Focus Adjstment - K7 with 55-300.

I believe my 55-300 is focusing behind the subject that is in focus (to the best of my ability) in the viewfinder.
Some help please:

At what focal length should I test-focus the lens?

At what aperture?

Is the process reversible?

I'm using the Tim Jackson test chart, version V2.00.


Many thanks,

Roger.

Test it wide open at 55mm and 300mm .. if you get the same result then make the alteration on the K-7.

If you get a different result for each focal length then decide which you use the most then adjust for that (I use mine almost exclusively at 300mm) or find a happy medium.

Yes it is fully reversable in menu.

Thanks, Mike.
Will let you know how I get on!

Roger.