compression artifacts on motion and detail in 24p mode

commanderspike

commanderspike

Carbonite Member
Sorry to revisit this old chestnut.

But I am never shooting in 24p again with the GH1.

It didn't so much ruin my shoot, but it took away all the advantages of the full HD mode, and the advantage of the AF tracking mode, and then some. This time, the problem was not so much mud, but the variable compression rate of AVCHD in full HD mode. There simply isn't enough detail left on moving shots to make the footage look like full HD.

A bit of background to the shoot first: it involved a singer / song writer moving around against a backdrop of park trees, with the camera mounted to a steadicam for slow, smooth, floating motion. This does not cause mud of course, but it DID cause compression artefacts which were MUCH higher than with tripod mounted scenes, to the point where no fine detail was visible at all - a nasty surprise and proof that the full HD mode on the GH1 is even more fragile than I thought.

I decided to use the kit lens AF tracking 'hands off' for most of this, so that the singer could dance around the frame, get closer and further away, without me having to pull focus whilst the camera was delicately floating around on it's stabiliser rig while shooting!! So AF tracking = great feature? NO! Not in 24p mode, because it doesn't work properly! The kit lens' AF tracking went to pieces. It was as good as useless.

But not so in 720p with it's higher frame rate. It was fantastic - always locking on to the moving actress as the camera floating silkily towards her or around her.

Having a GH1 reminds me what an essential feature AF can be, and why this shoot would have been impossible with the equipment I had on me, had I used a 5D Mark II.

But 24p? Meh.

If your camera moves... at all... don't use it.
 
Trees, leaves and grass are the worst, for sure. Lot'a detail in there. It's my opinion, that you will get the most mud when using the kit lens on auto, although I haven't done a proper test to prove that yet. :)
 
You shouldn't be using auto focus at all in video. It's NEVER going to work right. Especially on a tracking shot where the subject moves closer and further away from the camera. There are reasons why people pay a lot for wireless follow focuses and good first AC's. If you can't afford those then maybe you should design your shot differently.
 
Tim Joy said:
Trees, leaves and grass are the worst, for sure. Lot'a detail in there. It's my opinion, that you will get the most mud when using the kit lens on auto, although I haven't done a proper test to prove that yet. :)
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Exactly, green color is the nemesis of this camera.
 
Weird - I just shot a 9 page short entirely in 1080p24, and didn't have a single frame with mud. Outdoor shoot, lots of green and foliage. Some handheld stuff (albeit with a "steady" hand). Lots of use with kit lens with facial auto-tracking on (which worked perfectly, it's one of my favorite features now - there are shots that would not have been possible without it). I've had my doubts with all the chatter, but everything worked a treat, and the footage looks amazing. I'll post some screen grabs later today.

My one trouble I did have, though, was red-shadow detail. One of the actors wore a red shirt in a scene, and any red shadow (especially his face) showed banding. This was the only time banding was a problem, too. However, for some reason, once I did the pulldown removal, the banding was significantly less noticeable, to the point that if you weren't looking for it, you'd never see it.

I would happily shoot 1080 with the cam, and if I review the first shot on a large external and it looks muddy, then I'll switch over to 720. But that hasn't happened yet.
 
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Matty_g said:
You shouldn't be using auto focus at all in video. It's NEVER going to work right. Especially on a tracking shot where the subject moves closer and further away from the camera. There are reasons why people pay a lot for wireless follow focuses and good first AC's. If you can't afford those then maybe you should design your shot differently.
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I totally disagree!

You think a wireless follow focus is the future?

I can't afford a good first AC. I can't afford a follow focus never mind a wireless one. My style is to carry as little as possible in a camera bag to the location and direct.

I had a small camera, a small stabiliser, a small kit lens and it was heaven. Letting the camera use it's intelligent AF tracking to make possible shots that wouldn't have been possible otherwise. There is no AF hunting in 720p but in full HD the camera preferred to focus on the background. Unfortunately this isn't very noticeable on a 3 inch LCD when depth of field is not so shallow (at F4).

I think once this kind of AF tracking and face recognition technology is refined, it will be the future of indie film making.

There is not a chance I could have done the shots I did on a small stabiliser with a 5D or 7D.

I am gonna do a test... compare the detail of a down-sampled (in Photoshop for highest quality sampling) 1080 24p frame with the in-camera 720p AVCHD shot and in camera 720p MJPEG.

I am betting what the order will be, and the 1080p shot will have nothing like near 1080p worth of detail in it, for highly detailed scenes. So what's the point? Where 1080p works well on static shots, macro shots, or portraits where the shallow focus knocks out the background completely maybe there is a tiny amount of benefit but certainly not enough for me to be hassled in future about whether to switch between 720p and 1080 on one shoot.
 
cowpunk52 said:
Weird - I just shot a 9 page short entirely in 1080p24, and didn't have a single frame with mud. Outdoor shoot, lots of green and foliage. Some handheld stuff (albeit with a "steady" hand). Lots of use with kit lens with facial auto-tracking on (which worked perfectly, it's one of my favorite features now - there are shots that would not have been possible without it). I've had my doubts with all the chatter, but everything worked a treat, and the footage looks amazing. I'll post some screen grabs later today.

My one trouble I did have, though, was red-shadow detail. One of the actors wore a red shirt in a scene, and any red shadow (especially his face) showed banding. This was the only time banding was a problem, too. However, for some reason, once I did the pulldown removal, the banding was significantly less noticeable, to the point that if you weren't looking for it, you'd never see it.

I would happily shoot 1080 with the cam, and if I review the first shot on a large external and it looks muddy, then I'll switch over to 720. But that hasn't happened yet.
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Looking forward to seeing the frames from yours, and comparing. Were there NO moments of mud at all? Even when handling the camera whilst it was recording between takes? Even if you jerk the camera round to take the lens off whilst forgetting to hit stop? Surely there must be a moment somewhere. And I don't care about that. That's where mud doesn't affect us. I am more worried about what I saw in the none-mud shots - a complete lack of fine detail on scenes which should have been very detailed indeed... so the dilemma of 1080 24p remains - 24p is a nice film like frame rate, 1080p is great for bringing out fine details - but if you have too much detail in the scene and a bit of camera movement, the whole exercise falls flat and gives you a worst result than 720p MJPEG mode!! I am sure there are exceptions - but show me a tracking shot or a steadicam shot with a high detailed scene shot in 24p on the GH1 which hasn't degraded due to the codec. I have yet to see one. It depends what you define by high detail of course... by that I mean, grass combined with trees, all over the picture, with a moving camera, moving actor - the whole lot!! It's impossible... honest.
 
Commanderspike - I'll take a really close look this afternoon and see what I can find. I know there was no mud in any of the critical shots or print takes. I'll get some stills and maybe upload some clips for you to download and look at
 
cowpunk52 said:
Commanderspike - I'll take a really close look this afternoon and see what I can find. I know there was no mud in any of the critical shots or print takes. I'll get some stills and maybe upload some clips for you to download and look at
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Hey, it's okay. Save yourself the bother. It's not so much mud this time around that irked me, more the compression artefacts on motion and detail in 24p mode.

I should have named the thread differently, but can't think of a different name for the stuff which isn't mud.

How about 'slime'? ;)
 
commanderspike said:
Hey, it's okay. Save yourself the bother. It's not so much mud this time around that irked me, more the compression artefacts on motion and detail in 24p mode.

I should have named the thread differently, but can't think of a different name for the stuff which isn't mud.

How about 'slime'? ;)
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thread title changed
 
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