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04-25-2015, 09:22 AM   #1
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Shooting m lense on K-3

I just bought my K-3 and I also got a Pentax M 50mm 1.4 lens for it. I was taking pictures in raw and reviewing the (exif?) data in a program called UFRaw. In the program, all the pictures I took at various aperture settings show the aperture as F0. Does that mean the camera is not recording that data, the lens is not functioning properly or that I am doing something wrong? I have changed the camera setting to allow for the aperture ring to be used and have it set to manual focus. I am new to taking pictures with an advanced camera, so any guidance would be helpful.

04-25-2015, 09:29 AM   #2
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The camera doesn't know what the aperture is with any lens without electrical contacts (thats how it's communicated to the camera) so it shows f0. You're not doing anything wrong this is normal.
On the pentax film cameras this lens was designed for, the aperture was communicated to the camera by mechanical means - that second aperture lever connection opposite to the main one if you look at the bayonet mount. But this connection is not present on digital slr's - they have the "crippled" KAF mount.
04-25-2015, 09:43 AM   #3
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QuoteOriginally posted by marcusBMG Quote
The camera doesn't know what the aperture is with any lens without electrical contacts (thats how it's communicated to the camera) so it shows f0.
To put it another way...if the camera does not set the aperture, it has no way to record it in the exif.

04-25-2015, 10:56 AM   #4
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Great, thanks for the quick responses! I'm learning as I go.

04-25-2015, 01:36 PM   #5
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Read here

How to Use Manual Lenses on Pentax DSLRs - Tutorial Videos |
04-28-2015, 06:06 AM - 1 Like   #6
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This is not an answer to your question (and you have already got good answers), but there is a snag to the light metering method the camera uses that you most likely will experience sooner or later. What it does is to stop down the lens and then measure the light (this is why it works without needing to know the f#). As you increase the f# on the lens (by turning the ring) the light meeter sensor will receive lesser and lesser light through the stoped down lens. At some point there is too little light for the light meter to give you an accurate exposure (this point depends on how much light there is available in the scene). To circumvent this, when I am in doubt about whether there is enough light or not, I use the green button with the lens sett wide open. I then stop down to the aperture I want to use and increase the measured exposure time with equally many stops.

Hope this is of any help


(And excuse my English. It is not my native language)

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