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Sony VX2100 / PD170 / PDX10 Companion
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Old May 19th, 2005, 10:58 PM   #16
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Well, changing the "shutter speed" on the PD170 DOES change the exposure in a manner like a physical shutter would. If I increase the shutter speed, the exposure is decreased in the same way as a physical shutter that would decrease amount of time the CCDs are exposed to the light.

The previous posts were ill-worded. Shutters on film cameras do not control how much light enters the camera -- they control how LONG the film is exposed to the light.

For whatever reason camcorder manufacturers have used the shutter terminology. So as to not confuse people, it would seem to me that to state that "changing shutter speed has nothing to do with how much like enters the camera" is misleading at best.

The exposure that will get recorded by a camcorder on tape (or disk or memory) is a function of both f-stop and shutter speed.

Mike, do you have any references which discuss the actual mechanics and electronics of how "shutters" work on a camcorder?

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Old May 20th, 2005, 12:26 AM   #17
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Well, changing the "shutter speed" on the PD170 DOES change the exposure in a manner like a physical shutter would. If I increase the shutter speed, the exposure is decreased in the same way as a physical shutter that would decrease amount of time the CCDs are exposed to the light.

No it is not changed in the same way and it is not an accurate analogy although, in many cases, it is an OK working analogy.

The results that are recorded are the same, perhaps, but not the method. Thinking that there is a physical shutter inside the camera could lead someone familiar with film-based cameras to make some unwarranted assumptions. Play with the 'Shutter Speeds' in a video camera and you will see what I mean.

The previous posts were ill-worded. Shutters on film cameras do not control how much light enters the camera -- they control how LONG the film is exposed to the light.

Depends on where you measure the light inside the cameras but the statement is incorrect. The exposure is, in reality, the number of photons that strike the silver halide crystals. The number of photons striking the film can be controlled by varying the aperature and the duration of the exposure. For normal exposure times, a slower shutter speed has the same effect as opening the aperature further.

For whatever reason camcorder manufacturers have used the shutter terminology. So as to not confuse people, it would seem to me that to state that "changing shutter speed has nothing to do with how much like enters the camera" is misleading at best.

I do not agree. The amount of light that enters a camera is a function of the effective lens aperature among other things. Since there is no physical shutter, it can play no role whatsoever. Furthermore, changing the shutter speed leads to unwanted artifacts in some cases. Artifacts that would not be expected or accounted for by thinking the shutter is a mechanical device.

The exposure that will get recorded by a camcorder on tape (or disk or memory) is a function of both f-stop and shutter speed.

That is correct. The key word is 'recorded.'

Mike, do you have any references which discuss the actual mechanics and electronics of how "shutters" work on a camcorder?

Only technical references regarding how CCDs work and how they are deployed in video cameras. I'm citing personal knowledge since a startup company of which I was a part in the early 1980's, built the first digital cameras and desktop scanners.
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Old May 20th, 2005, 04:06 AM   #18
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Mike,

I guess I just don't follow your assertions.

I have "played" with the shutter speed many times, and even experimented some tonight. When the shutter speed is increased the exposure is decreased, just like it does with a still 35mm camera with a physical shutter.

So just like in most any other camera, the exposure is affected by both the shutter speed on the f-stop. Don't criticize me for using the term "shutter speed" with camcorders, since all manufacturers use that exact term. It is reasonable to expect that since the industry standard uses "shutter speed" with camcorders even thought there is not a physical shutter, that there is an analogy with the shutter on film cameras.

I would agree that the shutter is implemented differently on film cameras than on video cameras, but I would argue that using the shutter has similar effects.

In both film and video:
1. As I increase shutter speed, the exposure is decreased, and the action is captured with more sharpness.
2. As I decrease shutter speed, the exposure is increased, and the action is captured with less sharpness, even blurring the motion.

I can't see how you can conclude "Since there is no physical shutter, it can play no role whatsoever." when it is easily demonstrated that changing the shutter speed affects both exposure and image sharpness. I would imagine that if the shutter speed had no use on a video camera the manufacturers would quit providing that feature since no one would be using it.

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Old May 20th, 2005, 12:23 PM   #19
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Your analogy works to a point. But the real differences between a still film and a video start showing up as you change the 'shutter speed' very far from normal.

Yes, if you increase 'shutter speed', the individual frames with moving objects does have less motion artifacts. However, go very far and the resulting video looks strange. Try it and see.

If you decrease 'shutter speed,' very far, you will find that the camera stops delivering interlaced frames and just repeats a single field. Instant loss of resolution.

So while your analogy holds up for the exposure portion of the equation, it does not work for the artifacts changing shutter speed in a video camera may create.

That is exactly why one has to be careful how statements are made on the forum. There are people reading the posts who don't know the full set of issues attached to making adjustments on video cameras. Especially when the camera companies use misleading terms.

With regard to the presence of a shutter. If it is not physically there, how can it play any role in camera operation? If you had said, the shutter speed control, then that would have been accurate.
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Old May 22nd, 2005, 11:28 PM   #20
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Quote:
Originally Posted by Mike Rehmus
With regard to the presence of a shutter. If it is not physically there, how can it play any role in camera operation? If you had said, the shutter speed control, then that would have been accurate.
Mike,

Sorry, but I find this amusing. :-)

How can you accept "shutter speed" without accepting "shutter"?
IAC, my original post referred to "shutter speed".

Hey, look, we all know that there is no physical shutter in a camcorder. However, the manufacturers have chosen to implement a control called "shutter speed" that is pure electronics, and only mimics the function of a physical shutter. So, as long as it's called a "shutter", and changing the speed of it does in fact change the exposure and image sharpness in a manner similar to physical camera shutters, it is reasonable to discuss it as such.
Quote:
That is exactly why one has to be careful how statements are made on the forum. There are people reading the posts who don't know the full set of issues attached to making adjustments on video cameras. Especially when the camera companies use misleading terms.
I couldn't agree with you more. That was the motivation for my original post. To state that "Because the shutter speed has nothing to do with the actual shutter speed (since there is no shutter). " might imply to many that changing the shutter speed will have no effect. This is simply not true.

Changing the shutter speed on a camcorder has a similar effect to that of film cameras that have physical shutters, but may also produce other effects that may or may not be desired.

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Old May 23rd, 2005, 12:02 PM   #21
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Quote:
Originally Posted by Pete Wilie
Mike,

Sorry, but I find this amusing. :-)

How can you accept "shutter speed" without accepting "shutter"?
IAC, my original post referred to "shutter speed".

Best Regards,
Pete
Because this was your original statement: "How do you figure that changing the shutter speed doesn't change the amount of light that enters the camera?"

On a camcorder, changing Shutter Speed does not change the amount of light entering the camera. That is not what Shutter Speed does on a camcorder. Changing Shutter Speed on a camcorder changes the CCD's Integration cycle time.
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Old May 23rd, 2005, 08:30 PM   #22
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Well, I guess by now we've said all there is to say. I'm sure everyone by now thoroughly confused. :-)

Hopefully those interested will experiment with their camcorders to observe for themselves the effects of changing shutter speed, regardless of whether it has a shutter or not.

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Old May 24th, 2005, 10:25 PM   #23
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Shutter speeds.

One thing that I notice when I switch my shutter speed from 60 to 30 is that the image does look softer. The images does look more "film like" but that softness can hurt you if you're shooting in low light situations without a camera light.

Even with the sensitivity of the PD 150/170 and post production color correction, those images that you've shot with your shutter speed set at 30, shooting in low light without a camera light will look as if you shot it with a cheap consumer camera.

I would shoot at 30 all the time if I could, but I can always count on the images being sharper and cleaner when the shutter speed is on 60.
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Old May 24th, 2005, 10:40 PM   #24
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Because the camera drops interlace and just repeats a single field, losing 1/2 of the vertical resolution.
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