Just took delivery of one of these fantastic variable-setting neutral density filters (The Fader ND Mark 2 from Light Craft Worshop to be exact). Attach and rotate it at the end of your lens, much like a circular polarizer, and it will give you 2 – 8 stops of neutral density. Pretty ingenious design because you get 8 filters in one! Not sure what an ND filter is? See the wikipedia definition below:
The use of an ND filter allows the photographer to utilize a larger aperture that is at or below the diffraction limit, which varies depending on the size of the sensory medium (film or digital) and for many cameras, is between f/8 and f/11, with smaller sensory medium sizes needing larger sized apertures, and larger ones able to use smaller apertures.
Instead of reducing the aperture to limit light, the photographer can add a ND filter to limit light, and can then set the shutter speed according to the particular motion desired (blur of water movement, for example) and the aperture set as needed (small aperture for maximum sharpness or large aperture for narrow depth of field (subject in focus and background out of focus). Using a digital camera, the photographer can see the image right away, and can choose the best ND filter to use for the scene being captured by first knowing the best aperture to use for maximum sharpness desired. The shutter speed would be selected by finding the desired blur from subject movement. The camera would be set up for these in manual mode, and then the overall exposure then adjusted darker by adjusting either aperture or shutter speed, noting the number of stops needed to bring the exposure to that which is desired. That offset would then be the amount of stop needed in the ND filter to use for that scene.
Examples of this use include:
- Blurring water motion (e.g. waterfalls, rivers, oceans).
- Reducing depth of field in very bright light (i.e. daylight).
- When using a flash on a camera with a focal-plane shutter, exposure time is limited to the maximum speed -often 1/250th of a second, at best- at which the entire film or sensor is exposed to light at one instant. Without an ND filter this can result in the need to use f8 or higher.
- Using a wider aperture to stay below the diffraction limit.
- Reduce the visibility of moving objects
- Add motion blur to subjects
I know this sounds great and all, but I know what you REALLY want is to see this device in action! I will be demonstrating using photo strobes and a portrait subject, so check back the blog soon!
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