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24p and 180 degree shutter

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Bob Cole
24p and 180 degree shutter
on Oct 25, 2011 at 9:40:59 pm

Forgive my ignorance - these are basic questions that I've always just assumed I understood - until I realized that I don't.

John Sharaf has stated that it is important to implement a 180 degree shutter when shooting either 24p or 30p and seeking a "film look." (I hope I have quoted you correctly, John.)

I try to shoot interviews at a wide f/stop, but in many cases, I find that while there isn't enough light to use an ND1 setting, there is too much light to use a 180 degree shutter. So I have been turning the shutter on and using the shutter speed option, instead of the degree option, and choosing a shutter speed of, for example 1/125. I'm always a bit leery of playing with shutter speeds, though - especially with the many strange new energy-efficient lighting sources that are in the environment today.

On the other hand, sometimes a 180 degree shutter would mean that I have to use gain to get an adequate exposure.

Would someone please give me some guidance here? I'd like to know:

1. why the 180 degree shutter is so vital to the film look (is it just because the film cameras used it?), or whether choosing 24p alone is enough to give at least a partial "film look" while perhaps minimizing flicker?
2. whether there is any real difference between the "modes" on the EX1R, and if so, should I use the shutter or the speed setting. e.g., does 1/48 at 24fps = 180 degree shutter anyway?
3. when I need to use a wider f/stop, which shutter (or speed) settings are least problematic in a 60Hz country... ditto, 50Hz countries.

Thanks, and... be gentle.

Bob C
Sony EX1R


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john sharaf
Re: 24p and 180 degree shutter
on Oct 25, 2011 at 9:53:50 pm

Bob,

I believe when you refer to ND1 setting it is actually ND.9 or three stops of density. If this is too much light attenuation then the best solution is to use a .3 (one stop) or .6 (two stop) ND filter (usually mounted in a matte box). If you're using a modern camera like the EX1/3 (I think that's what you have) you could alternately use +6Db gain to "open up" a stop's worth of light.

Yes, the "filmlook" is a combination of motion similarities to an actual film camera accomplished by the 24fps (or 25fps in Europe) and a 180 degree shutter (1/48th @ 24, 1/50th @ 25). Of course in the real world of film the shutter is often adjusted from 172.5 (or even 144 for TV screens and computers) to 210 degrees (for a little extra exposure when necessary). Much more in either direction becomes an "effect" (a la the "skinny shutter" sometimes referred to now as the "Private Ryan" effect.

The advantage you have with the video camera is the "gain" control which effectively changes the ISO/ASA of the film by the flick of a switch, where as with film the same effect requires "pushing" or "pulling" the speed in processing. In both mediums however there are consequences in going to far in either direction. In film noise in push and contrast in pull. In video, noise in plus gain and highlight control in minus gain.

JS



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Michael Palmer
Re: 24p and 180 degree shutter
on Oct 26, 2011 at 1:34:44 pm

Now that John has given you a great answer and insight of what the shutter speed can do with motion similarities for a film look you may want to start exploring some picture profile settings that can soften the image slightly. Reducing the overall detail from these ultra sharp video cameras is also part of a good film look. The combination of motion blur and a saturated detail is what is expected from film. Motion blur is from camera movement and the shutter speed setting, image detail can be controlled by film stock or by advanced picture profile setting (on your video camera) and good lighting.

Good Luck
Michael Palmer


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Bob Cole
Re: 24p and 180 degree shutter
on Oct 26, 2011 at 2:12:47 pm

[Michael Palmer] "start exploring some picture profile settings"

Tell us more! I've just started exploring Picture Profiles - fascinating. There are quite a few blog posts on the subject online - do you have any recommendations as to where to start?

Another aspect of the 24p issue: most of our output is for the web. I assume that another benefit of shooting 24p as opposed to a higher framerate is that you can achieve a higher picture quality for a given data rate, if you have fewer frames to produce every second.

Thanks.

Bob C


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Michael Palmer
Re: 24p and 180 degree shutter
on Oct 26, 2011 at 2:44:46 pm

I stay away from telling anyone how to set PP's, but Alister Chapman was some good words and video on this topic.
http://www.xdcam-user.com/how-to-videos/

Contact me off line.

Good Luck
Michael Palmer


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Alan Okey
Re: 24p and 180 degree shutter
on Oct 26, 2011 at 3:24:42 pm

[Bob Cole] "I assume that another benefit of shooting 24p as opposed to a higher framerate is that you can achieve a higher picture quality for a given data rate, if you have fewer frames to produce every second."

You are correct. This is also true for DVD workflows. At a given bitrate, a lower frame rate will allow better quality per frame.


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john sharaf
Re: 24p and 180 degree shutter
on Oct 26, 2011 at 3:32:25 pm

Bob,

If "most of our output is for the web" then you should be shooting at 29.97fps. This preserves the progressive look and motion and is most friendly for compression algorithms that are in play for webcasting.

This is crucial information, and is one of the first things I discuss with my new clients when we start a project: what is the nature of the exhibition? The answer will determine our frame rate and gamma settings.

The difficulty in most cases is that they want theatrical, tv and internet. The fact is that very few (if any) are ever filmed out and exhibited on a large screen in the cinema, and that is one of the only cases where 24p is really appropriate. Another case would be to "mimic" what a film would look like (perhaps a satire) or to intercut with other 24fps material (like WW2 newsreels).

I'm afraid that you (and many others) are using 24p for the wrong reason, and principally because it is an available choice. Just like lens selection, what you focus on, iris setting, shutter speed and the like, these choices are best used when invoked for specific reasons.

I hate to be dogmatic, but I would generally propose that 24p be used only when you really wanted to shoot on film (and can't), or there's a strong possibility of filming-out to film for projection (or alternately as a source for digital projection) in a cinema setting.

If TV and the Web are your main outlets, the best choice is 30p (with 1/60th shutter) and finally if you want a "live" look like news or sports then 60p or 60i (shutter off).

Now the whole subject of cine gammas is another topic, and I had intended to continue on in this vein in my original reply but was distracted.

Making the video picture more "filmic" can also be accomplished by painting the picture. On some cameras this is done in a Picture Profile, in others by a combination of paint settings stored as a Scene File and is independent of your choice of frame rate. Color Correction in post can also be effective.

Again, it's important to know what your exhibition will be, as the gammas and color space for film-out, broadcast and the web are all different. If two outlets are expected, two versions with filmout gamma and broadcast gamma are usually created in the on-line finish.

The main distinction between video and film is films ability to reproduce a longer tonal range, usually referred to as Dynamic Range.
Whereas the latest video cameras have a latitude of as much as 8 stops, principally because of the use of aggressive knee and slope settings to control the highlights and extended S shaped gamma curves (often referred to as Cine gammas and/or HyperGammas); film and the latest Digital Cinema cameras can record in Log Curve Gammas that have as much as 14 stops of Dynamic Range.

These Log curves, S-Log for Sony and C-Log for Arri Alexa, require recording on 10-bit formats to survive the requisite post color correction without falling apart.

In addition these same cameras have internal Look Up Table generators (LUT) that can take the 14 stops and convert it to the HD Broadcast video standard (aka Rec 709) and retain the entire range and restore the color saturation that is removed by the Log curve. In this case what you have is a WYSIWYG picture that does not require color correction (but could be used if desired). This is the Holy Grail and eventually this capability will migrate to additional cameras in the Broadcast and Professional range (as it has already done in the Sony F3 with RGB444 upgrade).

In more typical cameras in the Sony and Panasonic lines there are Cine Gamma choices that (again like frame rate) mimic the tonality of some film stocks, which it is generally agreed (and for good reason) look better than the traditional linear gamma of video.

You'll notice that there are often choices of several or more of these Cine Gammas; some are designed for broadcast and limit the clip to 100%, others extend the highlights to 109% and generally the other choices are for scenes that are bright and scenes that are dark. It will be fairly obvious which is which by rolling through the settings when looking at these different scenes. Once you become familiar with the capabilities of each you can pick the most appropriate for use.

One caution is that if you are changing gammas, remember to reset it to normal or at least check it every time you start a new scene to make sure you're not shooting yourself in the foot with the wrong (inappropriate) setting.

Hope this helps!

JS



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Bob Cole
Re: 24p and 180 degree shutter
on Oct 27, 2011 at 12:18:22 pm

Thanks John. This is a clip-and-save.

Bob C


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Douglas Villalba
Re: 24p and 180 degree shutter
on Nov 22, 2011 at 9:09:51 pm

All of the above advise is good. However you mention flickering from room lights.
When ever your lights are other than sunlight or tungsten use 1/60 in the US.
One good reason to set angle instead of speed is that when you change frame rate lets say 24 fps at 180 degrees in speed it would be equal to 1/48. However if your frame rate is 30 fps at still 180 degrees, the speed now is equal to 1/60. 360 degrees is a full circle 180 degrees is half the circle. so if you were shooting slowmo at 60 fps at 180 degrees the actual speed would be 1/120 and that is how degrees maintain motion blur without going into the menu to change speed.
Confused yet?

Douglas Villalba

http://www.advertising-villa.com

info@dvtvproductions.com


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