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09-25-2011, 11:26 AM   #1
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Shutter speed with manual lens

I'm using a Tamron adaptall 60-300 lens on my K-5. I'm into a pretty steep learning curve, but starting to get reasonable results.

What I want is to be able to set the shutter speed and have the iso automatically adjust for exposure. Something similar to the TAV mode, but with the aperture set on the lens ring. I'm playing with the P mode but the shutter speed changes not the iso.

Any ideas?

09-25-2011, 12:06 PM   #2
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I could be wrong, but I don't think the K5 allows that. I know my K20D doesn't. With a non-AF or non-A-type lens mounted, Av is the only auto mode that works. So you can't have ISO floating within a range; just pick the highest ISO you're comfortable with, and adjust manually as needed. Now, there's a trick I haven't tried yet, of shorting certain mount contacts to fool the cam into thinking an A-type lens is mounted. That might allow TV mode, but I don't know with what accuracy.
09-25-2011, 12:37 PM   #3
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AV mode doesn't work either. With an M type K mount lens (no A setting on the aperture) you will always be shooting wide open in any mode except M. Auto ISO does not work in M mode because the camera has no way of knowing what the aperture is. It will always default to the lowest setting in your Auto Range (Pg 114). With a Preset type lens or other M42 that you can actually operate the aperture while mounted on the camera, any auto mode will default to Aperture Priority and Auto ISO can be used with Those lenses.

09-25-2011, 01:50 PM   #4
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QuoteOriginally posted by JeffJS Quote
With an M type K mount lens (no A setting on the aperture) you will always be shooting wide open in any mode except M.
I think that depends on which type of Adaptall mount is on the lens. My Tamron BBAR 28/2.5 has a bare-K-type mount, with no aperture-link lever, so it functions the same as a T2-type lens or cheap bellows or tubes, with working Av mode.
______________________________________________________________________________

EDIT: Ok, this brings up a peeve or quandary or whatever, about Pentax bayonet mount nomenclature. Pentax introduced the mount with the K1000 in 1975. [See the Wikipedia entry.] The original K-mount, which is the same on M-type lenses, has the bayonet blades and a mechanical aparture-link lever. That's the native PK mount. The KA mount has the aperture-control pins; later F-, FA- and DA-mounts include autofocus. No problem.

But there's an even simpler mount, which lacks the aperture linkage. Just 3 bayonet blades and nothing else. This is what I find on T- and T2-mount adapters, some Adaptalls, mount-reversal adapters, cheap macro tubes and bayonets, wide-flanged M42-PK and M39-PK adapters, mirrors, etc. Above, I called this a bare-K-type mount. But that's not good enough. WHAT IS THE NAME OF A BARE K MOUNT? I am like so perplexed.

Non-AF mount variants:

PKM - K- and M-type lenses
PKA - A-type lenses
PKR - Ricoh-pin A-type lenses

PK0 - zero-type lenses?


Last edited by RioRico; 09-25-2011 at 02:10 PM.
09-25-2011, 02:12 PM   #5
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QuoteOriginally posted by derekkite Quote
I'm using a Tamron adaptall 60-300 lens on my K-5. I'm into a pretty steep learning curve, but starting to get reasonable results.

What I want is to be able to set the shutter speed and have the iso automatically adjust for exposure. Something similar to the TAV mode, but with the aperture set on the lens ring. I'm playing with the P mode but the shutter speed changes not the iso.

Any ideas?
You can only set exposure time and aperture independent of each other in fully manual "M" mode and I don't think any Pentax camera allows for automatic setting of ISO in that mode.

I don't know the details of the K-5 but I wonder if you cannot set ISO to AUTO for the other modes (P, Av, Tv)? At least, I can on my K200D. If so, you can achieve some of what you want in Tv-mode: You can set your exposure time and leave ISO and Aperture to the camera.

HOWEVER, this requires that your custom mount for your Adaptall-2 lens is of the P/KA type - so that you can set the lens to "A" mode (in Tamron terminology "AE-mode") and not the more common - and substantially cheaper - P/K type.
You may read a bit more on this subject here:

Tamron Adaptall and Adaptall-2 Custom Mounts

- not ot speak of the Adatall Lens Club pages in this forum.
09-25-2011, 05:13 PM   #6
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I'm still not certain how this all works, in M mode, I set the iso top range higher, I tried 3200 iso, set the iso at that using the iso button, hit the green button, it comes up wiith a shutter speed for the proper exposure at 3200 iso. The front wheel can adjust the shutter speed, but I'm not certain if it is used when the shutter button is pushed. I'm going to have to do a bunch of shots with a notebook and figure out how it all works. There are three different settings for the green button in M mode, one shifts shutter, one uses the Program Line, the other shifts the aperture. The ae button can lock the exposure, and supposedly shift the aperture with the shutter speed, not sure how it applies here.

As I said, steep learning curve. I'll write it all up when I figure it out. Right now nothing seems predictable, which is frustrating when you want to catch action with a fast shutter. Exposures look fine.
09-25-2011, 05:37 PM   #7
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If you have a lens not in the A position, or a non A lens the K5 will in manual mode set the shutter to match the aperture whe green button is pressed, the lens will stop down when shutter is pressed

the camera will meter and shoot at maximum aperture in Av mode.

Knever tried autoniso in any mode but doubt it will work.
09-25-2011, 05:40 PM   #8
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Hi! Don't know for sure if this will work for your purpose. Yet I can use my "M" lenses and other manual ones in Program mode. Find a copy of Yvon Bourque's book on the Pentax digital cameras. In a nutshell the key is to mount the lens so that it is not locked in position. I have his books for the K10d and K7. He explains how it is done. I can take advantage of the camera's exposure control while I set the stopped down aperture. I can change the ISO as needed. Good luck.

Manuel

P.S. Here is a sample using a Pentax SMC-M 40mm at f8 (hyperfocal), ISO400.




Last edited by marosari00; 09-27-2011 at 04:02 PM. Reason: adding photo
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