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01-10-2011, 09:24 PM   #1
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Using the Pentax-M 50mm f1.7 with the K-x...

A foray into nice older (cheaper) glass, just picked up a 50mm M f1.7

I'm struggling a bit on the proper usage of this lens with my K-x....any clearly explained sites or input from fellow forum members on what settings, easiest way to use this lens? I'm excited to use this glass, I've heard great things and the reviews are flattering.

(e.g., I've enabled the "Permit using aperture ring", I believe that's my first step??

ANY help appreciated, in easy, "K-x/M Series Primes for Dummies" language

01-11-2011, 02:33 AM - 1 Like   #2
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Adam's sticky [ https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html ] covers the technicalities. Here's my rendition:

You've enabled the aperture ring. Excellent. Being an M-type lens, your M50/1.7 has no automatic aperture linkage. So if the Kx is set to an auto mode (P, Av, Tv, etc) it defaults to Av and the lens aperture is always wide-open. To stop-down, shift to M(anual) mode. Aim at a subject. Press the Green button -- that will stop-down the lens and take an exposure reading. If you like the shutter speed and aperture, then focus and shoot. The lens will stop-down for the shot.

Manual focus is the trick for those coming from AF-only shooting. Your camera's focus confirmation system will still work -- the green hex will appear in your viewfinder. You can also enable Catch-In-Focus (CIF). Aim at a subject, hit the Green button to let the lens stop-down, hold down the shutter, slowly focus, and when focus is achieved, SNAP! goes the camera. The Shake Reduction (SR) system works also. When you set SR on, you need to tell the camera what focal length to use, which for your lens is 50mm. That's 50mm, not 75mm -- forget you ever heard of Crap Factor. The SR robot only cares about actual focal lengths, not 'equivalences'.

Let's say you're in M(anual) mode and you've got a subject and you've hit the Green button and you've focused and shot. Now, chimp the picture. Too dark or light? Change the aperture or shutter or ISO manually. You have COMPETE CONTROL!! But don't let this godlike power go to your head. Be humble. Outsmarting a camera isn't easy. Mine humiliates me daily. But I'm a retired (obsolete) computer programmer, so I'm used to being humiliated by machines with less intelligence than a cockroach.

That covers the basics of technique. Everything else is a matter of style. Except flash. Flash with an M-type lens is a can of worms I won't open right now. Practice shooting manually. Have fun!
01-11-2011, 09:12 AM   #3
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RioRico---good stuff, I will clumsily exercise my complete control ;-D Thnx much
01-11-2011, 09:20 AM   #4
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Rio has pretty much covered it, I use a slightly different method.

I set the aperture I want, usually starting at f8, and use the +/- EV button tro set the shutter speed. Easier than using the green button because the green button is hard to reach in a hurry. It also does a pretty good job of setting exposure time, and after a shot or two I can change it manually if needed, and it stays put.

And as for Rio's comment

Manual focus is the trick for those coming from AF-only shooting.

All I can say is my usual advice to remember the three P's...

Practice, Practice, Practice.

You might want to try using smaller apertures at first, they tend to be a bit more forgiving with manual focus due to increased depth of field. Since you have more depth to work with, you can miss your focus slightly and still come out OK. Usually I can still tell I missed, but I get quite a few decent shots at f8-f11 that would be useless at f1.4.

I have that same 50mm f1.7 lens, I like it quite well. I've gotten plenty nice shots with it, I think you'll like yours once you get accustomed to the lens and manual focus. It's a good lens.

01-12-2011, 01:14 PM   #5
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My advice is: remove the aperture lever of the manual lens and voila! you can shoot in Av mode and no more metering problem.
01-12-2011, 01:35 PM   #6
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Excuse

Could you explain if it is a complicated operation to remove the aperture lever ? I know that metering with K and M lenses has difficulties and need a lot of trial-error tests , and so perhaps would like to carry out in some of my manual lenses.

Thanks in advance
01-13-2011, 01:47 PM   #7
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In M and earlier lenses, the lever moment is proportional to the diameter of aperture, while in newer lenses, it's proportional to the area (i.e. diameter squared). This is how the metering is affected. The simplest operation is to plug the hole with chewing gum or kid's play dough, then use a jewel saw to cut off the lever. This permanently alters the lens. I did this on a M50mm f2. To open the lens, you need 00 and 000 Phillips screw drivers. Remove the 4 screws on the stainless steel lens mount and carefully lift up the mount while holding the aperture ring. Don't remove aperture ring. In some lens, the lever is spot weld on the ring which rotates around the lens mount and you would have no choice but to cut the lever. I would suggest you go to the pawn shop to buy the old lens for experiment (about $5-10 per lens).

Last edited by violini; 01-13-2011 at 01:56 PM.
01-13-2011, 02:09 PM   #8
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QuoteOriginally posted by violini Quote
Remove the 4 screws on the stainless steel lens mount and carefully lift up the mount while holding the aperture ring. Don't remove aperture ring. In some lens, the lever is spot weld on the ring which rotates arou[...]
Alternatively, if you really don't like the 1.7 'M' then rather than reduce its value to $0 you can sell it for the same price you bought it for and buy a 1.7 'A' for $30-40 more. That'll work like any modern lens except it's manual focus. And it doesn't involve sawing or dismantling anything.

01-13-2011, 04:46 PM   #9
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Thank you Violini for your detailed explanation. It seems to be quite complicated surgery.
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