why focals aroun 40mm never became popular?

[john_parrish]

<p>I have the Leica CM predecessor, the Leica Minilux with the Leica Summarit 1:2.4/40mm which I greatly enjoy. It seems as though higher end fixed lens cameras go for either 28 mm or 40 mm, consider the Fuji "Texas Leica" range finder, or the Sigma DP APS-C format cameras.</p>

[joseph_wisniewski]

<blockquote>

<p>John Shriver - I think that SLR mirror box clearance issues is what pushed "normal" lenses up to 50mm, and many were 58mm. Until retrofocus lenses were perfected, 40mm lenses wouldn't clear the mirror.</p>

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<p>Oh my God, someone actually knows their history and basic photographic physics. John, thank you for restoring my faith in humanity.</p>

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<p>Frederick Muller - I think it's historical accident ... the first "normal" lenses that were easy to design and produce were of the 5cm variety</p>

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<p>You're close. John actually nailed it. A symmetric pair of achromats is a very good design, the reversed rear group cancels many aberrations of the front group, it makes the math and ray tracing easy, which was a "good thing" back in 1955, when lens designers drew large versions of the lens, and did their ray tracing by hand with ruler, pencil, slide rule, and lots of tables. At f1.4, the two most popular designs were the planar and the double Gauss, with the planar being easier to treat mathematically.</p>

<p>Both the f1.4 planar and double Gauss with late 1950s glasses are nearly "square" lenses, just about as thick as they are wide. A 58mm f1.4 double Gauss is about 43mm in diameter, and about 40mm thick, and the nodes are nearly coincident, the focal point is smack in the center, half the lens is in front of the 58mm plane, half is behind it, which brings it to about 38mm from the focal plane, just enough to clear an SLR mirror (24mm * sqrt(2) + 5mm for the shutter and film gate). Get your hands on the right glass, and you can make it thinner and push it to 55mm.</p>

<p>58mm was 1.34x the diagonal of the format. Photographers found this to be an awkward "dancing bear" of a lens, too long for a normal, too short to feel like a "portrait tele", which sort of starts at 2x the diagonal (the reason the 85mm is so popular with the 43.3mm diagonal 35mm format). Nikon, Topcon, etc. launched their 55mm and 58mm fast normals in the late 50s, and got laughed at by photographers. So, the camera companies went back to the drawing board and said "we can make a very ugly, asymmetrical 45mm f1.4, but it will not be as sharp as a 58, and it will have more distortion. Or, we can split the difference between 43mm and 58mm and do a 50mm, half as offensive, aesthetically, as the 58, half as offensive, optically, as the 45."</p>

<p>They made it, and it sold, and the rest is history. I find it kind of sad that Nikon launched a 35mm f1.8 as the "new normal" for their 28.5mm DX format, instead of a 28mm. Pentax launched what is arguably the optically best normal for a sensor that size, the 31mm f1.8 limited, sharp, gorgeous bokeh, about as good as it gets. I could post 31mm limited pictures, stripped of EXIF, tell you folks they're Leica images, and you'd buy it, hook, line, and sinker.</p>

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<p>Luis G - if you notice, lenses come in two mathematical progressions. One is basically by .7 the other by 2x.</p>

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<p>We can't notice things that didn't actually happen. The "wide progression" at 20, 24, 28, 35, and 50mm, is a mean 0.8x progression, then the "universal hole" from 50-85mm, and then the tele progression 85, 100 or 105, 135 is again a 0.8x progression. The exception, of course, being the rangefinder makers, who found themselves up against the double constraints of exactly how small they could make the framelines (no 135mm and few 105) and how much accuracy you could get out of a fairly short baseline rangefinder vs. what you needed for the shallow DOF of a 135, so they went to 75mm and 90mm, which is still 0.8x (0.83, if you get picky).</p>

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[Alex_Es]

<p>Why didn't the 40mm lens ever catch on big time. The 35 and the 50. The 40-45mm lens is a taint. Taint a 35 and taint a 50. I do love my Rokkor 40/2 and Pentax 43/1.9.</p>

[anthony_brookes5]

<p>There is an increasing demand for the 40mm Summicron as it fits the M8 and gives a 50mm image with the 4/3rds sensor. You coudn't give them away once. Now they are £400 - if you can find one.</p>

[JDMvW]

<p>In re the discussion of why 50mm and such came to the fore instead of the more 'accurate' 40mm something focal length, here are pictures of an earlier SLR with two of the lens created for the problems of mirror clearance and open aperture: the Biotar 58mm f/2.0 and the Angénieux 35mm f/2.5 Retrofocus Type R1.<br>

(I feel obliged to keep up my reputation as a bloviator with outsize jpegs)</p><div></div>

[Troll]

<p>The switch from 58mm to 50mm was a marketing reality, not a technical one.</p>

[mjferron]

<p>If I have one lens? 35-40. Perfect. My little Rollei 35's 40 does most everything I need.</p>

[jonathan_reynolds]

<p>Here's a slightly different take. At different times in my life, I have used all 3 focal lengths as my main lens. I came to the conclusion that the 35 approximates what I am aware of with both eyes open, while the 50 approximates what I see when I really pay attention to something or when I shut one eye. The 40 is a compromise between the two.</p>

 

[francesco_bertelli2]

<p>thank @<a href="../photodb/user?user_id=587835">Joseph Wisniewski</a>, is the kind of answer I was looking for, also the Mike Johnston's article is very interesting</p>

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[jonathan_reynolds]

<p>@Joseph Wisniewski and Francseco Bertelli:<br>

Surely 50mm was already regarded as 'normal' in Rangefinder days, long before SLR 35mm cameras?</p>

[larry_miller5]

<p>I love my Voigt 40mm/F2 pancake Aspherical lens on film. Wouldn't trade it for anything. Ultra sharp! There's a lot of different uses for it. The pics have a "Leica" look to them. Shot vertically it's a slight wide angle. I've never been disappointed with it. Got rid of my 50mm when I got this lens and never looked back.</p>