In what aspect ratio shoud one record with a DSLR?

Question

This Question is not about what aspect ratio should be chosen for the final film, it's rather about how to get the biggest "resolution" capable of the cammera.

When you take a photo with a Modern camera "usually" it's 4/3, I know you can change the aspect ratio, but that's not my point. I assume, that the sensors of DSLR cameras are the same ratio, because they are created for the purpose of creating photos, aren't they?

I guess focal lenght can be taken in account as well.

Now when you shoot Video in 16:9, I assume, that the image is "croped", because you can't change the size and ratio of your sensor.

So the only way, to have that aspect ratio, is to leave it blank or record on the top/bottom of the image (or both) a black bar.

Wouldn't it be smarter, to record with the fullsensor, to get "more" of the image"?

This might sound redicolous, because you'd have a bigge file size and have to put black bars over it in post. But like this you'd have some extra "room", for example someone dips the Microphone or the boom in the picture, you could just crop the clip a bit further down and still be able to use it.

More footage = better to edit, right?

Because you still have the same width of the sensor that you use, you just use all of the avaivable height as well.

Now here is my question: What aspect ratio, should you put your cammera into, to get the highest resolution.

Answer 1

When you take a photo with a Modern camera "usually" it's 4/3, I know you can change the aspect ratio, but that's not my point. I assume, that the sensors of DSLR cameras are the same ratio, because they are created for the purpose of creating photos, aren't they?

Actually, no. Only low-end digital cameras (mostly point-and-shoot) use a 4/3 aspect ratio, because they were designed to match the aspect ratio of computer displays (which used to be 4/3). DSLRs use the traditional 3/2 aspect ratio of 35mm film. So if you set your DSLR to 4/3 (for photos), a part of the sides gets cropped.

Wouldn't it be smarter, to record with the fullsensor, to get "more" of the image"?

Most DSLRs don't use their 'full' resolution for video because of technical limitations (mostly memory buffer, but also memory card transfer speed). For example: My Canon EOS 80D has a maximum resolution of 6000x4000 pixels for photos. However, the highest video resolution it can record in is 1920x1080p @ 50fps (IPB). IPB means every frame is recorded as a full frame, no interframe compression is applied. Recording 25 or even 50 frames per second at a resolution of 6000x4000 pixels would result in an absurdly high data rate that DLSRs simply aren't built to process and transfer.

What aspect ratio, should you put your cammera into, to get the highest resolution.

Depends on your camera. Either the camera menu or manual will specify the available resolutions for each aspect ratio, possibly it's a seperate setting as well. This way you can tell what combination gives you the highest resolution. If you can't find the resolution specified in the menu or the manual, take a test recording with every setting the camera has, copy the files to your computer and check each file's resolution with MediaInfo or a similar program.

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Note that apart from the resolution, the bitrate will have a much higher impact on your video quality than some pixels more or less. Make sure to get a fast SD card with a lot of space so you can always record at the highest bitrate (and I-frames only if that's an option with your camera). Also, it's good practice to film in the resolution that you want your final video to be in for more reasons than video quality. So if you're creating a video that is intended to be viewed on normal video screens, film in 16/9 from the start.