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04-05-2013, 06:37 AM   #1
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Green Button

Tried searching through previous topics started on this button but couldn't really figure anything out. As I understand it now, it is used to customize how the e-dials and itself function in any particular exposure mode. Page 163 of the manual doesn't explain a few things that I was hoping one of the experts here could help with. Mainly, what does "-->P" Return To P and "P Line" Program Line actually do?


04-05-2013, 07:32 AM   #2
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Hey, welcome. There are a couple threads on the Green button, since it is a Pentax specialty. Think of it as an extra button to help the photographer, something other brands don't really have in this exact way.
This thread is a bit old, but not bad:

But here is a quick rundown:
In P mode you can turn the dial for P shift. P shift basically keeps the same exposure value, but with a different ratio of aperture/shutter. Pressing the green button will return to default P.
The green button is also often the "back to 0" button, like if you press the +/- button and set exposure compensation to -3, the green button is basically a shortcut to jump back to 0.
In M mode it does metering. So if you use a manual lens, it will stop down to the aperture on the aperture ring and adjust the shutter speed for the correct exposure.
The green button can also be customized in the menu for all sorts of other functions, like turning focus peaking on/off, or DoF preview, which are all very useful features.

Last edited by Na Horuk; 04-05-2013 at 08:02 AM.
04-05-2013, 07:47 AM   #3
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Na Horuk summed it up very well. Pages 162 to 164 of the manual outlines all the different combinations that can be set for the E-dials and Green button.

04-05-2013, 01:24 PM - 1 Like   #4
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When I first got my camera off of auto, the green button completely baffled me, now it's my best friend! The "back to 0" description is very accurate. My most common usage is to reset exposure compensation back to 0 (press +/- then the GB), followed closely by metering manual lenses. I almost never use P, but when I do, the GB is there to return the program mode back to default.

When you set your mode dial on P, the automatic choice of aperture and shutter speed is called the "program line". The specific choices made depend on the lighting, but in general, tries to maintain a moderate aperture, low ISO value and a shutter speed around 1/ twice the lens length. There is a program line which "knows" where the best balance is, but that may not meet your needs. If you turn the e-dial, you "shift" the program line to faster shutter/larger aperture (smaller f number) or slower shutter/smaller aperture (larger f number). If you want the default setting back, the GB gets you there instantly.

Do this: set ISO fixed at 200, and point the lens at a moderately lit room. The lens should be set to its largest aperture and whatever shutter speed. Turn the dial, and the aperture and shutter values will change. Spin it a bunch, and it will change a bunch. Press the green button, and you are back to the largest aperture because that is what the camera will choose in a moderately lit room. Outside, the starting values will be different, but it works the same.

Last edited by Kozlok; 04-05-2013 at 01:31 PM.
04-09-2013, 06:20 AM   #5
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Great stuff. Thanks everyone.

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