I have recently bought X5S for my
I2 and I have to say that I am actually very pleased with how sharp the 15mm DJI lens is. Maybe I have been lucky and got a good copy but it is sharp as tack. The sweet spot seems to be between f5.6 and 8. I am a pro architectural photog and shoot my normal work with Canon 5DIV and TS-E lenses, so I know what sharp is. For this lens I use sharpening in LR 55, 0.7, 55, 5, shooting DNG. Than if I really want to make it pop even more or when printing, I apply a modest amount of USM in PS as a last thing.