Do you know that Spark camera switches to low res pictures mode 1440 x 1080 pixels when launched from the palm of your hand. This is a nasty little "feature". When operating Spark with your smartphone as controller you need to take off using on-screen button for photos to be retain 3968 x 2976 pixels size
Are you looking at photos through the DJI Go 4 app or on the SD card? I know the new version 1.2 of the manual says that photos taken in ActiveTrack are 1440x1080, but for what ever reason I am getting full 3968x2976 resolution even when launching from my palm (but I do have the RC connected, I haven't been brace enough to launch without the RC connected yet).