|Canon 50mm f/1.2 L IS USM|
1. Faster Shutter speeds
In low light conditions fast lenses allow you to handhold the camera eliminating the need to use tripods or flashes due to the faster shutter speeds it allows.
2. Brighter and clearer viewfinder
The camera does not stop down the lens to a smaller aperture (even if you have selected one) until the shutter release button is fully pressed. The camera uses the maximum aperture of the lens to present a bright subject to the view finder. As a result you have a brighter view finder image when using a fast lens than a slow lens.
3. Much easier to focus manually
As we have already explained above, fast lenses presents a brighter image at the view finder and so makes manual focusing that much easier to do if you require it.
4. Better auto focus performance
Since fast lenses present brighter targets to the camera's auto focus sensors, auto focusing works better when using a fast lens. In low light conditions slow lenses may cause the camera's auto focus sensors to hunt, at times making it impossible to focus in time or resulting in sub optimal focus rendering the image unusable.
5. Depth of field
The shallow depth of field obtained by using a wide aperture makes it possible to isolate a subject from other distracting elements in the frame making the subject stand out from the background. You will find this feature extremely useful while shooting portraits.
6. Ability to shoot at close range
The distance of the subject from the background is a major factor in attaining a blurred background effect, the greater the distance between the subject and the background the better the blur. But by using a fast lens you could position your subject very close to the background and still render the background out of focus by setting the lens aperture wide open. This is especially useful in macro photography.
7. Ability to use tele-converters
If you plan to use a tele-converter on your lens the loss of one or two f-stops can make a relatively slow lens unusable. But in a fast lens the loss of one or two f-stops might not be a big problem. For example imagine using your 70-200 f/4 with a 2x tele-converter the loss of two f-stops makes the lens a 70-200 f/6 making it unsuitable for many applications.
8. Shoot at low ISO settings
Fast lenses let you take photographs in very low light without the need to raise the ISO settings. The lower the ISO setting, the better the photo quality will be.
9. Better Bokeh
Generally fast lenses have more shutter blades than their slower counterparts making them highly suitable for stunning bokeh work.
10. Better build quality
As a general rule the faster the lens gets, the expensive it is to buy and vise versa and so is the build quality. Fast lenses are made with the professional user in mind and so they tend to be of better build quality.
Some fast lenses from Canon
Canon EF 50mm f/1.2 L USM Lens for Canon Digital SLR Cameras
Canon EF 50mm f1.4 USM Standard & Medium Telephoto Lens for Canon SLR Cameras
Canon EF 50mm f/1.8 II Camera Lens
Some fast lenses from Nikon
Nikon 50mm f/1.2 Nikkor AI-S Manual Focus Lens for Nikon Digital SLR Cameras
Nikon 50mm f/1.4G SIC SW Prime Nikkor Lens for Nikon Digital SLR Cameras
Nikon 35mm f/1.8G AF-S DX Lens for Nikon Digital SLR Cameras
In the next article we will discuss about Photography - Tips For Beginners - What is ISO in Photography? What it is and What it Does?