Using Pentax 645 lenses on a 35mm camera

[asimrazakhan]

1. Is it easy to find an adaptor that allows you to use 645 lenses on a

Pentax 35mm camera? Anyone know where I can find one?

 

2. If, for example, I use a 45mm lens (which is equal to 28mm in 35mm fomat)

on a 35mm camera, then what would the focal lenght be on the 35mm? Would it

remain 45mm or would it be 28mm?

 

3. Are there any limitations for using 645 lenses on a 35mm camera?

[bueh]

<blockquote><i>1. Is it easy to find an adaptor that allows you to use 645 lenses on a Pentax 35mm camera? Anyone know where I can find one?

</i></blockquote><p>

On that big internet auction site. Large store might also have them, but there they are usually expensive. <b><a href="http://www.zoerk.com/pages/p_mounta.htm">Zörk</a></b> also custom-builds them, but they are rather expensive (though high-quality).

 

<br> 

<blockquote><i>2. If, for example, I use a 45mm lens (which is equal to 28mm in 35mm fomat) on a 35mm camera, then what would the focal lenght be on the 35mm? Would it remain 45mm or would it be 28mm?

</i></blockquote><p>

Dude, a 45mm lens on a 35mm camera is a 45mm lens. What did you expect?

 

<br> 

<blockquote><i>3. Are there any limitations for using 645 lenses on a 35mm camera?</i></blockquote><p>

The aperture must probably be stopped down manually. P645 lenses are much larger, heavier and more expensive than regular 135 format lenses, but besides these obvious issues, they just are like the usual manual focus lenses. Adapters for PK and M42 exist, which means that if you stack adapters, you could also mount them on other camera bayonets (e.g., Canon EF etc).

[dougmiles]

Pentax made such an adapter, very similar to the one that allows P67 lenses to mount on a K bayonet body. I have one of the latter and find it a bit annoying to use, as it has no mechanical or electrical contacts that would allow communication between body and lens... For instance, you don't even get auto diaphragm.

 

By contrast the P67 to P645 adapter does maintain auto diaphragm and is thus useful in manual exposure and aperture-priority auto mode.

 

I've seen the P645 to K adapter a couple of times on eBay, so you might set up an automatic search there for one.

 

Focal length is focal length, same mm on any system. The three Pentax adapters above have no optical elements so do not change the optics in any way. You just end up using lenses that are larger and are capable of imaging a wider field than necessary for the smaller format.

[johan_de_groote]

Actually, the apparent focal lenght will go up because you will only use a smaller part of the image circle (about 1.5x). Same as using a 35mm lens on a crop camera.

[bueh]

No Johan, the focal length stays the same (45mm-->45mm). Only the angle-of-view changes, because the film format is different ("cropping"), as you said.

[NetR]

To be specific about the 45mm lens, on a Pentax 645 a 45mm lens gives you about the same the angle of view as you get with a 28mm lens on a 35mm camera. On a 35mm camera, the 45mm lens gives you about the same angle of view as a standard (50mm) lens. It isn't worth the hassle as good quality 50mm lenses for Pentax 35mm cameras are cheap and plentiful.

 

Regards, Ross

[johan_de_groote]

Can you 2 above fight it out please? :) Bueh says the angle of view changes and Ross says it stays the same???

 

I change to a different focal lenght to change the angle of view captured on the medium. So if the angle of view captured changes _because the cropping_ then it is the same as changing the focal lenght. Or not?

 

Like I said: same as using a digital crop camera. Your focal lenght stays the same, but your angle of view changes so it looks like the focal lenght increased.

[xato]

I was chasing several P645 to K mount adapters to mount my Pentas 300 ED-IF on my Olympus digital camera by also using a Pentax K to Olympus fourthirds adapter. But they were much too expensive. I ended up using a P645 to Nikon and Nikon to Olympus fourthird adapters. Works great.

 

As far as the focal length, just pick what angle of view you want, normal, telephoto or wide angle. Then next pick the focal length you need to obtain that angle of view. You just have to remember that depending on the size of your film or sensor, you have to pick the right lens. For example a 45mm lens on my E-330 digital acts like a telephoto, while on my Olympus OM-4 provides a pretty normal field of view but on a Pentax 6x7 it would be an ultra wide.

[gustavo_xavier]

I've been using a 35mm, a 55mm, a 75mm and a 120mm PENTAX 645 lenses on my Canon 1Ds2 35mm digital camera, using a ZORK Adaptor. The aperture must be changed manually, off course.

 

No problems with the adaptor. The main problem is the large flare that you get using this combination. You have to be very careful with any light source beside or in front of the lenses. When the light is beside to the camera it's easy to solve the problem, but when it's in front of the camera, a window i.e, you get a large flare and it's almost impossible to cut it off.

 

I'd like to listen if other users have the same problem. Maybe my lenses are uncoated.