Hi

I have got P3A with firmware 1.4.0010. Can I go back to 1.1.9?
Or is the 1.3.20 only choice?

I found out, the picture quality went bad after 1.4.0010. Before that the pictures and videos was very good. Now they are kind out of focus...

You can only downgrade to the previous one, which is v1.3.20 in your case, the method is copy the 1.3.20 BIN file into the aircraft and turn on the aircraft to downgrade, it's the same as upgrade. About the focus, the new firmware will not affect it, what is the temperature of your environment, please try to let the camera work at the temperature of 0-40 degrees.

Firmware 1.4.0010 bring support for 2.7K video, so it affect the camera, for sure. I know the focus is fixed on P3A camera, but the software have a big role for the final result.
Here is a interesting topic: http://www.phantompilots.com/thr ... mware-update.61668/

Here you can find two sample. Before 1.4.0010 and after.
https://drive.google.com/folderv ... ZUU&usp=sharing