Noise and artifacts. Is it RAW or a cheap CPL filter?

[Hawthy]

I shot about 900 photos while on holidays in Hawaii and did them all in RAW and mostly using a cheap Circular Polarising Filter. No problems with the colours but the photos all seem to be quite noisy with general noise plus oblong JPEG-type artifacts. Easily fixed using Topaz DeNoise but just wondering if this is typical of RAW images or if the filter was the culprit. I usually shoot JPEG but appreciate the flexibility of white balance adjustments in RAW. I used a Nikon D5100 and usually set ISO400 to allow a good balance between still and action shots.

Your advice would be greatly appreciated.

[Tannin]

A sample would be very helpful.

While cheap filters do some truly horrible things, I suspect that the culprit this time is simply the settings on your raw converter software. It's probably set to strive for maximum sharpness, and needs to be reset to some more sensible values. I have had similar issues once or twice in the past and found it useful to switch from my usual raw converter (was Bibble at one time, but mostly ACR these days) to the factory-supplied software (Canon Camera Raw in my case) because it is a very easy way to get a known, as-expected conversion - exactly the same, in fact, as the conversion the camera itself would have made if I'd shot in JPG. From that known, familiar conversion, it's easy to determine what's going on and then deal with it sensibly. Nikon don't have a direct equivalent to Camera Raw, but you may well find that your Nikon-supplied software is able to perform in a similar way.

[Mark L]

"Noise and artifacts. Is it RAW or a cheap CPL filter?"
You can do a simple test. Take two photos of something with some defined lines, maybe a white flower or something equivalent to the worst artifacts you got in Hawaii. Take the first with the CPL and the second without the CPL.
This should tell you if the CPL is the problem.
Learning to PP raw may also be the problem? While you're learning that, shot raw and JPEG maybe.

As Tony said, "A sample would be very helpful."

[Tannin]

"Noise and artifacts. Is it RAW or a cheap CPL filter?"
You can do a simple test. Take two photos of something with some defined lines, maybe a white flower or something equivalent to the worst artifacts you got in Hawaii. Take the first with the CPL and the second without the CPL. This should tell you if the CPL is the problem.

^ Yes, good advice. But watchout for exposure! Because the CPL robs you of a stop or two, you need to be sure that the different exposures are not contributing. In the worst case, for example on full auto, you might wind up with (say) f/8 for both shots, in identical light, 1/250th for both shots, but ISO 400 for one and 800 for the other! To avoid this, use a fixed ISO and aperture, and let the shutter speed vary (taking care only to be sure it's something sensible which won't make camera shake a factor).

[Hawthy]

Thanks for your help. I had another look at this and I think that it is a processing issue. I have been using Lightroom to process RAW images and then upping the clarity (maybe a bit over the top). I processed them again using the standard Nikon software NX-view and PS cc 14 and it is much better. Thanks so much.