GH2 GH2 in 24p: very strong "strobe motion" effect - why?

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PrimeHD

Well-known member
Clearly, ANY camera that only samples time at 24fps will have visible motion artifacts.


However, I find these to be more pronounced on the hacked GH2 than on any other 24p cam I used.


Not only in my own video tests, but also when I watch other folks' videos, everything looks Saving Private Ryan / Battle Royale to me.


As if shutter speed was super high. Except it actually wasn't set that way! In my tests, I keep 180 deg shutter (about) with 1/50 at 24p. So then, why do we get that strobing, high-shutter-speed-like look?

Am I seeing things, or is it a reality according to GH2?
 
I definitely haven't noticed it to that extent, but many people find that a shutter of 1/40 offers a noticeable improvement to the rendering of motion over 1/50 with the GH2. Kholi and others have written about this at some length. Do some tests at slower than 180° shutter and see if you like the results.

A slightly slower than usual shutter actually helps quite a bit with most CMOS cams that don't feature a mechanical shutter, but for some reason the GH2 seems a bit more susceptible than most.
 
stefancolson said:
many people find that a shutter of 1/40 offers a noticeable improvement to the rendering of motion over 1/50 with the GH2.
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Brilliant! Tested it in low light, and indeed no more of the harsh strobe effect when shutter is 1/40! Thanks much. Will do some more tests tomorrow in daylight, hope it will be satisfactory as well.
 
Same issue here, mainly when panning/tilting. I knew I needed to do it slowly but it seems like it wouldn't be this bad. Will try this out.
 
I have used 1/40 and it IS smoother - but you WILL see blurring/smearing when there is significant movement.
If you use the Panasonic lenses the lack of smoothness can often be worse due to edge artifacting caused by the additional over sharpening that is applied by the Panasonic lenses.
And no, you can't turn that off.
A Tiffen Black Diffusion #3 diffusion filter helps significantly with the Panny lenses - and it's inexpensive.
(works by softening the edges BEFORE the over-sharpening software in the lens can mess with it).

I really feel that "generally" the motion is rendered smoother by Canon cameras...but they have so many drawbacks of their own already.
I recently was involved in a 5-camera shoot of a dance performance and the GH2 won for best overall realism and color accuracy, but the Canon T3i and a $1500 Canon Video camera (I don't recall which model) really looked smoother. The shots from the 2 T3i's seemed more "artsy" in their image quality in a great way, but not as realistic as the GH2...we can do art in post.
 
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I'm also firmly in the 1/40 shutter speed camp. Big improvement.

I thought I was just seeing things with the strobing effect at 1/50.... until I plugged my GH2 and HMC150 in a large HDTV for comparison. Panning was definitely more strobe-y on the GH2. Dunno if the sharpening and additional resolved detail plays a role in this, but regardless, 1/40 for me.
 
Does the fact that it's 1/50 and not 1/48 have much bearing? What do Canon's use? Just curious.
 
cray- said:
Does the fact that it's 1/50 and not 1/48 have much bearing? What do Canon's use? Just curious.
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I'm pretty sure it has more to do with the way that CMOS sensors are read out. The improvement has to do with adding more motion blur than you normally would to cover up the slightly-too-sharp rendering of motion out of the cam. A global or mechanical shutter would likely solve these problems, though you're not likely to find one of those outside of the high-end of the market (think Sony F65).

The Canon DSLRs seem to do a little bit better than the GH2 does. My guess is that it has to do with sensor readout time and line skipping (the same reasons that the GH2 suffers from worse rolling shutter artifacts).
 
PrimeHD said:
Would you say 1/40 shutter renders smoother motion on both the stock Panny lenses as well as on the adapted manual lenses?
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I only have the Panny lenses, the 14-42 and the 20mm pancake. So I can't really comment on the vintage lenses. Definitely improves things w/ the Panny lenses, though they are supposed to be the most over-sharpened so they likely strobe the worst.
 
I'm also now a huge fan of 1/40th shutter. It helps out a lot on my GH1 and I even switched my HMC40 to 1/40th shutter. The HMC40 already had very smooth motion but I want everything to be consistant. I like 1/40th because it helps a bit in low light and works great with flickering lights where 1/50th and 1/48th can cause problems since the refresh rate is different then US electric current.

The motion is a bit blurrier but not so much that I found it distracting if shot with care. Overall it just seems to improve shots, especially hand held.

I should also point out that the 1/50th vs 1/48th thing has nothing to do with it either. My HMC40 also did 1/50th as the default for 24p and the motion is much smoother then some the GH2. There is virtually little difference between 1/50th and 1/48th. In fact I doubt many people would really know 1/40th from 1/48th.
 
Thomas Smet said:
I like 1/40th because it ... works great with flickering lights where 1/50th and 1/48th can cause problems since the refresh rate is different then US electric current..
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Shouldn't 1/60 (or 1/60) shutter be used to prevent lights flicker? Since the lights would tend to pulsate at 60Hz, which equals to 1/60 shutter.
 
PrimeHD said:
Shouldn't 1/60 (or 1/60) shutter be used to prevent lights flicker? Since the lights would tend to pulsate at 60Hz, which equals to 1/60 shutter.
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Yes 1/60th will work as well but it can also be a bit jerky (Saving Private Ryan) when shooting 24p. 1/40th can also be an even divisible by the 120 electric current. Not as good as 1/60th but a heck of a lot better then 1/48th which does not divide very well at all.
 
Most people wouldn't notice 1/60 either. I use it sometimes (on a different camera) when I am shooting fast motion. You generally have to get up into the 1/100 range before it starts to go "Saving Private Ryan" on you.
 
Apologies to the necrophobes, but I thought I'd offer a tentative answer to the "why" it would seems the GH2/GH1 has a harsher 24p cadence than other cams. The answer is that I think it doesn't. It's just an effect of the higher crop factor.

In other words, because the crop factor is higher in the GH cameras than, say, a 5D or even a 7D, an equal rotational speed (assuming a panning motion, for example), results in a faster spatial sweep across the frame. I think that if you pick a wider lens to account for the crop factor, the 24p cadence should be the same.

Just a theory.
 
MalfunctioningHuman said:
I'd offer a tentative answer to the "why" it would seems the GH2/GH1 has a harsher 24p cadence than other cams. The answer is that I think it doesn't.

because the crop factor is higher in the GH cameras than, say, a 5D or even a 7D, an equal rotational speed (assuming a panning motion, for example), results in a faster spatial sweep across the frame.
Click to expand...

Sounds like a very valid point to me.
 
PrimeHD said:
Sounds like a very valid point to me.
Click to expand...
Alex,

Didn't realize you were the guy that started this thread. I remember at least another thread where this very issue was discussed ad infinitum by individuals who will remain unnamed, but whose pixel peeping crimes are well known to all (j/k).

I think the "issue" in the GH cameras a combination of:
- Tighter crop factor.
- Ergonomics of the cameras (very light, and very small).
- Probably partially due to the higher resolution of the cameras as well, but I'm not sure about this, since motion blur should negate this fact mostly.

The first two items are easily handled by getting wider lenses, and by adding some heft to the camera (via something like a shoulder support, handles, cage, stabilizer, etc).

I quoted the word "issue" because I don't think this is a real issue, but just a characteristic of the camera that exists for logical reasons, and which is easy to work around (in other words, I don't think it's a defect intrinsic to the sensor or the way the moving images are processed and encoded).
 
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