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Forum: Pentax K-3 & K-3 II
12-02-2016, 08:35 AM
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Funnily enough, my experience in this regard IS with a 3rd-party KA-mount zoom, a Sigma 70-210 f/3.5-5.6
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Forum: Pentax K-3 & K-3 II
12-02-2016, 05:49 AM
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Yes, that's true. There are only two things Pentax A lenses won't do that the 18-135 does (apart from being weather resistant).
1) They won't focus themselves, of course. Never mind; you still get a focus lock indication based on centre-spot focus, so that's good.
2) A series zoom lenses will AFAIK not report their focal length to the camera. Because many of these change their maximum aperture depending on their zoom setting, this may occasionally throw exposure off or cause the wrong aperture to be written into the EXIF. It also means the shake reduction isn't optimised. The best thing to do there is probably to set the SR focal length (when the camera asks for it) to the maximum, unless (for example) you have a very large focal range (e.g. 35-135) and are shooting either zoomed all out or zoomed all-in a lot at low shutter speeds where SR is doing a lot of work.
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Forum: Pentax K-3 & K-3 II
12-01-2016, 05:55 PM
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Hope I'm not butting in, but I think what photolady's getting at is that if you either (a) have a hand-held light-meter or (b) have enough experience of various lighting conditions to take an educated guess at the shutter speed, you need only set it, set the aperture on the ring, and shoot. The camera will stop down appropriately when you take the shot. (See also "Sunny Sixteen rule", and variations thereon).
Depending on how your options are set up, you can have an EV indication in the viewfinder telling you how close (or off) you are, and use that as well.
With a DA lens, the green button forces an emergency revert back to the correct shutter and aperture settings (as determined by the inbuilt meter and its algorithms), handy for when I am shooting slowly and deliberately in manual mode but suddenly a dog or one of the kids does something cute across the room and I need to reset values for a different value of lighting without hesitation, or I want the camera's suggestions but also the right to vary them immediately without it taking over. With a K or M lens, or third party equivalent, the camera body doesn't have knowledge of the actual aperture but the nice people at Ricoh (and Hoya and Pentax before them) arranged for it to stop the lens down to its current set value, check the incoming light, and assign the appropriate shutter speed. Yay!
The only reason I have found to use the actual ring on the A and FA series lenses I own is when I'm using either "dumb" extension tubes or a reversing ring and there is absolutely no connection between camera and lens aperture systems, or when I'm comparing lenses of identical focal lengths but different eras (e.g. Takumar vs. M vs. FA) and want to make absolutely sure they are set for the same apertures with no surprises in-camera.
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