Well, I had a go yesterday morning at adjusting the focus. I have a Pentax DA 18-250mm lens which came with the camera but have not been entirely happy with shots taken with the lens wide open. It always struck me that the focal point was just in front of the subject rather than at the centre of the object.
So I set up three pencils and a plastic ruler on the kitchen worktop and, with the camera on a tripod, I went to work. All shots were taken by manually setting the focus to be as close as possible, and then auto-focussing to take the shot. This way, focus is not the same each time but relies on the camera having to re-focus on the same spot before taking the picture (Highly scientific, but there we are.)
The first picture shows the focus set without adjustment:
The focal point here was the tip of the central pencil. However, the shot shows that the focal point of the shot is actually set around 5.6" rather than 6" (the pencil tip).
I adjusted the AF setting by -50um and took another photo:
This time the focal point does seem to be at the 6" mark and ruler markings between 6" and 7" do appear sharper (especially when the two photos are viewed side-by-side)
So this has made a discernable difference, so may I add my thanks to the others here for your work setting up the guide.
Interestingly I tried two of my other zooms and noticed that my Pentax-F 35-135mm zoom looks decidedly soft in comparison. Here are the three pencils in Macro mode:
And here is the same picture through the DA 18-250mm set at 250mm:
Much better. And both were focussed the same way.
I've not had a chance to play outside as the batteries decided to die on me during this work, but I have got one photo from this afternoon that shows that focus looks about right....
Thanks again. Well worth the time and effort.
Cheers
Savcom