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 

7-1/2" #33 focus shift?

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



Joined: 24 Nov 2003
Posts: 715
Location: So Cal

PostPosted: Tue Mar 18, 2008 4:39 am    Post subject: 7-1/2" #33 focus shift? Reply with quote

I finally got my RB running again and now have a Graflex focussing panel for it so I can more easily use a loupe when i want. And what I saw when I tested it out surprized me. A ton of focus shift, enough to ruin a lot of images trying to shoot SLR style.
It's the old RB series B with the standard 7-1/2" 4.5 Anastigmat and very clean. I am wondering if this was common to these lenses and if so, how did folks cope with it.
Lens issharp wide open, and then when I stopped down to f~8 to 11 it really throws the focus out. I have to wheel the lens out closer to get sharpness back, quite a bit at 6-15 ft. Not a problem with a dark cloth and usingthe GG on the back, but not so easy using the hood without a focussing aid.
Surprise, I now know why I didn't like the crappy images I made with it a couple years back.
Back to top
View user's profile Send private message
45PSS



Joined: 28 Sep 2001
Posts: 3231
Location: Mid Peninsula, Ca.

PostPosted: Tue Mar 18, 2008 8:25 am    Post subject: Reply with quote

I had a 10 inch anastigmat that was razor sharp from wide open to stoped down and had no focus shift. I suspect that an element or group is out of alignment (mispositioned in the barrel) causing the focus shift in your lens. According to Graphic Graflex Photography 1940 the closest focusing distance for the 7 1/2 lens in a Series B is 27 inches and there was a 15 inch telephoto available. There is no mention of focus shift for any Kodak lens.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
troublemaker



Joined: 24 Nov 2003
Posts: 715
Location: So Cal

PostPosted: Tue Mar 18, 2008 7:53 pm    Post subject: Reply with quote

I'll take it all apart after work and see, but IIRC I already checked all that two years ago. anyway, I'll get back this evening.
Right now the thing is plenty sharp edge to edge and corner to corner wide open. More so than my Cooke 7" 5x7 which wont even cover 4x5 unless stopped down. So I think it is a shifty lens...
Back to top
View user's profile Send private message
45PSS



Joined: 28 Sep 2001
Posts: 3231
Location: Mid Peninsula, Ca.

PostPosted: Wed Mar 19, 2008 12:40 am    Post subject: Reply with quote

The only info I can find on Kodak Anastigmat lens is in the Vade Mecum and that is a quess. The lens diagram suspected of being used is:
Front element: Convex front, flat rear slight clip on edge at front /rear; air gap; double concave edge of rear side has cliped edges; aperture; double concave, cliped edges on side facing aperture possibally cemented to a double convex rear element.
Things to look for are the retaining ring lockscrews for an element or group usually enguage the lock ring at the center of the ring not the edge and the retainer screw/pin may go thru both the barrel and retainer ring (trying to remember how the ones I've had apart were assembled); discoloration of the barrel where not covered by an element or retainer.

Someone before you may have had the lens apart and reassembled it incorrectly.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
troublemaker



Joined: 24 Nov 2003
Posts: 715
Location: So Cal

PostPosted: Wed Mar 19, 2008 6:45 am    Post subject: Reply with quote

I took everything apart and all looks as it should be.
The front group has removable back element and standard front lock ring, and the rear has a lock ring on the inside facing forwardlike the older type 135 Optars. Not much to mess up, and all the elements appear to be seated properly. But I'll add this, when the lens is focussed it is nice and sharp unlike when one partially unscrews a back element etc.. to purposely soften. I'll go through it again tomorrow as time allows. And then I can take the whole camera apart again and see if I can get the mirror to lock all theway down as I found that to be out of whack also.
Thanks for the info.
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