[Leica] The Zeiss Choice

[Frank.Dernie at btinternet.com (Frank Dernie)]

PMFJI again, there is no way to do parallax compensation on the wider 
lenses using separate viewfinders. The DR summicron eyes contained 
prisms to deflect the field of view of the framelines for the last few 
inches of close focus, there is not a big enough viewfinder window in a 
normal camera to deflect the view that far, hence this is also one of 
the functions of the eyes for the 90 macro BTW.
The bigger problem of parallax on a viewfinder camera at close 
distances is the physical distance between viewfinder and lens. Since 
the viewpoint is, at wide angle of view and close subject, very 
significantly in a different place for the photographer compared to the 
film, the alignment of objects will be quite different on film than 
that seen by the photographer through the viewfinder. Imagine, in 
absurdam, taking a picture through a fence with the viewfinder up to  a 
knot hole, the lens would see nothing but fence!
Frank

On 13 Jan, 2005, at 15:46, Bill Marshall wrote:

> On Thursday, Frank Fillippone wrote:
>> "The issue of focusing a RF lens to.5m has 2 components . . . the 
>> movement of the lens focusing helix to .5m, and the parallax so that 
>> the 2 images line up at .5m. Given that no one has ever done this 
>> before, I suspect that the parallax adjustment in the rangefinder is 
>> the problematic part. The third issue is what part of the image area 
>> is obscured by the lens when you look through the viewfinder at .5m."
>
> Frank, starting with your last point first, I did not see a 
> significant problem with any wide angle lenses obscuring the 
> viewfinder at any focal length when I looked at the prototype in New 
> York, although I wasn't specifically looking for this issue. Some 
> thought was given to this camera when it was designed. In order to 
> create a longer base line, the viewfiner was moved about as close to 
> the edge of the body as is physically possible. This was accomplished 
> by moving the rewind lever to the bottom of the body - a move that is 
> unpopular with some people. Having the viewfinder moved farther from 
> the lens would minimize any problems with obstruction of the VF 
> window, I expect.
>
> Agreed that parallax is an issue. Leica seemed to be able to focus the 
> 50 DR down to 18", so I assume that RF focus is possible, but someone 
> will correct me if I'm wrong. However, I would think that parallax 
> adjustment for framelines is a bigger problem. All of these close 
> focusing lenses except the 28 require accessory viewfinders, so I 
> assume that the problem is handled there. It will be interesting to 
> see how parallax compensation for the 28 is handled, once the camera 
> is available. The literature indicates that the accessory viewfinder 
> for the 25 doubles as a VF for the 28. Since framelines for the 28 are 
> built into the VF, it's possible that the accessory finder provides 
> better framelines for close-up focus - unless it is just an 
> alternative finder for folks with glasses.
>
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information
>