Grass is hard. I’ve done it and it’s a retouching nightmare. You need a lot more images than you think and the least movement is apparent and will wreck your stack. At f/3.2 the need for many more images for the stack is greater than at double or triple that because the DOF becomes impossibly thin. You also have to take into consideration the distance the lens is traveling between focus points. If I were to try this I’d probably do a few things
-
get a dedicated stacker - Photoshop is not the best tool for this
-
take a lot more images - 20, 30, 40 - whatever you need to get the main areas of grass in focus. It’s far better to have more than you need than not enough.
-
up my aperture a bit - depending on how the background looks. With raindrops in the bg it can work depending on how the aperture blades in your lens render bokeh balls
-
do multiple stacks starting and ending with different focus areas
-
retouch like crazy and probably slabbing will help for not only the stacks, but more importantly the retouching. Zerene does slabbing internally and automatically and for anything over 20 shots in a stack I use it. Slabbing is basically making substacks and then stacking those instead of trying to do dozens and dozens at once and having to sort through a ton of source images for retouching.
-
oh and I’d also do a combination of DMap and PMax for maximum detail and smoothness of color and background.
Stacking is a crazy, but really wonderful technique that takes a LOT of practice. Here are links to a couple of discussions that might help -