What is Fast Glass or a Fast Lens?

When you hear sports photographers talk you will often hear them talking about fast glass or fast lenses.  What does that mean and why are they important for sports.

A fast lens refers to the size of the aperture opening.  The larger the opening the more light that is allowed to reach the sensor.  Because more light reaches the sensor more quickly, through the larger opening the shutter does not have to be open as long.  A faster shutter speed is better for freezing or capturing the motion in sports.  Fast glass allows you to shoot with faster shutter speeds which is a good thing when trying to freeze fast action.  It’s also a tremendous help in low-light conditions.  As the light get worse or less bright the longer the shutter must remain open, but since the aperture opening is larger more light is able to reach the sensor.

You can tell the speed of the lens or the speed of the glass by looking at the f-numbers associated with it.  The smaller the f-number the faster the glass.  It can be a bit confusing since what that means is the smaller the number the larger the opening/aperture.  So a f/2.8 lens is considerably faster than a f/5.6 lens.  That means the aperture in the f/2.8 lens can get much larger than the aperture in the f/5.6.  To give you a feel the f/5.6 lens will do well outdoors in good light, but you will need a f/2.8 or faster for low-light indoor sports.

You might be thinking well let’s just make a lens that has a huge aperture.  There are a couple of limits and challenges to that.  The larger the aperture the less depth of field in your photos, or in other words the narrower focus your photos will have.  The other challenge is cost.  The faster the glass the more expensive it is.  So fast lenses are more expensive, the lower the f-number is on the lens you are looking at the more expensive it will be.  So………you will have to make the decision, but there is nothing like the quick focusing beautiful photos a fast lens can help you take.

Low-light sports would be extremely difficult and require very fast glass if not for the improved sensors and their ability to collect light.  In the days of film fast glass was even more important because trying to use a high ISO film would cause a lot of grain.  In this digital age the sensors are much better and higher ISO settings can help compensate in low-light conditions without a significant increase in graininess.

There’s a lot to remember and it can be a bit technical, but for sports photography simply remember that a fast lens or fast glass will give you better shooting options in low light conditions, and that a fast lens has a low f-number.  Fast glass is essential for indoor sports photography where you will often be in  school gyms that have inadequate or poor lighting.  Fast glass is essential for you to catch or freeze the action and still have plenty of light reach the sensor.

The lens does not the sports photographer make, but it is extremely helpful and will make a good photographer better and a great photographer fantastic.

ProPix Photography
The Sports Photography Professionals

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