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I have an application where I need as large a physical aperture as possible. By physical, I mean actual aperture in mm, not as an f-number. I also need this lens to focus to about 0.5m. I have the 85mm Nikkor f/1.4, which has a diameter of about 60mm, but doesn't focus close enough for me. Sigma have a 180mm f/2.8 macro which should be about 64mm diameter. Is there anything commercially available that is larger?

Since people in the comments have requested why I'd like to have a large diameter, I have added this diagram to explain what I am trying to do. My goal is to maximize the angle, theta, which represents the proportion of scattered light that reaches my lens. For a fixed focal distance, that means maximizing the diameter of my lens.

enter image description here

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    \$\begingroup\$ Is it possible this is an XY problem? Can you explain why you need or think you need a large physical aperture? \$\endgroup\$
    – scottbb ♦
    Nov 8, 2017 at 3:39
  • \$\begingroup\$ I am trying to maximise the "collection angle", that is, the range of angles of the reflected light off my target. Given my focal plane is set my only variable is aperture. \$\endgroup\$
    – James
    Nov 8, 2017 at 6:53
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    \$\begingroup\$ It sounds like you're getting a bit too technical for your own good. I don't think there's going to be any detectable difference. Even if there was, you might lose whatever it was that you were trying to maximize by choosing a lens with lesser other qualities by only selecting it based on one property. I think if you explained in better detail exactly what you're trying to photograph that we could be of much better help. \$\endgroup\$
    – Mike Dixon
    Nov 8, 2017 at 11:00
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    \$\begingroup\$ @ James -- You are working under a false theory: The field of view changes with distance from rear nodal to image plane (back focus distance). We can trace imaginary lines to the edges of the format mask and measure the incident angles. The field of view will be a trace using exactly the same angles. Should the working diameter of the lens be enlarged, any extension of the field that results will fall outside the mask and thus be partitioned (not imaged). \$\endgroup\$
    – Alan Marcus
    Nov 8, 2017 at 20:08
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    \$\begingroup\$ This smells like a use case where building an optical system might be worth considering, edmundoptics.com/optics/optical-lenses/achromatic-lenses/… \$\endgroup\$
    – user50888
    Nov 8, 2017 at 23:13

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The 180mm F/2.8 EX DG OS HSM APO Macro has in fact the largest diameter among lenses which focus at 50cm or less. 64mm as you suggested.

This search was done internally on my database at Neocamera which includes all consumer lenses currently available, so over 1200 lenses. To find other options you may have to look at lenses for large format film cameras.

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  • \$\begingroup\$ To find other options you may have to look at lenses for large format film cameras. That's an interesting thought, but assuming OP wants to use a DSLR to capture the image, how would they cover the projected image circle? \$\endgroup\$
    – scottbb ♦
    Nov 9, 2017 at 1:05
  • \$\begingroup\$ In general large format lenses are pretty small. \$\endgroup\$
    – Aram Hăvărneanu
    Nov 9, 2017 at 14:52
  • \$\begingroup\$ Though the focal lengths of large format lenses tend to be longer relative to 35mm, the apertures tend to be smaller. Shutter size probably dictates. A Copal #3 has an iris of 45mm. Without needing to provide light for autofocus, narrow apertures are probably less of a practical issue. \$\endgroup\$
    – user50888
    Nov 9, 2017 at 19:21
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Your 85mm f1.4 can work in this close if you mount a close-up lens. These are also called close-up filter. They come in different powers. I think you should try a +3. You can test, go to the drugstore and buy a +3 reading eye glasses. Hold it before your lens to test. If this works, purchase a +3 achromatic. These actually work quite well but some will phoo-phoo. You can also add an extension ring. Please inform as to why you need a large working diameter lens.

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You're looking at third party lenses: this database of Nikkor lenses shows that the largest aperture you'll get with close focus of 0.5m is with an Ai or Ai-S 58/1.2 Noct, for an aperture of about 48mm; or an AF 200/4 D Micro for an aperture of 50mm.

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Astronomy is where large aperture "lenses" are commonly used. Look for "refracting telescope". There are two types: achromatic (not very good for photography) and "APO" or apochromatic (preferred choice but more expensive). The catch is: no AF, not designed for close focusing so the performance may suffer, much darker (f/6, f/7, f/8)

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    \$\begingroup\$ Seems like 0.5m subject distance is about the exact opposite of astronomy applications. =) \$\endgroup\$
    – scottbb ♦
    Nov 8, 2017 at 3:40
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    \$\begingroup\$ yes, but shhhhh....! the telescope does not know it is meant for astronomy. given enough distance rings, it can focus pretty close ;-) \$\endgroup\$
    – szulat
    Nov 9, 2017 at 0:32
  • \$\begingroup\$ lol. That's some out-of-the-box, or maybe out-of-the-optical-tube-assembly, thinking. =) \$\endgroup\$
    – scottbb ♦
    Nov 9, 2017 at 1:02
  • \$\begingroup\$ Used way out of the intended focus range, you may find chromatic aberration creeps back in with a refractor, because the design assumes essentially parallel rays coming in the front and you haven't got that \$\endgroup\$
    – Chris H
    Nov 9, 2017 at 9:19
  • \$\begingroup\$ That’s true. Macro lenses exist for a reason. \$\endgroup\$
    – szulat
    Nov 9, 2017 at 11:13
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I suggest an extension ring. Closeup lenses in large diameters tend to be prohibitely expensive. An extension tube will rob you of some light, but this need not be a problem with your application. In fact your application could have a problem with chromatic aberration common with closeup lenses.

You can purchase inexpensive set of Chinese extension rings on the well known auction site, and stack them as required. This will allow you to work with your 85/1.4 Nikon lens (if close focusing was the only issue you had with it).

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