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08-13-2013, 11:15 AM   #1
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Aperture priority?

Hi. I am a little confused about the aperture priority in my Pentax k30. The reason for my confusion is that I had been trying to use my lenses in the maximum aperture, while in aperture priority, but the camera won't allow me to. For example, I was shooting with my 18-55 wr lens which is f3.5, but the camera won't allow me to go faster than 5.6, which was fine for what I was trying to do, but got me wondering why, if I am in aperture priority, I couldn't choose the max aperture for the lens. Also, I was using 400 iso, on a sunny day, so the shutter speed was fast I mean over 125th.

I had checked the Operating Manual, and it says that I should be able to use it. I had shot nikon, canon, and even Sony, and they all works the same way Pentax should, so that's why I am confused. Any suggestions will be appreciated. Thanks and have a blessed day!


Kiko.

08-13-2013, 11:22 AM   #2
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What focal length were you zoomed to? 3.5 is the maximum aperture for that lens at 18mm. 5.6 is the max aperture at 55mm.
08-13-2013, 11:24 AM   #3
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Try to change your zoom level (18mm).
08-13-2013, 12:16 PM   #4
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There are different types of lenses.

Fixed focal length (aka prime lenses) have a given maximum aperture. Its the f-number (which is a fraction of how much the lens is open)
Fixed aperture zoom lenses - these are like 17-50mm f2.8. You can change the focal length, and all focal lengths have a the same maximum aperture, f2.8 in this example. These zoom lenses very often come in f2.8 or f4.0 versions.
Then there are variable aperture zoom lenses. They are written like 18-55mm f3.5-5.6. This means it is f3.5 at 18mm, and f5.6 at 55mm.

Typically prime lenses have top quality, fixed aperture zoom lenses are "pro" grade (f4 being the compact versions, f2.8 being the top notch zooms), variable zooms are usually cheaper and not as amazing in their output (for example, the kit lens. It delivers a lot, but it has its limitations). I think pretty much all the big brands make these types of lenses, for the different market groups (amateurs, prosumers, professionals)

08-13-2013, 12:19 PM   #5
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It has to be right on the limit at 18mm, just slightly beyond 18mm it will not be f3.5 anymore.
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