Focus speed, PL45 vs MZD45

There are two competing 45mm prime lenses in the Micro Four Thirds lineup. The Panasonic Leica 45mm f/2.8 macro lens and the newer Olympus M.Zuiko Digital 45mm f/1.8 portrait lens. While one is a macro lens, and the other could be categorized as a portrait prime lens, they can of course be used for a wide variety of other tasks.

I have previously compared the sharpness of the two lenses in various settings. While the comparisons are not always optimal, and could even be a tad bit misleading, I think it is clear that the Panasonic lens is a little bit better in terms of sharpness. This is not really surprising, since a large aperture lens contains more optical compromises, and usually cannot have the very best sharpness. As a general rule, one does not buy a large aperture lens for the optimal sharpness, but for using it wide open or near wide open, in which case sharpness is usually not the main concern.

People generally say that the Olympus M.Zuiko Digital 45mm f/1.8 features faster focusing. But is it true? The Olympus lens is rated as Movie-Still-Compatible (MSC), which means that the focus speed should be quite good.

I have compared them head-to-head in the same setup. The Panasonic GH2 camera was set up about 60cm from the subject, and I selected centre spot focus. The Olympus lens has a close focus distance of 50cm, and the Panasonic lens has a selectable focus limiter, which cuts off at around 50cm for better focus speed.

When powering on the camera, the lens is focused around infinity. Upon pressing the shutter release button, the camera focuses, and then takes the picture. I measure the time from the camera notes that the shutter release button is pressed, until the camera is ready to expose the image. The first event can be noted by the number of remaining frames being shown in the lower right part of the LCD display, and the latter by the green dot appearing in the upper right corner of the display.

Light background, daylight

Here is the comparison in daylight, the lightning was about EV7.



The focus speeds are rather similar:

PL45, focus delimiter off: 0.32s

PL45, focus delimiter on: 0.32s

MZD45: 0.26s

Dark background, dark room

And another test at EV2, which is very dark:



In this test, the Panasonic-Leica lens focuses faster:

PL45, focus delimiter off: 0.68s

PL45, focus delimiter on: 0.66s

MZD45: 1.12s and 1.08s (two tests)

Conclusion

	light	dark
PL45, limiter off	0.32s	0.68s
PL45, limiter on	0.32s	0.66s
MZD45	0.26s	1.08s, 1.12s

As people have been saying, the Olympus M.Zuiko Digital 45mm f/1.8 lens is indeed faster in terms of autofocus. But only by a small margin. And in dark conditions, to my surprise I found that the Panasonic-Leica 45mm f/2.8 lens focused faster.

This is just some few simple measurement, and in practical use, the experience might be different. During the time I have used both, I have generally found that the autofocus speed is comparable between them for practical, daily use.

Generally, the speed readings here are quite good. I have previously seen that the Panasonic kit zoom lenses achieve focus speeds of around 0.17s to 0.33s under similar conditions. But keep in mind that a much higher degree of focus accuracy is needed for a large aperture lens at f/1.8 than the kit zoom lens at 42mm f/5.6. With this in mind, a speed reading of 0.26s is in fact a very good achievement.

For video use on the Panasonic GH2, it is my opinion so far that the Olympus 45mm f/1.8 is better at keeping the autofocus correct during video capture. With the Panasonic 45mm f/2.8 lens, it generally takes more time before the focus is reached when there is movement in the image frame. But this is just my feeling so far, I haven't examined it in a scientific way.

The Olympus lens also appears to have a more silent autofocus operation.