Blackmagic Forum

Hello everyone,

I have been using the camera for almost 1.5 years, many times I wonder if there is a way to shoot with low shutter speed like 1/10, 1/5 etc. In full speed(not timelapse), to get a slow shutter effect.
If not, is it too difficult for blackmagic to make this possible with a firmware update.

Hope there is a way!

Traditionally, in cinematography, shutter speeds are tied to the framerate with angles denoting how long an exposure is per frame. So with 24 fps, the slowest speed you could get is 360 degrees or 1/24 second. Any longer exposures than that and you are asking for impossibilities. Because you are asking the camera to expose the frame with light that the frame can't be exposed with because the next frame is using it.

In older videocameras, some manufacturers got around this limitation of reality and physics, by slowing the samling to a slower rate on the sensor, buffering it in camera and copying existing frames on to the tapes frames multiple times. So you slow the samplings to say, 8 fps, with a 360 shutter, for a 1/8 second exposure and record each frame to tape three times before asking for a new frame from the sensor.

In film... It's called step printing. And you can run the camera at 8 fps and get that slow shutter speed (though 360 degrees is kind of hard as you need at least some time to move the film in darkness, 180 degrees would be the standard like usual). Then you tell the processing lab to step print the resul when doing the printing to 24 fps to get the motion at the right rate so the speed is 1x instead of 3x

So. To do this with the BMPCC and resolve, you'd use the HFR mode and set it to run at the desired speed. My 6K gen 2 goes at 5 fps as the slowest speed. So I could set it to 5 fps with a 180 degree shutter that gives me 1/10 second exposures. When I play it back in the camera, it will be timelapse. At 4.8x speed when at 24 fps project playback. I kind of have to live with that until in Resolve where I can right click the footage and set it to 5 fps playback speed to get it back to 1x speed. I would probably opt out of any frame interpolations as I prefer something like this to use whole frames throughout. But I'm not you and I don't know your needs on that point.

You can go even slower by using the timelapse function in camera but you can't set the shutter rate slower than 1/5 because of hardware limits in the sensor for these cameras as I understand it. You can get a slower framerate, yes, but it does so by throwing away the incoming frames instead of increasing the exposure time. Basically reverse step printing.

TLDR?

Use HFR mode to get the framerate you want. Match that framerate in Davinci Resolve for that clip and Resolve will take care of the frame doubling needed. You cannot play back in camera slower than 23.976 fps (as far as I know with my camera) but you can fix the speed in post.

This all made a bit curious so I wanted to try slow shutter/slow framerate out myself on BMPCC and Resolve.