Depth of Field Preview feature ?

Started Jul 16, 2013 | Discussions thread
Barrie Davis
Barrie Davis Forum Pro • Posts: 21,460
Re: Depth of Field Preview feature ?

will222 wrote:

Leonard Migliore wrote:

I find DOF preview quite useless on the optical viewfinder of an autofocus SLR. That's because the screen is too clear to show focus. It is, however, useful in live view.

On Nikon DSLR's, live view defaults to having the lens stopped down to the taking aperture. But what's really bad is, if you change the taking aperture, the diaphragm does not respond until you take the picture. So you can't look at the effect of changing aperture.

I'm not sure I understand what you mean by the screen is too clear to show focus. Would you mind elaborating a bit?

Modern focusing screens are made to be as transparent as possble, in order to be as bright as possible.... closer in brightness to the viewing experience enjoyed in full frame 35mm cameras of 30 years ago. This transparency means they tend to look "in focus" all the time, even when they are not.

Why are they not so bright as 30 years ago?

a) The APSc mirror and screen assembly is not so big, so it gathers less light... some being diverted to AF system.

b) Lens maximum apertures are generally rather smaller in today's zoom kit lenses, f/3.5 is typical, where 30 years ago our fixed f-length 50mm would likely have been an f/2

That's strange re: the Nikon. Seems to defeat the purpose if you can't see the effect of adjusting the aperture.

I guess the Nikon (according to the D7000 manual) has an option called "modeling flash" which, if I'm reading it correctly, lights the subject (I would asssume continuous light not a flash so it seems like an odd name for it) when you press DOF preview so the effect of small aperture can be seen (i.e. not darkened). I could be wrong on that though.

Still, if you can't adjust aperture from there, to see the effect, it doesn't seem to add much and you might as well just take the photo and review it and repeat.

PS, does live view refer to using the LCD screen not the viewfinder?

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