Leica Q3 43: The Filter Size Is 49mm, Not 43

If a friend called me from a camera store parking lot holding a brand new Leica Q3 43 and asked what filter size to buy, I would tell them straight: buy a 49mm filter. Not 43mm.

The official Leica filter thread specification is E49. That means a 49mm screw thread with a standard 0.75mm pitch.

Yet every week, someone orders a 43mm filter for this camera, rips open the box in their car with cold fingers, and gets into an infuriating fight trying to thread it on. The ring slips right past the outer rim and rattles against the front glass. Camera naming is clumsy like that. The "43" engraved on the top plate is the focal length of the APO-Summicron 43mm f/2 ASPH lens. It has nothing to do with the physical thread size.

If you are searching for the Leica Q3 43 filter size, remember that number: 49mm.

The number on the box is not the thread size

Misreading focal length as thread size is the first trap. It happens constantly on fixed-lens cameras—people bought 28mm filters for the original Q, and now they buy 43mm filters for the Q3 43.

The little ø symbol on the underside of the barrel or in the spec sheet tells the truth: E49.

I run XT Filters, and I see these returns arrive on my bench with scratched anodizing and torn envelopes. A 43mm ring will never mount to a 49mm mouth. You cannot finesse it, and cross-threading a mismatched ring into a five-figure camera is an agonizing way to learn patience. Check the ø mark before tapping buy.

Thread size, square hoods, and macro travel

Once you have 49mm locked in, the real field headaches begin. A lot of shooters assume any generic 49mm filter in their bag will work.

It will not. That is where Leica forums hit "Filtergate."

You have three separate physical realities competing for space on the nose:

First, the thread itself. That is a standard 49mm female thread inside the nose.

Second, the compact square hood. Leica ships a machined square hood that threads onto the outer barrel. In the manual, Leica explicitly notes that the compact hood and a filter cannot be mounted together. Ordinary 49mm filters have frames thick enough to foul the hood, so it never seats flush.

Third, the macro mechanism. Twist the barrel into macro mode, and the internal front optical group extends forward. If your filter rim sits too deep or an aftermarket hood pinches inward, that forward travel binds. In cold weather, with cold fingers racking between street distances and a close-up, a tight ring can bind up completely. A twisted-dead bind-up between moving optical elements and an outer filter ring can lock a lens barrel hard.

On my Panasonic Lumix GH7 with the Olympus 12–40mm II, I slap on almost any filter, twist the bayonet hood over it, and move on. The Q3 43 has zero margin for sloppy tolerances.

The dedicated cut and what we will not promise

When generic 49mm filters fouled the factory hood, accessory makers rushed in. NiSi launched a dedicated UV filter for around $98, claiming its custom slim profile lets you keep both the factory square hood and macro mode intact.

At XT Filters, we cut a dedicated 49mm(Q343) frame for our XT996 PRO. The threads are true 49mm, and the outer black frame is milled down flush.

Here is the plain field reality: we have not finished testing that dedicated cut through months of gritty shooting to guarantee it clears the factory square hood during repeated macro travel in dirty conditions. Tolerances can differ by fractions of a millimeter between factory batches. Until our team logs the miles with that exact setup, we will not promise you can keep the original hood and macro mode simultaneously.

Generic 49mm filters fight the factory hood. Whether our dedicated cut clears both without friction is something we leave for verified shooting. If keeping the factory square hood during macro is non-negotiable, test clearance by hand before torquing anything down.

Choosing the right glass for the 49mm front

If you are setting up your Q3 43, your filter choice comes down to how you shoot:

For everyday lens protection: If you remove the factory square hood or swap to a screw-in round hood, our XT996 PRO in the 49mm(Q343) cut gives you high-transmission optical glass in a clean, matte black frame. The front element on an APO-Summicron is irreplaceable; a hardened sacrificial layer protects against grit, salt spray, and dirty cloths.

For creative diffusion: The 43mm APO-Summicron is clinically sharp. Wide open at f/2, modern sensors render portraits with unforgiving contrast. To take the digital edge off:

• The 49mm XT888 (Bottom Black Mist 1/4) softens harsh light sources and blooms street lamps while keeping shadows clean.
• The 49mm XT925 provides classic, balanced mist across the entire frame.

When running diffusion glass, you will shoot without that compact factory square hood. Treat the filter as your front barrier.

Before you head out

Do the fit check at home on the table:

1. Match the 49mm thread, never 43mm.
2. Thread the filter finger-tight. If you feel resistance in the first quarter-turn, back it off. Never force cold aluminum threads.
3. If you run a hood over your filter, test macro travel slowly by hand. If the barrel feels stiff, pull the hood.

Shop 49mm for your Q3 43. If you are unsure about macro clearance or the factory hood on your body, email me before ordering. I would rather help you verify your setup than hear about another parking-lot fight.

— Leo Liang