/r/photography is a place to politely discuss the tools, technique, art and culture of photography and to post topics that would be of interest to other photographers.

Focal lengthof lens formula

Without an AR coating, lenses have noticeable glare, which means light reflects off their surfaces, limiting the quantity of light traveling through the lens. This can make your vision less clear and lower your ability to detect contrasts, especially at night.

Lenses and focal lengthcomparison

For optimal clarity throughout the day, anti-reflective coatings can be applied to regular optical lenses as well as sunglasses.

AR lenses have  a specialized coating that is made of a microscopic layer of metal oxides that neutralize reflections, allowing it to minimize glare from the front and back surfaces of each lens. They aid in the transmission of light through the optical lens and into your eye.

AR coatings can also help prevent eye fatigue and digital eye strain. Your eyes don’t have to work as hard to capture a quality image since they get more light.

Lenses and focal lengthchart

Anti-reflective coatings allow 99.5 percent of light to flow through the lens, compared to 92 percent for regular lenses.

How does this work? Is it somehow related to the size of the projected image circle? I also noticed that micro4/3 lenses have a "sweet spot" at a lower focal length.

Canonlenses and focal length

Anti-reflective (AR) eyeglass lenses reduce glare and reflections that are distracting and affect how well you see. That’s why anti-reflective coatings are one of the most popular lens choices among people who wear glasses.

Another advantage of AR coatings is that they make your glasses and eyes look better by nearly eliminating distracting reflections and glare that would otherwise bounce off your glasses.

When you have AR coatings on your lenses, driving at night becomes a lot easier. The halo effect around car lights is reduced considerably.

How does focal length affect physical lens size? I noticed that as you go from telephoto to shorter focal lengths, lens size decreases, quite obviously. But around 35mm (?) the trend reverses, and wider angle lenses become bigger and bigger. The Canon 40mm f/2.8 for example is ridiculously small, but the Canon EF 20 mm F2.8 USM is quite huge, again.