finally manage to downgrade back mine to black 8.0 . camera much more better color and focus than cyan. and faster.  my camera always hang on cyan.

most of the the guide is in here. follow each step carefully.

http://techglen.com/2014/06/21/how-to-inst...-windows-phone/

for downloading each version firmware (amber/black/cyan) u can also try on navifirm.
but its required username and password. kindly PM me i can give u login.

personally i never try amber. but i already satisfied with black coz i know the trick to get good picture.
plus its much stable than cyan. maybe 1020 too old for new firmware (denim?)

u can ask me if u stuck on the process. 

I read, that denim wont improve N1020's camera speed

How long does your camera load takes, now?

interesting...my lumia takes 3-4 sec
standard nokia camera takes less than 2 sec
Lumia beta camera takes less than 2 sec