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09-06-2011, 08:02 PM   #1
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What do I need to know about the A and M Lenses for my K-x ?

So I see these manual focus lenses going for cheap in the marketplace. I'm fine with manual focus, but just wondering if there is anything else that I will need to set manually or should I spend extra and get the F, DA or FA lenses ?

09-06-2011, 08:22 PM   #2
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Manual focus SMC Pentax-A lenses will work just fine on a K-x. Just remember to keep the aperture ring set to "A". The camera will then give you access to all available apertures just like F, FA and D FA lenses.

Manual Focus SMC Pentax-M (and the original K-mount) lenses will need a change in the custom setting to allow the use of the aperture at settings other than "A". After that you can use the lens at all apertures in Manual mode and set the correct exposure using a button on the camera. See the manual for which button to push (varies between models). You can also set the lens to its maximum aperture and use the lens in Av mode, where the camera will pick the corresponding shutter speed based on the light coming through the lens.

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09-06-2011, 08:28 PM   #3
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M lens requires manual aperture control via the aperture ring. A lens does not have that requirement.
09-06-2011, 09:02 PM   #4
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You might want to consider getting a split image focusing screen if you are going to Dona lot of MF work

MF lenses , especially ps tax ones are very good and perform well, even the oldest takumar lenses

Check the lens club forum for the takumar, K , and M clubs.

09-06-2011, 09:07 PM   #5
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Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html

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09-06-2011, 09:50 PM   #6
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Manual-focus lenses won't tell the camera what their focal length is, so you have to set it manually for SR to work. It's not a big deal for primes; zooms are a little more difficult.

The stock focus screen is usable but it's designed for AF. I would not switch it immediately. See how you like it first. For apertures faster than f2.8, the stock screen will show more depth of field than the image will have. Alternative screens have advantages and disadvantages.

The focus ring feels much different than focusing an AF lens.
09-07-2011, 10:50 AM   #7
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I currently have ~220 lenses, of which 10 are AF. The AF lenses cost me an average of US$255 each; the MF cost an average of US$20 each. Whew! I like AF zooms (for taking pictures) and MF primes (for making pictures). Besides what's already been said, be aware that you can use CIF (catch-in-focus), the poor hominid's AF. MFL's are no problem!
09-07-2011, 01:15 PM   #8
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Original Poster
QuoteOriginally posted by Lowell Goudge Quote
You might want to consider getting a split image focusing screen if you are going to Dona lot of MF work

MF lenses , especially ps tax ones are very good and perform well, even the oldest takumar lenses

Check the lens club forum for the takumar, K , and M clubs.
Hmm, never heard of split image focussing screens before. Read about it a bit on google. Can this be done on K-x ? Where do I find one ?

Is there one screen that is good for manual and AF, don't want to be changing screens in the field

QuoteOriginally posted by Just1MoreDave Quote
Manual-focus lenses won't tell the camera what their focal length is, so you have to set it manually for SR to work. It's not a big deal for primes; zooms are a little more difficult.
I'm looking for primes that are manual, so won't be dealing with manual zooms. How do I tell the camera the focal length ?

09-07-2011, 01:44 PM   #9
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QuoteOriginally posted by StDevious Quote
Hmm, never heard of split image focussing screens before. Read about it a bit on google. Can this be done on K-x ? Where do I find one ?
Also consider the Pentax magnifying eyecup O-ME53. They're quite inexpensive, dead simple to install and no down side. I installed one on my K-x. It made a big difference for manually focussing my inexpensive old primes. Check B&H they had them for under $40.00.

QuoteOriginally posted by StDevious Quote
I'm looking for primes that are manual, so won't be dealing with manual zooms. How do I tell the camera the focal length ?
When you turn the camera on with an A or M lens mounted, a screen pops up that asks for the focal length. If you don't enter a focal length, the camera will use whatever FL was entered last.
09-07-2011, 01:54 PM   #10
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Split image focusing screens are available for most pentax cameras. The "gold standard" is Katz-eye, but I have two different ones from china for my K10D and *istD. K7 still has the origonal screen.

Split image is good for MF and I find the freznel screen surrounding the split image is also useful, but there is a downside, you give up spot metering, and with lenses F5.6 and slower the center can go dark.

Since I use my older bodies for MF lenses this has not bothered me

If you search for one for your camera there are a couple I like,

I have a dual diagonal split from Jin Finance which I like more than a single split, and there is Katz Eye, as noted above.

Katz will give you the best support.

Although I have not required it some split image focusing screens require shims.
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