Anti-Fog vs. Thermal Lens System
A foggy lens can be the single worst experience on the paintball field, and one that is all too common with low-end and rental masks. The terminology is partially to blame for this as it is the 'anti-fog' lenses more prone to fogging. An anti-fog lens is one that has been treated with a solution to prevent fogging before leaving the manufacturer. These solutions wear out quickly, and are never foolproof, typically needing to be reapplied with aftermarket products between each and every game for best results. For a hassle free solution look for a mask with a thermal lens, also know as a 'dual pane' lens. A thermal lens, like dual pane windows in your home, prevent fogging by creating an insulating layer of air between two lenses by means of a layer of foam around the outer edge of the lens. This means that there will not be such a drastic temperature difference between the hot moist air inside the mask caused by sweat and your breath, and the outside air.
A good thermal lens will prevent fogging in even the most extreme conditions, but most will still have their limits. High humidity, rain, and in some cases extreme perspiration can still lead a goggle system to fog, though rare.
A few things that are important to avoid for the longevity of any lens is to not clean it with any harsh cleaners like Windex or glass cleaner, and to never submerge the lens in water. Harsh cleaners can strip to mirror or protective coating from the outer lens, and further damage the softer inner lens. Cleaning with 'too much' water, or submerging the lens can cause water to penetrate the foam layer and become trapped within the lens, leading to either water spots that can not be wiped away or permanent fogging. If the mask becomes excessively dirty we recommend removing the lens to hose the mask down, and let dry completely before reinstalling the lens. To clean the lens use a small amount of water, and a clean microfiber towel.
Field of View
Getting a goggle system with a large field of view make the difference between feeling like a horse with blinders and feeling unencumbered. Some masks accomplish this by either moving the lens closer to your face, or making the lens larger.
Quick Change Lens Systems
Quick change lens systems are becoming increasingly the norm for all levels of paintball masks, no longer reserved for the high end market. Often abbreviated as QLS, a quick change lens system allows the user so change the lens with out prying it from the rubber of the frame. Typically held securely by a few easily removed clips. This makes it easier to swap between different colored lenses for a given time of day or weather, or simply removal for cleaning.
When talking about the construction of a paintball mask some will have what is referred to as soft ears. This means that the front face plate and the ear coverings are separate pieces. This typically allows it to be made of a softer material which more securely wraps around your head.
One of the most crucial aspects of a mask is the breath-ability. It is important to make sure that the mask has proper venting to allow the hot moist air from your breath escape while providing adequate protection.
Like Shrek, good foam has layers, with most high-end masks having two or three layers. Typically consisting of a dense layer to prevent hard plastic of the goggle frame from digging into your face, a softer foam to better form to your face, and in some cases a third layer of a felt material for added comfort.
Hopefully this look at the different features helps set you on the right track into seeking out the perfect mask.