觀景窗

LEICA的觀景器又大又亮，這是非常大的優勢，特別對於手動對焦與低光度下，可達成準確對焦的要求。
關於本問題詢問『尺寸的問題』請恕我也沒有相關資料，僅就一些基本的東西做論述。

首先，關於觀景器本身，要讓人看得舒服（通常就是比較大），就決定於接目鏡的口徑（其實跟望遠鏡道理一樣），就個人使用不同相機，從早年的CANON的手 動相機、NIKON FM2這兩台，為了手動對焦的要求，接目鏡比較大，而容易觀景，就RF相機，高級的LEICA M或是ZEISS IKON也都較大，這當然帶給攝影者容易手動對焦的優點；而後來的自動對焦相機便宜的EOS500N還是近年便宜數位機，明顯的小很多，這當然有成本的考 量，而高檔的自動對焦相機，如NIKON F5一樣能做得很大，帶給使用者許多方便（畢竟它也設計給裝載手動對焦鏡頭使用）。這實在取決於廠商對於機身功能的要求，不過一昧的將接目鏡做大，並不會 帶來優勢，因為相對地要解決視野變大後維持影像品質與亮度的問題。

再來，就觀景器的亮度而言，SLR的光線經由鏡頭，再進入反光鏡與五稜鏡折射後進入眼睛，若要達成高亮度的要求，必須追求上述過程中，光線的損失最小的目 標，此時光學設計就非常重要，若仔細的觀察LEICA R6.2（或R8/R9）的反光版，就會發現，它是個半透明的鏡子，有趣的是，有部分的光線（印象中是30%）穿透供測光表使用，剩下才供作觀景，如此還 能夠這麼亮，實在是廠商的秘密了，另外日系廠商的頂級機身一樣很亮，如此可以推論，觀景器亮度成本不低。

另外，現在有些數位機身的配件有『觀景器放大鏡片』，說真的，不要期待太高，因為就算把影像放大了，也不會放大亮度，在光線較差的情況下，恐怕效果有限。

R6.2
觀景窗範圍：23x34.6 (垂直 96%，水平 96% 整體為 96% x 96% = 92%)
觀景窗倍率：0.80 (無視力矯正，搭配 50mm 鏡頭)
至於反光鏡：17層鍍膜，70%反射(觀景窗)；30%穿透(測光)

R8/9
觀景窗範圍：23x35 (垂直 96%，水平 97% 整體為 96% x 97% = 93%)
觀景窗倍率：0.75 (無視力矯正，搭配 50mm 鏡頭)
至於反光鏡：17層鍍膜，70%反射(觀景窗)；30%穿透(測光)

以上，請參考。

Leica R Mount SLR Lenses

While the Leica screw-mount and M bayonet

mount rangefinder lenses are familiar to most camera collectors, Leitz also produced a wide range of lenses for its single lens reflex cameras. These cameras have a long history, starting out with the original Leicaflex , the auto-exposure R3, the famous all-mechanical R6, and continuing on to the current Leica R9 which accommodates an 11-megapixel digital back.

With the exception of auto-focus, the Leica SLR system is just as advanced as their equivalents from Canon or Nikon. However, because Leica always stood for precision, ruggedness, reliability, and mechanical perfection above everything, they never went towards the lightweight plastics and looser focusing tolerances that auto-focus cameras entailed. Thus, all Leica R lenses are manual focus only. For the same reasons, Leica has not produced as many zoom lenses as its Japanese competitors. In fact, a couple of Leitz's SLR zooms are actually Minolta designs. Ask around, it's easy to find out which.

Leica R Lenses

For the most part, R lenses are interchangeable with any age Leica SLRs. Except for the newest ROM lenses which should not be used on Leicaflex cameras, at most you lose the ability to matrix meter, or to meter at full aperture (stop-down metering only).

There are some series variations in Leica R-Mount lenses:

• One-cam (Original Leicaflex). This is the silver-chrome triangular cam marked (1) on the photograph right. Leica doesn't recommend using 1-cam or 2-cam lenses on the R8 or R9.
• Two-cam (Leicaflex SL/SL2). This is the silver-chrome triangular cam at the top-left (11 o'clock) position in Exhibit A (behind the 3rd cam in the Exhibit B). Leica doesn't recommend using 1-cam or 2-cam lenses on the R8 or R9 because the cam may damage the ROM contacts if it's out of spec.
• Three-cam (Leica R series). The 'R-cam' or third cam is the stepped black metal cam barely visible in Exhibit A, right next to the silver wedge-shaped 2nd cam. The third or R-cam is used on R-series cameras (R3-R7). Three-cam lenses are the most compatible as they can be used on any Leica SLR ever made. In response to my lousy photo, reader Ken O'Kelley sent me a much better photo (Exhibit B) of the 3rd cam.
• R-only (Leica R series only). These lenses only have the stepped R-cam and cannot be used on the older Leicaflex cameras. Leica changed the mount slightly so they will not even mount on a Leicaflex. You need to make sure that you can see cams 1 and 2 if you want to use newerlenses on older bodies.
• ROM lenses: the latest lenses designed for use with the Leica R8 and R9 cameras which had electronic contacts between the camera body and lens. This allows the lens to transmit additional data to the camera. ROM lenses cannot be used on the original Leicaflex series as they will not even mount due to a slight bayonet change. They have the R-cam so they can be used on any R series Leica.

Upgrading older lenses / Using adapters

Although older lenses were originally made with 1- or 2-cams, Leica offered an upgrade service to bring them up to 3-cams (you can also modify a R-only or ROM-only lens backwards to 3-cam as well, although you lose the ROM contacts if you do this). So just because a lens has 3-cams doesn't mean that it is a second-generation lens. You have to use other factors in determining the lens version such as the distinct profile of each version, the serial number, the presence or absence of a built-in lens hood; or the weight.

Many people use their Leica R lenses on Canon SLRs (including digital SLRs such as the Canon EOS 20D) with an adapter that is widely available (see CameraQuest.com for a source in the USA). I use mine with the Hansa adapter which I bought in Japan (picture right). If you have an adapter, it does not matter if you have 1, 2, 3, or ROM cams on your R lens if you are using it on another camera system since you will always be shooting using open-aperture metering. The system works fantastically well. I have some photographs using the 180mm Elmarit on my gallery page.

In order for an adapter to work, there are two factors. The first is the body "lens registration" distance or the distance from the lens mount to the film surface. The second is the mount "throat size" or the diameter of the mount. For an adapter to slip in between the body and lens of differing manufacturers, the registration distance of the lens must be greater than the registration distance of the body; and the throat-size of the lens must be smaller than the throat size of the body mount.