A filter-selection guide for the Sony FE 24–105mm F4 G OSS, model SEL24105G. This is not a comparative filter test or a claim that every accessory below is in the author’s kit.
A filter that screws onto the lens can still be the wrong purchase. An ND filter controls how much light enters, a polarizer changes selected reflections, and a clear protector serves a different purpose again. Start with the problem in the picture, not a bundle containing every type of glass.
Quick answer: Sony specifies a 77mm filter diameter for the SEL24105G. Choose ND for exposure control, CPL for reflection control, and variable ND when adjustable density is useful and its compromises are acceptable. Check the exact lens model and front-thread size before ordering.
77mm Describes the Thread, Not the Focal Length
The 24–105mm marking describes the zoom range; 77mm is the filter-thread diameter in Sony’s specifications. Neither the FX3 nor the A7 III body changes that thread size. Confirm SEL24105G on the lens, especially if buying for equipment identified only as “a Sony 24–105.”
Check the entire physical stack: lens thread, any adapter ring, filter, hood clearance, and front cap. The cap that fits the bare lens may not fit the front of a particular filter. For example, HOYA says its Variable Density II uses a larger front frame and needs a cap one size above the lens-thread size. That is a design-specific example, not a rule for every 77mm filter.
Choose ND When the Exposure Is the Problem
Suppose a video exposure is too bright after choosing the shutter behavior and aperture you want. ND reduces incoming light so you can keep those creative choices within the available exposure range. It does not add light, improve the sensor, or automatically produce cinematic motion. Confirm the camera’s actual exposure before adding density.
A fixed ND provides one stated amount of reduction. A variable ND lets you adjust within a stated range. HOYA’s variable-ND explanation describes this adjustable exposure-control role. For a repeatable setup, write down the filter and setting used rather than assuming an unmarked ring position can be reproduced later.
| Reduction | Light remaining, mathematically | Common factor notation |
|---|---|---|
| 1 stop | 1/2 | ND2 |
| 3 stops | 1/8 | ND8 |
| 6 stops | 1/64 | ND64 |
Those fractions are exposure arithmetic, not measurements of any particular filter. Packaging may use stops, a factor, or optical-density notation. Read the manufacturer’s actual specification rather than treating every number following “ND” as a stop count.
Variable ND Needs a Wide-End Check
Before relying on a variable ND, test the intended density range at 24mm as well as your normal framing. HOYA warns that rotating its Variable Density II beyond the permitted range can create an X pattern. Do not assume the last part of the rotation is an extra usable dark setting.
A useful acceptance exercise is a plain, evenly lit surface followed by the intended scene. Compare the corners, overall color, fine detail, and bright light sources with and without the filter. Keep exposure differences accounted for; a much darker image is not a fair sharpness comparison. This is a suggested test, not evidence that a particular brand has passed it.
Choose CPL When Reflections Are the Problem
For glare on glass, water, or foliage, a circular polarizer may solve something that ordinary ND does not. Rotate the ring while watching the specific reflection you want to control. HOYA’s polarizer guide explains the reflection-control function and the accompanying light loss. The effect depends on the scene and angle; it is not a universal “make everything better” switch.
Do not add a CPL merely because the sky is visible. Ask whether the changed reflection helps the story, and check the whole frame before recording a move. A reflection can establish that a surface is glass or reveal useful context. Removing it is a creative decision, not an automatic quality upgrade.
Start With One Filter, Then Inspect Any Stack
Try the required filter alone before adding a protector underneath it. After adding another ring or filter, inspect the widest framing for darkened corners and check strong lights for unwanted artifacts. If a problem appears, remove one layer and repeat. That comparison gives a clearer answer than blaming the lens immediately.
A step-up ring can let a larger filter attach to a smaller lens thread, but it changes the physical setup. Check cap and hood fit and avoid forcing threads. If an accessory feels wrong at the first turn, stop and check alignment instead of tightening harder.
Buy for One Defined Job
For the next purchase, write a sentence such as “I need less light while keeping my chosen video shutter and aperture,” or “I need to control a window reflection in this composition.” That identifies a filter category. Only then compare size, usable range, physical fit, return terms, and price. No specific filter is ranked here because no controlled comparison has been performed.
The shared 24–105mm lens workflow covers the broader two-camera decision. A filter should solve a narrower problem within that workflow, not turn one zoom into every possible lens.