The Built-in ND Filter and the Freewell ND

A neutral density filter is sunglasses for your lens: it darkens the whole image evenly, costing you light without changing color. Why would you want less light? Because sometimes the creative settings you want, a wide aperture for shallow focus, or a slow shutter for motion blur, would overexpose in bright conditions. ND lets you keep those settings and still get a correct exposure. The GR IV gives you two ways to do this.

The built-in 2-stop ND

The GR IV has a mechanical neutral density filter built into the camera, worth about 2 stops, that you can switch on from the menu or a function button. Two stops is modest but genuinely useful. There are two main reasons to flip it on.

First, bright daylight at a wide aperture. Say you want to shoot a portrait at f/2.8 for a soft background on a sunny afternoon. At base ISO and f/2.8 the required shutter speed might exceed the camera's limit, or you simply cannot get the exposure right. Switch on the 2-stop ND and you regain the room to shoot wide open in full sun.

Second, daylight motion blur. To blur a flowing crowd or running water in daylight you need a slow shutter, but a slow shutter in bright light overexposes badly. The ND darkens things enough to let you drop to, say, 1/30 or 1/15 in conditions that would otherwise force 1/2000.

The Freewell ND set

Two stops is sometimes not enough. The optional Freewell magnetic ND8/16/32 set, around $79.99 as of writing, gives you three stronger filters: ND8 is 3 stops, ND16 is 4 stops, ND32 is 5 stops. These snap onto the same magnetic mount as your other Freewell filters.

Now the fun part. You can combine the built-in 2-stop ND with a Freewell ND. Stack the built-in 2 stops with the ND32's 5 stops and you have 7 stops of darkening, enough to shoot something like 1/4 of a second at f/8 in full sunlight. That opens up daytime long-exposure street work: blurred crowds in a sunlit piazza, smeared traffic on Via dell'Indipendenza at midday, a lone sharp figure standing still amid streaks of moving people.

ND plus IBIS, a powerful pairing

Here is where the GR IV's two strengths multiply. The in-body stabilization gives you roughly 6 stops of hand-holding headroom, and the ND gives you the darkening to use slow shutters in daylight. Put them together and you can hand-hold genuinely long exposures, a half-second, even longer, with the static parts of the scene sharp and the moving parts beautifully blurred, no tripod required. A tripod is conspicuous and slow on the street; this combination lets you make tripod-look images while staying mobile and invisible.

When not to bother

ND is a specialist tool, not a default. In normal shooting it just makes the camera work harder for no reason. Leave it off unless you have a specific creative goal: shallow focus in bright sun, or motion blur in daylight. And remember that a polarizer already costs you 1 to 2 stops, so if you are running the CPL you may already have enough darkening for mild effects without adding ND on top. Reach for ND deliberately, get the shot, then take it off.