How does a Speed Booster work?

Photographers and videographers who use a mirrorless camera with a crop sensor might have heard of the term "Speed Booster" or "Focal Reducer." But, what exactly is it and how does a speed booster work?

Speed boosters are special type of lens adapters that allows you to mount lenses from other systems to your camera. However, speed boosters provide extra benefits over a regular lens adapter.

The benefits of using a speed booster are:

• Wide field of view
• Larger and faster maximum aperture
• Better image quality

These are the three major benefits of using a speed booster or focal reducer. Quite a huge advantage over regular adapters, right?

What is a Speed Booster?

Speed Boosters or focal reducers is an optical element that is inserted between the lens and the camera body. 

It has two main functions:

1. It reduces the focal length of the lens by a certain factor, usually between 0.5x and 0.7x.
   
   This means that the lens will have a wider angle of view on the crop sensor camera than it would normally have on a full-frame camera.
   
   For example, a 50mm lens on a Micro Four Thirds camera with a 2x crop factor will have an equivalent focal length of 100mm. But if you use a 0.7x speedbooster, the equivalent focal length will be reduced to 70mm, giving you a wider perspective.
   
   
2. It increases the maximum aperture of the lens by the same factor as the focal length reduction.
   
   This means that the lens will be faster and brighter on the crop sensor camera than it would normally be on a full-frame camera.
   
   For example, a 50mm f/1.8 lens on a Micro Four Thirds camera with a 2x crop factor will have an equivalent aperture of f/3.6. But if you use a 0.7x speed booster, the equivalent aperture will be increased to f/1.3, giving you more light and shallower depth of field.

There are several models of speed boosters available. It all depends on the camera system that you are using.

Metabones, perhaps the most prominent speed booster maker, has a lot of models in their catalog. Make sure to select the right one for the camera body and lens that you are using.

How does a Speed Booster work?

Speed boosters work by using a concave lens element to compress the image circle projected by the lens onto the smaller sensor area. This effectively reduces the magnification of the image and increases its brightness.

A full-frame lens projects an image circle that is larger than the sensor area of a crop sensor camera.

This means that some of the light and information is wasted and cropped out by the sensor edges. A speedbooster or focal reducer collects this extra light and information and squeezes it into the smaller sensor area, making use of the entire image circle.

Think of a speed booster as a teleconverter, but in reverse.

A teleconverter increases the focal length and decreases the aperture of a lens by using a convex lens element to expand the image circle projected by the lens onto the larger sensor area. This effectively increases the magnification of the image and decreases its brightness.

What are the advantages and disadvantages of using a speed booster?

Using a speedbooster has some pros and cons that you should consider before buying one.

Some of the advantages are:

• You can use lenses from different systems and mounts on your crop sensor camera, expanding your creative options and possibilities.
• You can reduce or eliminate the crop factor effect of your crop sensor camera, giving you a wider field of view and more flexibility in framing your shots.
• You can increase the maximum aperture and brightness of your lenses, giving you more control over exposure and depth of field.
• You can improve the optical performance of your lenses, especially in terms of sharpness, contrast, and vignetting.

Some of the disadvantages are:

• You will add some extra weight and bulk to your camera setup, making it less compact and portable.
• You will lose some electronic functions and communication between your lens and your camera, such as autofocus, aperture control, image stabilization, and EXIF data.
• You will introduce some optical aberrations and distortions to your images, such as chromatic aberration, barrel distortion, and coma.
• You will increase the risk of dust and dirt entering your camera system, as there is an extra gap between your lens and your camera body.

Final Thoughts: Are speed boosters worth it?

Speed boosters can enhance your photography and videography experience with a crop sensor camera. It can give you more versatility, speed, and quality when using lenses from different systems and mounts.

However, it also has some drawbacks that you should be aware of before investing in one. It can make your camera setup heavier, less functional, and more prone to optical flaws and contamination.

Ultimately, the decision to use a speed booster depends on your personal preferences, needs, and budget.

If you are looking for a way to get more out of your crop sensor camera and your lenses, a speed booster or focal reducer might be worth a try.

In this age where full frame cameras are expensive, having an accessory that will upgrade your crop sensor unit is worth checking out.