AI 20mm f/3.5 and more modern "20" looking at a test scene

[Bernard Delley]

First image, the entire test scene with AI 20mm f/3.5 wide open. D800 at 1/4 image scale. -- At this largish internet image scale, I find not much to complain.

#2 near centre crop 1000x1000 comparison with AFS 14-24mm f/2.8, AFS 18-35mm f/3.5-4.5G and upscaled AFS 10-24mm DX on D7100.
Focus was done in LV at max mag, manually with the AI,  observing AFC operation for the AFS lenses.  RAW extraction in ACR with no processing other than cropping. Except, I did a minor exposure correction for the AI. Scene illumination kept changing because of thin clouds passing.
Observations: The AI has a bit lower contrast and lower resolution than the other FX lenses here. The upscaled DX resolution falls about even with the AI.  This sample of the AI had sharpest performance at its infty stop, which always makes you wonder if it could be sharper a bit beyond. But then sharpness right at the centre is very good as shown in my mountains image in an other thread.

#3 near centre at f/8.  The DX has lowest resolution, I think its primarily due to the lower sensor resolution showing through its 7360/6000 upscale factor.

#4 right upper corner at  wide open aperture. The 14-24mm is amazing!, but hey see the AFS 18-35mm G. The DX shows better her than the AI.

#5 right upper corner at f/8. The 14-24 keeps a clear lead, followed by the AFS18-35G. The upscaled DX is a clear step behind the FX zooms, but also clearly ahead of the AI.

Travel/hiking and other use considerations:
AI is my lightest option to 20mm (230g), its also impressively flare resistant as Bjorn observed long ago. This lens has been to remote places since 30+ years. It is also a convenient lens for around 10x magnification used reverse on the bellows.
The 14-24 is impressive in many ways! A staple for night sky scenes. 1kg ! Feels better when there is no need to carry it up 1000+ meters in altitude.
18-35 is sharp and I had no issues with flare. For 380g it delivers at 20 24 and 28mm and can be used at 18 and 35 too. I like it a lot, now often in the bag.
10-24 DX a serious ultra wide for DX travel and versatile across the wide range. Has been to many places.
 

[Bjørn Rørslett]

Thanks for these comparisons - very helpful !!

Also confirms my views about these optics. The 20/3.5 AI is mainly a lens for the near range, unless you can stop it well down.

The 14-24 is amazing and hadn't it been for the sheer size and a propensity to some lens flare under difficult light conditions, would be with me all the time.

I use the 10-24 DX mainly for IR, in which it does well.

The 18-35 is badly underestimated and really deserves a better reputation.

[John Geerts]

Very interesting test, Bernard.  The 14-24 is really impressive wide open.

[Bjørn J]

This test confirms my findings of the 14-24mm. The performance wide open is why it's my favourite for northern lights photography (which mostly is done with a fully open wideangle lens).

[PedroS]

Thanks for sharing.
Your findings confirm those of mine with both the 14-24 and the 18-35. Never used the 20 AI...
Only use the second when weight is at a premium.

[Jan Anne]

Thanks for the tests and writeup Bernard, predictable but interesting findings nonetheless.

Used to own the 14-24/2.8, awesome lens but used it at 14mm wide-open 99% of the time so switched to a much lighter Samyang 14/2.8 (which is almost as good).

Also had the Voigtlander 20/3.5 AE for a while, great compact lens but 20mm just isn't my focal length so sold it again.