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06-27-2010, 02:03 AM   #1
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Will this lens fit my kx?

I'm thinking of buying this used lens..

SMC PENTAX–FA 1:1.4 50mm PRIME LENS FOR PENTAX DSLR


Can anyone confirm if it will fit and work with AF, flash etc on my Pentax Kx?

Thanks


06-27-2010, 03:17 AM   #2
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Yes, it will mount on your KX and auto focus on your KX without any problem. I have a FA 31 and use it on my K20 and everything works just fine. Two items that you should be aware of.
1 - On all FA lenses, they have an “A” position on the aperture ring (the f stops). Engaging this setting locks the aperture ring and allows the camera to control the aperture setting with the E-dial on the camera body. There is a small button on the aperture ring immediately next to the "A" setting that you push and then rotate the aperture ring to the "A" position. This allows the camera to automatically control the aperture, otherwise you the user need to manually select the aperture by turning the ring to the desired f stop. The camera can be shot in any mode (with the camera automatically adjusting the aperture setting as required) just like with a regular modern AF lens. Placing the aperture ring in any other setting than “A” essentially turns it into an “M” lens (you manually control the aperture setting). You can put the lens into the "A" position once, and forget forever more and it will work just like your DA lens(es) that you probably have. Almost forgot, you should navigate to the Custom Function menu and change the “Using aperture ring” setting to “Permitted”. This will tell the camera that there is a possibility that the lens has an aperture ring that can be manually set. This too can be set once and never changed. It will have no effect on your DA lenses.
2 - FA lenses do not have the focus clutch that the DA lenses have. The focus clutch is a built in mechanical mechanism allows you to have the camera in autofocus (AF) and then with your hand, manually focus at any time with out switching the camera to manual focus (MF) - i.e., it disengages the AF mechanism when you manually turn the focus ring. On the FA lenses if you are in AF it will autofocus just fine, however if you try to manually rotate the focus ring it will resist (not turn). If you wish to manual focus, you need to flip the focusing switch from AF to MF.
Now, after writing (and you reading) all of that - there is nothing to worry about. I just saved you from posting 2 additional questions once you receive the lens - and worrying that either you did something wrong and broke the lens, or that you received a defective lens. Its a great lens, its just has a slightly older design than the DA lenses that you are use to using.

enjoy the lens...

Last edited by interested_observer; 06-27-2010 at 03:33 AM.
06-27-2010, 07:55 AM   #3
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Thanks interested_observer I had question about #2 now I don't need to ask.

That said, is there any "advantage" of DA over FA? It seems like FA primes goes up to larger aperture than DA ones.
06-27-2010, 08:35 AM   #4
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awesome, thanks for the very detailed answer.. just what i needed. And although there are parts of that answer that I don't yet understand, I'm sure I will once I get the lens and start using it

06-27-2010, 08:46 AM   #5
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FA lenses are full-frame lenses with aperture rings. They don't differ from DA lenses in terms of supported features on Pentax DSLRs. FA lenses can also be used on all manual and automatic Pentax film bodies. DA lenses, however, are designed for APS-C sensors and have no aperture ring.

To see a comparison of the Pentax lens series, visit PentaxForums.com - Pentax Lens Reviews & Lens Series Explanation or our lens database at Pentax Lens Review Database - Lens Listings
06-27-2010, 09:02 AM   #6
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FA lenses (especially FA* lenses) perform extremely well on APS-C bodies (k7, kx) because you're using the best, center most part of the lens.
06-27-2010, 09:35 AM   #7
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QuoteOriginally posted by Clinton Quote
FA lenses (especially FA* lenses) perform extremely well on APS-C bodies (k7, kx) because you're using the best, center most part of the lens.
This is another interesting point that makes me wonder if there's any good reason to get DA lenses over FA (assuming if I'm looking at comparable DA and FA lenses in terms of image quality)?
06-27-2010, 09:51 AM   #8
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QuoteOriginally posted by ruggiex Quote
This is another interesting point that makes me wonder if there's any good reason to get DA lenses over FA (assuming if I'm looking at comparable DA and FA lenses in terms of image quality)?
FA lenses were designed for film cameras with a full frame "sensor". DA lenses are designed for the APS-c sensor which is about 30% smaller. Thus, most DA lenses do not project an image on a full size sensor to sufficiently cover it. Currently, Pentax does not have a digital camera with a full sized sensor. Another difference, is that DA lenses have a coating on the rear glass element to reduce or eliminate light reflections from the sensor. I do not think that this has been a very large problem to date, as folks who use the FA Limited lenses tend to be very happy with them. Also DA lenses - the actual lens blanks can be smaller, since they only have to project a smaller image on to the sensor field. Being able to use smaller lens blanks, enables the overall size of the sensor to be smaller and lighter in weight.

Some folks hope and anticipate that Pentax will come out with a full frame camera body, thus they tend to only use full frame lenses.



06-27-2010, 10:20 AM   #9
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QuoteOriginally posted by ruggiex Quote
This is another interesting point that makes me wonder if there's any good reason to get DA lenses over FA (assuming if I'm looking at comparable DA and FA lenses in terms of image quality)?
FA lenses are typically larger and harder to find (all but 4 are out of production), and pricey- which is why post people stick to the DA consumer or kit zooms. However, they do tend to boast faster apertures, and the IQ is really good. Take the FA 35 and FA 135mm as examples and let's not mention the FA* lenses, which are among the best that Pentax has ever made.

Some DA lenses are weather sealed and have quick-shift focusing, which is handy for those who need it, on top of the smaller size.

In my bag this summer are the DA 35 macro, FA* 85, and FA* 200mm macro. Why the DA? Because it's quite a novel lens, and can double as a macro, while the FA 35 can't

AFAIK there's no lens in the DA series (yet, I hope!) to match the other two.
06-27-2010, 10:22 AM   #10
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QuoteOriginally posted by ruggiex Quote
This is another interesting point that makes me wonder if there's any good reason to get DA lenses over FA (assuming if I'm looking at comparable DA and FA lenses in terms of image quality)?
There are no such comparable lenses. Pentax doesn't put out DA versions of existing FA lenses - their Da lenses are all totally new designs in different focal lengths.

Best reason to get DA lenses is that the focal lengths are generally well-chosen for APS-C "cropped" digital cameras, and the coatings are supposed designed to work better with digital sensor, although this is always debatable. "Quick shift" (ability to touch up focus manually without leaving AF mode) is another nice feature of most DA lenses that older lenses lack. But if there a particular FA lens with a focal length and a maximum aperture you want, no reason not to get it.

Lens compatibility on Pentax is actually much easier than on other systems. You don't have to keep asking "will this lens work on my camera", or "will it have AF", etc. If the lenses says it's for a Pentax SLR and doesn't say M42 or screwmount, then it fits. If it ays M42or screwmount (only very old lenses), then it fits with an adapter. If the lens says it is an AF lens, then it will AF. If it's an AF lens, it's also autoexposure. If it's a manual focus lens, but it's an "A" series lens (has an "A" position on the aperture ring) then it has autoexposure. There aren't a bunch of special cases*, like some lenses from some series have autoexposure and others don't, or lenses that AF on only some cameras but not others or any of that other stuff that you get with Canon or Nikon.

*OK, there are one or two special cases - like some very new AF lenses that won't AF on some very old cameras. Nothing relevant to your K-x, though.
06-27-2010, 01:51 PM   #11
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Thanks for all the answers that was really helpful to see the whole picture!
06-30-2010, 08:08 AM   #12
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QuoteOriginally posted by Marc Sabatella Quote
There are no such comparable lenses. Pentax doesn't put out DA versions of existing FA lenses - their Da lenses are all totally new designs in different focal lengths.

Best reason to get DA lenses is that the focal lengths are generally well-chosen for APS-C "cropped" digital cameras, and the coatings are supposed designed to work better with digital sensor, although this is always debatable. "Quick shift" (ability to touch up focus manually without leaving AF mode) is another nice feature of most DA lenses that older lenses lack. But if there a particular FA lens with a focal length and a maximum aperture you want, no reason not to get it.

Lens compatibility on Pentax is actually much easier than on other systems. You don't have to keep asking "will this lens work on my camera", or "will it have AF", etc. If the lenses says it's for a Pentax SLR and doesn't say M42 or screwmount, then it fits. If it ays M42or screwmount (only very old lenses), then it fits with an adapter. If the lens says it is an AF lens, then it will AF. If it's an AF lens, it's also autoexposure. If it's a manual focus lens, but it's an "A" series lens (has an "A" position on the aperture ring) then it has autoexposure. There aren't a bunch of special cases*, like some lenses from some series have autoexposure and others don't, or lenses that AF on only some cameras but not others or any of that other stuff that you get with Canon or Nikon.

*OK, there are one or two special cases - like some very new AF lenses that won't AF on some very old cameras. Nothing relevant to your K-x, though.
There are also those old lenses that have the "powerzoom" feature which is no longer supported, although this is why I stick to Pentax, the lenses are all so compatible and doesn't give me a headache as to what I can buy (will work) and what I can't (won't work).
06-30-2010, 10:23 AM   #13
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True. But it should also be noted that if you don't need powerzoom to work - and why would you? - then you can still use a powerzoom lens just fine on any camera. That is, it will work exactly like a non-powerzoom lens.
06-30-2010, 11:33 AM   #14
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I have one power zoom lens (35-70mm, I think), that works fine on my K10D. Not all the power zoom functions are supported, but the basic ones, such as, well, power zooming, are.

When Pentax created the SDM lenses, with in-lens focusing motors, they re-used the power contacts from the PZ series of cameras, so my K10D provides power to the PZ lens.

I've heard conflicting reports as to whether the power zoom lenses work on all SDM-capable cameras. Everything from the K100D Super and later have these power contacts, but apparently, pz lenses don't work on all such cameras.
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