A Pro's opinion of EVF vs OVF

Started May 30, 2013 | Discussions thread
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Re: Uh, no. Not at all.
In reply to photoreddi, Jun 1, 2013

photoreddi wrote:

n057 wrote:

photoreddi wrote:

Bad assumption. I missed nothing. A large DoF will indeed mask focusing errors if you don't look too closely, but they're still very visible when you do. The point that you missed entirely (if you even bothered to consider it) is that the AF accuracy has nothing to do with the aperture used or with the DoF. All cameras stop trying to refine the focusing accuracy beyond a certain point. With the PD AF sensors we're talking about it's almost always done using the f/5.6 part of the lens ...
  (some stuff deleted)

"The f/5.6 part of the lens" ???

It has been described by others as lenses having concentric cylinders where the outermost cylinder of an f/1.4 lens is the f/1.4 cylinder. Of course they aren't real cylinders, you just have to make a mental picture of them. The next, smaller one would be the f/2 cylinder, continuing to the lens's smallest aperture. The AF sensors (most of them anyway) are designed to only see light coming through one of these cylinders. If you paint the outer lens surface with different colored dyes each covering the edge of one these cylinders, the photos would have an altered color cast, but it would be uniform because some of the light from every subject being photographed passes through each of the cylinders - if the aperture is wide open, that is. If it's closed down, light passes through fewer of the tinted cylinders, but it's still uniform, albeit a different tint. The important point is that the color used to tint the f/5.6 cylinder is the only color that the AF sensor sees because they are designed with prisms (like the prisms in rangefinder cameras) that only passes light coming from the lens's f/5.6 cylinder.

Some of Nikon's latest cameras have a few of their AF sensors tuned so that they only see light that has passed through the f/8 cylinder. The f/8 cylinders may be more properly called the f/8 exit pupil ring. If you're interested and don't mind searching a bit, Marianne Oelund has made many posts describing this in great detail along with some of the experiments she performed with her various DSLRs. Here's another post from Joseph S Wisniewski that goes into detail about it. Maybe more detail that most people would care about but I found that it had many interesting things to say.

Edit: DPR's editor swallowed the link I included so here's another attempt at it.


Sounds like FM to me, but hey, outside of computers and SQL, what do I know

Some cameras, some lenses, some computers

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Nikon Coolpix 995 Nikon D200 Nikon D500 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR Nikon AF-S DX Nikkor 35mm f/1.8G +7 more
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