question on bellows draw

[photodog57]

I am considering moving into lf with a 4x5 field camera. Some of the ads give a "bellows draw" in mm. Does this indicate the widest angle lens with that bellows?...ie 53mm draw means I could use up to a 53mm lens?

 

[SteveH]

No, it gives the longest lens focal length possible (when focused at infinity). Example, if a camera is advertised with 300mm of bellows, that means that you, at maximum, can focus a 300mm lens at inifinity.

Someone please correct me if Im wrong...

 

[Troy Ammons]

Lens lengths are usually close to the flange distance.

http://www.brucebarrett.com/large_format/LF_Lens_Coverage.html

Roughly speaking. Some cameras advertise max and min of actual draw. If those numbers are maxed out and for instance are 47mm and 300mm, and you have two lenses that require a 47mm and 300mm distance, you could use them , but just not with movements. It seems like the usable movement number is based on 80-85% of the max which means you could use around a 250mm lens with movements.

Of course that really depends on what movements you use.

Minor tilt and you could get away with a longer lens.

Tilt on a 47mm lens is probably not even required.

 

[bobfowler]

No, it gives the longest lens focal length possible (when focused at infinity). Example, if a camera is advertised with 300mm of bellows, that means that you, at maximum, can focus a 300mm lens at inifinity.

Someone please correct me if Im wrong...

Close, but not entirely correct. It's simply the maximum bellows extension. Many lenses have back focus (from rear of flange to film plane) lengths that are different from the optical focal length. For example, a Kodak 8" f/7.7 Ektar has a 7 1/2" back focus. Back focus information isn't always published in the lens brochures, though it should be.

Toss in that some makers measure only the length of the bellows, while others may measure from the front of a standard lensboard to the film plane. It's a bit of a shit sandwich trying to figure these things out sometimes...\

 

[SteveH]

Thanks Bob for clearing that up. I suppose I should have also put a word in about telephoto lenses...but I neglected to do so.

 

[rbarker]

When considering lenses and bellows draw, it's also helpful to consider what the closest focus distance will be with a particular lens and the maximum bellows draw provided by the camera. The formula for calculating this is available from various sources, and has been discussed here in the past.

Bob makes a good point, however, about the variations in the manufacturers' specs. Bottom line? Never eat at a deli started by a camera manufacturer.