But your eye does the same thing to a lessor extent. You may remember that I have previously posted that it is best if you accept the first apparent focus when focusing manually rather than rocking the focus back and forth trying to get it just right.
Now if you had a laser rangfinder it would focus at the exact distance.
graywolf http://www.graywolfphoto.com "Idiot Proof" <==> "Expert Proof" -----------------------------------
Don Sanderson wrote:
Tom, do you mean by this that the camera will put the subject you focused on *somewhere* within the DOF and consider it OK? In other words focusing on the same suject three times may yield three different results. If the camera was already in focus on the first, had to shorten focus on the second and lengtnen focus on the third, this would place the "plane of focus" at three different points within the DOF. Am I getting this? It would explain the odd behavior with short FL lenses.
Don
-----Original Message----- From: Graywolf [mailto:[EMAIL PROTECTED] Sent: Friday, December 10, 2004 10:36 AM To: [EMAIL PROTECTED] Subject: Re: backfocus (was: Survey:istD reliability)
No Amy, "backfocus" is the distance from the lens to the film or sensor, just as "focus" is the distance from the lens to the subject.
What you are talking about is misfocusing. If it is consistent as you indicate it probably is a problem with the camera. However before sending it in for service, check that it happens with all of your lenses. And make sure you are putting the proper focus point on the part of the subject where you want he camera to focus on. I presume you are taking about autofocus which brings up the idea that you should check and see if it does it when you focus manually. If it happens with manual focus too, it indicates that the focusing screen or the sensor is probably not in the correct position, definitely a camera problem.
You should know however the autofocus can only focus within the Depth of Field of the lens, which is something folks generally do not realize. That means your focus can be off quite a bit compared to measured distances and still be as accurate as the system is capable of especially with shorter lenses.
graywolf http://www.graywolfphoto.com "Idiot Proof" <==> "Expert Proof" -----------------------------------
Amy Hughes wrote:
backfocus problems
Could someone please explain what this means? I have a frequent problem with my D where the focus is behind what I thought I focused on. Is that "backfocus"? I'm currently assuming this is my fault, though I haven't had this problem with Pentax film cameras.
Amy
