framerate adjustment and no lightloss

[Vincent Visser]

When you double the framerate in the varispeed menu, you’re expecting to make a one stop light compensation on the lens, but somehow the exposure is still the same. I only noticed this when I went from 25FPS to 50FPS. Can someone explain me what the camera does when you’re just changing the framerate?

Thanks

 

[Vinit Borrison]

I personally find the best thing to do is to double the shutter speed to your frame rate 24fps = 1/48 shutter. 48fps = 1/96 shutter. This is where you will start to see the light loss occur and will have to make the one stop light compensation.

 

[Stuart English]

Shutter speed in varispeed

Shutter speed in varispeed

As an electronic shutter camera the RED ONE doesn't have to follow the same rules as a mechanical shuttered camera.

So as its default, it maintains the requested shutter speed as you adjust frame rate in varispeed.


If you want to operate as a mechanical shutter camera would, set the SHUTTER MODE to RELATIVE.

Then as frame rate increases, shutter speed will increase in the same proportion too, and vice verse...

 

[James T Mather]

Yes you are opening up the timeframe that an electronic shutter allows to pull more light in but at the expense of motion (which will become more "video" - yuk : for an example see some shots in Apocalypto) - make sure you are on relative and 180 degrees for the most film like rendition.

 

[Vincent Visser]

Ah, thanks for the RELATIVE mode tip. It let me reread the manual to make things more clear for myself. Just to recapitulate and correct me when I am wrong: When you enable the RELATIVE mode in the SHUTTER menu the camera will automatic correct the shutterspeed like a mechanical shutter camera with a fixed shutter angle.

When I now adjust the framerate from 25FPS to 50FPS the camera will automatic change the shutterspeed from 1/50th sec to 1/100th sec based on a 180 degree shutter.

Do I also need to adjust the SHUTTER info into DEGREES to make it all work? Or does the camera look at the TIME BASE setting to define what the angle is?

Thanks

 

[James T Mather]

The camera will give you a readout in degrees (ie: 180) and automatically do the maths to maintain the shutter duration consistent with that. In short - you don't have to worry about it - it works like a film camera. (make sure the shutter readout is yellow (or white) and NOT red as this is a warning that the shutter angle is incompatible with the camera fps.

 

[David Mullen ASC]

Basically exposure time / shutter speed determines exposure. Frame rate only affects exposure because it can affect the shutter speed.

 

[Dominic Jones]

Vincent:

Yes, with shutter set to relative, the exposure time will vary with framerate exactly as a film camera does. You do not need to set the readout to degrees, but it makes more sense to work in degrees with a relative shutter, and ACs will be less likely to get confused, in my experience.

Also, no need to worry about incompatible exposure times with relative shutter settings, as the shutter speed is calculated as a percentage of the framerate (of course) and not an absolute fraction of a second which may or may not be possible for the selected framerate (e.g. asking the camera to expose a frame for 1/48th sec when shooting at 100fps!). When operating in "normal" mode, James is absolutely right to watch out for a red FPS indication...

HTH,
Dom.

 

[David Rasberry]

So how do you set shutter to maintain the same exposure while ramping framerates during a shot?

 

[Dominic Jones]

Set the shutter to ¨normal¨ mode and ensure that the exposure time does not exceed the maximum possible exposure time for your highest framerate - i.e. 1/<max framerate> seconds...

Cheers,
Dom.

 

[rotten]

so I just have to set an appropriate shutter speed?
can you make me a partical example?
there is any quality loss in to do that?

 

[Stuart English]

Shutter setting in ramp

Shutter setting in ramp

so I just have to set an appropriate shutter speed?
can you make me a partical example?
there is any quality loss in to do that?

O.K say that you are ramping from X fps to Y fps where Y is the faster fps

Just set the shutter to NORMAL, and set SPEED to 1 / 2Y sec.


e.g for ramp 1 - 50 fps set shutter to NORMAL, SPEED 1/100 sec

This will give you a constant exposure throughout the ramp of 1/100 sec.

You could use any Shutter Speed setting down to 1/50 sec in this case ...

... but 1/40 sec would not be valid and the UI will show that speed in red text if you try.

 

[rotten]

thank you very much

 

[rotten]

if I change time base for example at 60fps (3K), than can I use varispeed to shoot at 25 fps?