ถามเรื่อง filter คับ

The most relevant difference between protective filters is the type of coating that is applied to the surfaces of the filters (other differences could include the type of glass used and the construction of the filter ring). The coatings on the filters reduce reflections and therefore increase light transmission. Straight glass reflects about 4% of the light per surface (i.e. 8% for a piece of glass), and these AR coatings reduce that. You can see the difference by looking at the reflection of a light source in filters with and without coatings. All of the lens elements inside your DVX are coated to reduce these unwanted reflections as much as possible.

Filters can be purchased that have no coatings, a single layer coating, and multi-layer coatings. Multi-layer coatings reduce reflections the most and are also the most expensive. They are also more sensitive to damage than the bare glass. Different companies have different techniques for reducing reflections and thus you have the variety of choices and costs.

What you stick in front of your lens is entirely up to you, but if protection is your aim, you probably want it to affect the image as little as possible, and thus a good multi-coated (MC) filter is best. In my experience Hoya's S-HMC filters are among the best, particularly for the cost. B+W and Heliopan are also excellent, but you pay more for the brass rings and German engineering. Some camera manufacturer filters (e.g. Nikon, Pentax) are also worth considering, though there is usually a premium for the brand. I'm not familiar with the Tiffen line, but I suspect that for the price you mentioned they are not multicoated. I think it's worth it to have a good MC filter in front of my DVX, but only you can make the decision for your needs.