The Fujifilm X100 series has no native filter thread on the lens barrel. That applies from the original X100 through the X100V and X100VI. Out of the box, no filter screws onto the front glass.
To mount screw-in glass, you must remove the stock front trim ring and install an adapter. Once that adapter is seated, the working thread size is 49mm. Not 39mm. Not 43mm. Exactly 49mm.
Yet on my returns bench at XT Filters, 39mm rings arrive in padded mailers almost every week. The return slips usually say the same thing: "Bought this for my X100VI, threads do not match."
Where the 39mm mix-up comes from
The mix-up usually starts with forum shorthand. Shoppers search for compact Fuji gear and see 39mm mentioned repeatedly.
That 39mm thread belongs to interchangeable XF lenses—most notably the pancake Fujinon XF 27mm f/2.8 R WR—along with classic Leica and Voigtlander L39 rangefinder optics. Because the X100 shares that compact rangefinder silhouette, buyers assume it uses the same 39mm mouth.
It does not. A 39mm filter ring slides loose over an X100 barrel without catching any threads. The bare nose has no internal 39mm threading, and no adapter steps an X100 down to 39mm.
Three physical steps from bare barrel to 49mm
Mounting glass on an X100 follows three distinct steps:
First, remove the decorative ring. Fujifilm covers the outer barrel threads with a slim cosmetic metal ring. Twist it counterclockwise with dry fingers. It spins off smoothly, exposing bare external barrel threads. Store that trim ring in your camera box.
Second, mount a dedicated adapter ring. You cannot thread a filter directly onto those exposed barrel threads. Beyond proprietary thread pitch, the primary barrier is optical travel: the 23mm f/2 lens extends its front optical group forward during close focusing. Seating a filter flush against the bare barrel causes that moving element to collide with the filter glass, jamming the focus motor.
A dedicated Fuji X100VI 49mm filter adapter—such as Fujifilm’s AR-X100, or third-party options from JJC, Haoge, and PolarPro—threads onto the outer barrel to supply that forward clearance. It creates room for optical travel and terminates in standard 49mm female threads with a 0.75mm pitch.
Third parties like Haoge, JJC, and PolarPro use this adapter-then-filter path, leaving standard 49mm threads open for whatever glass or hood you choose. NiSi engineered an alternative dedicated decorative-ring system that replaces the front trim ring directly with an integrated filter. Both protect the moving front element. But for swapping polarizers, mist, and clear filters freely, the adapter-to-49mm route offers standard compatibility.
Third, thread your 49mm filter into the adapter. Any standard 49mm circular filter threads straight into the adapter mouth. On the X100V and X100VI, this setup also completes the weather seal, protecting the moving lens group against moisture and street dust.
Matching glass to an adapted 49mm front
Once your adapter is installed, filter choices follow standard 49mm sizing:
For everyday lens protection:
The front element of a fixed-lens camera cannot be swapped like an interchangeable lens. If grit or salt spray chips the front coating, the camera requires a shop repair. For everyday clear protection after the adapter, our XT996S Lens Protection Filter ($44.99–$79.99) covers 49mm as an everyday clear barrier that does not shift color or the look of the lens.
On my own street setup—a Panasonic Lumix GH7 with the OM SYSTEM 12–40mm f/2.8 PRO II that I carry through Hong Kong—I keep an XT996S mounted during seaside walks to catch salt haze without visible optical loss. On that interchangeable zoom, the filter threads straight into the lens rim. On an X100, you screw that same 49mm XT996S into the adapter ring.
For a heavier black frame, our XT996 PRO ($64.99–$179.99) includes precision-milled cuts: a dedicated 39mm cut for lenses like the Fujinon XF 27mm, and standard 49mm for setups like the Leica Q3 43 and adapted X100 bodies. When outfitting an X100 after an adapter, choose 49mm. The 39mm cut will not mount.
Managing reflections:
Street shooting often involves wet asphalt, shop windows, and afternoon water reflections.
- For a lightweight carry that stays in the bag until needed, our XT003 CPL ($39.99–$69.99) provides clean polarization in 49mm.
- If you want smoother frame rotation and ultra-low reflection glass under harsh sun, the XT001 PRO CPL ($79.99–$189.99) covers 49mm.
Highlight bloom and night mist:
The 40-megapixel sensor on the X100VI and the sharp 23mm f/2 II lens produce crisp microcontrast. At night, bare streetlights can look harsh.
- The 49mm XT888 Bottom 1/4 ($49.99–$119.99) softens point light sources into gentle halos while keeping shadows clean across the lower tone curve.
Fit checks on your desk
Before heading out:
- 1. Thread the adapter on slowly. If it resists in the first two turns, back off. Barrel threads are aluminum and need a clean, square start.
- 2. Tighten the adapter snug by hand. Never wrench it down.
- 3. Thread your 49mm filter into the front mouth. Confirm the filter frame seats flush against the adapter ledge.
- 4. Power the camera on and rack focus from infinity down to minimum distance. Verify that the front optic moves freely inside the adapter barrel.
The mounting rule on the X100 does not change between generations. Pull the trim ring, screw the adapter on, and shop 49mm. Leave 39mm on the shelf for pancake XF lenses.
If you are outfitting an X100, choose 49mm across protection, CPL, or diffusion. If you are shooting an interchangeable XF lens like the 27mm f/2.8 instead and want to verify thread size before ordering, email me directly. I would rather check your lens model than see another return on my bench.
— Leo Liang
