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For some Nikon DSLR lenses, like 35mm primes, Nikon has two offers:
AF-S DX NIKKOR 35mm F1.8G ($200 USD)
and
AF-S NIKKOR 35mm f/1.8G ED ($530 USD)

From my understanding, the lenses differ for only two reasons:

  1. The first is a cropped frame lens, and this will create an automatic crop on a full frame camera.
  2. The second lens is an ED lens, meaning it contains extra-low dispersion elements.

My questions are:

  1. Are there any other differences between these two lenses?
  2. If not, is the optical difference of the ED elements noticeable, and could that image quality difference potentially justify the more than 2.5x cost of the FX lens for someone who only shoots with a DX camera?

Please note that I understand this is close to the line of opinion, but I am looking less for user opinions and more for factual optics information. Please comment or edit if this question does not make sense.

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  • \$\begingroup\$ They are two totally different designs which just happen to have the same focal length and maximum aperture. Nothing more. \$\endgroup\$
    – Michael C
    Commented Jul 24, 2017 at 7:19

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The second lens is an ED lens, meaning it contains extra-low dispersion elements.

These are quite different optical designs (see the number of elements and groups in the Tech specs on the page you linked to). internally these lenses would be completely different.

This means they can, in principle, have quite different optical characteristics. I think Lenstip.com has detailed tests of both lenses and typically that site will test an FX lens on both FX and DX bodies.

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    \$\begingroup\$ @WayneF Your edit did not reflect my views so I rolled it back. Perhaps you could comment so that I can clarify with you what your intent is before editing. \$\endgroup\$
    – StephenG - Help Ukraine
    Commented Jul 23, 2017 at 19:04
  • \$\begingroup\$ ? We might debate the construction of various ED lenses, however ED formal definition is only about use of low dispersion glass which reduces lens color aberration. But the definition of a DX lens is NOT at all about ED, and is solely about the sensor coverage area. There can be no debate about that. \$\endgroup\$
    – WayneF
    Commented Jul 23, 2017 at 19:25
  • \$\begingroup\$ @WayneF The corners will not be black when testing an FX lens on a DX body. If one were to test a DX lens on an FX body they might be if the FX body is set to not automatically switch to DX mode. But the latter is not what the answer references, it is the former. \$\endgroup\$
    – Michael C
    Commented Jul 24, 2017 at 7:16
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Your 2. about ED lens is correct enough, but 1. is not exactly worded correctly.

The numbers 35mm and f/1.8 have the same meaning in both lenses, so there should be no discernible difference if both are on the DX camera. But the FX camera will see a big difference, this way:

The difference is that that the FX lens is larger diameter, so that its projected image circle can fully cover the larger FX frame size (36x24 mm).

The DX lens is smaller and lighter (and cheaper), so it will only fully cover the smaller DX sensor (24x16 mm).
Roughly speaking, it might show only about a 30mm diameter (diagonal) on the larger FX sensor.

So, if ever planning on upgrading to a FX body, the DX lens will then be found to be insufficient.

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    \$\begingroup\$ Note though that Nikon does this thing with DX lenses on FX cameras.... \$\endgroup\$
    – mattdm
    Commented Jul 23, 2017 at 21:59
  • \$\begingroup\$ Yes, I have FX and am aware that Nikon FX will crop for a DX lens. We could debate if that lets the DX lens do all it ever did, or if it prevents FX from doing all it could otherwise do if with a suitable lens. :) \$\endgroup\$
    – WayneF
    Commented Jul 23, 2017 at 23:53
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The lenses have completely different optical designs. See chart below:

enter image description here

As you can see from the MTF charts, the FX lens is a lot softer in the corners than the DX lens. Also, the FX lens has field curvature in the fine resolution saggital lines.

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    \$\begingroup\$ Your diagrams would be a lot less misleading if you scaled then better - remember the corners on the DX lens are only 60% of the way across the FX graph. \$\endgroup\$
    – Philip Kendall ♦
    Commented Jul 24, 2017 at 6:38
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the g lens auto focuses on dx cameras while i think the ed lens does`nt

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    \$\begingroup\$ Any potential difference is between the D3xxx/D5xxx series (which don't have a built-in focus motor) and the D7xxx/D3xx/D5xx series (which do have a built-in focus motor), not between FX and DX. \$\endgroup\$
    – Philip Kendall ♦
    Commented Jul 23, 2017 at 16:15
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    \$\begingroup\$ Both lenses are AF-S lenses which means they have motors in the lens and should focus on any Nikon body. A "G" lens is one without an aperture ring. Read this compatibility page. \$\endgroup\$
    – StephenG - Help Ukraine
    Commented Jul 23, 2017 at 16:47
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    \$\begingroup\$ Besides the fact that that is just not true (per PhilipKendall and StephenG's comments) these are both G series lenses \$\endgroup\$
    – NoahL
    Commented Jul 23, 2017 at 16:49

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