Numerology and lenses

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rxmd

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Hi,

I just found stumbled across this striking numerological factoid about Soviet lenses:

Jupiter 3 + Jupiter 8 = Jupiter 11
50 mm + 85 mm (Edit: My bad.) = 135 mm

Are there other numerological secrets out there that could reveal the secret key to Soviet lens magic?

Philipp
 
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And I just found out that all numerologists are wrong somehow, for example in 8 != 9. Never mind. It's early morning for me :)

Philipp
 
The big mystery is why is a 50mm lens the "normal" lens for 35mm? 43mm should be the "normal" as that is the diagonal of the film plane. Every other format has a correct "normal" lens. Why not 35mm?
 
Finder said:
The big mystery is why is a 50mm lens the "normal" lens for 35mm? 43mm should be the "normal" as that is the diagonal of the film plane. Every other format has a correct "normal" lens. Why not 35mm?
Click to expand...

Not really. 6x6 are often supplied with 75mm or 80mm when it should be something like 86mm... the "normal" lenses often found with 4x5in Speed Graphic cameras
are 127mm or 135mm, or sometimes 150mm when it should be about 170mm...the standard silent movie frame is about 18x24mm, but 50mm is considered as "normal"... ah the mysteries! :D Maybe that's why Barnack adopted the 50?

Jay
 
I have also found something. The DOF at minimum distance of the jupiter 9 (or any 80/2 lens, for that matter) is numericallyt equal to the f/ number expressed in centimeters. To a 1-2% accuracy.

And i have also found that lenses with serial numbers that are divisible by 6 are sharper than the rest.
 
Thanks xaraa33, but it does not answer the mystery of the 50mm. While the author stresses 50mm is "normal," he also states "normal" is equal to the film diagonal, which is 43mm. The mystery is why 50mm was chosen by some unnamed optical engineer so long ago. The only answer that may explain it is based on the square root of two (1.4x). That when in the past a lens series was designed, it took focal lengths in that progression - 35mm, 50mm, and 70mm. But that does not make sense as it could have equally been 30mm, 43mm, and 60mm. The real reason may be lost in time.

Some oddities of the camera world are known. On digital cameras the aperture is usually given with a capital "F." It should be given with a small "f" as that is the symbol for focal length. Before the great digital revolution, film cameras used a 7-element numerical LCD display (just like the ones on calculators). With those LCDs, only capital "F" could be displayed. When digital cameras with monitors came along, the engineers were so used to displaying aperture with a capital "F" they continued to do so even though it would be possible to use a small "f" including the slash (/). But you never see the aperture written on a digital camera the proper way - f/5.6. So now we have aperture incorrectly displayed on digital cameras.

BTW, aperture should always be shown to two significant figures, but you will see camera manufacturers display F4 and F8 on the screen when they should be displayed f/4.0 and f/8.0. It seems like nit picking, but that zero has meaning.

Enough of camera trivia.
 
ZorkiKat said:
Not really. 6x6 are often supplied with 75mm or 80mm when it should be something like 86mm... the "normal" lenses often found with 4x5in Speed Graphic cameras
are 127mm or 135mm, or sometimes 150mm when it should be about 170mm...the standard silent movie frame is about 18x24mm, but 50mm is considered as "normal"... ah the mysteries! :D Maybe that's why Barnack adopted the 50?

Jay
Click to expand...

The diagonal of a 6x6 frame (56mm x 56mm actual image area) is 79.2mm. So an 80mm lens is the "normal." The image area (not film area) for 4x5 gives a diagonal very close to 150mm (the diagonal of the film area is 162mm).

But don't confuse a manufacturer's "standard" lens (like with the Speed Graphic) to the photographic definition of "normal."
 
Finder said:
The big mystery is why is a 50mm lens the "normal" lens for 35mm? 43mm should be the "normal" as that is the diagonal of the film plane. Every other format has a correct "normal" lens. Why not 35mm?
Click to expand...
I'd hazard a guess that the 50mm was taken based on the assumption that it's a normal for an approximately 36mm square frame. It has the same ratio of focal length versus long side as an 80mm on a 56mm square frame has. But on the small film format you merely chop off a portion of the top and bottom..
 
50mm is 2 inches (or close enough).

The physics of the glass itself. It's relatively easy to design a reasonably fast lens of this focal length to cover the 35mm frame. The wider you go, the harder it gets.

The first Leicas used this length, turning it into the industry standard.
 
Vince, it is not about the ease in making it. I asked our optical engineers (they design 35mm camera lenses), and it is not any more difficult to make a fast 43mm lens.

I think the real reason is lost. Perhaps the German designer just thought a slightly longer focal length was more pleasing. Our maybe you are right and it was simply rounding up a focal length in inches.
 
what I gather from what Wade K. Ramsey and others wrote, is that Leitz chose a 50mm focal lenght because most motion picture cameras came with that focal lenght of lens, which was rather long for a 18mm x 24mm format, but was prefered by most cinematographers of the day for its pleasing prespective and the comfortable camera distance to the subject being filmed.
 
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