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10-26-2009, 06:53 AM   #1
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What are the Pro and Cons of using an FA lens with the K-7 instead of a DA lens ?

I need a PRIME lens in the 30mm to 40mm range super fast, ideally f/1.4 or f/1.8.

Initailly I bought the Sigma 30mm f/1.4, it a GREAT LENS but I can not override the AF to MF from the focus ring, I have to move the switch in the camera itself, very inconvenient.

So I am thinking now using one of the Pentax FA lenses, like the FA 31mm f/1.8, but I do not know what I am loosing by doing that ?, what are the main differences between DA and FA ?

Right now I have the DA L 21mm f/3.2, it's a great lens, small and fast, but in low light situations it's not very good.


10-26-2009, 07:57 AM   #2
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I don't believe FA lenses have quickshift like your DA21. I think you'll have to use the on-body switch to go from AF to MF with them as well. (It's been a while since I used my FA50, so I can't be sure.)
10-26-2009, 09:17 AM   #3
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Quickshift is not available on the FAs. I have the DA 21 and 70 which I like a lot. I also have the FA31 which I also like a lot. I tend to use either autofocus or manual focus - I don't really take advantage of the quickshift so it is not that big of a deal for me.

The DA lenses have different/extra coatings to eliminate reflections from the sensor.

The DA lenses are a bit smaller.

You can still get some of the FA limiteds which were made in Japan. QC seems to have been better on those. I have sent my DAs back to Pentax to repair loose lens barrels. Quite a few folks have had an issue with this.

FAs are faster and are all very good wide open.
10-26-2009, 11:31 AM   #4
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FA 31 doesn't have quick shift, as has been noticed. Besides that, there's nothing you will lose, and everything you will gain. It is just a beautiful lens.

10-26-2009, 11:33 AM   #5
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Quick shift can be simulated on non-quickshift lenses with decoupling AF button from the shutter and pressing bayonet lock button (easily with your ring finger). Try at your own risk (but I use it regularly with my FA 50).
10-28-2009, 09:23 AM   #6
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QuoteOriginally posted by RawheaD Quote
FA 31 doesn't have quick shift, as has been noticed. Besides that, there's nothing you will lose, and everything you will gain. It is just a beautiful lens.

But the Sigma 30mm is a great lens as well. In Canon-land, this is the generally prefered "normal" lens for crop users (compared to the MUCH more expensive Canon 35mm f/1.4 L)

If you're happy with the Sigma 30mm, keep it! Not sure if you'd notice a whole ton of difference between it and the 31 Limited (especially in "handling" as both lack quick-shift focus)

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