Lenses and Filters

                                                                      LENSES

We have had powerpoint presentations during class and been given printed documents to learn the different aspects and equipment involved in photography. Lenses and filters were covered in such sessions as follows:-

Lenses fix onto the front body of the camera. There are 3 basic types:
                  Standard;  Wide angle;  Telephoto:
They are measured in millimetres and known as the focal length of a lens.
A 50mm lens is deemed to be a standard lens on a 35mm camera. Any lens with a shorter focal length than this is said to be a wide angle lens and any with a longer focal length is considered a telephoto lens.

Wide Angled Lens:
The most common of these are the 24mm and 28mm and are popular with landscape photographers because they offer a wide depth of field (meaning there is more of the picture in focus). They are great for highlighting the foreground with a fading into the distance background.

Telephoto Lens:
This being the opposite of the wide angle, they are great to focus right in on the subject, bringing far away objects closer with clarity, whilst leaving the foreground and background details out of focus. They reduce the depth of field and are a good choice for sports photographers. Focal lengths can be very high from up to 100/200mm, 300/400mm and higher.

Macro Lens:
These are used for close up photograph. Whilst they have similar properties to the standard lens they can be used to focus in more closer to the subject and are usually of very good quality.  Common focal lengths are 50/55mm or 90/100/105mm.

Fisheye Lens:
Shaped like the name, their angle of view is 180 degrees. They are distorted in the way that  the top, bottom and sides of the picture appear to be further away, while the centre almost comes out to meet you.

Shift/Perspective Control:
These are great for shooting tall buildings.  They are expensive but will get a whole building in shot, by still keep the camera upright, (no need to tilt it backwards) and the building will remain straight up.

Teleconverters:
These lengthen your lens distance, by sitting between your camera and the lens, they lengthen the focal length, but are not of great quality. They also reduce the amount of light getting through which makes focussing harder. There is a need to use slower shutter speeds or faster film with use and the optical quality is also reduced.  These problems are not pronounced as much on a 1.4x converted (used by professionals) so it would be best to buy a more expensive one if using.

                                                                    FILTERS

Filters can be used to:  Increase contrast
                                    Change the exposure
                                    Capture invisible light
                                    Minimize reflections

Just as there are a number of different lenses to use there are a number of different filters, for instance:

UV Filters:
These can screw onto the front lens of your camera and can be used to cut down on haziness like that found around mountains and coastal areas. UV stands for Ultraviolet which is the light invisible to the human eye. They can also act as a protective screen to guard your lens from scratches, dust and weather.

ND Filters:
Neutral density filters give you great control over exposure time. They are used to reduce the amount of light that reaches the sensor.  This enables photographs to be taken with a larger aperture for a longer period of time, ie. a waterfall with a slow shutter speed on a bright day.  Without one most lenses would be unable to use an aperture small enough for long exposures. They can be circular that screw directly onto the front of your lens, or square ones that slot into an attachment that is fixed to your lens, made to hold filters.

Polarizing Filters:
Most of these are circular to screw onto your lens and you can change the level of polarization by rotating the outer layer of the filter. The effects of these cannot be reproduced in after camera manipulation which makes them very useful and expensive. They are used to reduce reflections on non- metalic surfaces ie. water and glass making them good for urban and wildlife subjects.  They have the ability to totally change the outcome of a photograph.

Macro Filters:
These close up filters (or diopters) are not like ordinary filters. They are more like an extra lens you place in front of your lens, so you could put a macro filter onto your standard/telephoto lens to get in closer, instead of using a macro lens, but the quality would not be as good.  Several filters can be stacked ontop of each other for more magnification.
An Extension tube would be a better investment, as they change the closest possible focal length without affecting image quality as much as macro filters. These tubes can also be used together with a macro lens to enhance magnification.

In this section we also learned about White Balance:
When we look at a white object our eyes automatically adjust to the lighting conditions. Digital cameras are unable to do this so they have an adjustment control in the form of White Balance Presets to use depending on the shooting lighting conditions ie. auto, daylight, shade, cloudy, tungsten, fluorescent, and flash.