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Old June 26th, 2003, 06:06 PM   #46
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<<<-- Originally posted by Paul Mogg : In response to Steve's question, what it looks like is happening to me is that if I set the shutter to 1/30th, then go to lock iris to a setting it stays at 1/30th until there until the camera hits conditions that it determins require it to speed up the shutter. -->


I'm not trying to set a shutter speed.

I'm just wanting to know the read-out when you push the S/A button ONCE and TWICE.

I'm wondering if the speed stays at 1/60th until you get to f22. If it does, then by using an ND filter one should never have the speed move higher than 1/60th. Likewise, with AGC on -- I'm hoping the speed will stay at 1/60th as long as you keep the iris above F2.

This means that by adding light or using ND filter(s) there is no need to lock shutter-speed. It will safely stay at 1/60th.

Since neither speed or iris has been locked you are free to use the Exposure Control to trim the Auto-Iris -- and to lock it.


<-- Also, as I said before, my shooting so far leads me to believe that 1/30th is the ideal speed for the shutter on this camera, which gets rid of the jitter problems, not 1/60th as some are saying. -->>>

I believe you, but technically the correct shutter-speed is one-half the duration of a frame at 30fps. Thus 1/60th is one-half of 1/30th S. It should be the same as the DVX100: 1/48th is one-half of 1/24th S at 24fps.

What you (and I call "jitter") others call a film-look. You can get rid of it by using 1/30th -- but I expect I'll find it too blurry.
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Old June 26th, 2003, 06:10 PM   #47
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<<<-- Originally posted by Michael Pappas : Steve, when do you think you might be getting the camera? I'm hoping there will be good enough work arounds to control the image. -->>>

Next week when either the next load arrives or the ones at the show in LA get back to NJ.

Which is OK timing because I've got a Sanyo Z1 projector and a 1.42GHz DP from Apple. So I'll have FCP 4 ready to edit HD10 footage.
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Old June 26th, 2003, 06:38 PM   #48
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<<<-- Originally posted by Paul Mogg : In response to Steve's question, what it looks like is happening to me is that if I set the shutter to 1/30th, then go to lock iris to a setting it stays at 1/30th until there until the camera hits conditions that it determins require it to speed up the shutter.
Also, as I said before, my shooting so far leads me to believe that 1/30th is the ideal speed for the shutter on this camera, which gets rid of the jitter problems, not 1/60th as some are saying. -->>>

I've never really paid attention to that stuff, I usually set stuff based on how it looks on my NTSC monitor. I'm probably irritating a lot of people out there who rely on the tech stuff, but my results are good. This is with my soon-to-be-EXL-1. (har har.)

I'm psyched! I hope to get it for the weekend.

heath
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Old June 26th, 2003, 06:44 PM   #49
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1/30th, not 1/60th may be the best speed. Film is 24 fps, with 180 deg. shutter the speed is 1/48th. Larger shutter opening looks fine -- 225 deg. open shutter is equivalent to 1/38 sec. shutter. 1/30th lies in between. 1/30th deg. shutter will give you 2x more light sensitivity than 1/60th deg. shutter. There may be some kind of inherent design deficiency in the camera that makes the image jitter. If 1/30th looks better than 1/60th, then this may be the appropriate shutter speed to use.
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Old June 26th, 2003, 06:45 PM   #50
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<<<-- Originally posted by Joseph George : 1/30th, not 1/60th may be the best speed. Film is 24 fps, with 180 deg. shutter the speed is 1/48th. Larger shutter opening looks fine -- 225 deg. open shutter is equivalent to 1/38 sec. shutter. 1/30th lies in between. 1/30th deg. shutter will give you 2x more light sensitivity than 1/60th deg. shutter. There may be some kind of inherent design deficiency in the camera that makes the image jitter. If 1/30th looks better than 1/60th, then this may be the appropriate shutter speed to use. -->>>

I wonder if I'm going to have to get into the tech part since I am dealing with 30P, instead of 60i.

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Old June 26th, 2003, 06:57 PM   #51
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just see if 1/30 or 1/60 sec. looks better
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Old June 26th, 2003, 09:26 PM   #52
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<<<-- Film is 24 fps, with 180 deg. shutter the speed is 1/48th. -->>>

The math is: 24fps allows an exposure of up to 1/24th S. With a 180 shutter the exposure is 1/48th S.


30fps allows an exposure of up to 1/30th S. So a shutter speed of 1/30th S is certainly OK.

But following the same relationship as film at a 180 shutter -- and the same relationship as the DVX100 at 30fps -- the appropriate exposure is 1/60th S.

So you have a choice: use 1/60th S which the camera defaults to AND follow the "rules" on panning and zooming

OR

set at 1/30th which will let you not worry about the rules but which will have two side effects:

1. The image will lose detail on movement because of blur

2. By setting the speed to 1/30th S you totally lose the ability to adjust exposure. This leaves you helpless to adjust exposure in high contrast situations.

It's your choice. But JVC and Panasonic cameras default to 1/60th S at 30fps for good reason.

Lastly, there is the real possibility that for some folks 30fps just won't work. And I'd bet many of those never shot film.

On the other hand, some folks (likely those who have shot film) will love the look of 30fps at 1/60th. I love 720p60, but was blown away looking at DVX100 material blown to 6 feet. It really did look like film!
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Old June 28th, 2003, 07:58 AM   #53
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I said that I liked the 1/30th shutter speed look on this camera purely based on my personal tastes, not on any technical basis. I enjoy the look of film very much, and to me this gives something that looks very close to film motion and film motion blur. I'm also familiar with the (supposed) 30p look of the XL1 and GL1 in 'frame mode", and I can tell you that the JVC's motion is much much more natural and smooth than "frame mode", which I found to give a very stroboscopic effect when I used it. In 1/30th shutter speed mode on the JVC I find I'm only losing detail (if that's what you call it) in the motion blurred parts of a scene, which is how it should be.
Steve, a quick note, in one of your last postings you seemed to suggest that you could use the "Exposure" control while in S/A mode, to dial down the exposure when having the iris or shutter locked. This may have been my misunderstanding, but just to clarify.....Adjustments to the "Exposure" control on the JVC are only available on this camera when it's in AE mode (which lets you select the "spotlight/snow...etc" modes)). It is NOT available in S/A mode, (which let's you lock EITHER the shutter OR the Iris, but not both at the same time). The S/A and AE modes are mutualy exclusive in all ways, so it is not possible to access the "Exposure" control in S/A mode.
As someone mentioned, in the camera menus there is an "AGC ON/OFF" control that can be set. I have tried this both on and off and it doesn't seem to effect the cameras automatic adjustment of Iris if it's either on or off, so I haven't a clue right now what it IS doing.
As far as testing under exactly what changes in lighting conditions the camera is programmed to make adjustmets to the shutter speed, someone needs to do some accurate/controlled tests on this, and I don't ahve time to do it right now unfortunately.
I would suggest emailing Ken Freed at JVC and ask him to get an accurate run-down from his engineers as to what exactly this camera is programmed to do in that regard, they surely must know right? Then you could use you could use your ND filters in a more informed way rather than guessing when the camera is going to change the shutter speed.
Personally I think this camera will be reasonably controllable using ND filters to control light input and locking the shutter speed (which DOES stay locked), or enough to do most tasks in bright lighting conditions, which is where you will encounter problems. I bought 3 ND filters for it which arrived today, and plan to use at least one at this wedding I'm filming, so I'll let you know how it goes.
One last thing, when I talked about the "Jitters" on this camera previously, I was not reffering to the natural motion of the video when the camera is locked down, but to the 'Stuttering" effect that was noticed by many when panning or tilting the camera...and this is what seems to be cured when you use 1/30th shutter speed. But again, I haven't had time to do any rigorous tests.

Thanks
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