"Thanks for the responses. Lots of great advice.
The reason I ask is for my next thought.
Could you have a "Live" feed from the camera processing the image in realtime into NDVI image. 
Could you connect the camera upto the processing software on the…"

"Don't want to be the negative one but realistically, drones wouldn't be the best for treatment of the blackgrass problem.
The amount and manner that herbicides are applied to the blackgrass means that the blanket spraying of fields is not easy,…"

"Just wondering what your all spraying and what your setups are like?
From a practical approach the misters you use or suggest are almost certainly useless. They produce a fine spray and mist, which is completely inneffective for crop spraying.
The…"

"Agree with your response. 

Those that don't get a drone at this stage, will sometime in the future, be exposed to one if there agronomist or consultants have invested in one.
Blackgrass is an extremely invasive and prolific weed. It is quickly…"

"Its a good suggestion.
Bit over-specced for what i'm planning.
Don't need to carry huge weight so don't need bigger motors burning more power.
Just need capable, efficient airframe for few cameras. "

"I think it depends on 2 things;

the nature of the farm or agricultural business (value of crops, scale of landholding).
Attitude of the farmer. 

From experience within agriculture No.2 is the deciding factor. If they're interested in the…"

"Will probably not be a 3DR solo.
Nothing against that particular drone but want a more custom setup built to specifically match what i'm going to be doing with the drone."