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Guest George Markov

image "flickering" when shoot on progresive mode

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Guest George Markov

Hi ,

I?m a DP from Bulgaria and within nwxt two weeks I?m starting a tv drama. I managed to convince my producer and director to shoot it 25 progresive so I?ll shoot it on Panasonic AJ-SDX900 (PAL). Now I have this problem.: a kind of flickering in a certain muvements of the actors or the camera. esspecially when actors crosing frame perpendicular to the axes, and when I make left-right or right ? left pan. When I look stop frame of the shot whit this kind of flickering the picture is perfect and clear. Its obviously that the problem is related with shuter speed. ( I had some times the same problem in similar situation with 35mm camera). Its due to the movement of the object during shuter is closed. So the solution is to have more open shuter angle. I have some experience with Sony HDW-F900 and they solved the problem with shuter off. When shuter is on it starts from 1/50. Panasonic AJ-SDX900 shuter starts with 1/100. this mens for me that when shuter is off the shuter speed is 1/50. there is a new option for shuter ? SuperV, but I read in the manual its afect onlu number of lines of the pics. Do enybody had this problem and overcome this problem succesfuly, or the solution is to avoid pans and be careful whit the blocking.

 

Thanks in advance

George Markov

 

P.S. I shot my tests with

camera mode: 25p

v. res: progresive

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Hi,

 

Yes, the solution is to be careful with panning speeds and where you block people to move. I suspect that you are seeing a perfectly normal artifact of progressive-scan image capture, which is often distracting to peopel who're used to interlaced video. The motion does look more stroboscopic and jerky - that's the point. If you find it irritating, shoot interlaced.

 

Opening the shutter up will make it look smeary - see Collateral.

 

Phil

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Guest George Markov

Thanks Phill

I just wonder what will happen if I shoot

camera mode: 25p

v. res: interlace

 

and the other thing I don?t know whether the P.HALF SHUT function from <OPTION> screen was OFF or ON during the test. Now I believe it was set ON because we had no problem to change shuter speed for particular moment. Is it means that if this function is on OFF - it's OFF complitely or this only releases the rest of shuter speeds ?

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Thanks Phill

I just wonder what will happen if I shoot

camera mode: 25p

v. res: interlace 

 

and the other  thing I don?t know  whether the P.HALF SHUT  function from <OPTION> screen was OFF or ON during the test.  Now I believe it was set ON because we had no problem to change  shuter speed for particular moment. Is it means that if  this function is on OFF - it's OFF complitely or this only releases the rest of shuter speeds ?

 

 

P Half Shut is the Half Shutter and in general that would be on, that is the way it comes from the factory. You can change the shutter in progressive mode by going to the Synchro scan shutter and going up or down within that shutter range which can/could get yu down to 1/25th. The p. HAlf Shut would not have been 1/100th, you would have had to do that, it would have been 1/50th, and P. Half Shut is Progressive Half Shutter, so it is a division of the Profressive mode by 1/2.

 

 

The other thing you ask about is the V. Res: Interlace or Progressive. The camera is able to record 480 lines of or in PAL 576 lines of resolution. The Kell factor limits the amount of resolution a standard CRT device can display, in NTSC it is 360. In PAL it is lower than what the camcorder can record a well but then I really don't know the actual number. None the less, the v.res: is a a filter to roll off excessive resolution in the vertical mode. This is for shooting for Television release. If doing film work leave it in progressive. In either case you are still capturing in progressive just rolling off resolution in the v. res: interlace choice.

 

What this extra resolution looks like is interline twitter, or aliasing, you are simply sending the monitor too much information. If your destination is film, just live with it and be assured that it will go away once you upres for film out.

 

Hope that helps,

 

Jan

 

PS. You now have my entire knowledge base on the PAL version. ;-) I work foor the USA, and am vastly more familiar with the NTSC version.

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Hi,

 

I gather it would also make sense to leave the vertical filtering off if you were intending to deinterlace later, as that would maximise the info going into the delacer, which would then apply more than enough filtering to stop twitter.

 

Needless to say this wouldn't apply to an SDX-900, but many other Panasonic cameras (including mine) offer similar functions.

 

Phil

Edited by Phil Rhodes

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One small way to decrease the perception of 24p "strobing" is to minimize DOF; with less of the image in focus, there are fewer in-focus details to "jump" between frames. It won't make a huge difference, but it can help.

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Hey, I've sometimes syncro scanned down to 1/40 or 1/36 shutter to minimize the strobe/flicker (whatever) if I can't slow the action down any. The trade off is a bit more blurinessOther than that, I leave it at 1/48th standard, unless I'm going to slow-mo it in post, in that case I go up to 1/100 to minimize seeing a lot of slow blur. I came to this practice by watching Panic Room in which there is some great slow-mo work that had no blur to it, which I deduced that with the increased capture rate, the shutter was moving pretty fast to keep each frame sharp. This might see elemetery to film guys, but I don't know how many of us video guys think about how to capture for slow-mo.

 

I think the Goodman's Guide says that SuperV doesn't work in either progressive modes.

 

J

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Guest MDO

Hi

 

The whole point of using the 900 is for its real-time true Progressive mode. What you are seeing is the desirable result of this mode. In fact, you are not getting "flicker", (this is a cyclic change in brightness ) but motion judder...what film does, what this camera mimicks.

Compared to interlace mode, any motion relative to the camera will be juddery, so pans need to be film speed pans. Less d.o.f means you won't notice background judder as much whan panning with a subject.

 

Now, here's the technical bit that virtually nobody in the film world knows...

 

Judder looks worse on progressive video cf film because of the way the eye percives motion.

The eye/brain works out where things are in an image by locking onto what's known as "mid frequency detail" . This is measured by the "Modulation Transfer Function" or MTF. 35mm film has a better high frequency (hair etc) mtf than video, but not as good in the mid frequencies, here video has more detail.

This is the problem. To demonstrate this, look down the viewfinder when doing a fast-ish zoom, it looks awfull. Now look at it back on a monitor,no way near as bad. This is because the black and white viewfider has lots of artificial detail added (for better focussing) so judder looks a lot worse!

 

The solution:

 

You need to get into the detail settings in the camera and turn them down (not advised on location) I use settings researched by the BBC R&D dept. The results were great. Superb film look with no excessive judder.

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You need to get into the detail settings in the camera and turn them down (not advised on location) I use settings researched by the BBC R&D dept. The results were great. Superb film look with no excessive judder.

 

Yep, the settings researched and devised by Alan Roberts I believe. I believe he still does some freelance work too to help people set up their cameras for filmlook. His settings apparently aim to set up the camera for a much more filmlike response in the various frequencies as well as increasing dynamic range to the max.

 

I've been desperate to find out what settings the BBC use for XDCAM, but alas one has to actually be working for the Beeb on a project to obtain them. :(

 

The only settings I use for my 510 are the ones recommended by Swiss Effects, a film transfer house. http://www.swisseffects.ch

 

They keep settings handy for many different cameras, and despite not using filmout I tend to use their detail settings all the time as they drastically reduce edge enhancement detail while not making the picture overly soft. I'm sure if anyone who is interested in this contacted them they would give you their settings for the SDX too.

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Yep, the settings researched and devised by Alan Roberts I believe.  I believe he still does some freelance work too to help people set up their cameras for filmlook. His settings apparently aim to set up the camera for a much more filmlike response in the various frequencies as well as increasing dynamic range to the max.

 

I've been desperate to find out what settings the BBC use for XDCAM, but alas one has to actually be working for the Beeb on a project to obtain them.  :(

 

The only settings I use for my 510 are the ones recommended by Swiss Effects, a film transfer house.  http://www.swisseffects.ch

 

They keep settings handy for many different cameras, and despite not using filmout I tend to use their detail settings all the time as they drastically reduce edge enhancement detail while not making the picture overly soft. I'm sure if anyone who is interested in this contacted them they would give you their settings for the SDX too.

You could buy Paul Wheeler's book, "Digital Cinematography". He was a Beeb film DP for 15 years, then went out on his own. His book details all his settings for getting a Sony DVW-700 and 790 to best resemble a film-look. He doesn't specifically talk about doing film-outs (progressive) because he shoots shows for TV premiere (50i) but the settings should be similar. Those 2 cameras only shoot interlace.

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You could buy Paul Wheeler's book, "Digital Cinematography". He was a Beeb film DP for 15 years, then went out on his own. His book details all his settings for getting a Sony DVW-700 and 790 to best resemble a film-look. He doesn't specifically talk about doing film-outs (progressive) because he shoots shows for TV premiere (50i) but the settings should be similar. Those 2 cameras only shoot interlace.

 

I had thought about that in the past, but the menus and camera heads between cameras are vastly different. The settings for the 790 and 700 would not work effectively on, say, a 510 or the SDX.

 

People do tend to be quite protective about settings for cameras. I think Alan is the best bet for having the camera set up correctly. He seems to be the UK equivilent of Roger Macie. The filmlook such as the BBC settings being discussed are something that really needs a thoroughly experience engineer with various monitors and colour charts to sort out.

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People do tend to be quite protective about settings for cameras. 

 

I think people also overemphasize the importance of them. It's just the icing on the cake, if that. What's more important is what's in front of the camera and how it's lit and composed -- if that's REALLY good, then you could practically use the factory settings on the camera or turn every feature off and get decent results.

 

Personally, I think the motto for DIT's setting up a menu should be the same as the Hippocratic Oath: DO NO HARM.

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Guest MDO

Dave, it's a bit more than icing on the cake...getting an extra 3 stops of exposure range combined with achieving a convincing film look with no post production just by tweaking the camera settings..

It's a given that well composed/lit images are the starting point, but film-like images are held up as the standard to aim for. (Whether they should be is an entirlely different dabate) I welcome any research into achieving this, especially when the source is the BBC's own R&D dept. Check out their website, especially the white paper, "Filmlook - It's not just jerky Motion" :)

 

 

Simon,

 

I have Paul Wheeler's book, but he does not have the modified settings that Alan Roberts has researched. Paul's addenum is really no more than a check list of standard menu settings. Also the whole issue of gamma correction (fundamental to the understanding exposure range) is not, I feel, tackled in any depth.

I'm afraid that unless you work for the beeb or one of the listed camera manufactures they won't give you the passwords. :(

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Dave, it's a bit more than icing on the cake...getting an extra 3 stops of exposure range combined with achieving a convincing film look with no post production just by tweaking the camera settings.

 

You see, I just don't believe that after shooting eight HD features.

 

After playing around a lot with the menu for each project, I've come full circle back to doing very little in camera because it just doesn't necessarily improve the picture or make it more "film-like". Progressive-scan, frame rate and shutter speed have a more dramatic impact on the "film look" than things like Knee, Black Stretch or the Color Matrix. Remember, films don't have one look either, so the notion that making the camera more low-contrast is somehow more "film-like" ignores higher-contrast film formats like color reversal or skip-bleach or cross-processed film.

 

People who make claims that they've discovered some secret, magic formula of camera settings tend to be marketing themselves as having something the other guy doesn't.

 

If you can just get an extra three stops of exposure range just by changing the camera settings, then why isn't that the factory default setting?

 

You can certainly use knee and black gamma functions to pull more information into the high and low ends, but you also get things like noise or odd artifacts. Knee adjustments are probably the most useful tool but I question some of the playing around with Black Gamma that some people do.

 

I'm not saying that Gamma controls aren't useful -- they help in the DVX100 for example -- but they aren't that hard to figure out either.

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David, thats the beauty of Alans research. His settings aim to give the maximum dynamic range, filmlike highlight roll off, minimal artefacts/noise etc as possible. He's done a lot of research into the way film looks during movement. A big part of Alans settings, as MDO pointed out, is to replicate the frequency response of film, and therefore reduce the 'judder' that usually comes from straight progressive video with no tweaking due to the way the human eye perceives motion.

 

Alans can set up a camera to replictae whatever you need it to. But his base settings aim to replicate neg film, as well as giving as much range as possible so the picture can be worked with in post. Processes such as skip bleach are a process after shooting has taken place as you know. As such Alans settings are ideal for this kind of effect replication in post as it should be. Since the maximum dynamic range is available that the camera is capable of, the skip-bleach effect can be tweaked to perfection rather than being a hit and miss affair should the effect be programmed into the cameras menus. Same goes for cross processing and colour reversal. While with film cameras you have to live with what those types of film stocks give you at the end of the day, with digital there is no point in performing such actions in camera. Why risk it? Better to let the camera give you as much picture info as possible and then tweak it later.

 

The default settings on most cameras are also far too sharp. Blow up default settings onto a larger screen and edge enhancement sticks out like a sore thumb. I prefer the picture to have minimal digital edge enhancement.

 

Now as to why the manufacturers do not place these settings in camera as default settings, some of them do to a degree. The film gamma settings for filmout on a Varicam for example, the FLM gamma settings on the XDCAMs etc. They go a long way towards this. Now Alans settings will look very flat. A camera manufacturer generally wants their camera to look colourful, very sharp and bold. So many of the default settings on cameras are set waaay too high. If you want edge enhancement it is better to do this in post too where you will have a much more precise control over the line widths etc.

 

Now while it is possible for people to try messing around with the setting themselves, what guys like Alan Roberts do is much more precise and in depth, and is the result of years of specific research into exactly what they are doing. It can take 2 days or so to acheive the final settings on an unfamiliar camera with all the relevant test equipment, signals, and colour charts to work from. What Alan does is precisely measured.

 

Its a testement to his work that the BBC uses his settings as default, and believe me, the Beeb have the absolute highest standards when it comes to camera setup.

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I just have a problem with people borrowing someone else's camera settings without figuring out what they do themselves -- it gives the illusion that this is some mysterious technology that only the wizards on high can understand.

 

If you can get the camera image the way you need it to look by adjusting the settings, who's to say that your settings are "wrong"?

 

Also, the settings that are optimal for a color neg look for TV broadcast aren't the same that might look best in a transfer out to film. Playing around too much with the black gamma, gamma, and knee often introduces noise and other artifacts that become visible in the film out. There are limits to getting the camera to capture an image with a lot of dynamic range -- at some point, you have to work within its limitations and LIGHT and expose for the necessary detail rather than stretch and squash the signal like taffy and expect it to come out artifact-free.

 

I'm sure Alans settings are excellent, but anyone who has played with an F900 knows that many settings can be shifted up or down by quite a bit before the create visible changes in the image. So there's nothing magic about one specific number when it lies on a scale of 200 degrees of adjustment. Plus scene content plays a factor. Even color neg doesn't have one single contrast -- there's low-con neg stocks, you can push-process neg, even overexposing and printing down changes the apparent contrast.

 

I just think people should get their hands dirty and create their own settings rather than take someone else's wholesale without understanding what it's doing to the signal.

 

It's like those people who say "I'm using a 1/2 Black ProMist because I read that it will give me a film look" without understanding why some people think that, so they can question the logic of it. They just follow the advice blindly.

 

I've shot enough HD to see random artifacts pop up that has caused me to consider turning more and more features off that cause these artifacts, like the ITU-709 preset, Black Gamma, etc. Basically it's taught me that there are always consequences when working with such a color subsampled and compressed format as HDCAM -- you rob Peter to pay Paul in trying to force the signal to behave more like color neg, and sometimes you are better off working within its limitations rather than pushing the limits of the camera.

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Certainly one should make an effort to understand exactly what the settings are doing. But it is not an easy thing for someone without the right background to try and replicate what somebody who has made it their function in life to research these sorts of settings.

 

People may want to create their own looks for the camera. But it helps to know that the camera has the best baseline from which to work from as possible. At least then, depending on what you have asked the engineer to do, you will have one setting that you know makes you happy and works in the majority of everyday situations.

 

Yes, lighting is a big factor. But I might add that even here there are cinematographers who like to shoot in natural light. and with landscape shots, and places where there is no avoiding the high contrast in the background, I know I would personally be happier knowing that my camera is going to cope as best as the hardware allows, not just by guessing a setting, but by *knowing* a setting/s.

 

I am with you totally on avoiding digital enhancements as much as possible. This is a very good reason why I use setting, again that were researched using the right equipment, that reduce such things.

 

Only just now I have been playing around with turning the knee functions off completely to see the effect. I may try working with it turned off for a while to let the highlights blow out more naturally as I found the knee circuits, more often than not, were muddying the highlights. At the same time I found out just how much more latitude in the highlights switching the camera to FLM gamma gave. Compared to the standard video style setting the skies would blow out completely, whereas the FLM gamma kept the nice blues and cloud definition while also giving me a tad more shadow detail.

 

But rather than being about how I think the picture looks aesthetically, this is more a case of trying to get the camera to give me as much as it can.

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I don't really disagree with any of that.

 

I just think that the concept of a "film look" is rather subjective, if not reductive, since movies have all sorts of looks. Therefore the best thing is to adjust the camera for the way you want the image to look, shoot the best video you can, and not obsess so much whether it technically fits some engineers idea of a film look. The ultimate point isn't to copy film mechanically but to shoot pictures that tell a story with the appropriate mood. For one project, that may mean deeper blacks or less color saturation; for another, a different look.

 

This is why I tend to think that it's the progressive-scan frame rate & shutter speed that is more critical to the "film look" (technically, not artistically) because those vary less from movie to movie, whereas contrast, saturation, etc. tend to be altered to suit the project.

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This is why I tend to think that it's the progressive-scan frame rate & shutter speed that is more critical to the "film look" (technically, not artistically) because those vary less from movie to movie, whereas contrast, saturation, etc. tend to be altered to suit the project.

 

Yes. This is the main point about Alan Roberts settings. Obtaining the filmlike motion is more than progressive scan because it also depends on the differences in the ways film handles the different frequencies compared to video.

 

One of the largets parts of Alans adjustments involve making the motion characteristic of progressive HD video more match that of film by adjusting the frequency handling. Thats how I understand it anyhow. :)

 

So, as you rightly point out, the motion characteristic is the biggest part of the 'filmlook'. But out of the box progressive video isn't quite the same in the way it appears to move. In this respect Alans settings are universally useful no matter what look one is going for. But this kind of adjustment really needs someone who knows what they are doing. The BBC White Papers by Alan are very informative on this very subject.

 

http://www.bbc.co.uk/rd/pubs/whp/whp053.shtml

http://www.bbc.co.uk/rd/pubs/whp/whp034.shtml

 

Warning, the second paper will make your head explode!

Edited by Simon Wyndham

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Guest MDO

Dave, believe me , the BBC is not after your cash. This stuff is well researched, very technical and it works. Simon has dealt with why the manufactures don't give you three extra stops out of the camera; the images look flat on a normal monitor, emulating what the film world incorrectly describe as "low contrast" stock.

 

As for Progressive scan having more effect, that is the starting point. No progressive scan, no film look, nomatter how you light, compose, tweak.

Sure, if you xfer interlaced video (hidef or whatever) via deinterlacing

programmes, to film, then project it, it will of course look like film.

BUT, for the smallscreen, it has to be Progressive or repeat field later. That is why this camera is so popular. All Alan Roberts has done is to take this (and many other cameras) another step closer to emulating a film-look, or to be specific, a "low contrast" camera neg stock, without the inherent over judderyness you get with shooting progressive.

 

Alan may be an engineer, but if you can't measure it you can't define it. Anything else is waffle, and I'm sure you would agree, this industry has more than its fair share of that.

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I read his reports, and there's a lot over my head, but some of his conclusions just don't jibe with practical reality, like HD and color neg really having about the same usable exposure range once you do all the calculations and look at the charts, etc.

 

It may work out that way on paper, but everyone knows that pro HD cameras like the F900 are incapable of matching the full exposure range of color neg, or else Sony et al. wouldn't be working so hard to make the next generation of HD cameras BETTER at dynamic range -- to match film more closely. If they already matched it, why bother?

 

He seems rather dismissive of the information at the extreme ends of the toe and shoulder of film as being "useless" (not his word but it's implied) -- which is he suggests that HD and film are similar in their exposure range -- but it's because of the way film gracefully rolls off into that "useless" (no information) area that makes it so useful compared to HD.

 

It's a very well thought out paper though and he is pretty thorough in his thinking on the subject, but occasionally he seems to come to conclusions that only an engineer would think up and not someone who actually works with film and HD all the time (perhaps he does too -- but then I'm surprised at some of his conclusions.) Obviously he's a lot smarter than me on the subject; all I've got to rely on is experience and my eyes to guide me. I'm not very good at math.

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Hi David,

 

Alan hangs out at the UK based DV Doctor forums in the A/V Hardware section.

http://forums.dvdoctor.net/

 

It would be well worth popping over there to ask him any questions you may have about his research and setups as I am sure that the information given will be of benefit to a good many people. He's a very approachable guy. Besides, it would be nice to have some more 'names' over there :)

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I just glanced over at the site. I'm always surprised to read people suggesting that if you want a film look, it's better to shoot in interlaced-scan and process it in post with Magic Bullet than to shoot in progressive-scan. Makes no sense to me; how can it be better to get a 25P look by shooting 50i instead of 25P in the first place?

 

I might be maxed out on the number of sites I can hang out on...

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Hi David,

 

Yes, there are quite a number of people who suggest that for reasons that I too am completely baffled by.

 

It is amazing how many people do not understand what the progressive mode on their cameras does. Of course these people are mostly general users rather than people who do this for a living.

 

I may ask Alan about those points regardless as a general enquiry as I too would be interested in how he accounts for those. But as you mentioned previously, much of the time we should try and live with the limitations and work within them rather than chasing something that may not be there.

 

Incidentally, does the F900 and the SDX have film style gamma settings? And do you ever use them?

Edited by Simon Wyndham

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