Urth Variable ND Filter - 40.5mm ND2-400

ND2-400 refers to the range of light reduction. ND2 blocks 1 f-stop of light, and ND400 blocks approximately 8.66 f-stops of light. The 'Variable' aspect means you can adjust the density anywhere within this range.

Look for a diameter symbol (Ø) followed by a number (e.g., Ø40.5mm) printed on the front of your lens, usually near the lens cap. This is the filter thread size.

While technically possible, stacking variable ND filters is not recommended as it significantly increases the risk of vignetting, uneven light transmission, and 'X' patterns. It's best used as a single filter.

Use a clean microfiber lens cloth. For tougher smudges, apply a small amount of lens cleaning solution to the cloth, not directly to the filter, and wipe gently.

In most cases, the filter will not directly affect autofocus. However, in very low light or when set to maximum ND, the camera's autofocus system might struggle due to the reduced light reaching the sensor.

A fixed ND filter provides a specific, constant amount of light reduction (e.g., ND8 for 3 stops). A variable ND filter allows you to adjust the density across a range, offering more flexibility but potentially with trade-offs in image quality at extremes.

This often occurs at the extreme ends of the variable ND range. Rotate the filter ring to a less dense setting where the pattern disappears. Avoid using the filter at its maximum or minimum settings if artifacts are present.

Variable ND filters can sometimes introduce a color cast. Try adjusting the filter to a slightly different density. If the cast persists, you may need to correct it in post-processing or consider a fixed ND filter.

Ensure the filter threads and lens threads are clean and free of debris. Do not force the filter; try gently rocking it while screwing. If it continues to be difficult, the thread sizes may not be perfectly aligned, or there might be an issue with the filter or lens threading.

Adjust the outer ring of the variable ND filter to change the amount of light being blocked. Ensure the filter is set to the desired f-stop or shutter speed combination for your scene.