Camera and Lens


Have you ever heard the comment “those are really nice pictures… must have a really good camera”? A bit of a slap in the face to the photographer, but it does hold at least some truth nevertheless.

Although there are some pretty amazing point and shoot cameras capable of taking stunning pictures, most serious photography is still done with a (SLR)  single lens reflex camera. These camera bodies allow you to attach a variety of lenses to them from fixed focal length to zoom and from wide angle to telephoto. We will deal with those a bit later.
What does the term SLR mean? If you remove the lens from your camera body you will see a small mirror on an angle within the body. This mirror transmits the light that comes through the lens and reflects it upward to a prism which is also an angled mirror. This is the image you see when you look through the viewfinder of the camera. The light that is focused on this mirror must hit the sensor that sits behind this mirror to be captured by the camera.  Because the sensor sits behind this mirror it must flip up out of the way so light can get through.

SLR Prism
If you push the exposure button on the camera and watch you can see this happening.  You will also notice that the mirror stays up out of the way for different lengths of time with different shutter speeds. We will talk about shutter speed in a later lesson. The mirror is dampened with some foam so not to create unwanted vibrations as it goes up and down. This works well at normal shutter speeds. However at slower shutter speeds even the slightest motion will cause blurry images, so most cameras have a (MLU) mirror lock up setting somewhere in the menu. This locks the mirror up out of the way before the exposure is taken to eliminate potential vibration which can cause unsharp pictures. This is particularly helpful when doing macro, or close up images, where there is a lot of  fine detail in the image.
In the days of film the negative from SLR cameras was 24×36 mm in size. With the transition to digital, a sensor of this size became known as a full frame sensor. The amount of resolution that can be captured by the sensor is spoken of as megapixels. Most modern SLR cameras are now above 10 megapixels which is plenty for almost any application the average person would use. Because the sensor chips are expensive to produce full size sensors are limited to higher end cameras that many of us can’t afford. Camera producers began producing cameras with a smaller sensor to keep down the cost.

As you can imagine this also has some unwanted and sometimes wanted effects. One of the unwanted effects is a tendancy to have more “noise” on the resulting image from packing more light gathering pixels into a smaller area. Noise shows up as a mottled color appearance on the picture. It can also be accentuated by improper exposure setting which we will discover in a later lesson.  Another effect is an increase in apparent (DOF) depth of field.  DOF is how much distance in the image appears in focus, but more on that at a later time. One positive effect, especially for things like bird photography, is that because of the physics in the way light is focused on the smaller sensor you see an apparent increase in the focal length of your lens. Most lenses are meant to cover the area of a full frame 35 mm sensor, so when the light hits the smaller sensor it in effect crops down to a smaller area giving the appearance of having used a longer lens. The above picture demonstrates a full frame 35 mm sensor compared to a smaller sensor present on many consumer  SLR cameras.

You can see the cropped closer view you get with the small sensor. Most smaller SLR sensors crop to approximately 1.5 X original. This means that if you have a 400mm telephoto lens on your camera this becomes a 400 X 1.5 = 600 mm lens giving you the same view a 600 mm lens has on a full frame sensor. Thus your tiny little bird in the middle of the picture would look much larger because of the apparent increased focal length.  Camera sensors have come of age in recent years and most major camera manufactures are producing very affordable consumer camera bodies with excellent sensors capable of producing high quality images.

The camera body itself is basically a mini computer that allows you to transfer the resulting image to a flash card to be later transferred to your home computer for final processing  to produce the final outcome. We will deal with a few of the major control dials on the camera in later lesson to show how each image is affected by the setting used.

This brings us to the lens.

Another misused comment that is often heard is “you must have a really good zoom” when describing a close up shot of a subject. This is a misunderstanding by most people, so we will try to deal with that in this section. Although there are some specialty lenses they generally come in two categories, fixed focal length and zoom.



An example of a fixed focal length lens is a standard or 50 mm lens.  The angle of view from this lens is approximately what you would see with your naked eye. If you look straight ahead, and note how far you see out each side, this is approximately what your 50 mm lens will reproduce in a picture.


Lenses less than 50 mm are thought of as wide angle lenses. They generally range from about 10 to 35 mm ( the smaller the number the wider a view you would have). These lenses are generally quite short. This is an example of a 14 mm lens in that category.




A lens greater than 50 mm’s is thought of as a telephoto lens . The field of view becomes increasingly narrower as the millimeters increase. Short telephoto’s in the 85 to 100 mm range are often used for portrait work as they give a pleasing effect by slightly compressing a persons features. Macro lenses used for close up photography, like flowers and bugs, are usually in the 65 to 200 mm range. They focus closer than normal lenses of the same length. This is a 180 mm macro lens.


600mm-supertelephoto Long telephotos range from 300 mm to 800 mm  or more, and are generally used for wildlife and bird photography, however very nice compressed landscapes can be made with lenses in this range as well. The 600 mm lens that gives that nice full frame picture of a robin in the neighbors yard is not a zoom lens as may people seem to think. Here is an example of a 600 mm Canon super-telephoto lens.

1.4X-extenderTo reach even farther out, and increase your subject size, you can place an extender between the lens and camera body. In Canon they come in 1.4X and 2.0X extenders. The 1.4X extender would increase the 600 mm lens by 1.4 X 600 to turn it in to a 840mm lens. The draw back is that there is one stop of light lose because of the increased glass elements between the body and lens. There is also some image degradation. This is not as noticeable with a 1.4 X extender, but is definitely noticable with a 2X extender or doubler. Here is a 1.4X Extender.


A  zoom lens has a variable focal length. You can have wide angle zooms which may range from an ultra-wide 10 to 22 mm as pictured to the left,  to a 17-40more normal view zoom like this 17 to 40 mm lens pictured on the right.




70-200mm-medium-telephoto-zoomThe following image is an example of a short telephoto zoom ranging from 70-200 mm.  There is even a long zoom lens made by Sigma that zooms from 300 to 800 mm, but you may want to hire a friend with a strong back and a weak mind to carry it around for you. Zoom lenses allow you to stay in one place and change the subject size simply by rotating the lens collar to change the focal length. It has been said that even fixed focal length lenses can be used as zoom lenses. With a fixed focal length lens you must walk closer to or farther away from your subject to change the size of the subject in an image, so in effect your feet become the zoom.



An exercise that may prove helpful in understanding how different focal length lenses can change the field of view is to take piece of cardboard and cut a rectangular size hole in it approximately 2 inches by 3 inches. Hold this up in front of your face and look through the hole. This would show you the approximate view a wide angle lens would see. The following pictures demonstrate this. The image on the right is taken with a wide angle lens.






Now move the cardboard out extending your arm about half way from your face. This would give you the approximate field of view of a “normal” lens, or maybe a short telephoto lens.  The image on the left was taken at 70 mm.



Now move the cardboard out to arms length and you can see how a longer telephoto might render the view.  This image was taken at 2oo mm.  “Zooming” your arm in an out while looking through the hole will give you some idea of how a zoom lens works. You may even find it useful to carry a small cardboard with you when out photographing and when something  catches your eye you can pull out the cardboard and see approximately what the final image may look like at different focal lengths.


The next section will deal with  exposure  and how different settings allow you to properly expose an image for particular situations.

Camera and Lens images used by permission  KEH Camera Exchange  and  Canon USA