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Leaning ENG cameras


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#1 james smyth

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Posted 19 December 2006 - 09:46 PM

Hello,

Some time ago I bought a Sony EVW-300 to take advantage of the large CCDs and picture quality to output straight to a DV deck. Though the camera has many functions that I am at a serious loss to understand. I've put every odd button and menu entry into Google and have come up empty. Most important things I've figured out through trial an error, but much remains a mystery (and the manual is impossible to find).

Does anyone know of any books that go over these topics? I've managed to find out the difference between PCM and AFM, but have yet to learn what H/SC phase is (the switch that goes from 0 to 180 does nothing as far as I can tell), I have no clue why the 'alarm' goes off randomly, or why I have to make my focus adjustments in two places (I thought my lens was busted till I noticed the focus adjuster at the base of the lens).

Thanks!
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#2 Michael Collier

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Posted 19 December 2006 - 10:31 PM

PCM- pulse width modulation. It makes audio not by actually modulating the output, but rather by changing the duty cycle of a quickly cycling clock, and then smoothing it out with a capacitor....its all electronic mumbo-jumbo.

AFM-not terribly sure the specifics, so I will hold comment until someone can clarify it. I think its audio frequency modulation, where the clock speed changes, not the duty cycle, to modulate the audio.

H/SC phase is a setting for the video output, there will be no visible difference, it only sets the way the color band is phased over the lumenance track in the video. Really unimportant to know unless you have to connect your camera to a video mixer or frame sync with other cameras/graphics. Set right, they should all cut propperly. Set wrong and you get a video timing glitch when you cut from one source to another.

The alarm....thats troubling. There are several sensors that check the tape tension, humidity, etc and if any of them get tripped you get a warning. I would check with the manufacturer to see what the alarm is (does it provide you with a number after the alarm...that would help them)

And no you shouldn't have to focus in two places. The ring nearest the camera is your macro/backfocus ring. You should have a set screw that tightens the ring so it doesn't turn, and a knob to release it so you can do macro shots. To backfocus it, get a focus chart (looks like someone traced a wheel with its spokes, then colored each triagle alternating black and white. iris all the way open, shutter down so you can see what your doing, zoom in and focus with the front barrel (the focus ring with distance markings). Then zoom out, you will notice the center of the circle go out of focus first. Loosen the screw and turn the backfocus ring until the focus chart goes back into focus (make the fuzzy circle in the center as small as possible) then tighten the screw down. Now when you depress the knob to turn the macro lens, you can focus much closer to the front element, but when you turn it back to its start position, it should snap into place. When backfocus is correct, you should be able to zoom in, focus and pull out while maintaining focus on that point. When the macro is rotated, or backfocus is incorrect, the image will fall out of focus if you zoom in or out.
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#3 james smyth

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Posted 19 December 2006 - 11:00 PM

The alarm....thats troubling. There are several sensors that check the tape tension, humidity, etc and if any of them get tripped you get a warning. I would check with the manufacturer to see what the alarm is (does it provide you with a number after the alarm...that would help them)


Well, I guess it could be connected with some of the errors it constantly throws at me. It always thinks that the tape is near the end (even when no tape is inserted) and records only ~10 seconds at a time (when I first got it, it no longer plays or records anything), it complains about humidity at the driest of locations, and 'slack' keeps popping up in the viewfinder, again, with no tape inserted.
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#4 Alessandro Machi

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Posted 21 December 2006 - 12:52 PM

Well, I guess it could be connected with some of the errors it constantly throws at me. It always thinks that the tape is near the end (even when no tape is inserted) and records only ~10 seconds at a time (when I first got it, it no longer plays or records anything), it complains about humidity at the driest of locations, and 'slack' keeps popping up in the viewfinder, again, with no tape inserted.


You do have to focus in two places when first getting started. Back focus is critical. Zoom lens out to it's widest position. It's most useful to do this with the f-stop wide open but not overexposed, increase your shutter speed if you are doing the back focus adjustment outdoors and want to avoid overexposing. In the wide mode, set your back focus to what you think is sharp.

Zoom in all the way and focus on something far away, preferably infinity. Now zoom out and see if the focus holds. If not, reset back focus while in the wide mode, zoom in again to something at infinity, then zoom out and see if the focus holds. After you think you've nailed the back focus, you can then find an object closer to you, zoom in, check focus, then zoom out to wide and see if that holds focus as well.

In theory you can try and do this test indoors, but I think the backfocus adjustment may not be as accurate when you switch to outdoors work since one isn't able to do the infinity focus setting indoors.

You probably should run tape when you do these adjustment and when finished playback the tape to see if you nailed the back focus adjustment. You have correct backfocus when the lens stays in focus from complete telephoto zooming out to complete wide angle.

As for the warning lights, usually there is something wrong with the camera when those lights come on.
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#5 Matthew Parnell

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Posted 06 January 2007 - 11:29 AM

Using a backfocus chart(siemens star) will give the best results in adjusting it.

Open your widest stop.
With about 5+m between the camera and the chart zoom into the centre of the star.
Focus until the blury circle in the centre of the star is at its smallest.
Zoom out.
Adjust your backfocus until blury circle of the star is at its smallest.
Repeat to check.

I was always taught to get into the habit of doing this before you start your shift.
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#6 Alessandro Machi

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Posted 09 January 2007 - 08:15 PM

I've heard of doing the backfocus check outside so one can actually focus to infinity, I've been advised that checking back focus in a medium sized room works effectively as well, and now you're saying using a chart.

The chart probably works the best but there isn't always time to use a chart.

Which is more reliable as an alternative method, infinity or in a medium sized room?
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#7 Sam Wells

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Posted 09 January 2007 - 09:31 PM

PCM- pulse width modulation. It makes audio not by actually modulating the output, but rather by changing the duty cycle of a quickly cycling clock, and then smoothing it out with a capacitor....its all electronic mumbo-jumbo.

AFM-not terribly sure the specifics, so I will hold comment until someone can clarify it. I think its audio frequency modulation, where the clock speed changes, not the duty cycle, to modulate the audio.


PCM are your linear audio tracks, AFM are you're embedded-in-the-video-signal FM tracks (this was called Beta HiFi on consumer Beta)

Horizontal/Subcarrier Phase is for syncing multiple cameras so scanning starts same time on each...

-Sam Wells
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#8 Brian Drysdale

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Posted 11 January 2007 - 09:52 AM

It doesn't matter if you do it indoors or outdoors, you set the Siemans star chart usually about 2 meters (6 ft) [although you can place it further away, it does get a bit small further than 4 meters], from the camera with the lens aperture wide open and set the backfocus. For wide angle lens you might have to use the chart a bit closer You can also measure the distance and check that the focus scale matches - just be aware that on ENG lenses focus marks measure from the front of the lens, not the image plane.

A correctly set up video lens won't have any problems focusing at infinity when the backfocus is set up using a chart.

On film lenses they use a collimator, which is set at infinity for setting the backfocus. Zeiss make a unit that uses infinity for setting backfocus video cameras, however, most people don't use these, they use a chart and both methods give good results.

With SD you only need to check the backfocus when changing lenses, so you shouldn't have any problems. Checking the backfocus at the beginning of the shooting day will cover you if you're using the same lens all day. You don't need to check the backfocus every time you go from indoors to outdoors.

However, on HD you have to much more aware of possible temperature changes, but that's getting more complex.
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