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What manual aperature / focusing lens for K-50 with Aperature Block

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wil_war

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Rather than discarding my K-50 with Aperature Block (i.e., all pics dark), someone said I could buy a used "manual" 50mm, F1.4 lens and mount on my Pentax KAF2 fitting and be able to use camera?

Is this true and if so, what type lens should I try to get? I assume, I can use camera allowing shutter speed to determine correct exposure for the F-Stop I've manually set.

is this true, Any advice or is this a bad idea ?
 
wil_war said:
Rather than discarding my K-50 with Aperature Block (i.e., all pics dark), someone said I could buy a used "manual" 50mm, F1.4 lens and mount on my Pentax KAF2 fitting and be able to use camera?

Is this true and if so, what type lens should I try to get? I assume, I can use camera allowing shutter speed to determine correct exposure for the F-Stop I've manually set.

is this true, Any advice or is this a bad idea ?
Click to expand...
You can use any lens which has the aperture ring, you select the aperture manually on the lens, put camera in M mode, and use green button for stop-down metering. AF lenses with aperture ring will autofocus normally. With some practice it becomes almost automatic, only real work is having to manually set ISO all the time, as well as white balance in situations other then daylight (although AWB is not that bad on good lenses with no weird color shifts).
 
Won't an A series lens set the iso & shutter automatically once the aperture is set on the ring?

--
Regards Dean - Capturing Creation
N.B. All my Images are Protected by Copyright
 
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I know you asked about manual aperture/focusing, but as long as you have the latest firmware on your K-50 the 55-300mm f/4.5-6.3 ED PLM WR RE Lens should work fine with all functionality, since the aperture is controlled electronically (correct me if I'm wrong!)
 
You have got some answers, but I do not know if they are correct.

What do you mean with "Aperture Block"?

I guess that it means that the aperture level in the body is always set to fully stopped down aperture. Right?

If that is the case, then the advices you have got also are correct.

You can use any manual aperture (PENTAX, PENTAX-M) lens, and if the lens has an A position (PENTAX-A, PENTAX-F, PENTAX-FA) then you can use it, not using the A position.

The PENTAX-M 50/1.7 is a gem and cheap and easily available. The PENTAX-A 50/1.7 is also a nice one.

Here is the best source for finding old Pentax lenses https://www.pentaxforums.com/lensreviews/ .
 
Roland Karlsson said:
You can use any manual aperture (PENTAX, PENTAX-M) lens, and if the lens has an A position (PENTAX-A, PENTAX-F, PENTAX-FA) then you can use it, not using the A position.
Click to expand...
Presumably using a Pentax A lens with the aperture ring set to the "A" position would also lead to the black frame/aperture block problem right?
 
Andrew Gardner said:
I know you asked about manual aperture/focusing, but as long as you have the latest firmware on your K-50 the 55-300mm f/4.5-6.3 ED PLM WR RE Lens should work fine with all functionality, since the aperture is controlled electronically (correct me if I'm wrong!)
Click to expand...

This. The newer KAF4 lenses have the aperture control inside the lens. The Pentax 55-300 PLM is the only current KAF4 lens, but more will come. All K-50 cameras with busted aperture motors will be able to use those lenses with the latest firmware, so all hope is not lost. :-D

However, at the rate that Pentax is moving along, more than likely it's going to take a while for more KAF4 lenses to appear. :-P
 
theov39 said:
Presumably using a Pentax A lens with the aperture ring set to the "A" position would also lead to the black frame/aperture block problem right?
Click to expand...
So - lets analyze that situation.

The lens tells the camera that it is going to stop down to F8.

The camera assumes that the lens is at F2.

But - the lens is already at F8 as the body is locked in stopping down.

So, the camera think it is going to stop down 3 stops when it will not.

Therefore the camera increases the exposure time.

Therefore the image is going to be severely over exposed.

And actually - this is going to be the result for all situations where the aperture will not move, when it should (except for manual mode with aperture ring).

So, I do not understand why the OP gets dark images.
 
Roland Karlsson said:
theov39 said:
Presumably using a Pentax A lens with the aperture ring set to the "A" position would also lead to the black frame/aperture block problem right?
Click to expand...
So - lets analyze that situation.

The lens tells the camera that it is going to stop down to F8.

The camera assumes that the lens is at F2.

But - the lens is already at F8 as the body is locked in stopping down.

So, the camera think it is going to stop down 3 stops when it will not.

Therefore the camera increases the exposure time.

Therefore the image is going to be severely over exposed.

And actually - this is going to be the result for all situations where the aperture will not move, when it should (except for manual mode with aperture ring).

So, I do not understand why the OP gets dark images.
Click to expand...
 
DS21 said:
It is a mechanical failure, the aperture control motor gets stuck at F32 during exposure (in camera control modes, anything other then M lenses), so no matter what, images will be taken with aperture lever at at F32 at that moment. Camera does not know this is happening, and EXIF records the value it should have been. When in A mode on the lens, the camera controls the aperture (moves it where it should be), when not in A mode (manually set on lens), the lens controls the aperture, it acts as a hard stop until what point the lens should stop down (does not allow closing of aperture all the way, past the set point, let's say 5.6). The camera aperture motor will try to go all the way (default action in M mode, to let lens handle it), but it will be stopped by the lens and images are correctly exposed even with faulty aperture levers always going to F32 in lens A mode (camera control).
Click to expand...
Thanx for the explanation.

Then - yes - it will be dark if you use an automatic lens.

With a manual lens, everything will be just fine.

Back of my head I have a fuzzy memory though. One that Pentax uses two totally different methods for automatic aperture, one older and one newer.
 
Roland Karlsson said:
DS21 said:
It is a mechanical failure, the aperture control motor gets stuck at F32 during exposure (in camera control modes, anything other then M lenses), so no matter what, images will be taken with aperture lever at at F32 at that moment. Camera does not know this is happening, and EXIF records the value it should have been. When in A mode on the lens, the camera controls the aperture (moves it where it should be), when not in A mode (manually set on lens), the lens controls the aperture, it acts as a hard stop until what point the lens should stop down (does not allow closing of aperture all the way, past the set point, let's say 5.6). The camera aperture motor will try to go all the way (default action in M mode, to let lens handle it), but it will be stopped by the lens and images are correctly exposed even with faulty aperture levers always going to F32 in lens A mode (camera control).
Click to expand...
Thanx for the explanation.

Then - yes - it will be dark if you use an automatic lens.

With a manual lens, everything will be just fine.

Back of my head I have a fuzzy memory though. One that Pentax uses two totally different methods for automatic aperture, one older and one newer.
Click to expand...
 
Thanks DS21 and Roland! Very helpful explanations. Now to look for a M Pentax lens, preferably as wide as possible so I can at least use my K-50 with THAT lens.
 
theov39 said:
Thanks DS21 and Roland! Very helpful explanations. Now to look for a M Pentax lens, preferably as wide as possible so I can at least use my K-50 with THAT lens.
Click to expand...
My understanding is that A lenses with aperture rings can also be used, and they are more recent. You just have to set the aperture on the ring rather than using the 'A' position. Perhaps somebody can confirm this as I haven't tested it with my old A lenses.

I use my old Praktica lenses on my K50. They are M42 thread so I have a Pentax M42 adapter which I bought many years ago. I think some of the earlier Pentax lenses are also M42 so unless you want to buy an adapter make sure that you buy lenses with the Pentax bayonet mount.

Btw, I use the K50 in Av mode (rather than manual) a lot of the time with the old lenses. Focus wide open, close to desired aperture (counting the clicks!) and press the green button to meter.
 
peterpainter said:
My understanding is that A lenses with aperture rings can also be used, and they are more recent. You just have to set the aperture on the ring rather than using the 'A' position. Perhaps somebody can confirm this as I haven't tested it with my old A lenses.
Click to expand...
Yes, they should work, just as good as M lenses.

Manual focus:

PENTAX (Called K, for some reason)
PENTAX-M
PENTAX-A

Auto focus:

PENTAX-F
PENTAX-FA
 
theov39 said:
Thanks DS21 and Roland! Very helpful explanations. Now to look for a M Pentax lens, preferably as wide as possible so I can at least use my K-50 with THAT lens.
Click to expand...
You are welcome, glad to help. Imagine, if the KAF mount was not crippled (aperture tracking lever in the mount removed for cost cutting reasons), there would be no need for green button stop down metering with manual lenses, the camera would mechanically know where is the aperture ring on the lens (This is why even the M lenses were called automatic at the time, the operation was seamless just no P mode.)
 
Roland Karlsson said:
peterpainter said:
My understanding is that A lenses with aperture rings can also be used, and they are more recent. You just have to set the aperture on the ring rather than using the 'A' position. Perhaps somebody can confirm this as I haven't tested it with my old A lenses.
Click to expand...
Yes, they should work, just as good as M lenses.

Manual focus:

PENTAX (Called K, for some reason)
PENTAX-M
PENTAX-A

Auto focus:

PENTAX-F
PENTAX-FA
Click to expand...
 
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