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-   -   Re: Focus Fallibility: Lens Test Fallacies (http://www.velocityreviews.com/forums/t621522-re-focus-fallibility-lens-test-fallacies.html)

Don Stauffer in Minnesota 06-21-2008 02:05 PM

Re: Focus Fallibility: Lens Test Fallacies
 
On Jun 21, 7:35 am, Alfred Molon <alfred_mo...@yahoo.com> wrote:
> Here is an interesting article by Dave Etchells:http://www.slrgear.com/articles/focus/focus.htm
>
> I found it interesting that according to him manual focus through the
> viewfinder is not precise enough, while manual focus through live
> preview on an LCD screen delivers the best results.
> --
>
> Alfred Molon
> ------------------------------
> Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum athttp://tech.groups.yahoo.com/group/MyOlympus/http://myolympus.org/photo sharing site


Much of what he says is true, but somewhat irrelevant to the average
photographer who does not have access to an optics lab. I used to be
a lens designer and EO system analyst. We had a lot of nice
equipment. I no longer have access to such equipment but I still
normally use manual focus.

It is easy enough to check your eyesight and its effects with
viewfinder. With the lens on infinity look through at a very distant
(many miles) high contrast object, like moon or very distant feature.

Depending on the type of focusing screen in an SLR eye defects may or
may not interact between eye and camera lens. If the viewfinder shows
any recticle marks, such as focusing squares or exposure zones, are
they sharply in focus? If so than you can get a good manual focus.

The problem I see most with autofocus is with an object with a lot of
depth. Say a railroad track running from front to back. Where along
that object should you focus. You can use rules of thumb to do manual
focus, but I doubt the computer in the camera can use such rules.

Admittedly an LCD screen is far, far from resolution needed to judge
focus.


Paul Furman 06-21-2008 05:20 PM

Re: Focus Fallibility: Lens Test Fallacies
 
Alfred Molon wrote:
> In article <122465f9-3e52-4411-b3d6-4f240fe66274
> @x35g2000hsb.googlegroups.com>, Don Stauffer in Minnesota says...
>
>> Admittedly an LCD screen is far, far from resolution needed to judge
>> focus.

>
> But you can zoom down to pixel level and precisely adjust focus.


Not quite that close. From what I've seen the D300 zooms closer after
taking the shot than in live view.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

Matt Ion 06-22-2008 05:34 PM

Re: Focus Fallibility: Lens Test Fallacies
 
frederick wrote:

> It's excellent for critical focus / tripod work. I've found LV useless
> for anything else so far.



I'm finding it handy on my 40D for band photography... when I want to
hold the camera up above the crowd's heads, or go for an odd high or low
angle over the stage. I used to do that with my 300D as well, but it
was always a crap shoot if I was going to get the subject anywhere near
centered.

It's not perfect, especially since AF doesn't operate in LV mode and I
have to use the AF ON button briefly, but it's a damn sight better than
WITHOUT the LV :)


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