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Header image for article ALEXA Frame Rate Safety Guide

ALEXA Frame Rate Safety Guide

One of the most often misunderstood aspects of the ALEXA menu structure pertains to the camera's frame rate options. There are four separate places to set a frame rate and they all do something very different. Here I'll walk you through each one of them and give you tips on how to make sure you end up with the correct frame rate for your shoot.

Project Frame Rate: This can be found by navigating to MENU > PROJECT > Project frame rate. Your options are 23.976, 24, 25, 29.97, and 30 and they all represent playback rates. This should be set to your final deliverable's frame rate. If your show is being broadcast n the States, it might be set to 29.97fps or 23.976 (to emulate a film look). If your show is going to be shown projected on film, you'll want 24fps, and so on.

Sensor Frame Rate: This can be found by going through the Home Screen on the side of the camera and pressing the FPS Menu button on the top left. Here you'll see the available Sensor fps list, with an option to create your own ranging from .750fps to 60.000fps. Think of this as your variable frame rate option. If your project is set to 24fps and your sensor is set to 24fps, then what you see is what you get and you'll be able to record audio. However, if you wanted to shoot 60fps over 24fps for an over-cranked slow motion effect, you would keep your project at 24fps, but set your sensor for 60fps. At this point, your audio will be disabled.

Rec Out Frame Rate: This can be found by navigating to MENU > RECORDING > REC OUT> Frame rate. Your options are 23.976, 24, 25, 29.97, 30, 48, 50, 59.94, and 60 and they all represent output signals to send to an external recording device. The only way to access frame rates of 48 or higher is by changing your HD-SDI Format to 422 1.5G Dual Link or 422 3G Single Link. You also have the option of using the REC OUT frame rate to set your sensor frame rate. Scroll down to "REC OUT fps sets sensor fps" in the REC OUT menu and turn the option on. This is a good option to have turned on if you're recording both to an external device and the SxS cards, to make sure both recordings have the same frame rate.

Monitor Out Frame Rate: This can be found by navigating to MENU > MONITORING > MON OUT> Frame rate. Your options are 23.976, 24, 25, 29.97, 30, 48, 50, 59.94, and 60 and they all represent output signals to send to a monitor.

An easy way to see where all your frame rates are set is by hitting the INFO button and choosing FPS INFO. You'll see a list of all the places you can set a frame rate and what they're currently set to. It's really important to do this before shooting begins for the day. If you have ended up shooting the wrong frame rate, you can use Apple's Cinema Tools conform function to change the frame rate to the appropriate one.

Juliet McNally
Camera Tech Specialist, AbelCine LA

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