Posted: Mon Feb 15, 2016 1:08 pm Post subject: |
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Gerald wrote:
CBokeh wrote: |
I was always under the impression that "normal" was 43mm on 35mm format but 50mm was "close enough." |
The conventional definition of a normal lens is that one whose focal length is equal to the diagonal of the format. This gives a focal length of 43.3mm for 35mm and 79.2mm format for 6x6 format.
I prefer another definition: a normal lens is the one whose angle of view matches the angle of view of the person viewing a print of a picture taken with that lens. This definition can be extended to pictures viewed on a screen of a computer, TV or cinema.
I will try to explain with a simple example. Suppose an image captured by a FF sensor is enlarged by a factor M equal to, say, 10x to produce a print with dimensions 24 x 30 cm. If the print is to be viewed at a distance of 50cm, the normal lens is the one with a focal length of 50cm / M = 50 mm. However, if the print is viewed at a distance of 40 cm, the normal lens has focal length of 40 mm. And if the viewer is a young person that prefers to see the print at 20 cm, the normal lens is the 20 mm!
According to the second definition, the focal length of a normal lens is always given by:
FL = D / M
where:
D = distance of visualization
M = magnification of the displayed image relative to the sensor size
CBokeh wrote: |
Additionally, I'd like to point out that the previous article that I'd linked to on defishing an image mentioned the Defish Hemi filter.
I feel the Hemi filter is not perfect, but it does not remove as much of the edges as Photoshop does on its own. To me, the best results come from using both programs. |
The Fisheye-Hemi Plug-In actually makes a semi defishing which is very effective for photos of groups of people. For landscape pictures, the end result is like a panorama. Ken Rockwell does a good review of Fisheye-Hemi here:
http://www.kenrockwell.com/tech/fisheye-hemi.htm _________________ If raindrops were perfect lenses, the rainbow did not exist. |