Comparison between a Few 17-21mm Lenses

[Abbazz]

I have accumulated a number of wide angle lenses with a focal length of more or less 20mm. I love 20mm lenses. For me, 20mm is the most useful focal length for wide angle photography. I find 15-16mm or wider is too much for a rectilinear lens because the deformations near the edges of the frame are too unpleasant (I prefer to use a fisheye when I need a wider angle). On the other side, I find 24mm and 28mm not wide enough for most uses. That's why I have so many 20mm lenses...

Today, as the weather was fine, I decided to shoot a few pictures with my favorite 20-ish lenses. I have deliberately excluded the worst lenses (for example, my copy of the Vivitar 19/3.5 is awful, and the same goes for my Cosina 19-35 zoom).

Here are the selected lenses, ready for the shootout:


From right to left: Tamron Adaptall 51B 17/3.5, Pentax-M 20/4, Pentax FA 20-35/4, Pentax-FA 20/2.8, Super-Takumar 20/4.5, Carl Zeiss Jena Flektogon 20/4, Cosina Voigtlaender Ultron 21/1.8


The size varies greatly from one lens to the other and the fastest lenses are not necessarily the biggest!

The pictures were shot on my Sony A7 in raw format and processed with the same settings in Capture One without correcting for vignetting or chromatic aberrations. The camera was on a tripod, with 2 sec delay and I adjusted the focus with the help of the magnifier before each shot. I shot 3 pictures for every lens: one wide open, one at F/5.6 and one at F/11. I have posted the resulting images on a Zenfolio page:
http://abbazz.zenfolio.com/ultrawides

As I already knew what to expect from these lenses from an optical quality standpoint, the biggest surprise for me was the variation in field of view between these lenses. For example, the Flektogon 20/4 covers a much narrower field than the Super-Takumar 20/4.5.

Now, if you ask me which lens I prefer, I am afraid I cannot answer this question. They all have distinct qualities that make me prefer one lens or the other according to the subject, the light and the circumstances. I would not shoot an event in a dim nightclub with the same lens as a seascape in bright sun. I love the way Flektogon renders at F/11 but I find it too bulky to bring it with me when traveling. On the other side, the Pentax-M 20/4 is certainly not the sharpest lens but it is so tiny and renders such nice colors, that it often finds its way into my bag...

Cheers!

Abbazz

[Gerald]

Excellent comparison, Abbazz!

I have a Tamron SP 17mm F3.5 and your test confirms the good performance wide open, except in the extreme corners, which require some stopping down for true sharpness.

You noted that the Flektogon 20mm F4 has a real focal length greater than 20mm. The newer version Flektogon 20mm F2.8 has real FL of about 21mm. The same way, the real FL of the Pentacon 29mm F2.8 is more than 30mm. It seems that the rules used by optical designers in the former East Germany were poorly calibrated...

I noticed that for the Flektogon 20mm F4, coma is the dominant aberration in the corners, while for the Pentax-M 20mm F4 it is astigmatism. As a general rule, coma decreases very quickly with stopping down, but astigmatism is more persistent. This could explain why the Pentax-M is not sharp in the corner even at F11.

I was not impressed with the sharpness in the corners of the CV Ultron wide open. OK, the aperture F1.8 is wider than the other lenses, but nonetheless this goes against the myth in which many people believe, that a symmetrical wide-angle lens always outperforms a retrofocus.

I like the performance of the Pentax-FA 20-35mm F4. Very good for a wide-angle zoom.

[LifesShort]

Thanks for performing this test. I, too, have the Tamron 17mm f3.5 and wondered if I was missing anything by not trying other lenses. Based on your results, I think that I can say that there isn't a big enough difference between them for me to search out another UWA.

[cooltouch]

Well, let me also chime in and say that I also own a copy of the Tamron SP 17mm and yours is the first test I've seen using this lens with one of the Sony A7 series cameras. To me, the Tamron's results look very good -- a little soft in the extreme corners, but not really objectionable.

Your test is important to me because I've been seriously considering buying a clean A7, and one of the reasons why I want one is so I can use my ultra wides and extra wides on it (three 24s, one 20 and two 17s). So thanks very much for this!

[LifesShort]

[Abbazz]

[Abbazz]

[Abbazz]

[Abbazz]

[cooltouch]

[kds315*]

Well done Sebastien!!

I don't have that many, but if I need a wide one, I take my 17mm Tokina

[Abbazz]

[pinholecam]

[LifesShort]

[LifesShort]

[Abbazz]

[rudolfkremers]

[Gerald]

Abbazz,

I think all the lenses you have tested can produce excellent photos. Of course, any lens will show its flaws if the picture is looked closely enough. Current sensors work as microscopes that reveal all the residual aberrations of a lens.

The Flektogon 20mm F4 is a lens of great historical value. It is cited in many books as an innovative design of ultra wide angle lens. It is remarkable that it can still produce excellent images in digital cameras with high resolution sensors.

About the Tamron SP 17mm F3.5, it is important to remember that it is much more difficult to design a good 17mm lens than a 20mm or 21mm. Of course I'm talking of lenses for FF sensors. The 18mm lenses for APS-C are FF equivalent to 28mm, which is much easier to design than a 17mm.

In my experience, virtually all non-symmetrical lenses suffer from some lateral chromatic aberration, including almost all wide-angle retrofocus and telephoto lenses. A notable case of lens that is virtually free of lateral chromatic aberration is the normal 50~60mm lens based on the Double Gauss formula.

In my opinion, except perhaps for the last 400x400 pixels at the extreme corners, lateral chromatic aberration of the Tamron SP 17mm F3.5 is not stronger than other non-symmetric lenses. To show this point, I posted 100% crops of last 800x800 from the top left corner of 24MP (6000x4000) test images for Tamron 17mm F3.5, CZJ Flektogon 20mm F2.8, CZJ Sonnar 180mm F2.8, and Helios 44-4M 58mm F2.

All lenses were stopped down to F11 to minimize aberrations other than laCA. Obviously, the Sonnar 180mm F2.8 is not a wide angle lens, but you may notice that it also suffers from laCA. Interestingly, for a telephoto lens, the "hot" colors (red / magenta / yellow) fringes are on the interior sides of the black squares, and the "cold" colors (cyan/green/blue) fringes are on the exterior side. For a wide angle lens, it is just the opposite.

Tamron SP 17mm F3.5:


CZJ Flektogon 20mm F2.8:


CZJ Sonnar 180mm F2.8:



Finally, notice as a typical Double Gauss lens, such as the Helios 44-4M 58mm F2, hardly suffers from laCA. Nonetheless, these type of lens may suffer from loCA, spherical aberration, coma, astigmatism, distortion, etc.

Helios 44-4M 58mm F2:

[Abbazz]

[jamaeolus]

Nice stuff. I have the flektogon the super takumar and and also have a canon FD 20mm. I like them all. I will be picking up a AF minolta at some point. I dream of the Konica 2.8 but that will have to wait. LifesShort: You mention the fill flash with thyristor. Was taht manually accomplished or do you have a way to trigger it with the a7ii? I have several old thyristor flashes I would love to get some use from.

[LifesShort]

[luisalegria]

Excellent work!
And that is quite a collection!

[Abbazz]

[kuuan]

[anktonio]