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12-27-2018, 10:16 PM   #1
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New and confused

I have a K-x with a kit lens and want to upgrade to some new lenses but also in the future I am hoping for a K-1 body.....so I was hoping to get lenses I could use on both so as not to waste money on double lenses. I have read conflicting info online, some say all k mounts fit others say a ff lens wont work on a k-x or vise versa. I dont have old lenses or manual lenses. If anyone out there can assist I would be very appreciative. Cheers Geraldine

12-27-2018, 10:22 PM - 2 Likes   #2
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New Pentax Lens Compatibility Tool - Site News | PentaxForums.com

---------- Post added 12-28-18 at 12:26 AM ----------

Short answer, everything except the electronic aperture lenses using kaf4 mount work fine.
Pentax K-x - Pentax K-mount DSLRs - Pentax Camera Reviews and Specifications

The k-1 will need full frame coverage so the dfa, fa, f, A,M,K series k mount lenses are all good options. There are some da lenses that also work but those are exceptions.
12-27-2018, 10:59 PM - 1 Like   #3
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The Uncle has covered it.

Pay particular attention to the full frame (K1) lenses.....they will work on your KX, but be wary of any lens, particularly 3rd party lens (Sigma, Tamron etc) that are designated specifically for APS-C, they will work on your KX, but may not give you what you want on a K1 (full frame).

Yes, it can be confusing as all manufacturers use different codes/model names....if in doubt, write down the exact name of the lens and ask on here.
12-28-2018, 01:47 AM   #4
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GHolly, please understand that any K-mount lens will fit on both the Kx and the K1. However, a couple of the most recent lenses (DA 55-300 PLM and DFA* 50mm f/1.4) are KAF4 mount lenses and will not autofocus stop down (thanks Adam; dumb error on my part) on anything older than 2013, since the cameras lack the necessary electrical connections.

But more to the point, if you can mount a lens on the K1, it does not mean that the image will fully cover the larger full-frame sensor. By default, the K1 will crop to APS-C size (though this can be disabled), so any DA lens can certainly work on the K1, but it will not take advantage of the full sensor. There are counterexamples, e.g. the DA 40 Limited and DA 70 Limited, which do a pretty good job of covering the full frame sensor.

If you want to get a modern not-too-expensive walk around zoom, be aware that the DA 18-135 and DA 16-85 will be wonderful on your Kx, but won't cover the full sensor of the K1. However, the DFA 28-105 will do both, and provides a useful focal length range on both formats. If you want something wider, options are limited at present (the DFA 24-70 is expensive and heavy). Some of the older (discontinued) FA zooms may be of interest (20-35 or 24-90), if you can find them second hand. Or the old Tokina 20-35.


Last edited by Paul the Sunman; 12-28-2018 at 04:53 AM.
12-28-2018, 02:17 AM   #5
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Questions such as yours are common, so we've developed a tool to help you in the quest to find the right lens. Here is a complete list of current lenses which cover the K-1's image circle and also compatible with the K-x:

Full Frame Lenses compatible with the Pentax K-x | PentaxForums.com

Full Frame Third Party Lenses compatible with the Pentax K-x | PentaxForums.com

If you're looking for legacy lenses, anything with manual focus will generally be compatible with both cameras. Here's the list of supported legacy Pentax lenses:

Legacy Full Frame Lenses compatible with the Pentax K-x | PentaxForums.com

I'll add that there is one caveat to the first link above. There are some lenses (such as the DA 40mm F2.8 Limited or DA 50mm F1.8) which are not officially considered full frame lenses, but do in fact cover the FF image circle entirely (with only minor to moderate vignetting / corner softness). These lenses also happen to be affordable, and are therefore worth considering. We will soon be making a post on the homepage with more details on these lenses, so please stay tuned for that.


QuoteOriginally posted by Paul the Sunman Quote
will not autofocus
Actually these will autofocus, but will always shoot wide open (i.e. have no aperture control), on unsupported cameras such as the K-x.

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12-28-2018, 03:31 AM   #6
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Welcome

lots of friendly members here willing to help you out
12-28-2018, 03:38 AM - 2 Likes   #7
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Thank you everyone. So helpful and I appreciate your time replying. What a wonderful resource of information you are. I have checked the links for body lens compatability. Excellent. I was being tempted towards a Sony but I think I'll stay Pentax now. Thanks again.

12-28-2018, 03:42 AM   #8
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QuoteOriginally posted by GHollyPhotography Quote
I was being tempted towards a Sony but I think I'll stay Pentax now.
Great news Geraldine, there will always be help and advice here if you need it.
12-28-2018, 03:52 AM   #9
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QuoteOriginally posted by GHollyPhotography Quote
Thank you everyone. So helpful and I appreciate your time replying. What a wonderful resource of information you are. I have checked the links for body lens compatability. Excellent. I was being tempted towards a Sony but I think I'll stay Pentax now. Thanks again.
our job here ----

has just begun

let us know how we can help in the future
12-28-2018, 06:20 AM - 1 Like   #10
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One advantage Pentax has is third site... Lol. Adam should be paid by Ricoh.
12-28-2018, 07:08 AM   #11
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Welcome to the forum.
If you go with the K-1, be sure to get lenses that cover the full frame circle, because they will all fit and work on the K-x. Full frame lenses are quite expensive, but the standard cost-effective choices are Tamron 28-75 and 70-200, but this doesn't include a wide angle lens. Would you do enough of that kind of shooting that you would need one?

Last edited by Ash; 12-28-2018 at 06:17 PM. Reason: typo
12-28-2018, 07:46 AM   #12
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QuoteOriginally posted by Ash Quote
Welcome to the forum.
If you go with the K-1, be sure to get lenses that cover the full frame circle, because they will all fit and work on the K-x. Full frame lenses are quite expensive,. . .
consider me confused

if willing to use the lenses developed for the film SLR cameras, it may not be all that expensive to obtain lenses that will " cover " the 24mm x 36mm sensors of the K 1 and K 1 II

" modern " lenses that aren't designed for the full frame sensor may still work as well:

DA lenses on Full Frame: Test Shots thread

Read more at: https://www.pentaxforums.com/forums/54-pentax-lens-articles/31629-da-lenses-...#ixzz5azTjBDUg

Last edited by aslyfox; 12-28-2018 at 07:53 AM.
12-28-2018, 08:50 AM   #13
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QuoteOriginally posted by Ash Quote
If you go with the K-1, be sure to get lenses that cover the full frame circle, because they will all fit and work on the K-x.
Not quite correct. The K-x is a 10 year old design and the latest electronic aperture lenses (eg D-FA 50mm 1.4) will not fully function.... no aperture control.
12-28-2018, 09:46 AM   #14
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QuoteOriginally posted by pschlute Quote
Not quite correct. The K-x is a 10 year old design and the latest electronic aperture lenses (eg D-FA 50mm 1.4) will not fully function.... no aperture control.
the Pentax lenses with the KAF4 mount are the ones that won't work with certain Pentax Camera bodies

". . . A DSLR launched in 2013 or later is needed to operate this new system (the K-500 is not compatible). . . . "

Read more at: HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database

___________________

" It features the latest KAF4 lens mount*, which incorporates electromagnetic aperture control. . . .

* Cameras compatible with this system are K-1 Mark II, K-1, K-3 II, KP, K-70, K-3, K-S2, K-S1 and K-50. For K-1, K-3 II, K-3, K-S2, K-S1 and K-50, the camera’s firmware must be upgraded to the latest version. If this lens is mounted on a camera without proper firmware upgrade, its diaphragm control mechanism becomes inactive, making it impossible to obtain correct exposure. "


Read more at: HD Pentax-D FA* 50mm F1.4 SDM AW Reviews - D FA Prime Lenses - Pentax Lens Reviews & Lens Database
12-28-2018, 11:08 AM - 1 Like   #15
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There are very few KAF 4 lenses, and one of them , the DFA 50m f/1.4 is large and expensive. Would not be compatible with your K-x but would be with the K-1.

The main thing to fathom in your quest is, due to the difference in field of view (FOV) between cameras using a FF sensor and those with an APS-C sensor, lenses will not present images with the same framing on both cameras. An APS-C sensor, as is the case with your K-x, will present a narrower FOV- more tele-like compared to using the same lens on a FF body, which would present a wider-angle FOV. So a 28-105mm lens on a FF body will provide a wide-angle to mid-telephoto range, which is very versatile. But the same lens on your K-x would have no wide angle coverage, just mid-FL, while presenting a more tele image at the long end.

To get the same framing on a FF body that you would get from the very versatile DA 18-135mm on your K-x would require a lens of about 28-200mm. This same principal applies to all brands of camera. There are more mid-focal length, less extreme at both ends, compromises that are useful for both camera formats. For instance, a FL of 24mm will still provide a moderate wide angle FOV on an APS-C body- comparable to a 35mm lens on a FF body. So if you were to buy a zoom lens of say 24-70mm, it would provide the wide-angle to telephoto range versatility as such lenses are meant to provide, in both cases, but with a shift in emphasis at either end: if used with APS-C sensors would be comparable to 35-105mm on a FF body.

Lenses that are specifically designed for APS-C sensors, in order to take advantage of the smaller sensor to make a smaller lens, will usually cut the lens elements to a smaller circle, which would not quite reach the edges of a FF sensor, so using it on a FF body would create darkness (vignetting) around the parameter of the image. On the other hand, lenses made for FF use, including 35mm film bodies, are cut big enough for this coverage, and the edges of these lens elements being larger, would be in disuse by the edges of the smaller APS-C sensors- they would be actually fitting up to and using the central lens area, but not the edge, which would cause no optical disadvantage.

In other words, while it is usually quite safe to use a FF lens on APS-C bodies without optical consequences, that is very often not the case when putting a lens designed for APS-C on a FF body. The K-1, however, as has been mentioned, has the capability to switch over to APS-C coverage to successfully use these often-excellent APS-C lenses.

Last edited by mikesbike; 12-28-2018 at 01:55 PM.
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