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Filmmaking Dictionary: Number 0 / 0.6 ND
Definition
0.6 ND is a neutral-density filter strength that reduces exposure by approximately two stops, allowing about one quarter of the incoming light to pass. It is one stop stronger than 0.3 ND and one stop weaker than 0.9 ND.
The decimal number is an optical-density value. The equivalent strength on the filter-factor scale is commonly labelled ND4. Neither label means that the filter removes four stops.
How a Two-Stop Reduction Works
Each stop halves the transmitted light. The first stop leaves roughly 50%; the second leaves roughly 25%. At unchanged camera settings, inserting a 0.6 ND therefore darkens the entire image by two stops.
To maintain the same exposure, you can open the lens by two stops. Starting at f/5.6, that means moving through f/4 to f/2.8. On cinema lenses, the equivalent two-stop T-stop adjustment is used in the same way.
| Marking or measurement | Meaning |
|---|---|
| 0.6 | Optical density |
| 2 stops | Nominal exposure reduction |
| About 25% | Light transmitted |
| ND4 | Common filter-factor label |
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Example: Keeping the Lens at T2.8
Suppose an exterior interview is correctly exposed at T5.6 without filtration, but the intended look calls for T2.8. Adding 0.6 ND removes two stops of light; opening the lens from T5.6 to T2.8 puts those two stops back. The face remains similarly exposed, with shallower depth of field.
This is useful when the crew wants to preserve a chosen shutter angle and avoid changing the camera’s sensitivity setting between shots. It does not guarantee perfect continuity if the sun, cloud cover or lighting direction also changes.
Changing or Combining Filters
- 0.3 ND to 0.6 ND: Removes one additional stop.
- 0.6 ND to 0.9 ND: Removes one additional stop.
- Two 0.3 filters together: Give a nominal combined density of 0.6.
- 0.3 plus 0.6: Gives a nominal combined density of 0.9.
The arithmetic describes density, not the optical quality of a stack. Additional surfaces can create reflections or reduce contrast. Filter thickness, matte-box clearance and wide-angle coverage also matter. Inspect the frame after fitting the actual combination.
What 0.6 ND Does Not Do
A solid 0.6 ND does not selectively darken a window, reduce the key-to-fill ratio or replace diffusion. It reduces the light across the frame. If the subject is too dark against a bright background, adding camera ND alone does not correct that brightness relationship.
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Frequently Asked Questions
Is 0.6 ND the same as six stops?
No. In the optical-density scale, 0.6 represents about two stops. A six-stop ND has an optical density of approximately 1.8.
Can I use 0.6 ND with a polarizer?
They can be combined when the equipment allows it, but the polarizer adds its own exposure loss and changes reflections. Meter and inspect the complete combination.
Related Terms
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