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08-25-2007, 04:45 AM   #1
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Manual lenses with Pentax dSLR - compatibility options?

Hello Everyone,

First of all, I need to confess that I am not a Pentax shooter at all. I love my Olympus camers and lenses. However, I am increasing getting frustrated with the Olympus Corp. Unlike Pentax, there is no provision for full backward compatibility for - AF confirmation, valid exif data, auto aperture control, etc...

I have collected a large selection of lenses in Nikon, M42 and OM mount simply because the OMZ 4/3 is so adaptable to different lens mount and lens makers.

Can someone please help me as I need to know what type of manual lenses would be compatible to Pentax. Can you get Nikon-PK or M-PK adapters?

What about the exakta lenses? May be I will be fully restricted to just PK and M42 lens mounts?

Thanks,
Simon

08-31-2007, 11:28 AM   #2
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Pentax lens to film distance is just slightly shorter than OM and Nikon mounts. A bayonent-to-bayonet mount adapter is not possible at those tight distances unless you incorporate optical correction elements to preserve infinity focus. However, these are expensive to make and will degrade IQ.

Nikon F has only about 1mm of leeway. Can you design an adapter that can lock Nikon F lens mount to Pentax K body with the thickness of 1mm?

Pentax has retained some backwards compatibility with previous lenses by not changing their lens mount. However, they have removed the stop-down coupler in an effort to cut costs. This means having to use stop down metering on all non-auto (A) aperture lenses. (P-K mount and M42 lenses).
08-31-2007, 11:37 AM   #3
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If you want a real answer on compatibility of pentax equipment here goes

Pentax *istD and DS have TTL flash, and therefore can work with ALL pentax lenses, and can use all TTL compatible flashes.

all other Pentax DSLRs have P-TTL flash and therefore must read apature value from the lens electronically, therefore you cannot get P-TTL or TTL flash with these lenses. Additionally AF540FGZ and AF360FGZ are the only flashes you can use on later cameras as they are the only ones that have P-TTL capability. Note the AF540FGZ has a photocell so it can do non TTL flash metering (AUTO Mode) with K/M series lenses.

Obviously on all DSLRs K/M lenses (and M42 with adaptor) must be used in manual mode and stopped down metering (or green button).

All other / newer lenses can use all automatic modes.
08-31-2007, 11:47 AM   #4
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Hey Simon,

(I replied over at mff as well, check it out if you haven't yet.)

The only normal adapters for Pentax are for M42 (which work in stop-down but otherwise as intended) and for medium format, like Pentax 645. There is not enough distance to house the bayonet of a Nikon lens or of a Leica R lens, I have tried to fit both.

You can convert Contax/Yashica mounts to Pentax K mount with surgery that isn't too bad.

Other than that, you're restricted to Pentax K mount lenses. And as many of us here have discovered, if you use a pre-A lens (K and M series, or even M42 lenses) the newer bodies like the K10D have exposure creep as you stop down. There is no such problem with the *ist D or *ist DS, and replacing the focus screen in the K10D with one from the DS solved my exposure woes.

Good luck!
Sean

08-31-2007, 11:50 AM   #5
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QuoteOriginally posted by Lowell Goudge Quote
Obviously on all DSLRs K/M lenses (and M42 with adaptor) must be used in manual mode and stopped down metering (or green button).
M42 lenses must be used in stop-down mode; therefore, they support shooting in Av mode. You do not need to shoot in M mode nor do you need to press the green button to meter. (P mode defaults to Av mode with M42 lenses.)
08-31-2007, 12:04 PM   #6
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QuoteOriginally posted by carpents Quote
M42 lenses must be used in stop-down mode; therefore, they support shooting in Av mode. You do not need to shoot in M mode nor do you need to press the green button to meter. (P mode defaults to Av mode with M42 lenses.)
No they don't!

In Av mode the lens never stops down regardless of apature setting. You essentyally get full apature with shutter speed set to give exposure at full apature. This does not really meet my definition of working.

This happens because there is no manual apature connection to tell the camera where the lens is set.
08-31-2007, 12:08 PM   #7
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QuoteOriginally posted by Lowell Goudge Quote
No they don't!
Wanna bet?


All M42 lenses work in stop-down mode, period. Even the ones without an Auto/Manual switch will work with the proper adapter. I have exactly 31 M42 lenses - I am absolutely correct.

There is even a trick for getting K- and M-series lenses to work in stop down, by mounting them slightly skewed. Drilling a minor hole in the mount for the stopping pin is all you need to do.

Last edited by carpents; 08-31-2007 at 12:26 PM. Reason: Counted my M42 lenses.
08-31-2007, 01:44 PM   #8
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QuoteOriginally posted by carpents Quote
Wanna bet?


All M42 lenses work in stop-down mode, period. Even the ones without an Auto/Manual switch will work with the proper adapter. I have exactly 31 M42 lenses - I am absolutely correct.

There is even a trick for getting K- and M-series lenses to work in stop down, by mounting them slightly skewed. Drilling a minor hole in the mount for the stopping pin is all you need to do.
If drilling holes to partially mount a lens not fully engaged on the bayonette is your definition of compatible you need help.

I mean that when you snap them on they don't work. you mean that if you want to modify the mounts they can be made to work.

Big difference

08-31-2007, 05:17 PM   #9
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QuoteOriginally posted by Lowell Goudge Quote
If drilling holes to partially mount a lens not fully engaged on the bayonette is your definition of compatible you need help.

I mean that when you snap them on they don't work. you mean that if you want to modify the mounts they can be made to work.

Big difference
Dude, read my post.

There is a trick to use K- and M-mount lenses.

M42 lenses WILL STOP DOWN when you move the aperture ring. The camera can not press the plunger, so the lens must be operated in STOP DOWN (manual) mode. You only need the M42-to-Pentax K mount adapter! No modifications necessary.

If you are doubting what I am saying you obviously do not have M42 lenses and do not know what you are talking about.

Period!!
09-01-2007, 03:14 AM   #10
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Carpents is tottaly right, M42 lenses work in Av mode.

I don't know about the ones without A/M switch, but with mines i just need to put the switch on M, select Av on the camera and shoot.
09-01-2007, 05:10 AM   #11
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QuoteOriginally posted by Pornflake Quote
Carpents is tottaly right, M42 lenses work in Av mode.
99% of the time Av mode is the sensible and practical way to shoot M42s.

QuoteQuote:
I don't know about the ones without A/M switch, but with mines i just need to put the switch on M, select Av on the camera and shoot.
The only time I don't use Av with M42s is if I want to overexpose due to back lighting or something. Since the Takumars want +1.5 EV and the Chinese screen wants another +0.5 I'm already maxed out. In those cases I look at the shutter speed from Av mode, switch to M, and make the correction manually.

Lowell, the reason it works is, as you pointed out, the camera thinks it is metering for maximum aperture (as with M lenses). But since M42 users manually stop down the iris to the shooting aperture prior to shooting, the camera makes the adjustment to shutter speed with no problem.
09-01-2007, 05:31 PM   #12
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Also, for K100D users, unless the mount is covered with a conductor (i.e. a bare flanged adapter or foil), Av causes some bizarre underexposure with M42 lenses.

I normally have to use the AE-L button in manual mode and then I get a proper reading.

I have no idea why this is the case but I don't have a lot of screw lenses anyhow.
09-02-2007, 05:11 AM   #13
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Yes my k100d underexposes terrible with my takumar lenses, in AE-L and in Av, sometimes +1 EV compensantion is enough, another times i just use M mode.
09-02-2007, 05:41 AM   #14
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QuoteOriginally posted by jslifoaw Quote
Also, for K100D users, unless the mount is covered with a conductor (i.e. a bare flanged adapter or foil), Av causes some bizarre underexposure with M42 lenses.

I normally have to use the AE-L button in manual mode and then I get a proper reading.

I have no idea why this is the case but I don't have a lot of screw lenses anyhow.
I have several and use them extensively. I would love to hear more about this foil thingy.

I just did an experiment comparing Av with a +2 bump and manual metering via the AE-L button in M mode. The M mode underexposes a bit.
09-02-2007, 05:57 AM   #15
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QuoteOriginally posted by carpents Quote

You can convert Contax/Yashica mounts to Pentax K mount with surgery that isn't too bad.
HeySean!

Please point me in the right direction! I really wanna use my Zeiss glass on the K10D. Actually, I´ve been itching for a Canon just to be able to use them...

I hear switching the focusing screen to a catz eye split or a istD screen will take care of the stop down metering issues on the K10D as well.

// Mats

Last edited by matsoberg; 09-02-2007 at 06:13 AM.
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