high speed camera

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Henrik Schurmann
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Joined: May 20 1999

Hi
I need to make a movie with slow motion effects. I have tried, without luck, to search the net for video cameraes capable of doing this. The posibility to make slowmotion effect in premiere is not good enough, either is the JVC model that includes this feature.
I need a camera that is able to take up to (at least) 100 frames/sec in DV quality (720x576).
I know that it is probably going to be expensive but what the h.. If anybody know anything please let me know, and please give me www's if you know where to find additional info.

Henrik Schurmann

plettner
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Joined: Sep 6 1999

I wouldn't mind finding out the same info. I use MSPro 5.2 and find that slow motion works OK if the subject doesn't move too quickly. If I film everything steady enough, it works OK. In fast-moving action shots though, the slow motion video comes out too "choppy". Please help!!!

miker
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Joined: Apr 27 1999

If you capture full res at 50 fields/sec with a high shutter speed, you should be able to seperate out the fields to frames. You should be able to then convert this to around 10fps which should still look okay -- that'd give you 1/5 of the original speed.

tom hardwick
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Joined: Apr 8 1999

My remote control that comes with the TRV900E replays normally recorded footage with a beautiful fluidity in slow motion.

It means capturing to the PC via the S cable rather than i-link, but the slow motion so produced is far better than Premiere 5,2 gives me, and there's no rendering time involved.

Try it and be pleasantly surprised.

tom.

Henrik Schurmann
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Joined: May 20 1999

Thanks for the answers.
I still think that real slowmo produced by recording 100 frames pr sec gives better results. The slowmotion option in Premiere is ok in some situations but if you fx have a bird in flight (with fast wing beats) it dosn't work

Henrik

tom hardwick
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Joined: Apr 8 1999

Of course you're right, Henrik. The only real way to get the beauty into slowmotion is to take far more pictures per second, and domestic video cameras (that have to frame sync with our 50Hz tvs) are stuck with 25 fps. The new JVC breaks away from this limitation, but not without hugh tradeoffs in my opinion.

In Super8 days my Canon shot 62fps for a projection speed of 18fps, giving a very good slo mo. The Beaulieu managed 80 fps, and was unsurpassed.

Here at work we use a high speed 16mm film camera for airbag tests, and this can run at 2000 fps. When the film's up to speed the camera literally screams as it pulls the film through.

Of course at this franme rate there's no intermittant motion involved. The film travels through the gate at a constant linear speed, and the image is "wrapped" onto the film in the curved gate by a spinning prism located just behind the exit pupil. Needs lots of light at the high shutter speeds involved!

tom.

martynj
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Joined: Sep 17 1999

Hi
I`ve got a Panasonic nvd33, its so tiny and absalutly great performance.You can manually set the shutter speed yourself. which can go upto 8000 fps !!BUT bear in mind with ANY camcorder when you select a faster shutter speed the picture goes darker, but 100 is a piece of pi..
martynj

tom hardwick
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Joined: Apr 8 1999

A common mistake is to confuse frames per second with shutter speeds per frame, Martyn.

To get slow motion you have to shoot with a high speed camera - ie a camera that takes more frames/sec than you're going to project at. Simply upping the shutter speed will not do this - as you say it'll make the picture darker unless you
a)increase the aperture, or
b)increase the electronic gain, or
c)increase the lighting.

tom.

Henrik Schurmann
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Joined: May 20 1999

Tanks again for the answers
Tom you seems to know a lot about this subject. I wondered how they make those nice slowmotion pictures that you often see in sport programs. Why are they not stuck with 25 fps? I geuss that thy just have some exstremely expensive equipment but if you can by it for money it cant be a limitation in the 50 Hz television.

Martynj I think you have mixed things up a bit here. I am sure that you are talking about shutter speed, but that is not the same as frames per second (fps). The shutter speed tells you how much time light is allowed to reach the CCD for each frame So when shutter speed is 8000 it means that light is only allowed in 1/8000 sec. However fps tells you how many pictures you have each second and thats another thing. If you have more than 25 fps you create a slowmotion effect when the film is played back at 25 fps

Henrik

Alan Roberts at work
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Joined: May 6 1999

Henrick, you've asked the right question. You're taliing of image rate not exposure time.

The slo-mo cameras you've seen used on tv come in two flavours:

1 - a conventional camera run at 25 frames/second (actually, it's better to think of the field rate, 50Hz, because that's the image rate for motion portrayal). The shutter is set to something short, maybe 1/500 secd or less. The pictures are recorded and played back from a professional recorder at lower than normal speed. Machines such as DigiBeta can easily play back video at almost any speed, it's only a matter of setting the "Jog" speed". This gives a regular sequence of images from the tape, one field at a time, each sharp, played out several times. So you get sharp pictures and "jagged" motion, it jumps.

2 - a genuine slo-mo camera. There are currently not many of these about, only two types to my knowledge.

2a - Sony use a converted HDTV camera (1125/60Hz) which runs at 525/180 (i.e. 3 times field speed) and a modified HDTV recorder. The recording goes at 180 Hz, and the replay is at 60Hz. Clearly this is aimed at the US market, but it has been used successfully in Europe although it is expensive. The recorder looks like a conventional broadcast machine and has all the usual features.

2b - Philips have a special. It runs at 50Hz field rate, but has three separate outputs. Each output is a fully normal 625/50 signal, but taken from, respectively, the top middle and bottom third of the 20mS normal field interval. So, each output looks normal but with a 6.7mS shutter. The three outputs are routed simultaneously to a digital video store (array of hard drives), and can be replayed rfrom the store while still recording. But the clever bit is that the store can replay all three recordings, interleaved, at 1/3 normal speed. The images then have the correct shutter time for that speed and motion is perfectly smooth. That output can also be recorded onto tape and replayed at other speeds just as any other video sequence.

Hope that helped.

tom hardwick
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Joined: Apr 8 1999

Fascinating, AR, thankyou.
tom.

Henrik Schurmann
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Joined: May 20 1999

Thank you Alan, finally the kind of information I was looking for.

Still I dont undenstand why is is so hard to make a camcorder that is not too expensive. I understand that for DV everything has to work faster (compression and so on) if you record 100 fields pr sec. Also the CCD have to handle the data faster, but still I am not quit sure I understand where the limitations come from.

I have a Canon XL1 and it has a posibility to record in frame mode, that is the picture is not devided into fields. Would it have been technologically difficult (expensive) for Canon to have have included a option of say 50, 75, 100 frames pr second in the camera.

Henrik

Alan Roberts at work
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Joined: May 6 1999

Henrick, yes, it would have been difficult to offer higher field rates. There are several problems:

1 - the ccd and all the scan electronics have to work at the higher speeds. In the case of the Philips system I described, they got round that by parallel processing, the camera makes three outputs at the same time, so it contains three identical sets of video circuitry, so costs three times as much. In the case of the Sony system, the camera works three times as fast, which, surprise surprise, costs three times as much. The digital processing in DV and broadcast cameras runs at a clock rate of 13.5MHz, tripling that takes you into rather different areas of electronis, certainly rather expensive for domestic kit.

2 - the tape transport. In the case of the Sony system, the tape moves at three time normal speed, and the drum has to rotate at three times speed, but the mechanics also has to be able tyo work at normal speeds. That places rather hard constraints on the electro-mechanical system design and requires special tape formulation that can hold the correct curvature to the head drum at a wide range of speeds. Again, expensive. The Philips system gets round that by having an array of hard drives capable of handling four separate uncompressed digital video signals (216MB/s each) and recording 60 minutes of each. Three channels for record, one for replay. That's quite a stack of hardware.

There's no easy way to do this, except on film, high speed film cameras are fairly common, but you have to wait for film development, so they're no good for sport, but brilliant for wild-life (there are specialised units in both Oxford and Cambridge, as well as the BBC in Bristol who regularly use film to get slo-mo or macro pictures).

I think you should forget about a domestic version for some time, Sorry

Henrik Schurmann
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Joined: May 20 1999

Thank you very much Alan.
Now that I know how difficult it is to make such a camera I will wait for tecnology to solve it. In the meantime I will take a close look at the high speed film cameras, as I am a wildlife photographer, and need the slo-mo effect from time to time.

Henrik

Tunni
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Joined: Aug 9 1999

Alan is right again! I use super slo mo cameras every week, as one of the handheld ringside cameras for live boxing on Sky TV.

The main camera is a Sony 9000 and I've recently been using the Philips. They are VERY expensive, even to hire.

In the past I've used a bolex 16mm high speed camera for slo mo, It still leaves video standing on quality, but for cost and ease of use, nothing touches DV.

regards
Tunni

Mystic1
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Joined: Jun 17 1999

Just like to add one point about shutter speeds.
I also capture slow-mo video by using the remote control and it gives me a more than acceptable result.
However it will make a difference to the individual frames if the shutter speed is fast because as a camera pans for example each frame will be effectively frozen instead of the blur induced by a slower shutter and smaller aperture.Using the faster shutter speed will make each frame appear sharper and cleaner to the eye. At least that is what I have found. The remote control however should be tried by all who have it though, because it really is effective and saves "buckets" of rendering time.
Cheers, Neil.

Henrik Schurmann
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Joined: May 20 1999

Hi Niell
I am not sure I understand you. How is the remote involved? Is it used to play the tape in slow-mo so you capture slow-mo directly?

Cheers Henrik

Mystic1
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Joined: Jun 17 1999

Henrik, if you use the control that are on the video camera then, if I remember right then you will only get FF,RW and pause.
Most modern Camcorders come with a remote control and if you look at this, (I don't know if you already have a camcorder), you should see all the functions i.e. FF,RW pause , but on my Sony it also gives the option of Pause, Slow, and frame advance. Now Digital tape gives a fantastic still frame and frame advance,but also by pressing the slow button , the tape speed drops by approx. 50% and will give a more than useable (although I am not sure if it would be suitable for your requirements) slow motion feature.Used with a fast shutter speed the definition of the individual frames should be extremely clear.
So now when I capture in MSPro or Premiere and I think that I will need a slo-motion sequence, I capture both normal and Slow.when it comes to putting them on the time-line I can still choose if I wan't either and also I can still slow down the already slowed down sequence if i need to.
I hope this helps, but why not pop into a local dealer and ask to try one out, it's your money so make them work for it!, Cheers, Neil.

[This message has been edited by Mystic1 (edited 11 October 1999).]

Alan Roberts at work
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Joined: May 6 1999

Nice one, Neil. That needs shouting about

Henrik Schurmann
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Joined: May 20 1999

Thanks Niell. I will try how it works and I am sure it is useable. However as already mentioned above I mostly do wildlife and if you want nice slow-mos of for example birds in flight it is not rearly good. The reason is that the wing beat freguency is too high and you may only have 6-8 frames to describe one wingbeat. So actualy I think that it will only work for me if I am recording at a higher frame rate.
Henrik

tom hardwick
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Joined: Apr 8 1999

Using the slo button on the remote works fine, but nothing's for free. The vertical resolution drops by half as the timeline makes individual frames out of each (half res) field.

The slo mo itself may disguise this resolution drop as long as the scene doesn't change from normal speed into slo mo without a cutaway. The beauty of slo mo film is that 1) resolution is maintained
2) The shutter speed per frame is upped automatically.
3) more frames per second mean you've more chance of capturing the exact "moment-in-time". With our domestic video cams we've really only got 25 fps whichever way you cut it.

tom.

Mystic1
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Joined: Jun 17 1999

But look at it honestly and say that we don't all have that pot of gold to spend! Sometimes we just have to use what we have got and use different techniques to get over the limitations.