What's The Reason for 55 and 58mm ?

<p>Why did Nikon only make their F1.2 normal lenses, in 55MM? (All of their other normals are 50MM.) Perhaps it is difficult to build fast glass with a 50MM focal length?<br /> And why did Nikon, Topcon and others come up with the 5.8CM or 58MM as a normal lens? .</p>

<p>If memory serves correctly, in theory the field of view for a 58mm lens will enable you to keep both eyes open when using an SLR.</p>

<p>The "reason" they had 58mm f1.4 lenses is simply that they were easy to design. The reason they went away was that photographers wanted lenses that were "easy to shoot", not "easy to design".</p>

<p>Nikon, Topcon, etc. originally made 58mm normal lenses because 58mm f1.4 is the shortest pure double triplet (such as a double Gauss) that will clear the mirror on an SLR. A double Guass is nearly "square", it's thickness is nearly equal to its diameter. So, a 58mm f1.4 is about 42mm in diameter, 44mm thick, and about 20mm of that is behind the 58mm rear node, so the rear element is about 38mm from the film plane, just enough to allow for the mirror to swing by.</p>

<p>The "pure" 58mm f1.4 double Gauss performed well, very good color correction, low distortion, etc. but people hated the focal length. At 1.33x the iamge diagonal (43.3mm for 35mm) it feels uncomfortably long for a normal, and too short for a telephoto. Photographers made their feelings known (loudly, as usual) and the lens makers came up with retrofocus variations on the double Gauss that got it down to 50mm, at the expense of higher distortion and worse color correction. But despite worse optical performance, photographers were much more accepting of a normal that was 1.15x the diagonal. (Personally, my favorite normals were the 45mm f2.8 (1.04x the diagonal) and the 40mm f2.0 Voigtlander aspherical ultron (0.92x the diagonal).</p>

<p>This falls into my theory of the "universal hole". Photographers like variety in their wides, so Nikon, Canon, Minolta, etc. made a range of wides that went right up to normal in nice 20-30% steps: 20, 24, 28, 35, 50mm. They did the same with the short telephotos, 85, 100 or 105, 135, 180 mm. But there's a 70% "leap" from 50mm to 85mm, a "universal hole" that no manufacture can manage to sell lenses in.</p>

<p>As far as your question about f1.2 lenses: Nikon did make a 50mm f1.2, in addition to the 55mm f1.2 and the insanely expensive 58mm f1.2 NOCT.<br>

http://www.photosynthesis.co.nz/nikon/ais5012.jpg<br>

The 50mm f1.2 is actually a pretty nice lens, nicer bokeh than the 50mm f1.4.</p>

<p>Professor K, your memory does not serve correctly. The viewfinder magnifications of ealry SLRs were pretty low, you'd actually want an 80mm lens to be able to shoot with both eyes open and maintain binocular vision.</p>

<p>But that's not really an issue, because it does not take much practice to be able to shoot with both eyes open no matter what the focal length or viewfinder magnification.</p>

<p> Wow, great answer ,thanks.</p>

<p>It seems this has been discussed before:<br>

<a href="http://www.photo.net/classic-cameras-forum/00QNkf">http://www.photo.net/classic-cameras-forum/00QNkf</a></p>

<p> </p>

<p>Definitive Answer of the Day Award</p>

<p>(Not officially sanctioned)</p>

<p>Just for grins, I tried a few SLR's, and find that the Nikon F wants about 70 mm, with a slight difference in registration (images at different heights), the Konica T3 about 70 as well, with poor registration. The Nikon F3HP matches and registers nicely at about 75. But my Minolta X-370 and X-700 both are matched for a 50, and the registration is so close that when viewing with both eyes open, the camera appears transparent and the viewfinder and eye images cannot be distinguished. The Pentax K-1000 is nearly as good as the Minoltas.</p>

<p>Very interesting explanation. (Of course, I happen to really like the 58/1.4, and it's a great length for a crop-sensor digital.)</p>

<p >Press photographers who work the sidelines of sports events are always in danger of getting clobbered by the players. Press cameras and the Rollie and others featured a sports finder, a wire frame viewfinder. These give a true-to-life perspective that’s hard to beat when working the sidelines. With a 58mm mounted on an SLR one gets nearly the same perspective. Sideline photographers keep both eyes open. The magnification with the 58 is quite close to that of the unaided eye. Also these lenses were usually f/1.4 thus they were fast, suitable for artificially lighted events. The 58mm saved my butt -- over and over again. </p>

<p>Steve - thanks</p>

<p>Robert - thanks, too</p>

<p>Professor K, thanks for the link, and OMG, I'm the new Kelly Flanigan. Aargh!</p>

<p>Andrew, the 58mm is great on a cropped sensor camera. That's why</p>

<ul>

<li>The Nikon 58mm f1.2 NOCT (arguably the king of 58mm lenses, everywhere) went from under $1000 on the collectible market to a simply insane $3000 among people who started using it as the best short portrait lens for the D1 and D2 series digitals.</li>

<li>Cosina/Voigtlander introduced a "recreation" of the 58mm f1.4 Topcor. They even licensed the name and styling from Topcon for a small run, then switched styling and gave it the Noktron name. </li>

</ul>

<p><em>But there's a 70% "leap" from 50mm to 85mm, a "universal hole" that no manufacture can manage to sell lenses in.</em><br>

<br /> Just an fyi - Pentax offers an excellent 77mm f/1.8 prime.</p>

<p>Zane, wasn't that lens announced about the same time as the *ist, to give 1.5x crop shooters a nice "portrait" lens?</p>

<p>That is the 70mm f/2.4 DA lens, a digital-only design for the crop bodies. Both are fine lenses. The 77mm is full-frame.</p>

<blockquote>

<p>"I'm the new Kelly Flanigan. Aargh!"</p>

</blockquote>

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