Manual Exposure Controls

For those of you interested in venturing into Manual mode of your cameras, here is a quick overview of a few different ways you can control the look and feel of your videos.  The following three controls all affect exposure, or how much light is recorded by your camera's sensor.  Changing these manually allow you much finer control over the look and feel of your video:  

• aperture -  how wide open the camera lens is
• shutter speed -  how long the camera holds the shutter open for on a single photo
• gain (iso on still cameras) - how sensitive the camera is to light

Aperture (also called f-stop).   Strangely,  the LOWER the aperture, the wider open the lens is and the more light that comes in.  An aperture or f-stop of 2.8 is fairly low and lets in a bunch of light.  An aperture or f-stop of 8.0 is higher and wont let in as much light.  If you were to use an aperture of 8.0 you would need to slow down the shutter speed and or increase the gain to compensate for letting in less light.

The reason you want to control aperture is depth of field.  Depth of field is when the background blurs out quickly and it looks cinematic:


with a lower aperture (like 1.4 or 2.8) only a little bit of the image is in focus at a time.  With a high aperture (8.0) everything both close and far will be in focus.  In Manual mode on the pd170s you can set the aperture by scrolling the silver wheel on the left side of your camera that says iris.

Shutter Speed.  This is how long the shutter lets light in through the lens to the sensor.  It's measured in fractions of a second.  If your shutter speed is 200 on your camera that means 1/200 of a second.  If it's 30 that means 1/30 of a second.  The longer you leave it open, 1/30 being a lot longer than 1/200,  the more light comes in.   You have to be careful though because if you have the shutter speed at 1/30 or longer like 1/15 then you'll start to see blur.  If something is moving really quickly (like a bird or car)  then at slow shutter speeds you might notice it having some motion blur as the object moves while the shutter is open.  You can use a fast shutter speed like 1/200 to keep quick moving objects in focus.

Gain (or iso on still cameras) is how sensitive your camera is to light.  The higher the gain the less light the camera needs to properly expose the image.  Higher gain means you can take video in darker areas and indoors without extra light.  The downside is noise.  The higher the gain, the more noise (think tv static) there will be in your videos.  ALWAYS use the lowest gain possible that lets you use the aperture you want and shutter speed quick enough to prevent blurring