Here’s how to use a magnetic ND gradient filter: 

1. Attach the magnetic holder: The filter typically comes with a metal ring that attaches to your lens. The ring is magnetic, so it sticks to the holder securely.
2. Position the filter: The ND gradient filter usually has a dark portion that starts from the top or bottom of the frame and fades to clear. Position the darker part of the filter over the area you want to reduce light exposure, such as the sky in a landscape shot.
3. Adjust the gradient: Some magnetic ND gradient filters allow for adjusting the position of the gradient transition. You can slide it up or down to better match the scene you're shooting.
4. Check exposure: After setting up the filter, adjust your camera settings (aperture, shutter speed, ISO) to get the proper exposure. The ND filter will help prevent overexposure in bright areas, especially when shooting with a slow shutter speed or wide aperture.
5. Take your shot: With the filter in place, your camera should now capture the scene with more balanced exposure, preventing the bright sky from being overexposed while maintaining detail in the darker foreground.

In summary, this filter is perfect for controlling the exposure in situations where there’s a significant difference in brightness between the sky and the ground, like when photographing sunsets or landscapes with a bright sky and darker ground. 

However, while gradient filters (like graduated neutral density or GND filters) used to be essential in landscape photography, many photographers now prefer not to use them — and here’s why: 

1. Post-Processing Power

• Dynamic Range: Modern digital cameras have much better dynamic range than older ones, so they can capture both highlights and shadows more effectively.
• RAW Editing: Editing RAW files in programs like Lightroom or Photoshop allows for selective exposure correction using tools like gradient masks or HDR blending — often more precisely than a physical filter can.

• GND filters have a fixed transition (soft or hard), which might not align well with irregular horizons (e.g., mountains, trees, buildings).
• This can result in underexposed or overexposed parts of the image — especially if the horizon isn’t flat.

• Not using physical filters makes your shooting setup faster and more flexible — no need to fumble with filter holders or worry about stacking filters in windy or dusty conditions.
• Less gear = lighter kit, which is great for hiking or travel.

• Cheap or dirty filters can reduce image sharpness or introduce flares and color casts.
• Even high-end filters can add unwanted reflections when shooting into the sun.

• Many landscape photographers use exposure bracketing (taking multiple exposures for highlights and shadows) and then blend them in post — essentially creating their own “perfect” gradient.