Mirror Position Affects Image Aspect Ratio - EOS 70D

[rpmelvin]

I’m shooting a copy stand project of thousands of pages from an old diary. You can see examples of this work HERE.

I’m using the remote app so I can trigger the shutter with my phone. That app provides the option of shooting with the mirror up or down. I have the camera set to shoot in the 4x3 aspect ratio, because that best fits the diary pages I am shooting.

If I shoot with the mirror up, I get a 4x3 image at 2432x1824 pixels, which is exactly what I want. However, if I set the camera to shoot with the mirror down, I get an image with 2736x1824 pixels. This is not 4x3, nor is it 16x9. It's somewhere in between.

Why is this happening?

Is this something I can prevent?

[SamanthaW]

Hi!

To have a better understanding of your issue, please let everyone know the model of camera you have.

If this is a time-sensitive matter, please check out your other support options here.

Thanks!

[rpmelvin]

Sorry, I thought I had it in my profile, but I don't. It's an EOS70D.

[rs-eos]

According to the User Manual (see page 181), when you're using Live View shooting, the aspect ratio will be fixed at 3:2. I believe when you shoot with the mirror up, that will use this same ratio as Live View.

[rpmelvin · Accepted solution]

Well how about that! I missed that almost hidden statement in the manual. That certainly describes exactly what’s going on here.

Thanks, Ricky. We can consider this one solved!

[rpmelvin]

Actually, it is not solved. Upon re-reading this, I realized that my camera is bahving exactly backwards from what the book says.

If I shoot with the mirror UP (Live View on the screen) I get a properly sized 4x3 image at 2432 x 1824 pixels.

If I shoot with the mirror DOWN (view through the viewfinder) I get a 3x2 image at 2736 x 1824 pixels.

For my purposes it no longer matters because I know what to do to get consistently sized images. However, it seems strange that the camera is doing exactly opposite of what the book says it should do.