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03-16-2011, 10:40 PM   #1
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still don't understand stop down metering

i've read some of the previous threads here on using stop down metering trying to figure it out- if i have a manual lens, such as a pentax smc m lens, on a k5, what i've read is that i have to use ' stop down metering ' using the green button-- simply what does that do? and can i use it in any mode? P ? Av? M ? which is the best mode to use for that? ( i've tried understanding the manual too- i know ! )

03-16-2011, 11:30 PM   #2
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Have you read my article on the topic? You have to be in M mode. Also, just use the DOF preview button, as it doesn't require you to look away from the VF.

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03-17-2011, 03:39 AM   #3
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I was confused by this myself. It gets easier to understand once you try it.
In manual mode, with a manual lens, the lens is always held wide open (aperture). But you don't necessarily want to shoot it wide open? You want to set the aperture on the aperture ring on the lens! But since there is no communication between the manual lens and your camera, how can it set a proper exposure for an aperture it don't know?

This is where stop down metering comes in to play. Your camera has a setting to allow the use of a aperture ring. Enable that.

Now your green button should do the stop down metering for you. That just means that when you press the green button, the camera quickly stops down the aperture blades (to the aperture you set on your lens), takes a reading and calculate the correct exposure and then opens up the aperture again. All this is done so that you can actually see through the lens, and focus/compose. If we did not have stop down metering, focusing would be impossible on smaller apertures, due to low light passing through to your viewfinder.

What all this means in normal use, is one extra button to push.
set your aperture on the lens.
Point at where you want to take a picure and press the green button.
Your camera now has the correct exposure, and you can focus and compose your shot.
Take picture.

If you'r ok with shooting the lens wide open, you could just set your camera to Av and it would function fully automatic (but wide open all the time).

Hope this helps.
Good luck
03-17-2011, 05:19 AM   #4
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thank you , adam and skog, i'll read the article adam, and for what you have written, skog , makes it much more clear, do i keep the green button pressed while composing the shot and keep it pressed right through pressing the full shutter to take the shot?

03-17-2011, 05:36 AM   #5
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QuoteOriginally posted by dh4412 Quote
do i keep the green button pressed while composing the shot and keep it pressed right through pressing the full shutter to take the shot?
No. You only need to press and release the green button right before taking the shot.
03-17-2011, 05:43 AM   #6
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Just give it a quick press and it will set the shutter speed, you may want to chimp the first shot in a stable light situation as the exposure you want artistically may not be the one the camera chooses, then you can adjust up or down accordingly. I use manual lenses almost exclusively and it becomes second nature pretty quickly. You should note with an m42 lens you can use av mode with the lens in manual mode as the meter will be correct for the aperture set (if the lens is set to auto for focusing wide open just flip it to manual and shoot)

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