If this is your first black mist and you want the glow to actually show up in your photos, start with a 1/4. It is the grade where the effect is easy to see on a normal day, while blacks still mostly stay black. It is also the only strength XT Filters makes, so keep that bias in mind while you read.

What the fraction on the box means

Black mist glass carries a fine diffusing layer. The fraction is a density grade: lower numbers scatter less light, higher numbers scatter more. That scattered light does two jobs. Some of it spreads out from bright points (lamps, sun glints, highlights on skin), which is the halo people buy the filter for. The rest lifts the darkest parts of the frame a little. That lift is where the soft, filmic contrast comes from, and also where a heavy grade starts to look foggy.

So picking a strength is really picking how much halo and shadow lift you want before you start undoing it in the edit.

Why a lighter grade often ends up in a drawer

Very light grades are built for controlled sets, where someone watches a calibrated monitor and builds the look around it. A stills shooter checking a rear screen outdoors usually can't tell they're on. Flat overcast, midday sun, scenes with no strong light sources: the effect disappears.

That is the most common way a first mist filter gets abandoned. It didn't ruin anything. The owner just couldn't see what it was doing and stopped screwing it on.

A 1/4 avoids that. You see the change on the first evening walk, and you still get usable shadows in daylight. If it turns out to be more than you want for some jobs, you take it off for those frames. That tells you something. A filter you can't see tells you nothing.

When a 1/4 is the wrong call

  • Daylight product or client work where any visible haze gets rejected. Skip mist for that job.
  • Scenes with almost no contrast to begin with, like fog or a flat grey sky. There is nothing for the filter to soften.
  • You want a very heavy dreamy look. A 1/4 is an everyday grade, not a special effect.

Which 1/4 from XT Filters

  • XT888 135 Bottom 1/4: the entry mist, tuned for atmosphere over maximum sharpness, meant for focal lengths under 135mm. Sizes run 39mm to 105mm, including the 39mm Leica/Fuji threads and the 49mm size for the Leica Q3 43. Average transmission is listed at ≈88.8% with ≈0.3% reflectance from 28–36 coating layers per side, so you lose very little light. This is where most people should start.
  • XT925: also a 1/4, aimed at night portraits and mid-to-long lenses. Reflectance is ≈0.1% from 36–48 coating layers per side. That matters when lamps or neon are in frame, because it cuts the extra flare a filter can add on top of the glow you wanted. Sizes run 39mm to 112mm.

If you want to choose by scene rather than by grade, The Black Mist Strength You Can Leave On All Day covers daytime use, and A Softer Black Mist for Portraits, Not Night Lights covers skin.

A quick check before you order

Think about what you'll shoot in the first week. Evenings, street lights, backlit people, window light: a 1/4 will show you the look right away. Then read the thread size printed on the front of your lens and order that size. If you're not sure where to find it, the filter size finder walks you through it.

— Leo Liang