Canon MARK IV User Manual (en)

You can crop the image and print only 
the trimmed portion as if the image was 
recomposed. Do the trimming right 
before printing. 
If you set the trimming 
and then set the print settings, you may 
have to set the trimming again.
 On the print setting screen, select [Trimming].
 Set the trimming frame size, position, and aspect ratio.
The image area within the trimming frame will be printed. The 
trimming frame’s aspect ratio can be changed with [Paper settings].
Changing the trimming frame size
When you press the <u> or <y> button, the size of the trimming 
frame will change. The smaller the trimming frame, the larger the 
image magnification will be for printing.
Moving the trimming frame
Use <9> to move the frame over the image vertically or horizontally. 
Move the trimming frame until it covers the desired image area.
Rotating the frame
Each time you press the <B> button, the trimming frame will 
toggle between the vertical and horizontal orientations. This enables 
you to create a vertical-oriented print from a horizontal image.
Image tilt correction
By turning the <5> dial, you can adjust the image tilt angle up to 
±10 degrees in 0.5-degree increments. When you adjust the 
image tilt, the <
> icon on the screen will turn blue.
 Press <0> to exit the trimming.
The print setting screen will reappear.
You can check the trimmed image area on the upper left of the 
print setting screen.
Trimming the Image
Tilt correction