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 

Replacement Viewfinder?

 
Post new topic   Reply to topic    Graflex.org Forum Index -> Speed Graphic Help
View previous topic :: View next topic  
Author Message
bryanlaplante



Joined: 09 Mar 2002
Posts: 32

PostPosted: Mon Jun 03, 2002 2:34 am    Post subject: Reply with quote

I'm currently converting my 3x4 speed graphic to a 2x3 back. The 3x4 will give me a bigger lensboard and more movements, at a lower price - plus I can use barrel lenses.


What I need is a some viewfinder improvements. With a 105mm lens, the standard is too far back to raise the wire finder. A planned 90mm lens will make that worse. I could make/buy some replacement masks for the tube finder, but the speed's tube finder has such a small (half real) size image... has anyone 'hacked' a replacement finder? I'm sure Leica has some wonderful finders - but I'd like to find a source in a realistic price range. I'm a little spoiled by the finder I remember on the Rollei 35. Do I understand that the Crown came with a different finder that has a less negative less? Is it substantially better?


Lastly has anyone made up a finder from scratch? Can it be that hard?


Thanks!
Back to top
View user's profile Send private message
Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Mon Jun 03, 2002 12:14 pm    Post subject: Reply with quote

since the crown body is thinner, replaceable crown viewfinders were shorter, but the elements, masks, etc were the same.

there's a mamiya universal finder, used by some LF people to spot their shots, It's big but nice.

I'm guessing a 90 would not need any masks, on a 4x5 the 90 uses a supplemental neg element on the viewfinder to see everything, this is also used on the 2x3 for 65
Back to top
View user's profile Send private message
bryanlaplante



Joined: 09 Mar 2002
Posts: 32

PostPosted: Mon Jun 10, 2002 11:08 pm    Post subject: Reply with quote

I've done some research on the finder topic now, so thought i'd share my findings. Most viewfinders are reverse Galilean designs, which has a positive eyepiece lens and a negative objective. These have no place inside the finder which has a virtual image, and so there is no place inside to put a frame. The closest spot that is somewhat in focus is the front of the finder - hence the design on the speed graphic. After reading this I did look again and notice that the frame is not sharp when you are looking at the scene.



Leitz in their imarect accessory finder, wanted built in variable frame sizes, so needed a virtual image to be inside the finder. This can be done using a telescope design (two positive lenses), which are spaced at fl + fl apart. The ratio of fl/fl gives you the maginification ratio. Telescopes however invert their images, and so to correct this Leitz used a prism to re-invert the image. Getting all of this into a compact finder is a challenge.


I've researched some surplus optics and think I have a design for a finder which will produce a 0.75x image (the original is less than 0.5x), will be not too expensive (i.e. not $180 per focal length ala new Voightlander finders), and will cover a 58 degree field. One downside is I expect the finder to be nearly 4 inches long. This will stick out a bit from the body, but will help since I'll have a rollfilm back sticking out the back.


I expect to order parts tommorow - plan to keep the group updated.
Back to top
View user's profile Send private message
Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Tue Jun 11, 2002 2:04 am    Post subject: Reply with quote

Just before they came out with the mini-speed Graflex marketed a camera with a rotating back for 2x3 and used the 3x4 body. maybe the stole the RB part from a Graflex.

Just thought I'd throw thać out.

_________________
"In order to invent, you need a good imagination and a lot of junk" Thomas Edison
Back to top
View user's profile Send private message
bertsaunders



Joined: 20 May 2001
Posts: 577
Location: Bakersfield California

PostPosted: Tue Jun 11, 2002 2:43 am    Post subject: Reply with quote

I repaired a 2x3 with the rotating back, about 1987 for a local camera store owner!
It was a 3x4 body, and the back appeared to be from a 2x3 SLR model! Was not all that versed on the Graflex or Graphic models at that time, so did not get ser number or any other pertinent info on the camera
un-fortunately!!!! Have a couple of borrowed 1937 and 1939 catalogs with this camera listed, $120 w/Kodak Anastigmat
5 1/2" in Compur Shutter---it is not listed in the 1939 catalog, so assume that the Paine review has it right--1937/1938 only!! Bert
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    Graflex.org Forum Index -> Speed Graphic 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