Автор: Один
Дата: 16-01-06 22:02
Що е то корекция на паралакса и у кои фотоапарати намира почва? (леко на английски)
Докато не е станало късно, да уточня, че по-долу ще прочетете отговор на въпроса "Защо, докато фокусирам с Bessa, рамките на кадъра се движат"?
I feel a bit like Galileo here... "Nevertheless, it DOES move," IT in this case being the frameline, and this being true of all Bessas, all Leicas, and just about every other RF camera with parallax-compensating projected framelines.
It may LOOK as if it's the focusing patch that's moving, because in the dark viewfinder, your eye naturally tends to fix itself on the bright framelines, and interpret the relative motion as movement of the focusing patch -- kind of like how, when you're riding a train and looking out the window, your brain interprets the window as being stationary and the scenery as moving past it, even though you know intellectually that the scenery is standing still and it's really the window (and the rest of the train) that's moving.
But if you put the camera on a tripod and watch carefully as you focus from infinity to closest distance, you'll see that it's the framelines that move diagonally against the background scene.
If you look at a diagram of a rangefinder's optics (such as the one below, showing a Leica rangefinder, that I linked from Erwin Puts' website) you can see that the white framelines are created by a slotted mask (thin metal on most cameras; photographically printed on the Canon 7 and 7s) that's illuminated by the frosted window on the front of the camera. This mask is linked to the focus coupling arm, causing it to move diagonally as the camera is focused to and fro. (In the diagram, you can see the little pin that does this job on a Leica rangefinder in the upper-right corner of the mask.) This movement of the mask causes the framelines in the finder to move, so that as you frame the picture within the lines, you compensate for parallax (the difference between what the viewfinder window sees and what the lens sees. Since the lens is diagonally below the viewfinder on most cameras, the mask has to move diagonally to compensate for it.)
http://www.imx.nl/photosite/leica/technics/RFbasics/m6rf.jpg
Off the top of my head, I can think of only one family of 35mm projected-frame rangefinder cameras that works differently from this, and that's Fuji's erstwhile line of leaf-shutter cameras -- the ones that focused via a thumbwheel on the back. On these, as you focus, the entire front viewfinder window pivots from side to side as you turn the thumbwheel, moving the outer viewfinder image relative to the rangefinder's secondary image. This action also causes the bright framelines to move from side to side, compensating for the horizontal portion of the parallax. The frameline mask still has to move vertically to compensate for the vertical portion, but at least it only has to move in one direction. (So you Fuji owners who think you must be getting dizzy because everything seems to sway when you look through the finders of your cameras while focusing -- relax, it's supposed to do that!)
Честно, направо се чудя как е възможно да има фотографски форуми, в които човек да влезе, да постави въпрос, и да му се притекат няколко човека на помощ за да му дадат необходимия му отговор ... ![[smilie11]](https://photo-forum.net/forum/smileys/smilie11.gif)
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