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G2 Focusing Accuracy
- Thread starter keoj
- Start date
albert4321
Well-Known Member
I think the focus distance should be from the subject to the lens's nodal point.
http://www.edb.utexas.edu/teachnet/QTVR/NodalPoint.htm
Albert.
http://www.edb.utexas.edu/teachnet/QTVR/NodalPoint.htm
Albert.
wilsonlaidlaw1
Well-Known Member
Logic would dictate that the focus distance must be to the film plane on a G2 otherwise what on earth is the point of marking the film plane on the top of the camera. A typical use could be data back, time interval exposure shots, where you could dial in a manual focus distance, which you would measure to the film plane. The read out would not necessarily be to the sensors, as I think someone else has explained before, it would be very simple in the distance computation firmware, to have an algorithm, which added a constant to the sensed figure. Wilson
coodeville
Well-Known Member
About three hours ago, I set up my F100 along with a 50mm lens. It used a flower pot as my subject. I measured the distance between the film plane indicator and the flower pot. I set the lens to the measurement. I never looked through the veiwfinder at all and I turned off the AF. The negative was in perfect focus.
coodeville
Well-Known Member
Here's a picture of the film plane indicator on my black G2. The arrow points to it.
coodeville
Well-Known Member
I wonder why my Fuji S2 Pro II has the CCD plane indicator marked in black? My other Nikons are white. You can barely see the Fuji's.
D
ddai
Austin,
I apologize for not being accurate. What I mean here is that whether the distance reading is based on the front element or film plane depends on the manufacturer and the operatiing manual. For those sophisticated AF Zoom, more than often its front or rear nodal point or both are not outside the lens elements. To have a more attractive spec, they claim the closest focus distance based on the front element. Please image how can a lens focus at 25cm to the film plane while the lens itself is 28cm long. For some macro lens (Tamron SP90mm Macro f1/2.8), the second principle point is farther than the first one to the film plane (according to the diagram that comes with) to achieve a 1:1 magn. ratio.
Just a reminder for those users that will take that for granted. Always refer to the manual not personal judgement.
For the statement for Nikon zoom I had tested the 28-135 AF Zoom some years ago (now I don't own them any more). Accidental enough I picked up Contax was because I read the history of Nikon and found their fundamental designs were from CZ.
Regards, David
I apologize for not being accurate. What I mean here is that whether the distance reading is based on the front element or film plane depends on the manufacturer and the operatiing manual. For those sophisticated AF Zoom, more than often its front or rear nodal point or both are not outside the lens elements. To have a more attractive spec, they claim the closest focus distance based on the front element. Please image how can a lens focus at 25cm to the film plane while the lens itself is 28cm long. For some macro lens (Tamron SP90mm Macro f1/2.8), the second principle point is farther than the first one to the film plane (according to the diagram that comes with) to achieve a 1:1 magn. ratio.
Just a reminder for those users that will take that for granted. Always refer to the manual not personal judgement.
For the statement for Nikon zoom I had tested the 28-135 AF Zoom some years ago (now I don't own them any more). Accidental enough I picked up Contax was because I read the history of Nikon and found their fundamental designs were from CZ.
Regards, David
D
ddai
Sorry, Corrections. nodal points may be outside the lens....