reggietelly
Active member
I wanted to come up with a suitably inflammatory title so people would have a look at this because I think it is very important.
I have posted a video on Vimeo that I'd like people to take a look at. It illustrates what I think is a big problem with the AVCHD codec and is further to the pulsing problem noted elsewhere.
http://vimeo.com/15583689
Actually the Vimeo version still shows the problems so you will see them even at 1280x720. For a the full 1920x1080 picture please download the original. It's not too large at 60 Mb or so.
So I am having a huge problem with AVCHD footage. Although the hack has without a doubt made the camera better with moving footage, I think I have found it's Achilles heel and it is to do with tripods and locking the camera down.
I have shot 2 nearly identical scenes one with the camera on a tripod and then I have taken the GH1 off the tripod and just held the camera steadily on the same scene. The difference to my eyes at least is astounding. I am using lpowells 40Mbps AVCHD High Reliability Patch. I think a better test might be to actually try hand held then set the camera into the tripod since that would really show how locking the camera starts to introduce these artefacts on an identical scene.
Now this testing was essentially to do with working out the strobing issue or pulsing that is well documented around the forum. I have a feeling that the first shot might be slightly underexposed.
I first noticed the pulsing on the side of the tv. This is really noticeable and generates a very distracting boiling effect that is hard to not look at once you see it. I think 5DtoRGB does a pretty good job of masking this but it is still there.
But after I did the hand held test, I realised looking at the whole of the frame that overall detail had been compromised by putting the GH1 on the tripod. In particular look at the difference between the AKG headphones where there is a dotted grill. In the handheld this is pretty neatly resolved, but is not evident in the tripod one. Also the black leather strap has the pulsing or boiling and lacks detail, whereas the moving shot shows much greater clarity and no pulsing. Remember this same lens, same hack. Yes there is pulsing in the background of the hand held shot but that's much more of an exposure problem, and could be addressed using 5DtoRGB's better transcoding in my opinion.
The point I am making with this is, it's not about the hack or bitrate. It is just that the AVCHD codec and it's long GOP frames really screw up the picture when you lock the camera off. It makes large assumptions and to my eye it appears that you lose a great deal of detail. This could be anything that exhibits a uniform pattern in the background of an interview say and it could be perfectly exposed! Am I the only one seeing this or are we so enamoured of this camera and the constant search for the highest bitrate that we choose not to see it? I think this area is the one where for me this camera falls a bit flat.
To me this is pretty worrying, and anyone shooting interviews on tripods should really look at this.
Also I'd like it if other people could test because it is such an easy thing to do. Again this isn't about bitrate or hacks or low light, it is about one of the fundamental accessories we use with a camera.
all the best
Richard
Maybe I was a little hasty. I have tried some other tests and have been able to replicate it slightly but not to the degree of the first clip so I am a bit worried the first shot may have been a tad underexposed. Still doesn't explain the side of the TV boiling.The killer is underexposure I think as this tends to mute the colours to such an extent that they become hard for the codec to discern hence the mud. So bit of back peddling but still not convinced.
I have posted a video on Vimeo that I'd like people to take a look at. It illustrates what I think is a big problem with the AVCHD codec and is further to the pulsing problem noted elsewhere.
http://vimeo.com/15583689
Actually the Vimeo version still shows the problems so you will see them even at 1280x720. For a the full 1920x1080 picture please download the original. It's not too large at 60 Mb or so.
So I am having a huge problem with AVCHD footage. Although the hack has without a doubt made the camera better with moving footage, I think I have found it's Achilles heel and it is to do with tripods and locking the camera down.
I have shot 2 nearly identical scenes one with the camera on a tripod and then I have taken the GH1 off the tripod and just held the camera steadily on the same scene. The difference to my eyes at least is astounding. I am using lpowells 40Mbps AVCHD High Reliability Patch. I think a better test might be to actually try hand held then set the camera into the tripod since that would really show how locking the camera starts to introduce these artefacts on an identical scene.
Now this testing was essentially to do with working out the strobing issue or pulsing that is well documented around the forum. I have a feeling that the first shot might be slightly underexposed.
I first noticed the pulsing on the side of the tv. This is really noticeable and generates a very distracting boiling effect that is hard to not look at once you see it. I think 5DtoRGB does a pretty good job of masking this but it is still there.
But after I did the hand held test, I realised looking at the whole of the frame that overall detail had been compromised by putting the GH1 on the tripod. In particular look at the difference between the AKG headphones where there is a dotted grill. In the handheld this is pretty neatly resolved, but is not evident in the tripod one. Also the black leather strap has the pulsing or boiling and lacks detail, whereas the moving shot shows much greater clarity and no pulsing. Remember this same lens, same hack. Yes there is pulsing in the background of the hand held shot but that's much more of an exposure problem, and could be addressed using 5DtoRGB's better transcoding in my opinion.
The point I am making with this is, it's not about the hack or bitrate. It is just that the AVCHD codec and it's long GOP frames really screw up the picture when you lock the camera off. It makes large assumptions and to my eye it appears that you lose a great deal of detail. This could be anything that exhibits a uniform pattern in the background of an interview say and it could be perfectly exposed! Am I the only one seeing this or are we so enamoured of this camera and the constant search for the highest bitrate that we choose not to see it? I think this area is the one where for me this camera falls a bit flat.
To me this is pretty worrying, and anyone shooting interviews on tripods should really look at this.
Also I'd like it if other people could test because it is such an easy thing to do. Again this isn't about bitrate or hacks or low light, it is about one of the fundamental accessories we use with a camera.
all the best
Richard
Maybe I was a little hasty. I have tried some other tests and have been able to replicate it slightly but not to the degree of the first clip so I am a bit worried the first shot may have been a tad underexposed. Still doesn't explain the side of the TV boiling.The killer is underexposure I think as this tends to mute the colours to such an extent that they become hard for the codec to discern hence the mud. So bit of back peddling but still not convinced.
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