You can actually change the default back to locked state. If you complete the crop in the unlocked state, lightroom will default future crops to the unlocked state. To fix this, enter develop mode on a photo, press "r" to enter crop edit mode, then press "a" to toggle from unlocked to locked aspect ratio, then "r" again. This should default lightroom back to the locked state. The trick to avoid this is when you crop a photo to a non-standard ratio, make sure you relock the aspect ratio before completing the crop. This way you can use a non-standard aspect ratio for your photo without setting the unlocked crop as the default.
↧