El Guero
29th April 2009, 02:51 PM
So I decided to see how accurate my Nikon D300 system is with my manual focus Zeiss 100mm f/2 Makro lens. Even though there is no mechanism for the camera to focus the lens, the AF system is still active and it displays a green dot in the view finder when optimum focus is detected. With this lens wide open and the LensAlign ruler in position 4 or 5, it is very easy to see very small differences in focus.
When manually focusing this lens, there is a very small range, maybe a degree or two, in which the viewfinder indicator is on. In the middle of this range, there is a detectable amount of back-focus. If I rotate the focus ring counter-clockwise and then rotate it back just enough so that the indicator just flashes on, the focus is dead-on. My wide-open shots are coming out much sharper now that I have discovered this.
Perhaps there are easier ways to "fine tune" for manual lenses, but the LensAlign has proven extremely useful for me in learning how my lens and camera operate. I do have a Katz-eye focusing screen, but my vision isn't what it used to be; it is not too useful for wide-open shots.
Just thought I'd share this and see if anyone has any thoughts.
When manually focusing this lens, there is a very small range, maybe a degree or two, in which the viewfinder indicator is on. In the middle of this range, there is a detectable amount of back-focus. If I rotate the focus ring counter-clockwise and then rotate it back just enough so that the indicator just flashes on, the focus is dead-on. My wide-open shots are coming out much sharper now that I have discovered this.
Perhaps there are easier ways to "fine tune" for manual lenses, but the LensAlign has proven extremely useful for me in learning how my lens and camera operate. I do have a Katz-eye focusing screen, but my vision isn't what it used to be; it is not too useful for wide-open shots.
Just thought I'd share this and see if anyone has any thoughts.