Saturday, 25 December 2010

GH1 vs GH2: AF during video

When the Panasonic GH1 was launched, it was the only consumer system camera to provide continuous autofocus during video recording. Since this time, several competitors have launched their own systems, with the same capabilities. To regain the throne, Panasonic's most recent GH2 model must improve upon the original GH1. How does it fare?

To test this, I made a LEGO contraption which moves a paper sheet back and forth. The paper sheet has a printout of a sharpness test pattern. Here's how it looks:



But filming this and seeing how well the camera AF can keep up, we can compare the performance of the GH1 versus the GH2.

Lumix G HD 14-140mm

I set the camera up with the Lumix G HD 14-140mm superzoom lens at f=100mm. My experience shows that the lens performs best in terms of AF in the shorter focal lengths, so setting it at f=100mm is extra challenging. Both cameras were left in iA (intelligent auto) mode. Both were filming in 25 fps, 1920x1080 pixels

The camera was mounted to a tripod, not entirely perpendicular to the paper. That way, the test pattern can be seen to move a bit sideways, and not only back and forth.

Here are the results:



Panasonic GH1



Panasonic GH2

Based on these videos, it's easy to see straight away that the GH2 can keep up the focus in a better way. However, I wanted to check more thoroughly. So I studied the frames to see which were reasonably in focus.

What I found, was that the GH1 cannot keep up the focus at all. Rather, only the frames in which the paper is close to the initial position are in focus. The rest are out of focus.

The GH2, on the other hand, manages to follow the sheet's motion. The frames in which the paper moves most quickly are out of focus, but the camera regains focus when coming near the end-points, in which the paper sheet moves more slowly.

Based on my simple study, it is clear that the GH2 continuous autofocus is better than that on the GH1.

Lumix G 45-200mm

Using the Lumix G 45-200mm f/4-5.6 lens at 100mm gave the same result:



Panasonic GH1



Panasonic GH2

It looks like the GH1 with the Lumix G 45-200mm f/4-5.6 keeps up the focus a little bit better than with the Lumix G HD 14-140mm. This is consistent with my previous experience, in which I found that the 14-140mm is a bit slow to focus in the longer part of the zoom range, and that the 45-200mm is very fast except in the very longest end.

Leica Lumix DG 45mm macro

I also did the same experiment with the Leica Lumix 45mm f/2.8 macro lens. However, the lens was not able to keep up the focus with either camera. It is clearly not as fast focusing as the Lumix G HD 14-140mm lens.

7 comments:

  1. Very valuable test and conclusion!
    Thanks!

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  2. do you have a sony a55?or sony a33 to compare them?

    that would be really usefull

    that test is really difficult because the subject never stops at one part it has a behaviour that is not seen regularly in real life but if a camera is good at this test than its fantastic at anything else

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  3. Sorry, I don't have any Sony cameras.

    I agree that this is a challenging test for the camera. But it serves the purpose pretty well, since the GH1 fails, and the GH2 is pretty successful. That way, it shows that there has been a progress.

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  4. Didn't realise how complementary a good stock of Lego Technic was to the production of useful reviews... (smile) Great!

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  5. I would be as well very interested in the sony SLT a55 comparision, because i still did not took a decision which one to purchase next. perhaps a sony owner can drop by...
    because even if someonw could build the same construction and set the tripod on the same relative positon: how would you reproduce the light conditions?

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  6. LEGO is good for a number of different uses!

    As for the comparison to Sony, I am sorry to say that I don't have access to such a camera.

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  7. I am thinking of switching (or complementing) from a 60D to something with continuous focus. I've been looking (more like just reading up on) at the NEX series but your blog entries has been very helpful! I have made up my mind, for a lot of reasons, on going with the GH2. Thank you very much!

    ReplyDelete