|
Forum: Photographic Technique
06-09-2018, 02:37 PM
|
| |
Absolute aperture (size) determines the brightness of point objects like individual stars. With wide angle lenses, this can be problematic because even with low f stops, the absolute aperture can be small. "Extended" objects like nebulae respond to the actual aperture (f2 versus f8), so they can be rendered brighter even with a wide angle lens while the stars might be considerably muted relative to the extended object. Hence, contrast between stars and nebulae will be controlled by the size of the aperture and the f stop, and that contrast will depend on the focal length of the lens (generally speaking). Large f stops don't necessarily mean bright stars but for nebulae and aurora they do what is expected of a "fast" lens and prov beneficial for shorter exposures.
|
