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Photography Question 

Earl Blansfield
 

Problem using Hoya Filters


Up until a couple of weeks ago, I have been using Sigma Lenses (70-300 and 24-70) lenses on my EOS 20D. I used Quantaray UV and CP filters on both lenses and never had a issue using the filers with autofocus. My images were still sharp. Recently, I tried to step up my game and bought two L series Canon lenses; 100-400 4.5-5.6L IS USM and a 24-105 4.0L IS USM lens along with a HOYA 77mm CP and UV filter. At this point, I totally love both lenses and can see tremendous improvement in my image without the filters. However, when I put CP filter on, the image is terrible. The UV isn't good either. I never had a problem with the Sigma lenses and Quantatary Filters. Just looking for some help to solve the issue.

Thanks

Earl


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February 26, 2007

 

Alan N. Marcus
  Hi Earl,

Filters in the black&white days were a must. When shooting color negative films, filters are generally negated by the printing process.

A UV filter removes ultra violet light and affords some haze penetration greatly beneficial for aerial work. A skylight is a UV plus warming, both skylight and UV are somewhat effective for haze penetration in a non aerial location. Their main value is protection of the front element of the camera lens.

A polarizer is a joy to own. This filter cuts haze like a UV and darkens blue sky –vadds contracts – without altering colors.

Some cameras can’t tolerate a polarizing filter (screen). These are designs that that utilize a polarizing and/or semi-mirrored optic in their metering and/or auto-focus system. For them, we need a circular polarizer. In this design a standard polarizing screen is followed by second filter to unravel the polarized light created by the front filter. You still get the most of the effect plus the light passes to the camera un-polarized.

Now all filters regardless of brand or type subtract away from the camera’s optical quality. Generally the optical detraction is so slight that it can only be measured in the laboratory. However good advice says never mount a filter unless the benefit overshadows optical loss.

Now, how can your UV and CP be so devastating? Maybe the mount – maybe the glass is not flat. A filter must be flawlessly flat. It is more difficult to make flats than it is to make a lens. Your filters are known good brands; it is unlikely they are not flats. You can test yourself. Hold the filter in your hand; look at the surface of the glass. Look at the filter as if it were a mirror. Look and study a reflected image off its surface. I look at reflections of ceiling tile. Are stright lines straight, center to edge? Good flats produce a mirror like reflection with all straight lines ture center to edge. A poor quality is filter is easy to spot; reflections of straight lines will be wavy. Examine both sizes. Remember, for this test you are not looking through the filter, you are using it like a mirror. A good undistorted reflected view means the filter is OK.

Alan Marcus
ammarcus@eathlik.net


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February 26, 2007

 

Earl Blansfield
  Thanks Alan,

I have been using a skylight, CP and UV for a few years and I love neve had an issue. I actually kept the skylight on my lenses all the time. I never had an issue up until I bought my new lenses. I will take your advice and see if I can see any flaws in the filter. It doesn't make sense to me. Worse case, I shoot without the filters and adjust the best I can in photoshop.


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February 26, 2007

 
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