How All 72mm Lens Filters are Not Made the Same
The following is a comparative analysis of a 72mm lens filter from different brands, with a focus on quality-based differences.
Sigma Lens Filter
The Sigma lens filter is generally a great option if you are a new photographer and are just starting out. Generally most of the amateurs move on to the bigger and better Canon lens filters, but that happens after they have mastered the basics of the craft. Sigma lens filters employ a direct film coating to a standard lens; this is not as good as an inherently dyed glass (used by canon). Externally applied film coatings can cause spherical aberrations and other lens deformities no matter how good the machining of the lens is.
For the given price, a sigma lens filter is great value and is ideal for people who are into hybrid shooting. But, this is definitely not in the same league as the Canon lens filter.
Tamron Lens Filter
A Tamron 72 mm lens filter is even cheaper than sigma lens filter and is used by most photographers as a lens cover to protect the base lens of the camera from dirt and other foreign elements. Professional photographers, because of the amateurish finishing and low optical quality, seldom put the lens filter to its intended use. The lens filter itself is vulnerable to hostile weather and moisture. It is best used as sacrificial protection.