namsheetsim

各位師兄師姐，我是一新丁，已有一個 Minox BV 8x25 (太太送的禮物)，覺不夠光，太太用的 BV 10x42 比較光, 我正研究什麼望遠鏡才適合我，但有些問題解決不了，請指教。 (前題: 不怕重量)

1.        My lay thinking makes me to think that a larger objective lens allows me to see more, but looking at the Field of View (FOV) of the Minox BV series, the FOV goes down with larger objective lens, from 421 f @ 1,000 yd (8x33) to 389 (8x42) to 342 (8x56).  Difficult to understand.

2.        My BV 8x25’s FOV is 358 yd @ 1,000 yd, while the BV 10x42’s FOV is 342.  But the image I saw in the 8x25 is smaller than the image in the 10x42.  Why?

3.        If I exercise my lay reasoning that a larger objective lens give a bigger image, similar to using a 19-inch computer monitor vs a 15-inch monitor (everything else equal), will I get a larger image with a 10x52 (e.g. the Minox BL 10x52 FOV 342 ft) compared to my wife’s BV 10x42 (FOV also 342 ft) ?

4.        If a larger objective lens gives a bigger image, can I choose a lower magnification but a bigger objective lens, e.g. instead of choosing BV 10x42, I choose BV 8x56, the FOV are the same, but to expect the ’56 will give a larger image of the shrunken in size by the 8x (instead of 10x)?  But then the brightness factor will increase from 17.64 (10x42) to 49 (8x56)!

5.        The twilight factor is most difficult to understand, a high magnification bino easily gives a higher twilight factor.  If I found that the colours are usually darkened (from blue to black, from brown to black etc.) when looking from underneath a tree in shade, and I want less colour distortion, do I need a bino with a higher magnification or a bigger objective lens?  E.g. the twilight factor of Minox BL 10x44 is 20.98 and that of BL 8x52 is 20.4, is the colour distortion less with the 10x44 or the 8x52?

多謝指教。

namsheetsim

多謝提點, Thank You for your comments.

namsheetsim

Thank you for your comments. 多謝指教。  Everyone has his own problem. Mine are:
1. i spot bird, raise bino, original view OFF the line = so i need a bigger FOV to increase the chance to keep the object in view
2. i have peripheral cataract, so in dim light, my effective 'pupil size' is smaller than my actual 'pupil size' (which is probably just ~ 5.5 mm because of my age) - so i need a bright bino as that will allow a smaller pupil in me - a.) the peripheral cataract part is not required to function, and b.) a smaller pupil means a deeper DEPTH of view.
So I will prioritize:
a. FOV, b. Brightness (8x preferred), c. Price, d. Weight.

namsheetsim

多謝提點。但在新年時見鳥會 Minox promotion 已買了 BL 8x44, 感覺頗好。比太太的 BV 10x42 光。FOV 大些。但最好的是 focus 容易，景深大很多，舉鏡不用太多 adjustment 就找到目標,比 10x42 敏捷多了，tradeoff 是 image 細了少許，但暗影下的 image 明顯清楚很多.