How to calculate light loss in higher shutter speeds?

[Joel Arvidsson]

Perhaps the language barrier made it sound like I was calling you an asshole. I was merely shocked that you lack an understanding of the basic fundamentals of photography. Rather than ask here piece by piece, I was suggesting that if you read a book, you would get a better grasp on how the basics all work together. If you don't have an understanding of shutter speed and exposure, nothing else is going to make sense.

Cheers,

Nick

Perhaps.

Cheers
Joel

 

[Jaakko Rinne]

I use both, having come from a movie background and using shutter degrees all of my life, I recently started to also think in shutter speeds. This came into play recently shooting hi-speed and needing to verify that the shutter speed was correct for the shot if I wanted it to appear with "normal motion blur" at 24fps. Basically, if 24fps is 1/48th, then 48fps is 1/96th, 120fps is 1/240th, just double the fps number and you will get the "correct" shutter speed. In degrees, this would be 24fps is 180 degrees, 48 is 90, 96 is 45 and so on. I didn't have the epic reading degrees and couldn't find the menu item to change it in the heat of the moment and so had to think in shutter speeds. It's elementary math but very necessary.

I'm probably just reading what you said wrong, but it seems like you're saying that at 48fps 1/96th shutter speed is the same as a 90 degree shutter angle at the same framerate. For normal looking motion blur the shutter angle stays at 180 no matter what the framerate.

 

[Shane Kelly]

I'm probably just reading what you said wrong, but it seems like you're saying that at 48fps 1/96th shutter speed is the same as a 90 degree shutter angle at the same framerate. For normal looking motion blur the shutter angle stays at 180 no matter what the framerate.

I should clarify that, or try to. Thats the problem with using two terms which can mean the same thing.
In film, yes, that is the case as it is an actual spinning disc. It spins faster as the framerate increases lowering the time that the film is exposed to light.On red , if you are in relative shutter speed, the effect will be similar but it's an electronic way of doing the same thing. In relative mode the camera is doing the calculation for you.
In absolute shutter mode, in order to have normal looking 180 degree motion blur, you need to make the calculation. Therefore, in absolute shutter mode 48fps should have a 1/96th shutter, 60 fps a 1/120th etc.
I've probably made this more confusing. Where's David Mullen when you need him?

 

[Jaakko Rinne]

That was enough clarification, yeah. To boil it down: When changing the frame rate in absolute mode the camera keeps the shutter speed the same while the "angle" changes. In relative mode the camera changes the shutter speed to accomodate the new fps while keeping the "angle" the same.

 

[David Mullen ASC]

There is no actual shutter angle (a pie slice opening of a spinning disc) in the Red, it's all just time, but the advantage of setting a faux shutter angle is that as you change the frame rate, the shutter time is changed to compensate in order to maintain the same shutter angle.

 

[Shane Kelly]

Here's a good article for anyone interested in the exciting world of degrees vs shutter speeds:
http://provideocoalition.com/index.php/aadams/story/rolling_shutter_and_flickering_hmis/