Pentax-DA* 200mm F2.8 Review

Flare

Flaring is caused by unwanted reflections of light within the elements of the lens. The net effect of flaring is loss of contrast and the apparition of extraneous elements in the the composition of the image. Most, if not all, lenses are affected by flaring at some point, and flare can be caused by a variety of mechanisms.

The Pentax SMC DA* 200mm f/2.8 ED [IF] SDM includes two features that are designed to avoid or minimize the effects of flare in the image. One of such features is the lens hood, which helps to prevent light from hitting the lens' front element at angles outside of the lens' field of view. The other feature is the the Pentax SMC anti-reflective coating, or "Super Multi Coating", which reduces the reflection ratio of each lens surface.

In this test, we are mainly concerned with flare that occurs when a prominent light source is located outside of the frame. For our test scene, we chose to photograph a high-contrast scene in which the sun would be located just a few degrees outside of the field of view. Because of the fairly small field of view, the test images below were taken at early morning. We also wanted the position of the lens elements to stay constant, therefore focus was set at infinity. Lastly, we also took test images without the provided lens hood (in order to test the efficacy of the coating).

	With hood:	Without hood:
f/2.8
f/4.0
f/5.6
f/8.0
f/11
f/16
f/22

Verdict

Regrettably, our first impression is that the Pentax SMC DA* 200mm f/2.8 ED [IF] SDM is much less resistant to flare than expected. Although we could not induce ghosting, all of the above images exhibit significant amounts of veiling flare. As can be observed, the lens hood seems to significantly lessen veiling flare when used, but more importantly, it helps to prevent the effects of chromatic aberrations (or purple fringing) caused by light sources outside of the image's frame. Even with the lens hood installed, the purple fringing is not completely absent, it is clearly visible at f/2.8 and f/4.0, but becomes insignificant when stopping down further.

Although the flare resistance of the Pentax SMC DA* 200mm f/2.8 ED [IF] SDM is less than satisfactory in our test, we remind the reader that this scenario is deliberately extreme and it depicts the worse conditions possible for the usage of this lens. Because of the small angle of view of this lens, the angle of the sun in relation with the lens' axis is rather acute, therefore the amount of stray light hitting the lens' elements is significantly large (compared to lenses with smaller angles of view). When the Pentax SMC DA* 200mm f/2.8 ED [IF] SDM is used under regular outdoor shooting conditions, it is very unlikely that the user will encounter situations where the sun is located at such an acute angle. As a consequence, the effects of flare are much lesser in real life shooting than on this test.