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07-31-2007, 08:00 AM   #1
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Right focal lenght for shake reduction on s-mount lenses

Hello

I have many screw mount lenses which if found from fleamarket only for 5 euros and I found them the very next day I ordered my camera. I was so excited. With little patience I cleaned all up and now I have nice variety of manual lenses. Most proud I am for 50/1,8 which I like to use the most.
But what is correct data for shake reduction when I put power on the camera? Because lens is 50mm so do I have to put the real focal length 50mm or the multiplied focal length 75mm (50 x 1,5)?
While I watch shots in pentax photo editor there is 50mm in focal length line which I have picked before I have started shooting. So I think I should choose 75mm?

07-31-2007, 08:18 AM   #2
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No, use actual focal length. If you put 75mm in it will show up in the software as 75mm. When somebody else looks at it they will "ASSUME" the lens was a 75 not a 50. It gets confusing so stay with actual mm.

Regards,

Ken
07-31-2007, 09:02 AM   #3
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Ok, thanks

..and there ain't even option for 75mm, nearest is 77mm..
07-31-2007, 11:44 AM   #4
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QuoteOriginally posted by uPiX Quote
Ok, thanks

..and there ain't even option for 75mm, nearest is 77mm..
That's because Pentax never made a 75mm lens, come to that I don't think I ever saw a 75mm lens for 35mm or digital.

SR needs the actual focal length of the lens you are using, so it can accurately correct for shake. SR doesn't care what the crop factor is, it's a misleading term anyway. All 50mm lenses are just that, 50mm. Its only the FOV that changes with a so-called crop sensor. I think this has been done to death already, so I won't labour the point.


01-29-2008, 02:48 PM   #5
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Is there anything I need to do to have the SR ask me what lens I'm using?

My adapter just arrived today for my K10D, and I've put it in, put on my favorite SMC 135/ 1:2.5 lens, and I've turned the shake reduction off and on, tried manual focus and both autofocus settings, but can't seem to get the shake reduction working.
01-29-2008, 02:58 PM   #6
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What to put in for manual zoom lens

I have this question that I have no idea what to dial in if my lens is a manual focus zoom lens, powering on always prompt me the focal length. If my lens is manual focus zoom 28-70, what is the ideal length to put in there. I usually dial in the closest estimate that I intend to use, but I wonder if others know about a better way with reason. When I am off to a zoom end different than the one that I dialed in, I just turn off/on again and redial in the focal length. But that seems silly to do every time.

It is not a problem for me to dial in for fixed length prime, but it is a pain and awkward for me to guess my focal length to be used in a manual zoom lens. Any ideas to share, much appreciated.

Hin
01-29-2008, 02:59 PM   #7
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The camera should prompt you when you first turn it on. Try turning on shake reduction and then turning on the camera.
01-29-2008, 03:19 PM   #8
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I've turned it on with the SR on, with SR off, and in all different conbinations of AF settings.
SR works just fine with all my DA or FA lenses...but I've got some really nice (for me) old glass from my Spotmatic...which was the reason I went with Pentax in the first place!

Any other hints or suggestions?

01-29-2008, 11:02 PM   #9
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Turn cam to MF on the side -> Mount lens -> SR on -> It should now ask you when you flip it on...

Don't hit the shutter button, and if you have a grip try turning it off.

Your adapter sits inside the K mount, yeah?
01-30-2008, 12:27 AM   #10
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QuoteOriginally posted by hinman Quote
If my lens is manual focus zoom 28-70, what is the ideal length to put in there.
The best way is of course to dial in the new value when you change it. Instead of turning on and off you can also press Menu, UP, OK and you are there.
If you want to use one focal length then always use the lowest. In your case choose 28 or closest to that. I personally round down. Using lowest focal lenght is needed to avoid SR overcompensation (the result of that is even more shake than your hands produced).
01-30-2008, 04:50 AM   #11
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The K10D manual (p. 69) recommends setting the focal length for zoom lenses to the actual focal length being used. Start the camera up with the SR switch set to On. If you change the focal length on your zoom as you're shooting, go Menu>Shooting Menu>Shake Reduction to get to the Set focal Length command, or turn the camera off and back on as Procyon suggests.

Oh, and if your lovely M42 glass lacks the A position on the aperture ring (that's true of all the ones I have), I believe you're also going to have to go into the Custom Settings menu and set Using Aperture Ring to Permitted. BTW, I haven't yet bought Pentax's M42 screw-mount to K bayonet adapter, so don't know if it can adapt the auto-diaphragm switch and plunger mechanism on the Takumar lenses to function as though there were an A position on the aperture ring. I suspect not, but would appreciate it if anyone on the forum can inform me and others about this.
01-30-2008, 06:26 AM   #12
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There's no such thing as an "A" position on the aperture ring of M42 lenses. The crippled mounts of the digitals have no method of actuating the aperture on M42 lenses at all. You have to do all shooting in manual stopdown.

Easiest way:

1. Av mode
2. Focus
3. Set aperture
4. Shoot

You'll need to go into the Custom menu and set it for aperture ring permitted, for focus indicator with S lenses, and set the program line to Tv shift.
01-30-2008, 11:30 AM   #13
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QuoteOriginally posted by procyon Quote
The best way is of course to dial in the new value when you change it. Instead of turning on and off you can also press Menu, UP, OK and you are there.
If you want to use one focal length then always use the lowest. In your case choose 28 or closest to that. I personally round down. Using lowest focal lenght is needed to avoid SR overcompensation (the result of that is even more shake than your hands produced).
Thank you so much for the tips. I was doing it all along with the tip that 'Menu followed by up Up arrow, Ok' gets to Shake Reduction focal length. And thanks for the logical taking on the rounding down value closest to the focal length to be used.

Much thanks for the great tip,
Hin
01-31-2008, 07:39 AM   #14
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Thanks, Mike. That's about what I expected, but I asked since I haven't seen a very consistent description of what the various manufacturers' M42>K mount adapters do...some focus to infinity while some don't, some have a pin that is troublesome to use while others don't...I wasn't too sure what to expect with regard to stop-down behavior. Eventually, I'll add the Pentax brand adapter despite the fuss in the menu.
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