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I am often asked for my advice on accessories by people who have just purchased a new DSLR. I am going to break this in to several parts so I can provide some detail and thoughts about each

Part Three – A fast lens

I am a big proponent of expanding your possibilities and trying something different. Most people (me included) when they purchase their DSLR typically get the “kit” lens with it. Today this lens is often an 18-55 mm lens with a variable aperture of f3.5 – f5.6. This works ok in really bright situations or higher ISO speeds. Once you move indoors you either have to use flash or max out the ISO. Depending on what you are doing this can be limiting and not always giving you the photo you were looking for.

I am a big fan of candid shots with only existing light. I also like to blur out the background behind the subject. The tool for both of these is a “fast prime lens” which for me is either a 50 mm f1.8 or 85 mm f1.8 lens. These lenses are typically $100 and $400 respectively. An f1.8 lens is 2 stops faster than a lens at f3.5 and 3 1/3 stops faster than a f5.6 lens.

Said another way with two stops faster say your f3.5 lens requires an exposure of 1/25 of a second at f3.5 you could shoot at 1/100 of a second at f1.8 and at f5.6 if the exposure requested is 1/30 of a second at ISO 1600 you could shoot at ISO 400 and use a shutter speed of around 1/80 of a second. In the first example you would reduce the change of blur from hand shake and in the second not only would your potentially reduce the blur but also reduce the noise due to the high ISO setting.

As for the image blur (Brokeh) a fast lens provides a very narrow depth of field when shot wide open at f1.8. The depth of field or space in front of and behind the subject that will be in focus is about 4.5 inches (2.25” in front and 2.25” in back) if the subject is 5 feet from the camera. So if you focused on your subject’s nose their ears would likely be slightly out of focus. That is a narrow depth of field! You can have a lot of fun with a fast lens like this and enjoy a great deal of flexibility as well.

Another great advantage is the view finder will be much brighter since four times as much light (2 stops) is coming into the camera. It will also focus faster and quicker as well. Remember though when shooting wide open and close to your subject you have to choose where you focus very carefully or you will get out of focus pictures. Typically if you focus on your subjects eyes you will get the best results. I suggest everyone get a 50 mm f1.8 lens since they are relatively inexpensive and a great way to add a new dimension to your photographic bag of tricks.