Large Format Lenses on Pentax 67

[mike_sellers1]

Can anyone tell me if it is possible to mount a large format lens that is in a helical focus mount on the Pentax 67?If Alpa does this with their 12SW camera why wouldn`t it be possible with the Pentax?

[steve_rasmussen]

Not sure if what you ask is possible. If I were to consider using LF

lenses on the P67, I would buy a used Auto Bellows and replace the

front lens mount with a 4x5 lens board. Focusing would be via the

rail. SR

[milton_barrocas]

Its certainly possible but depends on focal length and infinity focus

requirements. Plus you need a mount converter of some sort. Is it

really worth it? How many lenses do you have? I have described the

restrictions for focal length elsewhere but in case you didn't see it

here goes. I'm assuming you require infinity focus as any LF lens with

helicals is bound to be a wide angle used for landscapes. The minimum

focal length of the lens you wish to convert is restricted by the

distance between the film plane and whatever mount the lens has. In

order to achieve infinity focus this distance must at least equal the

focal length of the lens. Now consider that for the P67 the film to

lens mount distance is already 89mm or so. So this alone would

restrict the min focal length to 89mm. However you still need some

type of lens mount adapter which adds to this distance. Also depending

on lens design the "built in helicals" may be at the back of the lens

and also contribute to this distance. So probably only lenses >120mm

could be converted. On the other end the amount of helical extension

you get will affect magnification. For 1:1 magnification you need the

lens to be twice the focal length from the film plane. The helicals

will give nowhere near this kind of extension but at least you can use

extension tubes. Remember how you need wide angle bellows for wide

angle lenses in LF, and the wide angle restriction is how much you can

squeeze the bellows? Well think of the P67 body plus mount adapter as

a fixed bellows which cannot be squeezed and hence restrict wide

angles. Heck just buy an LF camera.