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04-06-2012, 02:44 PM   #1
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question re: Vivitar 28mm/49mm 1:2.8 Lens for Pentax K PK Mount AUTO PRIME WIDE ANGLE

What does the "AUTO" mean on this lens?
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I don't see any A setting on the lense's focus/aperture ring. I might have either misinterpreted or misunderstood what AUTO means with the lense's description. I hope you could shed some light into my confusion.

04-06-2012, 03:21 PM   #2
dms
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auto means auto aperture--was more significant 40-50 years ago when many lens were manual aperture. i.e., auto=aperture closes down when shutter is released.
04-06-2012, 03:30 PM   #3
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dms is quite right. 'Auto' has different meanings in different eras. The lens shown is what we would call an M-type, with only a mechanical aperture linkage. On older PK cameras, the camera could sense where the aperture is set. On our current dSLRs with 'crippled' mounts, such a lens can be used two ways:

* With the camera in any Auto mode, it defaults to Av, and the lens only works wide-open.
* With the camera in M mode, press the Green button for stop-down metering and exposure.

M42 screwmount lenses may also be labeled Auto, but they don't work automatically at all on modern cameras, except for Av-type automation. And our newer A-type and AF lenses probably aren't labeled Auto at all. Go figure.
04-07-2012, 09:55 AM   #4
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What everyone has said except to be clear: "Auto" for this type of lens means that it will stay open wide while you are focusing prior to shooting. This is a convenience since as the lens closes down the viewfinder will get dimmer, obviously. If your camera is set to M mode then you can set the lens to the aperture that you want, and the camera will change the lens aperture to your selection as you press the shutter release. Of course, you need to use the green button prior to taking the pic so you can meter and set the shutter speed and iso for a proper exposure.

P.S. There are many M lenses that have this feature.

04-09-2012, 02:56 PM   #5
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I appreciate the replies. Thanks all.
04-14-2012, 03:39 AM   #6
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I have one of these. It's not a favourite, but I still use it occasionally. I find the colour rendering subdued, a bit on the cold side. Contrast isn't wonderful either, but you can work with it. It's sharp enough for a cheapie, especially stopped down a little.

It's equivalent to an M lens, as said above. One potential (but easily fixed) gotcha is that you'll have to lightly sand part of the lens mount to short contacts to properly use stop down metering on some camera models (K-r for one). It's a two minute job. I recommend something like 320 grit silica sandpaper, but 640 grit would be fine, too.

It's not an expensive lens, by any stretch. I picked up mine for $20. It's a bargain if you're on a budget and want something of this focal length. If you can afford better and aren't in a rush, maybe skip it.
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