New User HELP

I am new to Digital SLR Photography, being I have always been an SLR film format Photographer.

I am a little lost as to how the lens system works.
I currently own a 135mm telephoto lens Non Digital If I wanted to purchase its equivalent in digital fomat what would this be and how do you convert

Many thanks

Nicholas

The Pentax DSLR has a magnification ration of about 1.5, so a 90mm would get about the same field of view as a 135mm on a non-DSLR full frame camera.

If field of view is all you're concerned about, that should do it, but there are of course other factors, dictated by physics, that go into defining the characteristics of a lens. Some of which are likely not so easy to state an "equivalency" for.

e.g. DOF for example does not change, but visually through a DSLR you magnify the image such that it appears as though you have more area in focus.
I haven't a clue how to go about conversions for that, if there even are any.

Amiringello

Thank you so much that is very helpful to me.

Now I just have to save

FYI, In my hurry with trying to type while at work , I forgot to mention that if you do want info on how DOF differs, there are of course some nice converters and software available on the web. e.g.: http://www.dofmaster.com

another thing it is important to realise is that the differences between "digital" and "non-digital" lenses are largely marketing spin. There are some improvements in glass coatings and digital lenses may have been re-designed to reduce the dreaded purple fringing, but in terms of what is and is not in the picture, and what is in focus, your 135 pre-digital lens is exactly the same as a digital optimised 135 if both are attached to the same camera.

If you intend to continue with film, assuming you are using pentax bodies, you might want to steer clear of digital lenses as you may experience some vignetting, and some have no aperture rings.

Steve

Depends what is meant by "digital lens". Some have a reduced image circle (which causes some vignetting on a film camera*), some are full-frame and are only called "digital" because of the coatings.

* In some cases, I understand, it's just at the wide end of a zoom. Apparently vignetting isn't a problem on a film camera with the DA 16-45mm from 20mm onwards.

quite true, I should have made that clear. See, even those of us who should know better get confused!!!

Ice is right about the 16-45, and the 18-55 is also more or less fine from about 24mm onwards. The 50-200 on the other hand is sub full frame throughout its range (although it does have a somewhat oversized image circle for APS-C).

The safest assumption is that Pentax lenses called DA anything (other manufacturers have their own designations and confusion increases still further!) are only suitable for digital cameras.

I did this years ago to explain the crop factor...
it may help
http://www.photon.me.uk/matt/cameras/pentax/istd_focal.htm

Enjoy!
Matt