ND filter takes a photo with a big "X" on it.

Any professional landscape photographer will not recommend adjustable nd to his friends, nor will he recommend square ND with more than 4 gears (except special lens). X appears mainly because your lens has a wide focal length, and the dimming effect of adjustable nd is different from that of real ND. Finally, ND is used with CPL or gradient lens. Under such a thick adjustable ND, there will be a series of problems such as occlusion, color block and X symbol. The wider your lens is, the more obvious this problem becomes.

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You can avoid a lot of x, and the biggest problem in adjustment is several.

1, 2 CPL superposition, the picture quality decline is very, very obvious, and the price is 2 CPL.

2. The border is too thick, which leads to the serious dark corner of the film.

3. Due to the principle of CPL, uneven light is suppressed and color patches appear, especially under the ultra-wide-angle lens.

4, also because of the CPL principle, if you need extinction, then CPL is up or down, and the frame will be better if you continue to go up. At this time, it will be blocked instead of dark corners. ND is outside and CPL is inside.

5. Adjustable ND files are not allowed, and are generally marked less.

6. Generally speaking, the adjustable ones are not three-proof, and the three-proof CPL is 1 thousand, so the adjustable nd sells for at least 2000, and there is no market.

7. Advanced Nds, especially high-end Nds, have IR infrared suppression (without IR, films above 8 files will be seriously red, and those without low pass will be worse) or special tone (many warm NDS).

8. In practical use, two ND8 and ND400( 1000) are enough. The former is used to smooth water ripples during the day, and the latter is used for long exposure during the day.