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PostPosted: Sat Feb 13, 2016 7:06 pm    Post subject: Reply with quote

visualopsins wrote:

50MM LENS HE'S TALKING ABOUT IS THE NORMAL LENS FOR HIS CAMERA (I needed tg shout that Laughing)

In modern terms he refers to the "normal" lens, i.e. for crop sensor camera that is 28mm or 35mm focal length...


Sure, 50mm is the "normal" lens for the "small format" 35mm.

Normal lenses, normal people, normal photographers, normal artists... What about Picasso and David Douglas Duncan?

Picasso's portrait by David Douglas Duncan:

"Fish-eye Picasso. 1963. The Nikon camera company's engineers sent me a prototype of a new lens to test. I did, at the beach in Cannes, using as my subject the greatest portrait distorter of all time." Viva Picasso, p. 149.


PostPosted: Sun Feb 14, 2016 6:24 pm    Post subject: Reply with quote

[quote="Gerald"]
visualopsins wrote:

Sure, 50mm is the "normal" lens for the "small format" 35mm.


I was always under the impression that "normal" was 43mm on 35mm format but 50mm was "close enough."

http://petapixel.com/2013/06/15/a-mathematical-look-at-focal-length-and-crop-factor/


PostPosted: Sun Feb 14, 2016 7:46 pm    Post subject: Reply with quote

Also, there is this article by Roger Cicola of Lens Rentals.

http://petapixel.com/2012/11/17/the-camera-versus-the-human-eye/

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. A month ago I was researching a fisheye lens I was considering and came across a blog post that demonstrated why this filter is superior to just using Photoshop's native tools and I felt the author made terrific points. Unfortunately, I couldn't find the original blog post I'd read on the Hemi filter so I posted the defishing how-to link instead.

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.


PostPosted: Mon Feb 15, 2016 1:08 pm    Post subject: Reply with quote

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