Meaning you've not seen any difference?
That really matters if so!!

Hi guys,

I'm new here so firstly many thanks for all the hard work in making this an invaluable resource for GH2 users.

I hope this is the right place to post this, someone reported similar problems here but then the focus seemed to shift more towards an issue of stuttering when panning.

I bought my GH2 last week and installed 'reAQuainted' INTRA GOP1 176M. I'm experiencing some strobing effects on the video. It does not seem to occur on every shot. I am able to see the strobing in the monitor so I know when it is going to happen but as I'm very inexperienced with the camera I'm not really sure what is causing it or how best to avoid the problem.

I'm using an Auto Revuenon 1.4 55mm lens with an M42 to M4/3 adapter - faster lens than the kit. The strobing seems more apparent when wide open at 1.4. I have not seen the problem on the kit lens but will test more to see if it occurs.

I've uploaded to vimeo to try and explain what is happening.



Sorry for the shaky cam on a few of the shots.

Many thanks for your help.

@paglez

Thanks for your reply. I am in PAL land. Still trying to get used to the best way of shooting with my new baby.

I recently became interested in the "judder" issue when panning in 24p mode. Recently got the e-image/fancier FC-04H Mod Fluid head + CT7402 legs deal off the site and really started noticing the juddering motion during slow pans particularly...thought I'd share my research on the issue.

Btw if anyone wants to test for themselves just slow pan with any decent fluid head tripod past a bookshelf. The text on the book spines will "vibrate" and jerkily "judder" past on the horizontal plane. I would urge anyone unsure of what judder is to do this at 24p. Then compare to 50/60p.

Do not confuse this with tearing (where the top half of the screen seems infront/behind the bottom half - check your v-sync options in your gpu) or strobing caused by a bad camera frame rate and ac mains powered lights Hz combination. Judder can also cause a kind of strobing in my opinion (as the details in the image/light seem to pulse as they pass the camera)

Anyway to sum up "judder" looks like a 24p issue rather than a GH2 issue. Google 24p motion judder and check out the wealth of info in the subject. Some Blu-ray and projector combos make for some extreme motion judder artefacts apparently when watching commercially released movies.

Some cheaper HD cameras seem to judder more than others however. The jury seems out on exactly why but as mentioned earlier in the thread, sharpening each frame (and therefore reducing the natural motion blur) seems to make things worse. This could be the issue in GH2. Other issues such as playback monitor refresh rate seem to increase or decrease the perception of the effect, in some cases masking the issue until the same footage is viewed on another screen/refresh rate.

Blurring in post and shooting out of focus both seem to reduce the effect pointing to increased sharpness/contrast exaggerating the effect.

I'm shooting with sharpness and contrast at -2 with a Canon FD 50mm. I can post some examples if anyone is interested.

@Blackout1, that's interesting info and makes a lot of sense. I think that a digital senor could simulate this by ramping the sensor gain at the start and end of each frame capture. I don't know if current sensors can adjust their sensitivity that quickly, but if not it will probably be possible in the future.

@Blackout1 I’m going to have to disagree with you. I don’t see how fading helps with smooth motion. As far as the film frame is concerned, you’re just exposing it for 1/48th of a second, the entire area of the frame. Digital sensor readout (CMOS), on the other hand is not instantaneous and even the fastest sensors are a far cry from being “on and off in a perfect fashion.”

I think the excessive amount to judder in digital cinema has more to do with its availability to the general public. The sheer number of amateur videos shot at a “magic” rate of 24 fps outweighs the number of films shot professionally. Hence all the judder/noise/which-setting-is-better discussions.

By the way, a few months ago I did some cursory reading on the subject of judder, and was surprised to see the same discussions on the RED forums.

You’re right about the panning speed rule being very old. It predates digital cinema by a few decades. The reason it became a rule (well, a guideline, rather) was because following it created smoother motion.

Someone posted a short clip recently (with one of the newer Driftwood settings, I believe) demonstrating a perfectly smooth pan. No judder whatsoever, an extremely filmic look.

Here’s another thought to ponder: given the size of Arri and RED cameras, it would be very easy to implement a small rotary shutter in them. Heck, you could even have it at the same 45º angle as in film cameras! Then you could synchronize sensor readout with the shutter’s rotation and presumably get the same look. And yet neither Arri nor RED has implemented such a feature. Why haven’t they done that?

EDIT: Well, I’ll be! It turns out that some manufacturers of digital cinema cameras do use a mechanical rotary shutter. The Sony F65 has one, for example. The purpose is to eliminate (or at least to alleviate) the rolling shutter effect.

Interesting, but I don’t see much difference in their test footage (aside from the rotating disk example). The judder is still there.

Also, it turns out the Arri Alexa Studio also uses a rotating shutter: http://arri.com/camera/digital_cameras/learn/alexa_faq.html

@jackbauer interesting. In your experience, which hack provides less studdering?

@JackBayer Care to post some sample footage? I'd be interested to examine it.

EDIT: Here´s the test I shot

Embedding wouldn´t work.

2 other videos from the shooting I mentioned are uploading right now.

@JackBayer Thanks for the quick response, this is the kind of testing that is most helpful to me. However, the Vimeo pages currently have MOV files available for download, I'd need to examine the original MTS files.

@LPowell

Ok, here it is:

GH1 piece first (I guess you won´t need it, but it could not hurt:

an here GH2 with FloMo:

I´ve just uploaded, so maybe it´ll take Vimeo some time to finish the process (seems so...).

Thanks!