Graflex.org Forum Index Graflex.org
Get help with your Graflex questions here
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Focal length and distance

 
Post new topic   Reply to topic    Graflex.org Forum Index -> Lenses Help
View previous topic :: View next topic  
Author Message
HowardT



Joined: 03 Aug 2002
Posts: 4
Location: Western PA
PostPosted: Sun Jan 05, 2003 5:00 am    Post subject: Reply with quote
How is the focal length of a lens measured? From film plane to what point of the lens assembly. From what point on the complete camera is the distance to the subject measured. I would like to calibrate the focus scale to the ground glass image on my Speed Graphic. Is this question asked a lot?
Back to top
View user's profile Send private message
Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI
PostPosted: Sun Jan 05, 2003 6:23 am    Post subject: Reply with quote
In the lab the focal lenght is measured from the "rear nodal point" which is where the image inverts itself. This point usually lies somewhere just behind the lens board.

For practial purposes, use the lensboard to measure out the distances on your scale. 15 feet or 15feet 1/16" won't make that much difference.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Graflex.org Forum Index -> Lenses Help All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group