Pentax-DA 35mm F2.4 AL
Aberrations and Flare
Imperfections in an optical design can lead to chromatic aberrations such as fringing, lens flare, and ghosting, all unwanted symptoms of having a strong light source enter your field of view. When used in conjunction with a lens hood, modern glass coatings do an excellent job of suppressing lens flare, and some better than others. Pentax has been widely regarded as having some of the best coatings in the industry, a reputation built over decades through their "Super Multi Coating," largely known via the iconic smc, and most recently with their improved High Definition, or "HD," coating.
With an older lens design that hasn't exactly been given the "premium build quality" treatment, how does the super multi coated Plastic Fantastic hold up in this regard?
Flare Test One - Center-of-Frame Sunlit Flare
During our first test we centered the sun in the frame and free of any obstructions (i.e. not peeking through any of the tree branches). The lens was set on a tripod and tested from wide open until F16.
Click on any image below to open an enlargement and cycle through them.
| F2.4 |  |
| F5.6 |  |
| F9.0 |  |
| F16 |  |
Flare Test Two - Edge of Frame
For this test iteration, the sun was repositioned to the very edge of the frame, a location that is typically problematic for lenses to deal with. Once again the lens was set on a tripod and tested from wide open until F16.
Click on any image below to open an enlargement and cycle through them.
| F2.4 |  |
| F5.6 |  |
| F9.0 |  |
| F16 |  |
Aberrations Test
For our testing of chromatic aberrations, we took a shot of a car that was exhibiting a very strong reflection from the bright sun. Coupled with a definitive line with stark contrast, it would be a breeding ground for our sought after unpleasantries. The below image shows the entire frame, and from which we grabbed our 100% crops:
| F2.4 | |
| F4.0 | |
| F5.6 | |
| F8.0 | |
Verdict
Pentax's 35mm AL prime did a great job of resisting massive amounts of flare considering the situations we put it in. We attribute this equally to the excellent performance of Pentax's smc coating as well as the very simple lens design that would have less elements for the light to bounce around and reflect against. Just as a demonstration of and comparison against poor flare management, here's an image taken from the recent Sigma 18-35 F1.8 "Art" review, a lens with triple the amount of lens elements. It was also set to 35mm and under similar conditions as the above tests. The aperture used was F11:
Demonstration of sub-par handling of flare as exhibited by the Sigma 18-35 F1.8 "Art"
In short, the DA 35mm AL did an excellent job managing flare, and it only seemed to get "out of hand" at around F13-16. One caveat to this was that ghosting could have been a bit better controlled in the flare test shots. There was an obvious lack of contrast in the trees and branches because of this.
As far as aberrations go, the lens did an outstanding job of keeping purple fringing at bay. Closing down even a minor amount reduced it significantly, with no traces to be found after F3.5 during our testing. Considering that this lens is "wide open" at F2.4, that's nothing short of a remarkable performance.
