Promaster UV filter quality or lack of it.

[tedh]

Today I purchased a Promaster UV filter for my Canon EF 70-300mm f/4-5.6L IS USM.
After taking about 70 or 80 shots with it at various distances and settings I have decided that the filter degrades the sharpness of the photos to an unusable level.
Is it just hit and miss with these filters or are they consistently poor?  I paid about $36 for the unit.
With the lens in place the camera will auto focus but the image is just severely degraded.  Manual focusing wont' resolve the issue and there isn't enough f-stop in the work to make this filter sharp.
If Promaster wont' cut it then what brand should I be looking at?

[Mt Spokane Photography]

Post some of the unusable photos.  All filters degrade the image quality, and a cheap or defective one might be the worst.  However, I've never seen a cheap filter produce a unusable unusable image.  They may certainly have a effect, but unusable?
I stopped using filters a few years back, images are now sharper and better, but my old images were certainly usable.
 

[neuroanatomist]

I'd skip the Promaster.  Camera shops like to sell them because they have a high profit margin (they are, or at least they were, re-branded low-end Tiffen filters).  If you want a protection filter, get a B+W MRC or Nano, or a high-end Hoya (S-HMC or HD).

[skitron]

Same story here...when I first started in DSLR I tried a Best-Buy house brand UV filter on a 28-135 and it was very noticable degredation. Bit the bullet for B+W mrc after researching and asking around and LOL, it turns out everybody was right.

I tried a Hoya Digital Pro that came with a used lens I bought and its pretty good. I thought it was garbage at first, but after inspecting it and thinking it didn't need to be cleaned, I cleaned it anyway and then it was fine. Apparently something about its coating can aggregate a not so visible residue over time that really softens the image.

[TexasBadger]

B + W, expensive but worth it.

[chenbro]

I agree with neuro. If you want a protective filter, get a high quality multi-coated one. Multi-coated filters will also reduce glare and flaring originating from the filter itself. I've attached an example of what a cheap Tiffen can do to the images coming out of a 24-70L (I was young and naive back then, ok?). When I got my first B+W filter, I thought that B&H had sent me an empty filter ring, whereas the Tiffen makes it really easy to spot the glass.

[skullyspice]

Yes B+W are great. I like Heliopan also.
I worked in a camera store a few years ago and most of the Promaster stuff wasnt very good. We got a lot of returns.

[tedh]

Here are just two examples.
I replaced it with a Zeiss and the issue was resolved.

[JHPhotos]

I had a similar experience with one of the standard UV filters. I bought it on the recommendation of a friend.When I complained to him that I thought the images were a little soft, and maybe he had steered me wrong we got together to compare. What I discovered is that I paid around $30 for my filter and he had paid almost $100. Both Promaster UV filters. The salesman tried to sell me the better filter but did a really bad job of explaining why I needed it except it was easier to clean. I took the filter back to the store to return it and get a B+W.  The store manager took the time to explain the real difference between the standard filter and the better filters including both the B+W and the Promaster better filter. It seems that most of the inexpensive filters from Hoya, Tiffen, Sunpak, Promaster, or others are only coated on one side of the glass or not coated at all. The higher end filters are coated both sides with multiple layers of coating that helps eliminate the ghosting which impacts the image sharpness. Anyway, the manager convinced me to trade for the Promaster HGX and save the extra $30 since it had the same level of coating etch as the B+W MRC. They said if I was unhappy, they would swap me for the B+W. So far, no soft images and I am as happy as my friend.