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11-24-2010, 09:36 PM   #1
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Is my K-m/K2000 a aps-c DSLR?

I have purchased a Sigma 18-20mm f3.5-6.3 DC lens and I am wondering if I purchased the wrong lens because the descriptive information about the lens lists it is for a aps-c camera and I have a K-m/K2000. Did I purchase the correct lens for my camera? Simple question, but I have looked everywhere for the simple yes or no.

11-24-2010, 10:02 PM   #2
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Quick answer: Yes.
11-24-2010, 10:02 PM   #3
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Yes, the k-m is APS-C, as are all Pentax DSLRs. As long as you bought the K-mount / Pentax version of the Sigma, it is the right lens. (I assume you are talking about the 18-200mm, which I also have). Enjoy your lens!
11-24-2010, 10:19 PM   #4
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Longer answer:
All Pentax DSLRs, with the exception of the 645D with its gigantic medium format sensor, are equipped with an APS-C sensor.
Other companies such as Canon, Nikon and Sony have different sensor types depending on the model.
A lot of people are requesting from Pentax a full frame sensor as it is larger, actually the size of a 35mm film.

For lenses, lenses that were made for film cameras cover the surface of a 35mm film, and they can be used just as well for APS-C cameras. Pentax hasn't changed their mounts since the film days.

The only thing is that since the image is on a smaller sensor, it looks bigger by approximately 1.5x than if you had a full-frame film camera. So your 18-20 (Shouldn't it be 18-200?) lens is actually behaving like a 27-30mm lens (or if it's 18-200, it's behaving like a 27-300mm)

You can look up "crop factor" for more details.
If a lens was made especially for APS-C sensors, the image it sends fills the surface of the APS-C sensor.

Should you switch that lens onto a film camera, you would end up with a big black circle called "Vignette" as the image wouldn't fill the whole surface of the 35mm film.

If it was made for full-frame, it doesn't matter as it fills more than the sensor size. The crop factor remains the same for both type of lenses.

I hope this helps!

11-24-2010, 10:24 PM   #5
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11-25-2010, 07:52 AM   #6
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Thank you to all!
I have been using Pentax film cameras for a long time and have a collection of lens but I am new to the digital world. All answers where easy to understand and explained a lot.
And yes, the Sigma lens is a 18-200mm, oops ;-).
11-25-2010, 11:23 AM   #7
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If you have a collection of Pentax (or compatible) lenses for film cameras, you might want to look at the thread regarding the use of old manual lenses on dslrs:

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html

If your lenses are all auto-focus, then you can ignore the thread. Those lenses will work just fine on your camera. If, however, any of your lenses are manual focus or do not have the "A" setting on the aperture ring, that thread is for you.

Paul Noble
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