In the recent school holidays (end of September), I took my two sons to Kings Park, to have a look at the wildflowers. There were lots of wildflowers, and we spent some time wandering through the flowerbeds, taking photos of wildflowers that each of us throught interesting.

Here's a few of the photos I took on that afternoon - but I'm only including photos of red flowers here. I'll include photos of some of the other flowers in a future blog post.

Nematolepis phebalioides

Kings Park, Perth, Western Australia
Canon EOS 50D, 24-70mm f/2.8L @70mm, 1/250 sec, f/3.2, ISO100

This is the fifth article in a series on "understanding your camera" that I am writing as I teach camera basics and camera operation to my children.



This post provides descriptions of some lens terminology that many people take for granted, but are not be clearly understood by everyone, namely

• focal length
• angle of view
• field of view

I'll start with some definitions. Reference the diagram immediately below when reading these definitions.

field of view, angle of view and focal length (top view)

Focal Length

The focal length of a lens is the distance from the optical centre of the lens to the sensor (or film) when the lens is focused on an object at infinity.
The focal length is fixed for any lens, and doesn't change when the lens is mounted on different camera bodies.

The focal length of a lens is one of the key specifications of a lens. For example, the focal length of the Canon EF-S 18-55mm f/3.5-5.6 IS lens ranges from 18mm to 55mm, depending on the zoom set by the lens' zoom ring. On the other hand, prime lenses such as the Canon EF 50mm f/1.8, have a fixed focal length that cannot be varied (ie, 50mm).

This is the fourth article in a series on "understanding your camera" that I am writing as I teach camera basics and camera operation to my children.

The shutter speed is the length of time that the camera's shutter is open, ie, how long the camera's sensor is exposed to light through the lens.
While the aperture determines the size of the hole in the lens which allows light in, the camera's shutter is designed to accurately expose the camera's sensor to light for a specified amount of time.



This table (taken from the first article in this series on understanding your camera) provides a summary of the effect of varying the shutter speed:

impact of varying the shutter speed

A shorter shutter speed will reduce the amount of time that the shutter is open, and allows you to freeze motion, due to the image being exposed for a much shorter amount of time. Conversely, a longer shutter speed allows you to capture motion, because the image is being exposed for a longer time period, so any moving objects will have moved during the time the shutter was open.

Using longer shutter speeds can be a problem if you are hand-holding the camera, as you cannot hold the camera still for the duration of the exposure, and this will cause the image to blur due to the camera movement.

Another photo from the Lesmurdie Falls area, this time of a Eucalyptus flower. It was great wandering around, enjoying the many wildflowers.

purple eucalyptus flower

Lesmurdie Falls National Park, Lesmurdie, Western Australia
Canon EOS 50D, 24-70mm f/2.8L @63mm, 1/250 sec, f/5.6, ISO200

I'm in a predicament. My Canon EF-S 17-85mm f4-5.6 IS USM lens is dying.

I purchased it brand new about 4.5 years ago, have taken many photos with it, and have found it to be a great general-purpose zoom lens. A couple of years ago, I bought a Canon EF 24-70mm f/2.8L lens to replace it, but kept the 17-85mm for my children to use.



Last week, while on a photography road-trip with my two boys, my oldest son was using the 17-85mm lens on his Canon 350D camera. Focusing was fine, but any attempt to take a photo would result in the 350D showing "Err 99" on the LCD, and the camera had to be turned off and back on to clear the error.
"Err 99" is a generic catch-all error code on the 350D, and can mean almost anything (lensrentals.com have a great article on Err 99).

Trying the 17-85mm lens on a Canon 50D resulted in a more specific error: "Err 01 - Communications between the camera and lens is faulty. Clean the lens contacts."
Not surprisingly, cleaning the lens contacts with a pencil eraser didn't do anything to resolve the error.

While geo-caching near Lesmurdie Falls earlier this week, I found this moth on an everlasting flower. The moth was happy to pose long enough for me to get some photos.

Moth and Everlasting Flower

Lesmurdie Falls National Park, Western Australia
Canon EOS 50D, 24-70mm f/2.8L @70mm, 1/1000 sec, f/4.5, ISO400

As far as I can tell, this flower is one of the many varieties from the Rhodanthe family.