Could a cheap or defective circular polarizer cause soft images on a Sigma 150-500mm lens?
Asked 2/8/2019
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I used a Sigma 150-500mm APO HSM to photograph surfing and fitted an AGFAphoto 86mm circular polarizer. The images looked out of focus even though autofocus seemed to lock correctly, depth of field should have been sufficient, and the filter was clean. When I removed the filter, the problem disappeared. I don’t see the same issue with another lens and its polarizer. Could this be caused by a poor-quality or defective CPL, and what should I look for when choosing a replacement?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
1
That AGFA one cost, what, $20? The Firecrest is $200 and the Lee $240...Singh Ray goes up to $400, though your 86mm would be ~$320...ish...
I don't think that AGFA found some super cool way to manufacture quality CPL's for less than 1/10 of the guys at the top. Fact is, with filters, manufacturer quality does generally go up with price. There are some good ones lower down and some junk ones up above, as with everything, but the general trend is: you get what you pay for.
I highly suggest you look for reviews on landscape photography sites. Look for reviews that mention build quality, color cast, ghosting, contrast loss, and other items that additional glass in front of your lens can cause.
Also, check out this question: How do I choose a polarizer?
And this one: How do you handle the varying sizes of filters in your kit?
Your best bet is to spend the money and get quality filters, at the largest size that you need, and use step-up rings for smaller lenses. Now, whether that's a few circular filters or a square kit (Cokin, Lee, Formatt-Hitech, etc)...that's a whole other question.
Originally by user67377. Source · Licensed CC BY-SA 4.0
user67377
7y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — a cheap or defective polarizer can cause soft-looking images, reduced contrast, ghosting, or autofocus problems. Since the issue disappeared when you removed the filter, the filter is the most likely cause.
One possibility is poor optical quality. In general, filter quality tends to improve with price, though price alone isn’t a guarantee. Another possibility is that the filter is defective or not functioning as a true circular polarizer. Autofocus systems can misbehave with a linear polarizer, and a faulty CPL could cause similar problems.
For a replacement, don’t choose by brand name alone. Look for reviews that discuss:
- optical sharpness
- color cast
- contrast loss
- ghosting/flaring
- build quality
Sticking with a reputable CPL from a well-reviewed filter maker is the safest route, especially on a long telephoto where any loss of sharpness is more obvious. Also note that polarizers reduce light, which can make shutter speeds slower — important for surfing shots.
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AI7y ago
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