Borg 71 FL變成支有光圈鏡頭

[kwong]

Borg層層疊其中的好處是可任意配撘
今次就把一支m42 135mm f2.8鏡頭
裏的鏡片除下自己做了個
M55轉m57接就完成一支真正相机鏡頭
可惜光葉位置和尺寸不好收光圈後有黑圈

[littleming]

[鄧登凳]

收光圈在鏡前加一片中間開孔的膠片(step down plate)更簡單和合理。

Borg 71FL不加平場鏡或減焦平場鏡, 會有明顯的場曲(field curvature)引起的問題, 不利用DSLR機, 但你這個接法, 無法加入平場或減焦平場鏡。

[Eddy So]

一台長炮

[Chanlunlun]

The aperture stop must be added at the ENTRANCE PUPIL of the optical system otherwise you will have serious vignetting.

For refracting telescope the entrance pupil is always at the front element of the objective lens. Hence what you should do is to install the aperture blades at the front but not the back of the telescope. However you need a very big aperture stop, same size as the aperture of telescope.

[kwong]

The aperture stop must be added at the ENTRANCE PUPIL of the optical system otherwise you will have serious vignetting.

For refracting telescope the entrance pupil is always at the front element of the objective lens. Hence what you should do is to install the aperture blades at the front but not the back of the telescope. However you need a very big aperture stop, same size as the aperture of telescope.

但Borg原厰也有在鏡後的光葉，不知是否我現在光葉位置不對而出問題
因現有的鏡頭光葉也在鏡裏
應是位置不對請問是否有計算方式找出光葉位置
至於鄧sir説的平場减焦和濾片庒也準備了
就是我找到光葉位置就可安装上去

[Chanlunlun]

The aperture stop must be added at the ENTRANCE PUPIL of the optical system otherwise you will have serious vignetting.

For refracting telescope the entrance pupil is always at the front element of the objective lens. Hence what you should do is to install the aperture blades at the front but not the back of the telescope. However you need a very big aperture stop, same size as the aperture of telescope.

但Borg原厰也有在鏡後的光葉，不知是否我現在光葉位置不對而出問題
因現有的鏡頭光葉也在鏡裏

That is only for small chip CCD ( actually very small chip ) where vigneting is not a serious problem ( still a problem).

For full frame chip ( or relative bigger chip ) aperture blade must be installed at entrance pupil to avoid vignetting. If the aperture blade is too close to the focal plate it becomes a field limiter instead of an aperture stop. That's why you see a circle.

[鄧登凳]

Borg原廠的那個光圈是加在物鏡(objective lens)前, 或緊隨物鏡的, 不是用來放在管尾(相機那一方)的。





(圖來自廠方網頁)

另原廠減焦鏡安裝位置和感光片的距離有嚴格規定。

[kwong]

支borg終於搞到没有黑圈
在用央加了個52mm光可控52-5mm
可以拍正常照片