Tuesday, 29 December 2009

GH1 autofocus speed comparison

I have made some tests of the autofocus speed of the Panasonic Lumix GH1 camera with various lenses. The camera focused from infinity (the default position of the lens when powering down) to near the minimum focus distance, and I used a LEGO figure as the subject.

The test was done in indoor lightning, about EV6. The focus time is measured as the time from my finger presses the shutter button until the green focus confirmation light comes up in the display. The picture is taken immediately after focus is achieved, within one tenth of a second.

You will hear the shutter operating twice, since the camera was in multi exposure mode. I did confirm that all the images were indeed in focus, as is expected with a contrast detection autofocus system (CDAF).

Summary

Before going into the details, here is a quick summary

Lumix G 20mm1.23 seconds
Lumix G HD 14-140 @ 18mm0.53 seconds
Lumix G HD 14-140 @ 50mm0.40 seconds
Lumix G HD 14-140 @ 140mm1.63 seconds
Lumix G 45-200 @ 45mm0.33 seconds
Lumix G 45-200 @ 100mm0.36 seconds
Lumix G 45-200 @ 200mm0.87 seconds
Olympus 4/3 9-18 @ 9mm2.90 seconds
Olympus 4/3 9-18 @ 18mm1.50 seconds


What is a bit surprising here, is that the 45-200mm lens is quicker than the HD 14-140mm. The latter is marketed as a very quick focusing lens, optimized for video, hence the HD designation. However, the 45-200mm lens has an advantage, since it's close focusing distance is 100cm, twice that of the HD 14-140mm. So when focusing from infinity to the minimum focusing distance, the HD 14-140mm has a longer way to travel.

Lens: Panasonic Lumix G 20mm f/1.7
video
Autofocus from infinity to 23cm: 1.23 seconds.
The minimum focus distance of the lens is 20cm.

Lens: Panasonic Lumix G 14-140mm HD f/4-5.8

Focal length 18mm (36mm in 35mm camera equivalent), f/4.3:
video
Autofocus from infinity to 53cm: 0.53 seconds.
The minimum focus distance of the lens is 50cm.

Focal length 50mm (100mm in 35mm camera equivalent), f/5.6:
video
Autofocus from infinity to 53cm: 0.40 seconds.
The minimum focus distance of the lens is 50cm.

Focal length 140mm (280mm in 35mm camera equivalent), f/5.8:
video
Autofocus from infinity to 53cm: 1.63 seconds.
The minimum focus distance of the lens is 50cm.

The outcome for f=140mm deserves some more comments. As you can see from the video, the focus is hunting a bit before settling. I tried to redo this experiment several times, and found that the outcomes were very consistent. My speculation is that I have been operating close to the minimum focus distance, and that perhaps this distance is slightly longer in the tele setting. Indeed, moving the subject a bit further away from the camera gave focus speed consistent with 18mm and 50mm focal lengths.

I have also tested this with the firmware versions v1.2 and v1.3, and concluded that the issue has been fixed. The lightning was comparable, and even though I moved the figure around close to the minimum focus distance, I was not able to reproduce the focus hunting. Rather, the focus speed has improved a lot with the newer firmware, it seems.

Lens: Panasonic Lumix G 45-200mm f/4-5.6

Focal length 45mm (90mm in 35mm camera equivalent), f/4.0:
video
Autofocus from infinity to 1m: 0.33 seconds.


Focal length 100mm (200mm in 35mm camera equivalent), f/4.6:
video
Autofocus from infinity to 1m: 0.36 seconds.

Focal length 200mm (400mm in 35mm camera equivalent), f/5.6:
video
Autofocus from infinity to 1m: 0.87 seconds.

Lens: Olympus Zuiko Digital ED 9-18mm f/4-5.6

Note that this is not a Micro Four Thirds standard lens, but rather a lens for the Four Thirds DSLR system. To mount this lens on a Micro Four Thirds camera, you will need and adapter. I used with the adapter Panasonic DMW-MA1, but the Olympus MMF-1 adapter is functionally the same, and would have done the same job.

Not all Four Thirds lenses can autofocus on Panasonic Micro Four Thirds bodies, like the GH1. Here is a list.

Focal length 9mm (18mm in 35mm camera equivalent), f/4:
video
Autofocus from infinity to 25cm: 2.90 seconds.
The minimum focus distance of the lens is 25cm.

Focal length 18mm (36mm in 35mm camera equivalent), f/5.6:
video
Autofocus from infinity to 25cm: 1.50 seconds.
The minimum focus distance of the lens is 25cm.

Conclusions

The autofocus speed of the Lumix G HD 14-140mm lens is the fastest in this comparison, which is as expected. The unexpected result in this context was the significantly slower autofocus speed at full tele, 140mm, however there is reason to believe that this was related to operating close to the minimum focus distance, as discussed above.

Just as with the superzoom above, the Lumix G 45-200mm features very impressive autofocus speed. The exception is at full tele, however, the speed at 200mm is still very good. The autofocus is virtually inaudible.

The Lumix G 20mm lens does indeed focus slower than the HD lens, and also somewhat more audibly.

Using autofocus with the Olympus 9-18mm Four Thirds lens is possible, but pretty slow. Especially at the wide angle setting. Focusing with this lens is also quite noisy. Taking pictures of moving subjects, e.g., children, with this lens could pose some difficulty with autofocus. In this case, it could be wise to prefocus, and set the camera to manual focus (MF) while composing the image. That way, you can take the picture nearly instantly when pressing the shutter, rather than having to wait some seconds for the autofocus to settle.

Lumix G 20mm1.23 seconds
Lumix G HD 14-140 @ 18mm0.53 seconds
Lumix G HD 14-140 @ 50mm0.40 seconds
Lumix G HD 14-140 @ 140mm1.63 seconds
Lumix G 45-200 @ 45mm0.33 seconds
Lumix G 45-200 @ 100mm0.36 seconds
Lumix G 45-200 @ 200mm0.87 seconds
Olympus 4/3 9-18 @ 9mm2.90 seconds
Olympus 4/3 9-18 @ 18mm1.50 seconds


Mostly, you will not focus down to near the minimum focus limit of the lens, and so autofocus will usually be faster than these examples. The Olympus 9-18mm lens is a bit of an exception to this, however, as even focusing on a distant subject takes virtually as long time as focusing close.

Rumors say that future Panasonic models, like Lumix G2 and Lumix G10, will focus faster with Four Thirds lenses on an adapter.

4 comments:

  1. Wow, that's an old post but thanks for the work. I am just considering getting the 45-200mm.

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  2. The 45-200mm is hardly a perfect lens. But for the price, it has a very good performance. Unless you dislike using tele, I'd say it's a must have lens.

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  3. I have an Oly 18-180 mounted on a GF5 via a Viltrox adapter (MMF-2 equiv(?)) AF is horrendously slow. Feels like 5 seconds as it sometimes steps through a large range to finally focus. Disappointed, but the set up looks good on the table! LOL

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    Replies
    1. Yes, the Olympus 18-180mm lens is not among the CDAF compatible lenses, so the autofocus will be very slow. This goes even when using it on the most recent Micro Four Thirds cameras.

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