Thoughts on the 50mm focal lenght

[Roger Hicks]

The standard focal length for a film format is usually based on measuring the corners diagonally, in the case of standard 35mm, this is 43.26mm and therefore a 43mm might be considered as `standard` in theory. A focal length of 40mm-55mm will give what many will perceive as a `normal` perspective.

Dear Keith,

Yes, but only when viewed from 43mm. Enlargement size and viewing distance are of fundamental concern -- see my post 51.

As for printing, I taught Frances how, then she got better at it than I am...

Cheers,

Roger

[Keith Tapscott.]

Dear Keith,

Yes, but only when viewed from 43mm. Enlargement size and viewing distance are of fundamental concern.



Cheers,

Roger

Blimey, does that mean that we should only view photographs taken with a FISH-EYE Lens, when under water?

[Roger Hicks]

Blimey, does that mean that we should only view photographs taken with a FISH-EYE Lens, when under water?

Nah, that's just codswallop.

[Dorian Gray]

I've never found any sense in the notion that a 50 mm lens, or any lens for that matter, somehow more closely corresponds to our eye than another lens. Personally my angle of vision is close to 180 degrees horizontally (i.e. I can peripherally see things directly to my left and right simultaneously). This is wider than any lens except the odd fish-eye. But my visual area of sharp focus is vastly narrower, similar to a super-telephoto. If I want to closely observe the letters in one of these words on the screen, I must move my eye slightly for each letter, such is the narrowness of my acute vision.

Then there is perspective. Perspective is not a property of any lens. The lens merely crops an area of the scene and records it on film; the perspective of that scene is determined by the subject to camera distance, and when viewing the print, the viewing distance and enlargement factor as outlined by Roger. However, I don't strive to manipulate the enlargement factor and viewing distance to "normalise" the perspective. In fact, I use a wide-angle lens precisely to allow me to shoot from closer, thereby stretching the perspective, which I make no attempt to "fix" in the print. In any case, with very wide lenses it's impractical to normalise the perspective at the print viewing stage because the print has to be so large and/or the viewing distance so short.

I very much enjoy shooting with a 50 mm lens. But I prefer the 35 mm. The latter offers excellent control of depth of field, from sharp everywhere to completely blurred backgrounds, in normal lighting conditions with normal film speeds. Wider than 35 mm and it's difficult to blur the background unless the lens is extraordinarily fast and the camera to subject distance is small. Longer than 35 mm and getting a large depth of field requires too much light or a tripod. I find the 35 mm just right.

[George Hart]

Dear Keith,

Yes, but only when viewed from 43mm. Enlargement size and viewing distance are of fundamental concern -- see my post 51.

As for printing, I taught Frances how, then she got better at it than I am...

Cheers,

Roger

Realistic perspective is obtained if the viewing distance is fn, where f is the focal length of the lens and n is the linear magnification of the negative (Adams book 3). For a contact print, n=1. As the near point is about 10", for realistic perspective the lens should therefore have a focal length greater than 10" (250 mm) and for comfort, allowing viewing at 12", greater than 300 mm. Therefore 5x7 format is too small for realistic perspective from a contact print even at standard focal lengths (210 mm) and 10x8 is barely OK for a gentle wide-angle (240 mm).

PS this post is more than a bit tongue-in-cheek!

[bruce terry]

And George ... amazing that nobody has pointed out that the dorphallic kinetic of the transvariated angular transit of the midpoint of both the human eyeball and the pupilian excrementus of the convexual threshold of any given processed transparent solid is .0069478.

In otherwords, what you consider 'normal' will always be determined by your personal Dorphilian Excremus, times your personal opinion.

[Black Dog]

Nah, that's just codswallop.

A bit of a red herring really