I'm not planning on using the distance scale on the lens but rather if I know I need to focus at something 20m away to get everything from 5m to 40m in focus, I want to use a range finder to locate something that far away, be it a tree, stone, etc.
On the other hand if the camera could tell the distance, that would be perfect.
Here is a
current thread where this is being discussed:
First, don't let diffraction bugger you totally. Yes, diffraction onset happens earlier in high density (smaller pixel size) cameras, but DOF sharpness is usually a better trade than trying to limit diffraction blur. Obviously if you can shoot an image at f/8, then shooting it at f/16 is a waste. But if you need f/16 for DOF, then you are usually better shooting at f/16 and accepting the diffraction losses.
Using a rangefinder, you need something that can accurately measure the near point of focus, the far point of focus and point at which the lens needs to be focused to get the near and far points withing your limits of acceptable sharpness (Which is going to depend on your own definition as determined by the Circle of Confusion you specify for any DOF calculations). Hunting/Sports rangefinders typically will not measure short enough. They tend to be limited to no nearer than 5 or 6 Meters! I did find a
Leica DISTO D2 short range one with a range from 0.05m to 60m.
This is Nikon related, but ever since the AF-D series of lenses, the lens reports to the camera the distance at which it is focused. Unfortunately, the camera does not impart that information to the user! It was originally used for Flash exposure. If Camera companies weren't so stupid, the camera would provide the hyperfocal distance (it knows focal length and aperture) and the current near and far DOF points based on the current distance at which the lens is focused. Of course, there would need to be a setting in the camera for the Circle of Confusion to be used for these calculations.
How could this be used? Well it could be reported to the user as above and let them deal with it. Or the User could be allowed to specify, say by Auto focusing on a near and far point letting the camera know the DOF range you want and given the current focal length and CoC, it would select the aperture necessary (and warn if not). Alternatively, the camera could have built in focus stacking where you give the near and far focus points and given the current focal length and aperture it would determine how many shots and at what focus distance to shoot each shot and then drive the camera when you say go.
