Yes, but the edge comparison accuracy necessary is only to what can be
resolved with lens and film. We seldom need to know if the object is at 50
feet or 55 feet. We can't place the barrel of the lens that accurately on
most lenses. Look at any lens commonly used by most folks, including pros.
Exactly how much rotation of the barrel do you think there is between 50 ft
& 55 ft? - 100 ft & 110 ft? Exactly how much change would be made in the
distance between the lens and the focal plane would we be talking about? We
don't need the accuracy of a long base optical rangefinder - we're not
calculating bullet drop here. The further away an object is, the less the
need for super accurate distance measurement. So long as the aperture is
sufficient for the split prism, focal length is generally irrelevant. No
this is true for most of what I do. YMMV!
Regards,
Bob...
--------------------------------------------------------
"Art is not a reflection of reality. it is the reality of a reflection."
-Jean Luc Godard
----- Original Message -----
From: "graywolf" <[EMAIL PROTECTED]>
> If your eye is exactly in the right place, and your lens is the right
> focal
> length, and the f-stop is correct, then a split image rangefinder is
> fairly
> accurate. Remember the offset is all but non-existent. It can not compare
> in any
> sense to a long base optical rangefinder, and compared to a ruler it is
> problematic. I can say from personal experience that it is not accurate
> enough
> for an 85mm lens at 3 feet and f/2.0 when you want the subjects irises
> razor
> sharp every time.
>
> Bob Blakely wrote:
>> If you have a split image scree that is not dead on accurate, you have an
>> improperly designed and/or manufactured screen. It would mean that the
>> center line where the prisms cross is not in the same plane as the ground
>> glass's frost. FYI, I believe they are "optical" plastic now.
>>
>> ----- Original Message -----
>> From: "graywolf" <[EMAIL PROTECTED]>
>>
>>
>>> Just to give the other point of view, I hate split image focusing
>>> devices.
>>> To me
>>> they are annoying, right in the middle of the picture where I want to
>>> see
>>> what I
>>> am looking at, and they are not as accurate as you guys seem to think
>>> they
>>> are.
>>> Plain ground glass with grid is my choice. It is interesting how many
>>> folks do
>>> not trust their eye.
--
PDML Pentax-Discuss Mail List
[email protected]
http://pdml.net/mailman/listinfo/pdml_pdml.net
to UNSUBSCRIBE from the PDML, please visit the link directly above and follow
the directions.
