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12-11-2009, 08:22 PM   #1
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SR and green button

I know how to turn on SR, but, what is considered reasonable expectation for SR?

With N*/C* offerings, the VR and IS you can "see" it working and can learn to time the click (sort of but you know what I am trying to get at). I am asking because I see this 1/F or 1/(F*1.5) formula floating around. Does this mean that if I shoot at F100, I need 1/100 (or 1/150) shutter to curb shake? Is that with SR/VR/IS or no?

One big big push for pentax for me is because of in-body SR. I would like to take full advantage if possible.

I read the sticky on green button... very cool. I discovered that because k-x "ok" button is for adjusting focus, ok + green button will reset it to center as oppose to auto ISO like the sticky said for other models. Though I can't get green button to do auto iso on the K-X. but, that's not my question.

I know you can assign green button in menu to do many things. The new firmware added more to the pick list. I recently also got a manual lens. I had originally set green button to do DOF preview. In manual mode, I can't meter with it like the manual lens sticky said. I had to undo green button assignment. This is a pain. Since I want to retain whatever function I assigned with auto focus lens and have green button to function as the nifty button that it is... is this possible?

Also, how far do you screw in the lens? I did it till snug. There are no markings or click to tell me to stop. Is this right? The focus and aperture are just off center to the right when snug for me and the manual/auto is center below flash.

sidenote, I think I know why 3rd party adapter makers use the flange on some models. The pentax original or non flanged adapter leaves all the contacts exposed!! The flange would at least cover them up?

thanks

12-11-2009, 09:57 PM   #2
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QuoteOriginally posted by slow2focus Quote
I know how to turn on SR, but, what is considered reasonable expectation for SR?
People typically say maybe around 2 stops - meaning a shutter speed four times slower than you would otherwise.
QuoteQuote:
I am asking because I see this 1/F or 1/(F*1.5) formula floating around. Does this mean that if I shoot at F100, I need 1/100 (or 1/150) shutter to curb shake?
Well, don't say "F100"; that doesnt mean anything. focal lengths are expressed in millimeters: 100mm. So yes, the basic rule of thumb is that for a 100mm lens, you need a shutter speed of 1/100, and that was for film. For a digital camera with a 1.5 crop factor, you'd start by assuming 1/150. That's before SR. A two stop advantage would mean you could maybe be just as successful with a shutter speed 4 times slower - around 1/40.

But that's that's a rough guess. It's going to depend on how steady your hands are, on how big you print, on how picky you are about the results, etc. You need to test for yourself to get a sense of how fast a shutter speed *you* need in order to get results *you* are comfortable with. See this thread:

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/83033-shutter-s...al-length.html

QuoteQuote:
Also, how far do you screw in the lens?
Any K-mount lens should click. Sounds like maybe you are talking about a screwmount lens, since you mention an adapter?

No idea on your green button question.

Last edited by Marc Sabatella; 12-11-2009 at 10:06 PM.
12-11-2009, 10:38 PM   #3
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QuoteOriginally posted by slow2focus Quote
I

Also, how far do you screw in the lens? I did it till snug. There are no markings or click to tell me to stop. Is this right? The focus and aperture are just off center to the right when snug for me and the manual/auto is center below flash.

sidenote, I think I know why 3rd party adapter makers use the flange on some models. The pentax original or non flanged adapter leaves all the contacts exposed!! The flange would at least cover them up?

thanks
I don't know about the rest of the questions (I think Marc answered them) but if you are mounting an M42 lens with the M42-K adapter, make the lens snug - finger tight. The distance scales and aperture ring will orient to (your) right of vertical and the Auto/Man switch will be directly under the flash protrusion. Your lens mounts just the same as mine - and others have asked the same question. That is normal.

Last edited by monochrome; 12-12-2009 at 10:58 AM.
12-11-2009, 10:52 PM   #4
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QuoteOriginally posted by slow2focus Quote
...Also, how far do you screw in the lens? I did it till snug. There are no markings or click to tell me to stop. Is this right? The focus and aperture are just off center to the right when snug for me and the manual/auto is center below flash.
Snug should be fine. You don't need excessive force. The lenses might end up slightly rotated from their intended orientation, but this is not usually a problem as long as they are fully screwed in. It's sometimes easier to read the scales if they aren't hidden under the flash hump.

QuoteQuote:
sidenote, I think I know why 3rd party adapter makers use the flange on some models. The pentax original or non flanged adapter leaves all the contacts exposed!! The flange would at least cover them up?
The flange also allows you to use the camera's lock and release button, instead of messing around with a spring. But its thickness will prevent most lenses from focusing to infinity, kind of a problem. The contacts are covered with some lenses, exposed with others.

12-12-2009, 08:15 AM   #5
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Yes, I am talking about pentax m42->K adapter.

Thanks guys for all the answers. I need to find a chart that maps Av vs Tv stop for stop.

I'll do more search on the green button

thanks
12-12-2009, 08:55 AM   #6
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Regarding how far to screw a M42 lens into the adapter...

I usually mount the adapter to the lens and then mount the assembly to the camera. That is a lot easier for me at least.

There is one small caution. Many Russian and (I suppose) other lenses have recessed screws on the lens mount surface. This is not a problem with M42 bodies, but can be an issue with a K-mount body. The retaining pin on the body tends to "catch" on these screw holes. As a result, it may be difficult to mount/remove the lens. I have gotten in the habit of always depressing the lens release button when mounting/removing my screw mount lenses.

Steve

P.S. While Monochrome's lenses may orient with the m/f switch under the flash, this varies from lens to lens depending on design. Ditto with where the index point lines up relative to the body. I have two M42 Vivitars that line up exactly with the body, but only with one of my two adapters.
12-12-2009, 11:08 AM   #7
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QuoteOriginally posted by stevebrot Quote

P.S. While Monochrome's lenses may orient with the m/f switch under the flash, this varies from lens to lens depending on design. Ditto with where the index point lines up relative to the body. I have two M42 Vivitars that line up exactly with the body, but only with one of my two adapters.
Oops - to clarify: In my actual experience the Asahi Pentax S-M-C T35/3.5, T50/1.4, Super-Tak 200/4 and the SMC T55/1.8 orient the way I described. The only one of those I still have is the 50

(and



before that lens goes).
12-12-2009, 11:56 AM   #8
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QuoteOriginally posted by slow2focus Quote
I need to find a chart that maps Av vs Tv stop for stop.
What do mean by this? Are you just looking for a list of the f-stops? 2, 2.8, 4, 5.6, 8, 11, 16, 22. Those correspond to a doubling / halving of shutter speed - eg, going from 1/30 to 1/60 in shutter speed would need to be compensated by going from f/4 to f/2.8.

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