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 

500mm lens on Baby Speed?

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



Joined: 13 May 2001
Posts: 302
Location: Midwest

PostPosted: Sun Oct 27, 2002 4:52 am    Post subject: Reply with quote

Anyone notice the 500mm Kalimar lens mounted on a Baby Speed on EBAY? Wonder how that works, notice it has a support and sticks out about a foot in front of the camera. Russ
Back to top
View user's profile Send private message Send e-mail
Les



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

PostPosted: Sun Oct 27, 2002 1:29 pm    Post subject: Reply with quote

First off, let's talk about telephoto lense vs normal lenses. A normal 20" lens, say a process lens will need 20" from the rear nodal point to the film in order to focus at infinity. That's not a problem with an 8x10 Deardorf or a 24z36 galley camera.

But when we want the focal lenght without the bellows draw, we have to cheat. If you take an 11 3/4" norma lens and add a 1.7 negative element to the back, the image will get spread out over a large area. If you keep the same format, taking only the center section the image will appear to have been magnafied--magnified to the same image size as a 20" lens, but with the bellows draw of an 11 3/4" lens. However doing this imparts distortion on the image and the outer area of the image circle suffers. This isn't a problem because you are only using the 'sweet spot' of the image circle.

This is how the 8",10, and 15" teleoptars work. The 15" tele will easily cover 8x10. but I wouldn't call the image sharp.

The stronger the negative element, the worse the image is.

with 35mm equipment the bellows draw to focal lenght is even worse. We have the audacity to demand a 8" lens to focus with a 1 to 1.5" bellows draw (the thickness of the body). In truth what most lens makers do is add a large tube to the back of the lens, so that in effect the body is deeper. That's why that 500 and 1000mm Hassy lens is so light. Others may add another element to the back to help correct the pin-cushin distortion. Which is what I think the Kalimar has.

In short. I think it will do what he says it will do, but I wouldn't expect to make tack sharp 20x24s from the neg. You'll be doing well to make good 11x14s.
Back to top
View user's profile Send private message
Dan Fromm



Joined: 14 May 2001
Posts: 2119
Location: New Jersey

PostPosted: Mon Oct 28, 2002 1:59 pm    Post subject: Reply with quote

Quote:

On 2002-10-26 21:52, jdman wrote:
Anyone notice the 500mm Kalimar lens mounted on a Baby Speed on EBAY? Wonder how that works, notice it has a support and sticks out about a foot in front of the camera. Russ
Take a look at http://medfmt.8k.com/bron400mm.html . I think the ideas carry over cleanly to 2x3 Speeds.

On the other hand, I have a 500/5.6 Century in T-mount and a 700/8 Questar, also in T-mount. Neither will cover much more than 24x36 because of mount vignetting, and I'm not about to take a hacksaw to either. Some things, especially Questars, are sacred and anyway a test published in MP suggests that the Q700 won't cover much more than 24x36 no matter what.
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