When I shoot, I like as little glass between me and my subject as possible. Obviously I need a lens, but as little extra glass as possible is good.

The reason is that glass can distort, and it can introduce extra flare.

• If glass is not optically great, this will be more easily noticeable (use drug store glasses, look though airplane windows, or old windows).
• If it interferes with filters, e.g. with a polarizer (try shooting through your car windshield with a polarizer).
• If you shoot at an angle.

When you shoot through an aquarium, for instance, do not shoot at an angle. Because this results:

Look closely:

Ouch. We call this “chromatic aberration”.

The solution: shoot straight, and avoid wide angle lenses.

No aberration even when you look up close.

So glass can cause problems – which is why I use as little as needed. Meaning I do not use filters on my lenses except when needed. Like “Protection”, “Daylight” or “UV” filters. Yes, I have them in my bags in case it starts raining or snowing, or I am in a sandstorm or on a  beach, but unless those things are happening, I will not use them. Every little bit of clarity helps.