The tractor isn’t the source of the vegetables, the way the sensor or film is the source of the image. The photo is a representation of the dog, not the dog itself. You could take a photo of an organically sourced vegetable. The veggie would be organically sourced, while the photo is not.
By that logic, farmers couldn’t use tractors to harvest their organically sourced veggies.
The tractor isn’t the source of the vegetables, the way the sensor or film is the source of the image. The photo is a representation of the dog, not the dog itself. You could take a photo of an organically sourced vegetable. The veggie would be organically sourced, while the photo is not.