The Hoya filters are the favourite among the professionals for more than one reason. Of course, the most important among them is the quality of the filters. This is apparent even among the least expensive models of the manufacturers. There are several features of Hoya filter that makes it even more indispensable possession for both the professional as well as the amateur photographers.
One of the great features of the Hoya filter is that it can prevent the ghost images. Also, the multi coated filters of the lens are available in all the different colours. This is where it has excelled even Nikon. For, Nikon does not provide multi coated filters for A2 or 81A. However, there are some cheaper versions of green box filters but, they are almost in the extinct race. Moreover, the Hoya filter is generally made of solid glass. However, there are exceptions such as the grads and the multi image filters.
Now, if you are wondering about the authenticity of Hoya, it is important that you understand that Hoya is world's biggest manufacturer of the optical glass. In fact, they have retained this title for a few decades now. Though it is strictly unofficial, it is often claimed that branded manufacturers such as Nikon, Leica, and Canon use the Hoya filter and glass in their models.
This is specially so when they need some special products that they can't get otherwise. Also, Hoya manufactures special glass on order if others ask for it. Here, you have to keep in mind that glass production involves a lot of trade secrecy. So, even if some company knows perfectly well what the glass used by Hoya do, they still can't come up with an identical product.
Another great thing with the Hoya filter is that they are the least expensive filters available in the market. Nevertheless, if you are not a professional, you need to know the process to check out the quality of the filter. This can be done easily by looking through the filter with a telescope or one side of the binocular. Ideally, the image you are looking at should appear unchanged. However, if you magnify the power, you will be able to detect even the most insignificant amount of unevenness.
Now, when you are buying the Hoya filter, you can be rest assured that they are flat. Also, they are available in thousands of different types. As far as the size of the filters is concerned, Hoya filter stands apart from others. They manufacture single coated filters that are as big as 95mm. Again, their HMC filters can range up to 86mm. Finally, there is the Kenko broadcast brand that delivers as big as 127mm filters. On the other hand, they also manufacture lens as tiny as 39mm.