According to the manual, it appears that the "iris" and "gain" are tied together. There does not appear to be an actual iris.

Page 84 states:

CLOSE...(F16 to F1.7) OPEN... (0dB
to 18dB)
Value closer to [CLOSE] darkens the image.

Value closer to [18dB] brightens the image.

When the iris value is adjusted to brighter
than [OPEN], it changes to the gain value.

To return to auto setting, press the iA/
MANUAL button again.

When setting both the shutter speed and
the iris/gain value, set the shutter speed
and then set the iris/gain value.
Manual shutter speed adjustment

When the shutter speed is set lower than
1/15 in the Still Picture Recording Mode,
using a tripod is recommended. Also,
white balance cannot be set. The shutter
speed will be set to 1/30 when the power
is turned on again or when the Quick start
is performed.

You may see a band of light around an object
that is shining very bright, or highly reflective.

During normal playback, image movement
may not look smooth.

If you record an extremely bright object or
record under indoor lighting, color and
screen brightness may change or a
horizontal line may appear on the screen.
In this case, record in the Intelligent Auto
Mode or set the shutter speed to 1/60 in
areas where the power supply frequency
is 60 Hz, or 1/100 in areas of 50 Hz.
Manual iris/gain adjustment

Luminance level and histogram are
displayed during the iris adjustment.
(see pages 76, 77)

If the gain value is increased, the noise on
the screen increases.

Depending on the zoom magnification,
there are iris values that are not displayed.

It is vital that you learn how your camera operates, because no two are exactly alike. Any advice I give you (based on my EX3) will be of no value to you and your HDC TM-700.

So if aperture and iris are the same thing then why have two different settings for both?
According to the manual, there is one entry for iris and another for shutter speeding indicating they have separate functions. But now that I think about it, why do video camera's even have a shutter speed? It's not like a camera where the shutter opens and closes every-time a picture, or in the case of video a frame, is taken, is it? But it would seem to be so as the camera quite clearly has shutter speeds like my still camera.
The manual also says that adjusting the iris changes the gain. Too bad, I wonder why they put these two functions into one.

The aperture/iris would be the "hole" in the lens, similar to the one in our eye, which opens and closes (gets larger or smaller) to adjust the amount of light entering the lens.

Today's camera lenses do not have "shutters" that open and close as they did in the analogue days. Today's shutters are electonic, they determine how long the "shutter" is opened on each frame. For example, if you're shooting 60 fps, then the shutter will be open 1/60 of a second for each frame.

Shutters (even electronic ones) are there for the same reason. The longer it's open, the more motion blur is introduced to each frame. However, it does not adjust the exposure as in the analogue days.

The reason the iris and gain are tied together are a matter of economics. This is a consumer camera--aim and shoot, almost. They have provided some control, albeit limited.

The "exposure" is a combination of "Shutter speed" and "aperture" (F Stop). If you set the camera on "Auto" then it'll usually select a middle of the range shutter and aperture which may give you boring looking footage. But if you select a larger aperture the camera will select a faster shutter speed to compensate for the lager aperture. Using a larger aperture will give you a shallower "depth of field" (DOF) which will blur the background while your main subject is in focus.

Onto Liquids point about how to lighten a scene. I assume you mean after you've downloaded your footage and now see your footage is too damn dark, otherwise use lights.

Do this: Make 2 tracks. Put the same dark footage on track 1 AND on track 2. On top track change compositing mode to "Add". Adjust the amount by dropping opacity on the top track. If you still want more add "Sony levels" filter to bottom track and adjust to taste.

It's not perfect but hey..............

"Shutters (even electronic ones) are there for the same reason. The longer it's open, the more motion blur is introduced to each frame. However, it does not adjust the exposure as in the analogue days"

Whilst electronic shutters obviously do not control the amount of light reaching the sensor they certainly adjust exposure, the outcome is the same as when a mechnical shutter is used, halve the time the shutter is open and the sensor "sees" half the light.

For low light most video cameras do have some form of long exposure time where the shutter is open for more than one frame's time. This is a trick that couldn't be done in a mechanical camera. Apart from this given the sensor more time to capture photons it does also make motion very blurry or dreamlike. You really want the camera on a tripod when using this.

Liquid,
bottom line. Cameras need light. By far and away the best solution is to simply add more of it. You can buy quite cheap LED lights off eBay such as the Z96 (around USD 70) and using one or more of those to add some light will make the world of difference to the quality of your video and more so with a cheaper camera. I own much the same camera as Jay and as great as they are at sucking in light I still add more of it where I can when shooting indoors.

Bob.

"Whilst electronic shutters obviously do not control the amount of light reaching the sensor they certainly adjust exposure..."

Yes, technically, you are correct. However, we do not adjust shutter speeds in motion picture photography as we do in still photography, unless you're after a special effect or look in the motion.

For example, in still work, if you need an additional two stops of exposure, you would slow down the shutter speed two steps--from 1/125 down to 1/30 of a second (or any such combination). If you were to attempt this in video, it would create some motion blur issues. Slowing from 1/60 to 1/15 would render the video useless, under most conditions.

When shooting at 24p, we normally use 1/48 shutter speed, 30p or 60i we normally use 1/60. Rarely is the shutter used to make exposure compensations as they are in still photography.

"Rarely is the shutter used to make exposure compensations as they are in still photography."

Indeed except if your video camera is in Full Auto or some such or if it doesn't have any manual control then it will adjust shutter speed.
This can really confuse you. On many Sony cameras even when not in Auto if you adjust iris the camera will adjust shutter speed to compensate. This really had me confused for a while, on the PD150/170 you have to cycle through the manual adjustments to lock them out of auto or else switch the shutter Off.

Bob.

Bob, I don't know of any professionals who use their camera set on full auto, nor do I know any professionals who use such (consumer) cameras (except as a throw away in dangerous situations). Thank heavens, I learned back in the day when there was no such thing as "auto" anything on a camera.

"On many Sony cameras even when not in Auto if you adjust iris the camera will adjust shutter speed to compensate."

Yes, as I explained above, such is the case on most, if not all, consumer level point-and-shoot style cameras. And the resulting footage looks anything but professional in most instances.

Wow, what an enlightening conversation! Jay and Farss, I love your back and forth, it's like an expert panel on cameras and lighting! Where do you guys find time for this!
Well my question has been answered. Thanks!
Also, to address the last point Jay made, I agree, there is no auto anything. I've completely given up on even trying to use automatic features, except focus as that seems to work a great deal of the time (still I only use auto about half the time on my video camera, but all the time on my still camera).

Where do you guys find time for this!

It's their responsibility to know this stuff. Yours too.

In motion picture work you usually either adjust the iris, add light, or use something more sensitive to light. You don't normally adjust a shutter unless you're going for a specific effect like more (or less) motion blur. Less motion blur will give you a kind of staccato motion effect.

In professional situations I often find that the DP wants to work at a specific aperture and the only allowable option is more light. This is because the DP has already made decisions on all the other factors.

Difference between iris and aperture? The iris is the mechanical part that creates an aperture. The aperture is the hole that allows light through, an iris makes the hole adjustable.

On my last consumer DV camera I handled shutter speed problems by locking the setting and then using an ND filter on the camera to cut reduce the daylight reaching the sensor. The same can be done professionally if, for example, you want to shoot with a wide open iris in full sun. You'd need ND filters to get the exposure right.

Gain will generally lead to more noise in the image so that's something you'd normally avoid. The best course is to add more light.

A big problem with lightening the image in post is that you won't have a lot of picture detail to work with. If the usable image was recorded between values of 0 and 100 that's a lot less information than if it had ranged from 0 to 255.

Rob Mack

"Where do you guys find time for this!"

LOL - today is "one of those days." I've been working on script for a client's instructional video and waiting for their feedback on some changes.