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Old June 13th, 2011, 06:51 PM   #241
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180 degree shutter angle needed?

Andy and Geoffrey suggested a 1/100th sec shutter to help with exposure in bright light... good advice in my opinion, since shooting at 50 fps (or 60) this gives us a 180 degree shutter angle. One is supposed to NEVER film with a greater than 180 degree shutter. 1/50th second shutter speed at 50 fps frame rate gives a shutter angle of 360 degrees, open all the time! This can cause smearing on fast moving objects, you would hardly ever want to use 1/25th shutter at 25fps would you? That would also be 360 degrees, only when pushed by lack of light might it be considered.

Conversely you can have a faster shutter than 1/100th but except for static scenes without much movement then as Geoffrey said, with an unnatural stuttery look.

You can of course break the 180 degree shutter rule but it helps to understand it before you do and I found these two articles with videos demonstrating the effect very good at demonstrating the various results.

180 Degree Shutter - Learn It, Live It, Love It

The 180s of Filmmaking: Part 2 The Most Commonly Broken Rule The Art & Business of Filmmaking & Photography
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Old June 13th, 2011, 10:50 PM   #242
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Re: The Panasonic TM900 Users Thread

I'm afraid I can't really agree with you about this Claire..... ( that's the the "NEVER film with a greater than 180 degree shutter" bit I mean)

What you say is true for 25P and 24P shooting, but at the higher "images per second" rates of 50i or 50P I don't think blur is the same problem than it would be with a 1/25th shutter in 25P.

A conventional 50 field per second interlaced video camera would always (historically) have used an exposure of 1/50th sec per field, which is essentially a 360 degree shutter. It was certainly the norm for the old standard definition TV tube cameras. ( 59.94 fields per sec. and approx. 1/60th sec per field shutter in U.S.A. of course)

I always try to shoot in 50P with a 1/50th shutter which will give traditional video motion analysis for 50P and when converted to 50i or, by losing every other frame, traditional film style motion analysis for 25P.

Having said that, I would agree that a 1/100th shutter is not too damaging to the motion, and will give actually the best matching "film" style motion for half speeding to 25P..... but other than that, I think 1/50th is best.

dave

Last edited by Dave Jervis; June 14th, 2011 at 01:52 PM. Reason: ....just clarified which bit I wasn't agreeing with.....
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Old June 14th, 2011, 09:39 AM   #243
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Re: The Panasonic TM900 Users Thread

Geoffrey and Claire

Thank you for this explanation, I was looking for such usefull information.
So a maximum of 1/100 s for the shutterspeed is recommended, when you film with 50 frames/second.
That means that you have to go fully manual with this camera and don't let the iris float.

It also means that you have to be carefull with a (long) panning shot, because the settings of your fixed shutterspeed and your fixed iris allow only a limited range of lightconditions.

Last edited by Anthony Schrijer; June 15th, 2011 at 01:20 AM.
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Old June 16th, 2011, 03:46 PM   #244
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Re: The Panasonic TM900 Users Thread

I love the footage I can capture with my TM900, but, after a couple of months with it, one thing is annoying me. Getting a decent representation of what I am shooting on the LCD. I am spoilt I guess by using a Sony EX1 every day, amazing LCD, which displays, exposure, colour and focus extremely accurately. I appreciate that the LCD on the TM900 is not particularly high res, but I do like to set LCDs up fairly tightly. I have tried many settings, and checked via HDMI on my two HD TVs. Still cant get it as close as I would like. The VF on the TM900 is way oversaturated, with an almost pastel shade to it. There is of course only brightness adjustment on the VF. Its fine for framing shots, but not a lot else. Also I find the two indoor mode white balance presets virtually useless, both produce a bit of a murky, turquise cast. I have tried to tweak all settings, still cant get it just so. Manual white balance is fine in daylight, but under decent artificial light it tends to produce oversaturated blues/ deep colours and undersaturated yellows and other light colours. Has anyone found a group of settings that they they are happy with ?
Feedback appreciated.
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Old June 19th, 2011, 05:55 AM   #245
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Re: The Panasonic TM900 Users Thread

Hi

Quote:
Originally Posted by Anthony Schrijer View Post
Geoffrey and Claire

Thank you for this explanation, I was looking for such usefull information.
So a maximum of 1/100 s for the shutterspeed is recommended, when you film with 50 frames/second.
That means that you have to go fully manual with this camera and don't let the iris float.

It also means that you have to be carefull with a (long) panning shot, because the settings of your fixed shutterspeed and your fixed iris allow only a limited range of lightconditions.
I'm not sure the 180 degree rule fully follows through to 1080/50p on modern HD video cameras. The idea of the rule is really for film where mechanics are involved (hence the degrees bit as that was to do with the shape of mechanical shutter wheels) and with modern cameras we talk about shutter speeds.

With modern film cameras using shutters rather than rotating discs the 180 degree rule was a nice nostalgic way of saying keep the shutter speed at twice the frame rate, a good rule with 24fps as using a fast shutter speed with such low frame rates causes us to stop perceiving motion and we start perceiving a series of static images shown one after the other, that is where the judder comes from. Using a slow shutter speed allows anything moving to blur in each frame which is essential with slow frame rates in order for us to be fooled into perceiving motion. The 180 degree rule is simply to help work around a limitation of film.

With 50 (or 60) progressive frames per second, it doesn't matter if each frame is frozen in time, as there are enough frames to flick past our eyes to allow us to still see motion. Factor in 100Hz TVs which interpolate extra frames, then they will do a much better job at that if each frame isn't blurred.

The only time you might need to worry about shutter speeds on modern 1080/50p cameras is where you know you are going to deliver at slow frame rates later, perhaps to the net at 30p, or you will convert down to 25p for the 'film effect', which ironically the film industry is trying to leave behind. Even then you could do that in post.

Fixing the shutter speed in bright conditions will mean the camera has to close the iris further than it otherwise might which means it is operating out of the sweet spot of the optics.

Personally I've seen no issues at all with high shutter rates on 50p, movement is still fluid and perfectly natural. Why shoot in HD at 50 or 60 progressive frames a second than allow each frame to blur using the 180 degree rule that was for mechanical film cameras running at 24fps? The big benefit of 50p is the ability to capture movement without that movement becoming blur and dropping in resolution due to interlacing, so it seems pointless to me imposing an outdated 180 degree rule just to re-introduce a drop in resolution when anything moves!

I think we need to embrace HD video and work to it's strengths, not shackle it with old rules that personally I can't see how they apply now.

Regards

Phil
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Old June 19th, 2011, 08:04 AM   #246
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Shutterspeed

As far as I understand, the shutter speed in a digital videocamera is managed electronically, there is no mechanical shutter.
A compilation:
The difference is that, rather than using a mechanical device, the shutter speed is adjusted by electronically varying the amount of time the CCD/CMOS is allowed to build a charge. The shutter speed does not affect the frame rate, which is completely separate and always stays according to your framerate-setting.
The main effect of higher shutter speeds is that individual frames appear sharper, due to the minimisation of motion blur. Motion blur occurs when the subject moves within the frame while the "shutter" is open. The less time the shutter is open (i.e. the faster the shutter speed), the less movement will take place.
The side-effect of higher shutter speeds is that movement appears more jerky. This is because motion blur tends to smooth consecutive frames together.

An example, the framerate is 50p, film time is 1 second, only a part of the frames are shown:

---------- stands for the time one frame exists, in this case 1/50 second.
x stands for the exposure time due to the shutter (opening) speed.
The gap between the frames is the time needed for the unloading of the image-sensor.

Shutter is closed:
---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- etcetera untill 50 frames.

If we use a shutterspeed of 1/500 second, then each frame will get light during 1/10 of it's existence.
x--------- x--------- x--------- x--------- x--------- x--------- x--------- x--------- etcetera untill 50 frames.

If we use a shutterspeed of 1/100 second, then each frame will get light during 1/2 of it's existence.
xxxxx----- xxxxx----- xxxxx----- xxxxx----- xxxxx----- xxxxx----- xxxxx----- etcetera untill 50 frames.

If we use a shutterspeed of 1/50 second, then each frame will get light during 1/1 of it's existence.
xxxxxxxxxx xxxxxxxxxx xxxxxxxxxx xxxxxxxxxx xxxxxxxxxx xxxxxxxxxx etcetera untill 50 frames.

That means, in principal, that de slowest shutterspeed, for a framerate setting of 50p, is 1/50 second, because you can not expose a frame longer than the existence of the frame itself.
In some camera's it is possible for the "shutter" to be open for multiple frames, the shutter speed can be set as low as 1/5 second; accumulating light across 10 frames (at a frame rate of 50 frames per second).

Last edited by Anthony Schrijer; June 19th, 2011 at 09:14 AM.
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Old June 19th, 2011, 07:22 PM   #247
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Re: The Panasonic TM900 Users Thread

I don't have any great TM900 footage of fast shutter speeds on fast moving objects, but I did dig up a brief clip shot with an XHA1 of running water using I believe 1/250 or 1/500 shutter speed. Other than compression artifacts due to HDV compression, what I see is droplets suspended in time as one would expect from a fast shutter speed.


For this piece, this is the exact effect I wanted, so I used fast shutter for artistic reasons. I wish would have had 60fps HD, but you use what you have (or had in 2008).
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Old June 19th, 2011, 08:37 PM   #248
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Re: The Panasonic TM900 Users Thread

Decided to attempt similar footage with the TM-900, the best my kitchen sink and two high powered LED flashlights could afford! Here's water at 1/30; 1/60; 1/100; 1/250; and 1/500 on the TM-900. I kept the iris constant on all shots and varied gain to try and achieve correct exposure, with varying success.:


So, as I look at these two very different digital camera examples, the faster shutter increasingly freezes the action in each frame and breaks down the blurred stream of water in the slower frames into individual droplets in the faster shutter speeds. I don't see anything unexpected or the image otherwise marred by the faster shutter. A "strobing" effect may be desirable in some situations if you're going for a certain look.

Last edited by Roger Shealy; June 20th, 2011 at 04:56 AM.
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Old June 20th, 2011, 07:33 AM   #249
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Re: The Panasonic TM900 Users Thread

@Roger

Thank you for your "practical" clips.
Your demonstration corresponds with the theory ...
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Old June 20th, 2011, 05:05 PM   #250
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Re: The Panasonic TM900 Users Thread

I love it when theory and reality mesh!

Here's a great piece on how cinema is adapting to the capabilities of the digital medium and the lack of mechanical shutters (someone else posted this on DVinfo a while back):

http://www.youtube.com/watch?v=NkWLZy7gbLg

Last edited by Roger Shealy; June 21st, 2011 at 12:07 PM.
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Old June 21st, 2011, 08:01 AM   #251
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Re: The Panasonic TM900 Users Thread

@Roger

Rather not, what will the next Panasonic camera be if the designers theories do not deliver what is expected ... poor us.

The clip nicely explains why I never will use a lesser framerate than the maximum; the 50p is the reason why I have bought the Panasonic HDC 900, together with the great image stabilization of course.
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Old June 21st, 2011, 10:43 PM   #252
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Re: The Panasonic TM900 Users Thread

I agree to an extent, and 50P was one of the main reasons I bought my TM700, but I believe it's wise to think about fast shutter speeds and high frame rates as two different things. I notice in the clip that Douglas Trumbull specifically makes the point that his high frame rate system captures all of time (effectively a 360degree shutter)..... so I assume that means 120fps uses a 1/120th shutter speed.

I am not saying you should never use a high shutter speed, just that it changes the nature of the perception of motion. Looking at Roger's water fountain test, it is clearly identifiable as a water fountain at 1/30th and 1/60th shutter but becomes a more abstract set of sparkles at the higher shutter speeds.... so much so that you could almost convince yourself you are looking down at a puddle in the rain. It really all depends on what you are trying to achieve.

The early specifications of the three new 1/3" 3 chip cameras from Panasonic suggest they use the traditional range of frame rates (1080 at 25p, 50i, 24p, 60i etc.). Disappointing.....

dave
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Old June 30th, 2011, 03:56 PM   #253
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Re: The Panasonic TM900 Users Thread

I am new to this forum, but I have read all the postings on this thread - some of them more than once. I am also new to videography, having yet to buy my first camcorder. However, I am an intermediate-level amateur DSLR photographer (Nikon D200) and have been doing 35mm and/or DSLR photography for the past 50 years. What I'm fairly good at is composition, color, and light, and the interrelationships between shutter speed, lens aperture, and film or sensor speed, also white balance. But I know nothing about the "mechanics" of videography, and am trying to learn about the interrelationships between shutter speed, frame speed, gain, resolution, format, etc.

I've decided that now is the time to jump in. I plan to buy a camcorder in July and practice on it for at least four months before making a six-week trip to equatorial Africa, where I will be in a village with no electricity. Because I want to do serious filming, I'm seriously considering buying the TM900. I recognize this is a fairly sophisticated camcorder (and fairly expensive), and I'm wondering what experienced videographers think about someone like me taking on the TM900 as my first videocam.

Let me tell you why this camcorder appeals to me, based on what I've read here and in the Users' Manual):
- Small size and light weight
- Excellent(?) Leica lens
- Good zoom characteristics
- EVF - essential for my poor eyes in bright sunlight
- Appears to be able to take a good wide angle adapter - desirable for those group shots as well as panoramic ones
- Good marks for low-light situations
- Excellent image stabilization
- Will operate with a 64GB Ckass 4 SDXC card (Can be bought for about $110)
- Reasonably decent still picture capability

My biggest concerns are: (I realize some go beyond this particular camcorder)
- Power - Is there a TM900 external charger available yet? (I could hook it up to a solar-powered charger or drive 25km to the nearest electricity source.)
- Storage - I'll have to resolve the best way to back up my files while in the bush
- Understanding AVCHD (HA/HG/HX/HE) vs. 1080/60p, when to use each, and why

I have dozens of questions, but I'll continue to try to find answers to most of them and will limit myself to two here.
1) Am I biting off more than I can chew by buying this sophisticated machine?
2) Can anyone direct me to a site that explains the difference between AVCHD and 1080/60p and when I should use each? (I have been searching through other DVInfo threads.)

Thanks very much for any help you can provide. I hope I haven't bored all you experienced, professional videographers, but I have found this discussion forum very educational, and I appreciate all the effort that you put into it.
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Old July 1st, 2011, 02:28 AM   #254
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Re: The Panasonic TM900 Users Thread

Hi George and welcome!

1. No, if you ever get daunted just press the iAuto button and let the cam do all the work! You won't get the best results that way (especially regarding exposure) but you'll soon learn your way around the menus and get skills in manual modes while having fun learning.

2. 1080p50 (or 1080p60 in NTSC countries) is a bit of an awkward animal to edit with many NLEs as it falls outside the "rules" or normal AVCHD being both higher in bit rate (28Mbps as opposed to the 24Mbps max AVCHD that is allowed) and of course is double the normal frame rate. I (and many others) still use this new format because on the TM900 it gives razor sharp 1080p and lovely smooth motion, especially if used for slow motion effects in post. However, few NLEs currently handle it (Vegas does, and Edius) and you'll need a pretty recent decent spec Windows box to handle the files. I've not got very far (mainly because of time/work pressures) in experimenting with getting those 1080p50 files to be editable on my Mac systems in Final Cut.

AVCHD files give a less impressive result on the TM900 (still pretty good) I think partly because Panasonic only went with 17Mbps data rate for their 1080p30 (or 1080p25) setting, not the maximum allowed (24Mbps), as used on the latest prosumer Sony cams like the CX700 (I believe from memory).

Got to go out but hope that gets you going!
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Old July 1st, 2011, 04:49 PM   #255
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Re: The Panasonic TM900 Users Thread

Thanks, Andy. That's a great start. I'm going to get the TM900. If I bite off more than I can chew, then I'll just chew a little bit longer. I'm hoping I can wean myself from the iAuto button ASAP, since I like to decide for myself what shooting compromises I'm prepared to make.

The biggest exposure challenge in Africa will be, I think, capturing very dark faces in bright daylight conditions. I could do exposure bracketing on my D200 and quickly adjust if I had to. I suspect that's more difficult with motion photography.

Another challenge, I suspect, will be in capturing outdoor sound (music, speaking, birds/animals, etc.) in breezy or windy conditions. I will get an external mic. and a deadcat (I love that term) based on what I've read elsewhere in this thread.

And, as I mentioned previously, backup storage is going to present a challenge. I will need something with high capacity and low power consumption. I'm thinking of an inexpensive netbook coupled with an external drive that powers off the USB only, since I will be away from reliable, continuous power for six weeks.

I'm wondering how others may have solved these problems.

And thanks for clarifying fps for me. I'm still confused as to how bit rate fits into the equation (except, of course, to guess that faster is better). Does it affect image quality, or is quality purely a function of resolution? And does bit rate affect file size? Still a puzzlement to me.

I won't be offended if anybody suggests I go to a different thread with these questions. I do realize that they are not specific to the TM900. But I'm confident I'll have more specific questions once I get my hands on the beast!

Thanks again.
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