Somehow getting 60 unique frames in 1080 on GH2!

sam rides a mtb

sam rides a mtb

Active member
Just received my GH2. Been a long time GH13 user. Thought I would try a little experiment. Shot some footage (on GH2) in the FSH mode (1080 60i) - NOT the 24H (1080 24p) mode. First with a shutter speed of 1/30th, then with a speed of 1/60th. Dropped both clips into a 1080 30p and 1080 30i timeline in Adobe Premiere CS5. Slowed both clips down to 50%. The clip shot at with a 1/30th shutter showed doubled up frames - each frame appeared twice back to back - as I expected. Then I went frame by frame on the clip shot with a 1/60th shutter and to my surprise, no doubled up frames! I can assure you I do NOT have frame blending enabled - which has wisely been disabled by default in CS5.

Perhaps every other odd frame is made up from the upper field and then every other even frame is the lower field, though wouldn't that mean my vertical resolution would be halved? Does not look halved to me.

The first pan in this clip is the 1080 60i (with 1/60th shutter) at 100% speed. The second part is the same clip at 50% speed.


Clip is still processing. Going to bed for now. Could be my tired eyes playing games with me, so will experiment more with this tomorrow.
 
Matthew P said:
That's because the GH2 can shoot in 30i, not just 24pF like the GH1. :)
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I understand this. My question is whether when I slow this 30i or really 60i (to be technically correct) down by 50% and still get 30 unique frames per second, whether or not the resolution is halved or not. Even if so, it still looks really good.
 
it is on old trick... and you are right... it is taking upper, then lower field for each frame. I used to do it on my FX1. The results are not as bad as you would imagine... but you are definitely losing data.
 
My understanding from the testing that I have done is that anything below 1/60th of a second with 1080i is just 1080i @ 30 FPS psf. Is that not correct?
 
sam rides a mtb said:
I understand this. My question is whether when I slow this 30i or really 60i (to be technically correct) down by 50% and still get 30 unique frames per second, whether or not the resolution is halved or not. Even if so, it still looks really good.
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Yes, if you take the 60i signal and play it at 50% speed, it will take each field and make a full frame out of it. The resolution of the image will be cut in half. But the motion will be accurate. You might want to compare how this looks, vs. 720/60p. Same motion signature, more horizontal but less vertical resolution from the 60i version, less horiz but more vertical from the 720/60p version...
 
mpgxsvcd said:
My understanding from the testing that I have done is that anything below 1/60th of a second with 1080i is just 1080i @ 30 FPS psf. Is that not correct?
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That is correct. You cannot have a shutter speed that's longer than the frame rate -- if you try, the camera will drop its frame rate to compensate. So 1080/60i @ 1/30 or 1/40 or 1/50 results in the same as 1080/30p.
 
Hey, 1080/60i is totally valid for the "live" look. For the GH2's target market (hybrid stills/video camera) it's probably far and away the preferred mode. It's just for the indie filmmaker types who would prefer 24p and despise 60i...
 
Barry_Green said:
Hey, 1080/60i is totally valid for the "live" look. For the GH2's target market (hybrid stills/video camera) it's probably far and away the preferred mode. It's just for the indie filmmaker types who would prefer 24p and despise 60i...
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I disagree. The difference between the horizontal resolution of the 720p file vs. the 1080i file is negligible since neither really go above about 850 Lines per picture height. The 720p file gets you the same overall resolvable resolution without any of the deinterlacing headaches. Now if your distribution method for the video requires 1080i then of course that would make sense. However, if you are shooting with the GH2 purely for the most resolution with 60 FPS, the 720p mode is your best choice.
 
stonebat said:
I'd prefer 720p60 for live look until 1080p60 is available on GH3 or 4 or whatever.
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So do I. Always progressive over interlaced, always. But customers who want "full hd" and don't want the "stuttering" of 24p, seem to be quite happy with 1080/60i.
 
mpgxsvcd said:
However, if you are shooting with the GH2 purely for the most resolution with 60 FPS, the 720p mode is your best choice.
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Granted. But the target market of the GH2, being consumers who want a "convergence" camera, most likely aren't shooting for purely the most resolution. That's all I was saying.
 
Barry_Green said:
Hey, 1080/60i is totally valid for the "live" look. For the GH2's target market (hybrid stills/video camera) it's probably far and away the preferred mode. It's just for the indie filmmaker types who would prefer 24p and despise 60i...
Click to expand...

I have not played with this.. but how is 60i handled by modern widescreen lcd and led TVs? I don't understand how ANYTHINGi still exists when all 1080p sets are progressive displays are they not? What am I missing here?
 
Blackout said:
I have not played with this.. but how is 60i handled by modern widescreen lcd and led TVs? I don't understand how ANYTHINGi still exists when all 1080p sets are progressive displays are they not? What am I missing here?
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It's handled ok by progressive displays, but the end quality is dependent on the specific deinterlacing processing algorithms used by that TV set. Higher end sets use much better algorithms, lower end sets use simple algorithms and the quality sucks with lots of deinterlacing artifacts (look like jaggy edges and aliasing)

CRT's handle 60i much better , CRT's are the only way interlaced content can be displayed properly

How does NFL football or NHL hockey look on your display? Most affiliates broadcast at 60i
 
Blackout said:
I have not played with this.. but how is 60i handled by modern widescreen lcd and led TVs? I don't understand how ANYTHINGi still exists when all 1080p sets are progressive displays are they not? What am I missing here?
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Anything you've ever watched on CBS or NBC is 1080i. They only broadcast 1080i. Progressive TVs turn it into progressive.
 
Barry_Green said:
Hey, 1080/60i is totally valid for the "live" look. For the GH2's target market (hybrid stills/video camera) it's probably far and away the preferred mode. It's just for the indie filmmaker types who would prefer 24p and despise 60i...
Click to expand...

Interestingly, according to the Abel Cine blog, 1080/60i is also a good frame rate for bypassing AVCHD and recording directly to ProRes with the Atomos Ninja:

The Ninja was able to handle any HD resolution and frame rate I threw at it, including the tricky 1080/60i (not 59.97) from the GH2.
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Barry_Green said:
Anything you've ever watched on CBS or NBC is 1080i. They only broadcast 1080i. Progressive TVs turn it into progressive.
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I don't watch much TV, but this was what I was thinking... so is 1080i really 1920 by 540 at 60fps, and then it gets doubled? I understand how
interlace works on CRTs but I haven't seen a HD 1080p widescreen CRT in a looooong time. Yeah I have a few sony pro editing CRTs that can do it, those big grey monsters that were standard in all studios for a while that weigh a few tons... I don't think I have even turned it on in a year I have two of them in the garage.

Aren't there tons of 'jaggies' then in this 1080 60i mode on a progressive monitor?
 
i play my GH2 1080i50 on my 65inch panasonic plasma and it looks awesome cant say can tell the dif to the 720p50 mode to be honest im very happy with it

Blackout said:
I don't watch much TV, but this was what I was thinking... so is 1080i really 1920 by 540 at 60fps, and then it gets doubled? I understand how
interlace works on CRTs but I haven't seen a HD 1080p widescreen CRT in a looooong time. Yeah I have a few sony pro editing CRTs that can do it, those big grey monsters that were standard in all studios for a while that weigh a few tons... I don't think I have even turned it on in a year I have two of them in the garage.

Aren't there tons of 'jaggies' then in this 1080 60i mode on a progressive monitor?
Click to expand...
 
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