Magnification/Focal Length

Hi folks - new here. Currently using Mz30 film camera with various Sigma lenses. Seriously contemplating going digi with *ist. Just wondering what the equivalent focal length this camera gives compared to 35mm film camera? Some lenses I am currently using:
Sigma 17-35mm ex
Sigma 70-200 f2.8 ex
Sigma 70 - 300 dl (4-5.6).
Also, for example in the case of the dl lens, - if effective focal length is different, what happens to the aperture sizes?
Hope someone can offer some advice.

John,
There's no difference in aperture sizes. Just multiply the real focal length by 1.5 to get the effective focal length.
The *ist-D gives a "crop" of the 35mm frame since it's APS sized.
Check out my diagram I did a while ago:
www.photon.me.uk/matt/cameras/pentax/istd_focal.htm

Enjoy
Matt

Hi Matt
Thanks for that. Yes,that makes sense.
Whilst on the subject any comments on how lenses such as the ones I mentioned at top perform with the ist?

A good film lens should normally be a good digital lens, but there is one practical consideration to bear in mind.

A lens with good centre resolution and poor edge resolution will work better on a digital camera (with an APS-sized sensor) because the edges will have been cropped off.

Generally speaking, a lens has to perform better with digital because the smaller "negative" size (ie: sensor size) requires a greater magnification. So, avoid bad lenses.

George

Sigma 70-200 f2.8 ex

Works an absolute treat. A joy to use.

jayson not cheap, but no regrets

Jayson?

yes forgot to log in

thats better.