Several EOS cameras offer the possibility to define a different crop ratio when you take the picture.
In-camera the EOS 5D Mark III offers the following crop ratios below. They are set in C.Fn3: Others.
- square – 6:6
- 3:2 – labelled as OFF since this is the sensor ratio
There is also an option to change the crop when shooting in Live View mode, and if the Live View mode aspect ratio is anything other than 3:2 then the crop ratio in C.Fn3 are not selectable.
The in-camera crop function is not commonly used by me or other photographers because it does not actually crop the image but puts a marker in the image file. It is this marker that can cause some troubles if you shoot RAW images.
With Canon’s Digital Photo Professional (DPP) I can un-crop a RAW or JPEG image to get the original 3:2 ratio or move the crop box within the whole image that was captured.
RAW image is cropped for ever in Photoshop
I opened a RAW image from my EOS 5D Mark III that was taken with the crop set to 6:6 – square. I found that I could not un-crop the image in Adobe Camera RAW (ACR). Particularly I wanted to move the crop box slightly to the right to give a bit more green space to the right of the rose.
The only way to recover to the full file was to process the RAW image in DPP to create a 16-bit TIFF with the crop removed then work with that in Photoshop. In ACR is possible to crop a portion of the image, or change the aspect ratio of the crop – however it is not possible to expand the crop or move the crop to one side as I was able to in DPP.
Opening a JPEG image that was taken with the camera set to crop 6:6 in Photoshop presents no such problem, the full file without it’s cropping information is always available.