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Re: [OM] Field free from microprism or split prism

Subject: Re: [OM] Field free from microprism or split prism
From: Moose <olymoose@xxxxxxxxxxxxx>
Date: Sun, 01 Jun 2003 15:23:40 -0700
Does the fact that you don't have a 21-400mm zoom give you any clue?
If there were a perfect ALL AROUND screen for all lenses and uses, would camera manufacturers be selling many different screens? They might try, but nobldy much would be buying.

Here's the problem in a nutshell, the screens designed for long and/or slow lenses are not ideal for wide and/or fast lenses.

For matte screens or parts of screens, the issue is the fineness of the 'texture'. Long telephotos are easiest to focus with very fine matte finishes, hence the 1-8 screen. Wide angles are easiest to focus with coarse matte areas, hence Jeff's comment "I've found the 1-8 useless for short focal length lenses." Ah, no wonder Oly says of the 1-8 "This screen is ideal for use with super telephoto lenses of 300mm or more in focal length, or for astrophotography. The extreme fineness of the matte surface permits outstanding field definition." The 1-4 is an effort to resolve this issue, with a finer matte inside the circle and coarser outside it.

For split image and microprism parts of screens, the issue is one of geometry. The average angle of the light hitting the screen varies with focal length and aperture. Thus, the angle of the prism that is ideal for fast and/or wide lenses is quite different from the angle that works best with tele/slow lenses. The angle used in the 1, 3, 13 and 14 screens is optimized for 50mm, relatively fast lenses and works quite well for moderate WA and moderate tele lenses. With wider, longer and slower lenses, parts of the focusing aid prisms go black. For specialized uses there are all the other screens. the 1-2 and 1-6 are biased towards slightly longer lenses and the 1-5 for wider angle lenses. The 1-7 and 1-8 are for really long and slow lenses. The 1-7 is amazing, with a microprism focusing area that doesn't black out at 1000/11.

With a 21mm lens, you probably will not find the 1-8 useful. All the others you mention are general purpose screens that should work reasonably well with all your lenses. You can, of course, use a 2 series screen with a 2n by cutting the larger tab to fit. The ideal is then to have the meter adjusted to the brighter screen. Auto exposures will be unaffected, but the viewfinder meter will read too high.

Moose

daniel wrote:

Aloha I prefer a clear-cut view field free from microprism or split prism Having the OM 2n & 4Ti; 21mm 50mm 180mm 400mm I want an ALL AROUND
screen
Between the plain ground 'glass' ones
1-4 (gone?)
1-4n
1-8
2-4
I like the 2-4 for the 4Ti and 1-8 for the 2n
With the lens parameters I have I guess I have no choice but the 1-8 for
the 2n unless it's modified for the 2-4 or find a used 1-4?
Am I on in what I'm wanting to archive, as far as an all around clear
field view?
Thanks
Dan



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