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09-19-2010, 01:34 PM   #1
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Can I use a Canon 50mm f 1.8 on my K-x

I have this lens that I used on a Canon A-1. I think it is a F lens.Thanks

09-19-2010, 01:55 PM   #2
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F-mount is a Nikon lens. The A-1 used FD-mount lenses. It can be mounted on a K-x but needs an optically corrected adapter that acts as a short teleconverter.

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/96884-ada...addiction.html
09-19-2010, 01:56 PM - 1 Like   #3
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QuoteQuote:
Can I use a Canon 50 f 1.8 on my K-x
NO
All Canon lenses have a shorter register (lens-mount-to-sensor distance) than do Pentax-compatible lenses. Long-register lenses can go on short-register cameras, but not vice-versa. Nikon has the longest register of major brands, a bit longer than Pentax, and is thus a "universal donor". Canon has the shortest register of major FF and APS-C brands, and is a "universal receptor". Canonites can steal our Pentax glass away from us and use it, but we can't reciprocate. And that's why I'm selling all my fine, useless Canon lenses on eBay [ID: r*m].

OK, let me clarify. A Canon lens *could* be used on a Kx, but either with an optical adapter that reduces image quality, or for closeups or macros. The optical adapter takes away whatever was special about the Canon lens. There are many many many fine 50-55mm f/1.7-2 lenses available REAL CHEAP on eBay and elsewhere, many of which would cost less than an optical adapter, and which will deliver better images that the Canon+adapter rig. Look for an SMC-M 50/1.7 or a Takumar 55/1.8, both of which are excellent and cheap.
09-19-2010, 03:02 PM   #4
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There's a dozen cheap Pentax SMC-M 50mm F1.7 for sale on ebay. Here's an example for $50:

SMC Pentax -M 1:1.7 50MM Lens - eBay (item 260664168453 end time Sep-20-10 11:04:52 PDT)

There's some Pentax SMC-A versions too. Here's another example (but this one is bid only, not buy now):

http://cgi.ebay.com/SMC-Pentax-A-50mm-1-7-lens-Film-Digital-/150495435277?pt...item230a3a1a0d

I just picked up a Pentax ME Super with flash and a SMC-M 50mm F1.4 from a forum member for $125 shipped. I plan to keep this film system together to use.

09-19-2010, 06:40 PM   #5
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Thank you all. Been looking at 50mm also.. in A and FA. Should I get 1.7 or 1.4? Appreciate you thoughts.
09-19-2010, 08:57 PM   #6
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QuoteOriginally posted by tkossally Quote
Thank you all. Been looking at 50mm also.. in A and FA. Should I get 1.7 or 1.4? Appreciate you thoughts.
Faster costs more. AF costs more. Usually. It all depends on your desires, and your finances. Check the llens review database for evaluations of possibilities. If you can deal with M42 threadmount lenses and adapters, the Takumar 55/1.8 is much beloved. And the 55/2 has EXACTLY THE SAME OPTICS as the 55/1.8, just a slightly slower aperture, and can often be had for around US$10. Another renowned cheap favorite is the Helios-44 58/2, still available for ~US$25.

Fast glass has a few things going for it.

1) Brighter image in the viewfinder.
2) Thinner depth of field.
3) Wider aperture for a "sweet zone" of sharpness.
4) Bragging rights. Woo woo...

That thin DOF is what many crave. But the longer the focal length, the thinner the DOF. So a 58/2 has thinner DOF than a 55/2, which is thinner than a 50/2, etc. DOF of a 58/2 is somewhere between those of 55/1.8's and 50/1.4's, at a lower cost.

Pentax A and F and FA lenses are easier to use than Taks and K and M types. And they cost more. What the hell, it's only money, eh?

Last edited by RioRico; 09-20-2010 at 04:37 AM. Reason: fixup
09-20-2010, 05:32 AM   #7
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A nice table to help with the bewildering array of Helios 44 lens versions. Just keep in mind that any 44M other than the original variant are Auto only and have to be modified to use stop down metering. The 44-2 & 44-3 are pre-sets & tend to wobble when mounted on the camera.

Helios 44 M42 Lenses Pixelfarmize
09-20-2010, 08:48 AM   #8
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First question to answer - why do you want a 50mm lens at all? It's kind of an oddball focal length on APS-C. The answer to that question will help determine whether you need to pay the premium for AF, whether you need autoexposure support, you'd be happier with the f/1.7 or f/1.4 versions, etc. If it's for portraits (the most common application for a 50mm lens on APS-C), then I'd say AF is not needed, but autoexposure - not for the exposure itself, but for flash automation. And f/1.7 or f/1.4 won't matter. So the A50/1.7 ends up making most sense at around $100. Or if you'd like to go cheaper, the A50/2, but it's definitely not as good optically.

If your purpose is something other than portraits, then you'd have to be more specific about what it is in order to understand how valuable AF or AE would be for that purpose.

If you're simply thinking about getting a 50mm because back in the film days everyone had one, then you need to be looking at 35mm lenses instead, because of the "crop factor".

09-20-2010, 09:12 AM   #9
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Marc,

So true, that's why i'm interested in the DA-L 35mm F2.4 about to be released. It's MSRP is 1/3 of the 35mm Limited I see on ebay. I'm not concerned that it can only auto-focus and needs to be stopped down in camera instead of having a ring. For a walk-around lense it bears consideration.
09-20-2010, 09:34 AM   #10
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I thought the reason you want a real 50mm lens is because there's no perspective distortion and not because of the field of view
09-20-2010, 07:24 PM   #11
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Perspective is a function of field of view, not of focal length. If 50mm produces no perspective distortion on film, then it's 35mm that does the same on APS-C.
09-21-2010, 12:20 PM   #12
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Mark, you hit it on the head with your last paragraph. Everybody had a 50. I always thought a 85 is the ideal portrait lens, hence my looking at 50s...close when x 1.5. I will look at 35s also. Thanks all.
09-21-2010, 01:34 PM   #13
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QuoteOriginally posted by tkossally Quote
Mark, you hit it on the head with your last paragraph. Everybody had a 50. I always thought a 85 is the ideal portrait lens, hence my looking at 50s...close when x 1.5. I will look at 35s also. Thanks all.
Then a 55 or 58 is even closer.
09-22-2010, 02:02 PM   #14
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QuoteOriginally posted by tkossally Quote
Mark, you hit it on the head with your last paragraph. Everybody had a 50. I always thought a 85 is the ideal portrait lens, hence my looking at 50s...close when x 1.5. I will look at 35s also. Thanks all.

Well, really, since the 85 is my favorite film camera lens and I like the FOV, (Personal taste, really, but I do like my framing and composition a bit tighter than most, anyway) . I think it's great that there's all these little fast 50's out there. I don't think it's particularly bad for people to be using 50's on crop cameras: when 50's were ubiquitous on film, you used to want to crop down a lot of their shots, anyway.

Since they're so cheap and common, especially, they're a fine lens to use, (And, for the OP, if it's an AF lens you want, you'll find that the FA 50 1.4 is probably about the same price as a (Pentax- F) 1.7: this is because the FA's only came in the 1.4 and are thus a lot more common, and both are fine lenses. I built my Pentax system around my 1.4: it was on order before my K20d. ) Manual focus ones run the gamut of price ranges, plenty of good ones out there for cheap. (Cheaper than trying to adapt old Canon, as Rico mentioned... though I wonder what he's selling off in FD mount: I still use my old Canons. )

Of course, what everyone says about crop factors is true: something in the range of 30-35ish, or a 28, will be more versatile for you.
09-24-2010, 11:32 AM   #15
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QuoteOriginally posted by future_retro Quote
I thought the reason you want a real 50mm lens is because there's no perspective distortion and not because of the field of view
Perspective is determined by the distance from the lens to the subject.

And what is a "real" 50mm lens? Is it different than a "fake" 50mm lens? A "virtual" 50mm lens (sorry, been playing with VMWare and VirtualBox for too long)
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