In photography, a neutral density filter or ND filter is a filter that reduces or modifies the intensity of all wavelengths orcolors of light equally, giving no changes in hue of color rendition. It can be a colorless (clear) or grey filter. The purpose of a standard photographic neutral-density filter is to reduce the amount of light entering the lens. Doing so allows the photographer to select combinations of aperture, exposure time and sensor sensitivity which would otherwise produce overexposed pictures. This is done to achieve effects such as a shallower depth of field and/or motion blur of a subject in a wider range of situations and atmospheric conditions.
For example, one might wish to photograph a waterfall at a slow shutter speed to create a deliberate motion blur effect. The photographer might determine that to obtain the desired effect a shutter speed of ten seconds was needed. On a very bright day, there might be so much light that even at minimum film speed and a minimum aperture, the ten-second shutter speed would let in too much light and the photo would be overexposed. In this situation, applying an appropriate neutral-density filter is the equivalent of stopping down one or more additional stops, allowing for the slower shutter speed and the desired motion-blur effect. http://en.wikipedia.org/wiki/Neutral_density_filter
Longtime Longtime will help you to calculate long exposure times automatically when using ND Filters instead of reading exposure tables or calculate exposure times in mind.
UsageFind a suitable position for your composition as you would do for any shot. Note it’s vital to use a tripod with these shots due to the long exposures. Once you have the shot composed the next step is to work out what exposure will be needed. Provide Longtime with your desired ND filter and the mettered shutter speed by your camera. Adjust the shutter speed of your camera to the calculated exposure time. Set your camera to „Bulb“ or „B“ if shutter speed ist more than 30 seconds.
Für die Langzeitbelichtung verwenden viele Fotographen Filter vom Typ ND (Neutral Density) um die Belichtungszeiten bei Tageslicht deutlich zu verlängern. Beliebt ist der Filter B+W ND1000 welcher die Belichtungszeit um 10 Blendenstufen verlängert. Für die Berechnung der verlängerten Belichtungszeit soll die App „Longtime Exposure“ dem Fotografen eine Hilfestellung geben.
download at the App-Store
Coming soon: LongTime 2
- improved user interface
- Apple Watch integration
- calculation for multiple filters attached