Just a quick note to remind you of the BLPG meeting, Thursday, August 1.
At the last meeting, Joel Sartore’s Great Courses “Fundamentals of Photography” lecture on Aperture and Depth of Field was shown.
In his lecture, Joel gave a number of tips:
- You want as big a hole in the lens (i.e as small an f-number) as possible in order to increase your shutter speed;
- For a small aperture (f/22 or higher), you need strong light and/or a slow shutter speed;
- Spend your money on good lenses;
- Try it before you buy it.
Joel also set a Homework Assignment:
With the same subject in the foreground, take a series of photos (using aperture priority), changing the aperture from small f-number (large hole) to large f-number (small hole). See what happens to the background.
You should observe that the background is blurred when you use a low f-number (big aperture) and comes increasingly into focus as the f-number gets bigger (aperture gets smaller). That’s because the Depth of Field grows bigger as the aperture grows smaller.
When we take a photo, most times we have a subject that we want the viewer’s attention to be drawn to.
One way to do so is to have the subject in sharp focus, and all the other distracting background elements unfocused or blurred. That’s what adjusting the aperture can make happen.
On the other hand, if we are taking a landscape photo and want everything from the foreground to the background to be in focus, we need to use a high f-number. Since a high f-number means a small aperture, to collect an adequate amount we have to have the shutter open for a longer time, thus a slower shutter speed (longer exposure). If there isn’t bright illumination of the scene, the shutter speed might have to be slow enough that there is danger of “camera shake” so a tripod is necessary.
One conclusion from this is that once the f-stop has been chosen to get the effect you want, the length of the exposure depends on the available light. And that is the topic that Joel will cover in the next three lectures, the first of which is Light I – Available or Ambient Light.