC, 30P = 1/60th second
Weird old land of cinema, 23.98P = 1/47.96th second
Example HFR, 800 frames per second = 1/1600th second
And so on.
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Thanks Stuart, that's a very good explanation, and much appreciated.
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(...) I'll be stuck on the 180 degree rule, using other methods i.e. iris and ND filter, to control exposure. Basically it maximises the amount of light in whilst maintaining a normal look.(...)Yes!, That was exactly what I was talking about... Why should we stuck to 180º as a general rule bearing in mind our light problems shooting underwater. I'm sure below -20 you will never use ND filters at all and you will feel happy if you chose a fast lens to open as much as you can.
Why should we consider 180º our way to achieve a "normal" look since things down there behave in different ways?
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What I've found (where I am) is that suspension in the water is always blurred on every frame if I run 25fps and 1/25 Shutter Speed. (360' degree) - and it really confuses FCPX when I try and stabilise footage.
Fish and the like are actually fast movers (plus our floaty movement in water - if not locked down) - if you look at your footage frame by frame, you'll see most frames aren't sharp (or that elements are always blurry) - I find my underwater footage really needs some post work (no doubt as I'm rubbish) - and running a at 1/100 shutter speed helps.
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Yes!, That was exactly what I was talking about... Why should we stuck to 180º as a general rule bearing in mind our light problems shooting underwater. I'm sure below -20 you will never use ND filters at all and you will feel happy if you chose a fast lens to open as much as you can.
Why should we consider 180º our way to achieve a "normal" look since things down there behave in different ways?"Normal" means image playback on a screen will look the same to us as it would if we were sat there underwater with the scene in front of us, ie our eyes are seeing things in a way that our brain expects. It doesn't matter whether you're looking at an underwater scene, your kids playing in the park or a mountain vista with clouds scatting across the sky, your brain still processes that image in the same way. The more you deviate away from 180 degrees, the more the image will have the potential to look odd to your brain, you will add either a smeary effect or a staccato effect, depending on which way you push the shutter... which is why I tend to be stuck to 180 underwater, because I tend to be filming natural environments and behaviour, I don't want to add an effect to the look.
As for trying to gain that extra bit of light by increasing the shutter, I think you need to put that into perspective. If your shooting for PAL land, you'll be running at 25p, so at 180 degree you're shutter is going to be 1/50th. By definition, the maximum you can increase that to is a 360 degree shutter, i.e 1/25th second, which is an increase of just one stop... if you're struggling for light that much, then you're already in trouble. Get some video lights, and/or shoot that scene when conditions are more favourable....
But, with all of that said, 180 degree shutter is no different from all the other rules in photography, they're there to guide you, give you the benefit of the wealth of experience that's out there, give you an idea of what you may expect if you abide by them or ignore them. But at the end of they day, it's your choice, you're the creative that's pointing the camera, play around and see what works for you, see what parameters you are personally happy to work with. That way, if you are ever faced with a low light scene that you know you're unlikely get another chance, and you need to get some more light from somewhere, you'll know whether to flick the gain on or open up the shutter. -
This explanation of "normal" look pointing the similarities between human vision and 180º shutter speed is based on some percepcion theories (as some gestalt stuff) or is based on scientifically proven facts?
This is not a rhetoric question. I really would like to know because I've never heard of conclusive conclusions of many "subjective" properties of human vision since it is really a complicated combination of optical a mental processes really hard to compare with our recreation of movement with our cameras.
English is not my mother tongue, but I think I sound quite pedantic here ... -
This explanation of "normal" look pointing the similarities between human vision and 180º shutter speed is based on some percepcion theories (as some gestalt stuff) or is based on scientifically proven facts?
This is not a rhetoric question. I really would like to know because I've never heard of conclusive conclusions of many "subjective" properties of human vision since it is really a complicated combination of optical a mental processes really hard to compare with our recreation of movement with our cameras.
English is not my mother tongue, but I think I sound quite pedantic here ...
I'm not entirely sure what better way of proving something than with your own eyes
, neither am I sure that I can explain it any better or clearer than I already have... but one last go, just for you 
- 360 degree shutter angle causes smearing on playback, it can be highly visible depending on the subject.
- Moving towards 0 degrees shutter angle causes staccato on playback, again it can be highly visible depending on the subject.
- 180 degrees sits in that middle ground, enough motion blur to blend two frames together and maintain the impression of movement without causing smearing and/or lose detail and definition in the the subject
If you've taken the time to have a look at the time lapse video I linked to in my first post, then you would have seen these extremes with your own eyes....
Over to you. You have a visible example where you will clearly see the extremes, and you have multiple explanations. Trying to argue that it doesn't exist or isn't correct is quite simply a waste of time, it does, unquestionably... if you can't see it then you're not looking hard enough. Just decide whether you care, whether it would be visible in what you shoot, and if so whether it would detract from the quality of the end piece.
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I totally agree with you. I never tried to deny the obvious effects of different shutter speeds. I just try to reframe the apparent need for setting up something as "the normal thing". I think don't waste time when arguing... I learn a lot. I do so with the purpose of being convinced rather than be convincing. Thanks
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I totally agree with you. I never tried to deny the obvious effects of different shutter speeds. I just try to reframe the apparent need for setting up something as "the normal thing". I think don't waste time when arguing... I learn a lot. I do so with the purpose of being convinced rather than be convincing. Thanks
"I do so with the purpose of being convinced rather than be convincing"
For somebody who doesn't speak English as a first language, you have a wonderful way with words. I may borrow the above on occasion, if you don't mind!
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"I do so with the purpose of being convinced rather than be convincing"
For somebody who doesn't speak English as a first language, you have a wonderful way with words. I may borrow the above on occasion, if you don't mind!
I would be really proud!!!!
I wish my sophomore english teacher could see this...
