[steve500]

I'm looking into a few new lenses.
First I need to know what's going to be directly compatible with my k20d

Do the FA series primes and zooms (ill use the 300mm prime F2.8 as example) work directly along with AF with the K20D ?

OR will I be better of getting a DA* of the same focal length?

I just don't understand why the DA* series is so much cheaper than an FA lens of the same focal length.


Anyone willing to clear me up I surely do appreciate
thanks
-steve

[Vinfer]

I'm looking into a few new lenses.
First I need to know what's going to be directly compatible with my k20d

Do the FA series primes and zooms (ill use the 300mm prime F2.8 as example) work directly along with AF with the K20D ?

OR will I be better of getting a DA* of the same focal length?

I just don't understand why the DA* series is so much cheaper than an FA lens of the same focal length.


Anyone willing to clear me up I surely do appreciate
thanks
-steve

DA* and DA are specifically designed for digital...so they are the natural choise for your K20.
But many FA lenses work fine and in af on K20, especially due to the possibility of setting f/b focus on K20.

[steve500]

thanks!

What is F/B focus selections?

Do the FA series lenses offer more for the money though? Or am I going lower in quality with the DA/DA* ?

[newarts]

I just don't understand why the DA* series is so much cheaper than an FA lens of the same focal length. ...

FA lenses cover a full frame sensor or film; DA lenses cover an APS-C sensor which has less than half the area.

Typically, lens prices increase rapidly with the area they must cover, other things being equal. (Edge performance is where lenses fall down; an FA lens has a lot more & harder to reach "edge" than a DA lens.)

Dave

[stevebrot]

Your K20D manual should cover lens compatibility as well as the features available with each lens type. All F, FA, and DA lenses as well as third-party AF should work on your K20D without modification or special effort on your part. It is possible to fine-tune the focus settings. That is what the previous post was referring to with the comment about F/B setting. Again, your manual is your best friend.

Out of curiosity, what FA, DA, and DA* lenses were you comparing for price? As for performance, you might want to browse the lens review database on this site.

Steve

[RioRico]

My FA lenses work (and autofocus) just fine on my K20D. I have some DA's but wouldn't buy any more because I expect my next Pentax to be a (FF) full-frame body, upon which the (HF) half-frame DA's won't be sufficient. Others here may (do) disagree with me, but my take is that DA's should be avoided unless you 1) have a compelling need RIGHT NOW for a specific lens, or 2) don't intend to migrate from HF cams anytime soon, or 3) have money to burn. Note: a "compelling need" might include shooting in rainstorms, in which case the weather-sealed DA*'s are great.

[Vinfer]

thanks!

What is F/B focus selections?

Do the FA series lenses offer more for the money though? Or am I going lower in quality with the DA/DA* ?

Open the manual, page 106, AF Adjustment. It's all written there.
One of the most beautiful features of K20, allows you to perfectly adjust the focus on each type of lens...so you can use all type of lenses. It will free you from the front / back focus problem, typical problem of the digital.

[Ben_Edict]

I'm looking into a few new lenses.
First I need to know what's going to be directly compatible with my k20d

Basically any lens with a K-mount and M42-lenses, T2-lenses via adaptors. In the latter case you can still use the Av automatic of the K20, but you don't have AF, P-TTL, matrix metering or automatic aperture. All later K-mount lenses, beginning with the A-series will give you all camera functions, including P-TTL, except AF. Any Pentax AF lens, beginning with the F- and FA-series, will work with your K20, without problems. The same is true for most third party lenses.

Do the FA series primes and zooms (ill use the 300mm prime F2.8 as example) work directly along with AF with the K20D ?

Yes.

OR will I be better of getting a DA* of the same focal length?

There is no general rule. The FA* lenses were of very high quality and some don't have a complement in the DA-world. So, when it comes to a FA 24/2.0, 85/1.4 or even the 80-200/2.8, you are bound to get the FA and pay the according price on the secondhand market. Also, the example you chose, the 300/2.8 is withou a current complement and there is no indication, that Pentax plans to make a lens like that in the foreseeable future.

There were also cheaply made FAs and they don't have any advantage over the DAs, which in general have a good quality, even if if made to a budget (like the 55-300).

I just don't understand why the DA* series is so much cheaper than an FA lens of the same focal length.

DAs (as others already wrote) have a smaller image circle, which makes the lenses smaller and cheaper to make. Also today the production of some advanced lens geometrics, like aspherical lenses, is much(!) cheaper, than it was 15 years ago. The the DAs don't have an aperture ring anymore and can save the according mechanics.

All in all, the DAs are an optimized choice for the current APS-C cameras and maybe for a coming Pentax with a 1.2 or 1.3 crop factor, whereas the FAs will be usable on Pentax film cameras, even fully mechanical ones (due to the aperture ring) or even a future (if it ever comes) full-frame Pentax DSLR.

I must confess, that I possess only exactly 1 DA lens, the 16-50/2.8 and it is well-made. though I still prefer the heavier mechanical make of my FAs. But that is more a matter of taste, than a quality issue.

There are in fact only a few lenses, that can really be compared, like the FA 50/1.4 and the DA 55/1.4 or the FA 300/4.5 versus the DA 300/4. In both cases the DA lenses have a slight edge in terms of sharpness and contrast (though it is so slight, it might not be visible in many shots) - this at least is the conclusion, I personally draw from all the image examples I have seen here and on other sites.

Ben

[roentarre]

Moved to SLR lens section