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01-20-2010, 11:37 AM   #16
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QuoteOriginally posted by Marc Sabatella Quote
... So DOF preview is a way of getting the camera to stop down the lens long enough for you to see the change in DOF in the viewfinder - the fact it *also* happens to be a way to get a meter reading with manual lenses is just gravy (but delicious gravy at that!)
I didn't know that before I read this thread - I just thought of it as a DOF preview and hadn't noticed the meter! Truly delicious!

01-20-2010, 11:41 AM   #17
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QuoteOriginally posted by deiberson Quote
so when i meter with the green button b/c of the optical preview option that i selected, i'm actually looking at a dof preview as well?

i understood what the dof was, just not how it was used in the preview option. your explanation of the preview stopping down helped.

i was holding the green button down, looking at the ev value and metering to zero. but i was not paying attention to my dof preview. that might explain the out of focus pictures.

can i apply my af focus points using the same techinque with a and m series lenses?
just be careful my experience is the DOF preview in the finder shows a little more in focus than what actually is. you will need to experiment a bit to know the real range of in focus., it is a useful tool but not perfect
01-20-2010, 11:42 AM   #18
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QuoteOriginally posted by deiberson Quote
so when i meter with the green button b/c of the optical preview option that i selected, i'm actually looking at a dof preview as well?
Yes. Takes a moment for the eye to adjust to the dimmer viewfinder, so it can be hard to see the effect at first, but once you know what you're looking for, it's pretty straightforward.

QuoteQuote:
i was not paying attention to my dof preview. that might explain the out of focus pictures.
Well, if you tried focusing while stopped down, that would be a mistake - you're way better off focusing wide open. The viewfinder is brighter, and since DOF gets larger as you stop down, if it's in focus wide open, it's *definitely* in focus stopped down. This is the reason modern lenses are designed to allow for wide open focus - that's why your lenses stays wide open until you hit the button.

So if you were focusing wide open like you are supposed to, then no, out of focus pictures are not because you weren't doing it right. They'd be simply because you missed, or, in the case of very large apertures (beyond f/2.8), the viewfinder actually shows *too much* DOF due to the design of the focus screen, and the DOF preview can't help with that. So when shooting a 50/1.7 at f/1.7, for instance, the viewfinder might show 6 inches in focus whereas the actual shot will only have 2. The viewfinder basically just lied about those other 4 inches. So if the thing you were focusing on happens to be in the 4 inches that the viewfinder lied about, your picture will appear out of focus. The trick is to learn to anticipate this - to place your subject in the right 2 inches, not the wrong 4.

If on the other hand you were getting out of focus pictures at apertures smaller than f/2.8 (ie, larger f-numbers), then that's just a simple matter you not being careful enough (unless perhaps your focus screen is poorly adjusted, but that's not *nearly* as likely).

QuoteQuote:
can i apply my af focus points using the same techinque with a and m series lenses?
Not sure what you mean by "apply my focus points". Obviously, these are manul focus lenses. but as far as the focus confirmation goes M lenses only confirm center point. I think A lenses might let you choose if you're in that mode, by I never used that mode, and seldom use A lenses, so I'm not sure.
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