Sigma 20mm f/1.4 ART or Nikkor 20mm f/2.8

[CardBoardBoxProcessor]

Wonder what y'all thoughts are on these lenses. I have the Sigma. it is quite the lovely piece of glass. But I am starting to relaly love old Nikkor manual focus lenses. how would these 2 compare?

[John Harkus]

I have a 20mm f/4 manual focus, and a 20mm f/1.8 AF - the MF is lovely, small, great engineering but can't compete in image quality terms with the newer model.
hth
John

[Akira]

Unlike some members here (like "Longzoom"), I haven't found any decent sample of 20/2.8, MF or AF.  The (not too far) corners are always smeared even at f8.0.

On the other hand, I enjoyed my Ai 20/4.0.  Although the image quality was not up to that of the current AF-S 20/1.8 at the same aperture values, it performed way better than any of the 20/2.8s I have tried so far.

[CardBoardBoxProcessor]

Is that so?
I just did some testing of all my lenses. Assuming that they had the same image for all frames. At F/8 all my lenses are very sharp just as sharp as the Sigma. amazingly the sigmas is not as sharp in the corners as these old lenses.. at f/8. Very interesting.

the 20mm f/4 is appealing.

[Akira]

Yes, at least according to my own humble experiences.  Also recently I tried several Ais 20/2.8s at a Nikon specialist shop with my D750.  A few were maintained by a very reputable repair shop whose founder are retired Nikon tech persons.  Even such samples performed poorly at the peripherals (not the far corners) of the image frames at f8.0.

The Ai 20/4.0 I had wasn't super sharp but at least offered even image quality over the entire frame at f8.0.

[richardHaw]

I know the 20/2.8 AF-D very well. for many years that was my only landscape lens

to answer you, get a modern optic. the 16-35 f/4 is a VERY good lens at 20mm

[longzoom]

Akira, if you have friends in repair shop, ask them to open AFD or AF 20mm lens from the front side. (Be absolutely sure, that your lens IS NOT DECENTERED! In this case, do not even try!). They have a special pipe-key gears to perform that. Then, there is the special aluminum ring inside, by turning one left or right, not more than 1mm each step, you will find the optimal position to get an critical sharpness to extreme corners, at f4.0 - 5.6. It is extreme time-consuming operation, of course. Try 1mm, left. Put everything back, check. Better? Try 1mm more. Better? One step more. Too much? Back 1mm, you are done.  Or turn that aluminum ring to the right, the same operation. Perform it with the distance ring at infinity! At the first try, it gonna take you about 3 days. With some experience with this lens, next time gonna take 2-3 hours, not more. (BTW, you need to perform the same operation to clean the aperture, if needed. Never ever open this lens from the mounting back side!).  Do not know about Ais lens, have never touched one  to fix.  Good luck in any case!  LZ

[Akira]

LZ, thanks for your advice.  According to Bjørn, the AF 20/2.8 is rather vulnerable internally.  That's why I opted for the MF version.  Am enjoying your images, nevertheless.

[longzoom]

Yes, of course, if you open it from the mount side! Your opinion on my images is very valuable, thank you so much! LZ

[CardBoardBoxProcessor]

Gosh people open and calibrate their lenses huh? Any before and after examples? One reduced tension on an MTO mirror lens and that made it so much sharper. but nothing like proposed here.

[Øivind Tøien]

My AF 20mm f/2.8 (non-D) opened itself up from the front side a few times by itself. The front element which is part of the CRC mechanism tends to screw itself loose. If this happens the corners get very bad. I never noticed any screws inside it though so I guess one would have to go deeper for that adjustment.

My copy of the lens is very sharp at infinity in the dead center, more so than my 12-24mm at the same focal length. However the 20mm is inferior to the 12-24mm away from the center. On D200 the corners also showed strong CA, I have not used it much on later bodies.  It is possible that the high resolution in the center makes the less performing corners more obvious. Close up it is performing well but flares easily. I have the impression it worked better on film bodies. It did improve a bit after our local repair shop had a go at it again.

Here s to examples, the first at f/8, the second at f/10:

[richardHaw]

on my sample, the complaint was more of a very "outdated" look. 

[longzoom]

Gosh people open and calibrate their lenses huh? Any before and after examples? One reduced tension on an MTO mirror2017-01-15 002-1-2 by longzoom, on Flickr l2017-01-15 002-1-3 by longzoom, on Flickr2017-01-15 002-1 by longzoom, on Flickr

The Nikkor AFD 20mm at F4.0, after calibration. 2 Crops, from the center and extreme corner. For full resolution images, click on any sample to go to Flickr.  THX!  LZ

[Akira]

LZ, when I saw these images for the first time, I didn't notice the flare in the right below corner.  The image doesn't look smeared there, but have you figured out the reason for the flare?

[longzoom]

Not likely flare, because the Sun was back of me, covered by the buildings. So would you please make a screenshot and show it? Reflections from energy panels, maybe? Thank you!  LZ