bellows draw and focal lengths... newbie questions

[Ishotharold]

I just finished building my 4x5 (prbly shoulda asked this before eh?) and I don't see the lens I have on there now working. I put a lens from a kodak autograph into the lens board. The lens is marked 152mm. I have to scrunch the bellows down WAY too small to make this lens work at any sort of usable distance and I'm sure the image quality will be lacking some. I am not sure where to go lens wise as I have about 11" of comfortable bellows draw. Is a 210 a good option? it seems that would work with my bellows nicely. Also is the lens from the kodak going to require the same bellows draw as any other large format 150mm or are there differences in the lens design? I really don't know a lot about the lenses so any help is appreciated.

(and a picture of the camera...)

 

[Dan Fromm]

What do you mean "have to scrunch the bellows down WAY too small to make this lens work"? That lens' diaphragm-to-film distance at infinity should be around 6", will be longer at nearer distances. If your 152 wants to make infinity with much less than 6" extension, it has a problem.

If you took your lens from a Kodak Autographic folder, it may not have enough coverage for 4x5 or may cover 4x5 but not allow much in the way of movements. Please tell us more about the lens. What's engraved on it besides focal length and maximum aperture?

Most 6" lenses for LF want around the same draw at infinity; there are no retrofocus lenses (would want more draw) and few, if any, 6" teles that will cover 4x5 (would want less draw).

A 210 will want around 8 1/4" extension at infinity.

 

[Ishotharold]

my thinking was that 122 roll film was 5 1/4" the long way (right? memory is a little shaky on that) so if the lens could cover that then it should cover very nearly my 4x5, like I said it's not a long term solution. My bellows are homemade and seem perhaps a bit too stiff so that could be part of my problem. it sounds like a 210 would be about right for me given to bellows length.

 

[jonw]

Here is a reference chart available on the View Camera website....free article section which provides you comparasions to 35mm through LF. http://www.viewcamera.com/images/focalchart.gif

Hope this helps. Jon

 

[Jim Jones]

my thinking was that 122 roll film was 5 1/4" the long way (right? memory is a little shaky on that) so if the lens could cover that then it should cover very nearly my 4x5, . . .

Close enough. 3.25 x 5.5

 

[Donald Miller]

The correct way to approach this is to determine the so called normal for the focal length for the format. This is determined by determining the diagonal of the film format. The dimension of the diagonal is determined by the formula that (hypotenuse/diagonal) squared equals the sum of the other two sides squared. Thus for 4X5 this would be 4 times 4 and 5 times 5 added or 41 being the hypotenuse. When we determine the square root of this value we come up with a value of 6.4.

When we convert the 6.4 to milimeters. (6.4 X 25.4) we have a normal length for he format of 162.56...so the nearest focal length lens for 4X5 is normally listed as being 150 mm.

This 150 mm lens or normal (none telephoto design) lenses will require a bellows draw of six inches at infinity.

Your camera having 11 inches of bellows draw will allow 279 mm at infinity...far less than that for any closer exposures. You might get by with a 240 mm lens if most of your work is at infinity. 210 mm lens would probably work better in most cases. If you plan on doing any table top photography (extreme closeup) you might be better off with 120 mm or even 90 mm.