Render resolution lock I wonder why this hasn't been implemented yet. Cinema 4D has a lock ratio so you can change the X size and Y will resize accordingly. I know I can use the percentage but this is not accurate if you want to for instance make the render exactly 1000 pixels but maintaining the exact frame the camera already has.

Any ideas about that?
As far as I know, Blender doesn't have that feature. And settings the percentage doesn't work, because it is limited to whole numbers.

Here is a workaround using math.

Lets say the resolution is 1920 x 1080 and you want to scale the width down to 1000, then the following will keep the aspect ratio.

width  / previousWidth * newWidth = newWidth
height / previousWidth * newWidth = newHeight


The same applies the other way round.

Since the current width is already input in the resolutions X field, we can go into that field and add the number for previousWidth x newWidth. When exiting the field the value will be calculated. Repeat the same in the resolutions Y field with the same data.

This is how it looks in action.



Since pixels are whole numbers, the exact proportions can not always be retained.