On Sun, 18 Aug 2002 08:37:08 -0400, "Alexandre Vovan" wrote:

>I currently trying out a Tamron SP 60-300mm zoom lenses to go with my Nikon
>F, and I'm having a hard time position my eye in front of the viewfinder
>(normal prism - not the photomic) to see clearly through the focusing
>circle.
>
>It seems to me that with these lenses, the top half of the focusing circle
>gets dark very easily, depending on the horizontal position of my eye in
>front of the viewfinder - it makes it hard to focus precisely. Is that
>normal behavior for a zoom lenses? Could it be because the Nikon F
>viewfinder is not quite compatible with the newer Tamron lenses? I have an
>old, fixed 85mm Nikkor that is not at all sensitive to this - the focusing
>circle is always totally clear and transparent.
>
>Also, if that's normal behavior, is there a way to make this focusing circle
>darkening less sensitive to my eye position? Or to make it not happen
>altogether?

The split image SLR "focus aid" (I dislike them...) is
optimized for particular lens speeds (and possibly FLs
too) - go outside of that range, and unless your eye is
centered in the VF, half will go dark. Best is to
use the "ground-glass" area outside the split-image
circle, though you may need eye correction to see that
area sharply (look for the article on 4-way glasses,
on my web page, listed under "I babble", if you use
or need eyeglasses...).