On Apr 22, 2009, at 13:21 , Toralf Lund wrote:

Christian wrote:
Graydon wrote:
On Wed, Apr 22, 2009 at 03:15:24PM -0400, Christian scripsit:
Graydon wrote:
Which is certainly a good thing, but _how_?  What about the matte
screen indicates that you're in focus, or the location of the plane

When I had an LX and a matte (grid) screen I guess my eyes and brain agreed with nature on what was in focus. I never seemed to have the trouble you seem to have and I guess I never really thought about it too much either.

I also wear glasses and have calibrated the viewfinders of all my SLRs to be pretty much perfect for me.

Hmmm... I always thought I had problems focusing just because I'm wear glasses or contact lenses, but I there goes that theory... I won't say I can't focus manually at all, but I certainly never experience the "snap into focus" others are talking about. I mean, there is always a certain point where I can tell that the image goes from out-of-focus to sort of in focus, and one where it goes (completely) out of focus again (if I keep turning the focus ring in the same direction), but between those points there is always a certain area within which I have a very hard time deciding where exactly the optimum focus setting is. If you know what I mean...

I know exactly what you mean. I am never sure when focusing manually when the subject is truly in focus. See below.

I'm also find it hard do choose the appropriate step on on the viewfinder focus setting (on the one body I have where there is actually such a setting.)

I think this is caused by an astigmatism, from which I suffer to some degree. When trying to set the focusing frames to their sharpest, the more vertical lines come into sharp focus a click away from the more horizontal lines (referring to the spot metering ring there). This would also explain why manual focusing is difficult, and why some say their plane of focus seems to be deeper than it should be, but never really 'snaps'. Combine that with the zoom lenses dim apertures at longer focal lengths, it's surprising anything is in focus manually.

I also find that only in bright sunlight with my DA 18-250 mm will the auto-focus usually render a sharp image from 150-250 mm. Even will catch up (never starts out right) with predictive auto-focus of a dog running towards me. But a cloudy day. 10% if I'm lucky.

I'm going to have to have a pair of glasses made that I can keep on while I focus manually, with the magnifying eyepiece on the camera. Plastic frames so I don't scratch the LCD, and a small 4.00 bifocal at the bottom so I can chimp properly. :-)

I never tried a plain matte screen, tough, although I've attempted to focus by looking through the matte area of matte and split image screens...

One of the LX screens I love, the SD-21, has a small central spot that is clear, with a cross hair. The matte area keeps your eye properly focused on the screen, the clear area allows you to see quite well when sharpest focus is achieved. Made for microscope, telescope, high magnification situations, but works well for me with all my long lenses and long zooms..

Joseph McAllister
pentax...@mac.com

http://gallery.me.com/jomac
http://web.me.com/jomac/show.me/Blog/Blog.html






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