Do you do noise reduction?

alehel · 04-06-2009, 03:31 PM

I was wondering how many people here use noise reduction on their high ISO shots. I've just recently done a few shots using ISO 1600 purely for the sake of experimenting. I was extremely pleased with the results. The only anoying thing was what seems to be a dead pixel close to the center of the picture. A small green dot.

Apple Aperture does a small amount of noise reduction on RAW images automaticly which also eliminated the dead pixel. Apart from this, I've set the camera so it doesn't apply noise reduction, as I prefear to do this myself on the computer.

I have Noise Ninja plugin for Apple Aperture, and after having run a few shots through the program, I have to admit, that on every picture I actually prefear the shot that hasn't been sent through noise ninja. I find that if you just avoid pixel peeping and view it at a size which equals what one would view when printing, the noise isn't intrusive and noise reduction just ends up killing a lot of the details. I found that I'd much rather have my images unprocessed by noise reduction software.

I started wondering if others feel the same. What are your views on noise reduction.

I also tried turning off the Aperture noise reduction that it performs by default, and the only difference I can see when viewing at normal size is that it eliminates dead pixels. The rest of the noise reduction I can only see when pixel peeping, and so it doesn't seem to damage the detail. I therefore keep it turned on so I don't have to deal with the dead pixel myself. I also noticed that the in camera jpeg also removes the dead pixel, but even the unprocessed PEF file looked better than the jpeg. Mind you though, as I said, Aperture has a bunch of presets it uses on RAW files and the values depend on which camera the RAW file came from, so I'm not really looking at a pure RAW file.

This shot was taken at ISO 1600. I was not expecting this amount of quality from the K200D concidering it's relatively cheap price. It's certainly good enough for documentation purposes such as photography for local newspapers which I have done a couple of times.
Go to here to download the jpeg with full resolution.

**Marc Sabatella** · 04-06-2009, 08:58 PM

Originally Posted by alehel

I was wondering how many people here use noise reduction on their high ISO shots.

I do, sometimes, but usually just a little. Like you, I tend to prefer to keep detail, even if that means noise, as opposed to aggressive NR that smears detail. But I do try to find a balance.

This shot was taken at ISO 1600.

And it looks fine - especially at this size, of course!

*OregonJim* · 04-06-2009, 09:48 PM

I turn off any in-camera NR, and only use Noise Ninja (sparingly) if I'm going to print larger than 8x10 and ISO was > 400. That's with a K200D 10MP.

alehel · 04-07-2009, 03:14 AM

The size I displayed it at is roughly the size the local newspaper would use, which is why I no longer hesitate with using ISO 1600. The only problem though is that you have to ensure that the picture isn't underexposed when you take it, which I feel is easier said than done on the pentax.

*falconeye* · 04-07-2009, 03:17 AM

Originally Posted by alehel

Do you do noise reduction?

You already did do noise reduction by downsampling your image.

A 500 x 334 (0.167 MP) image downsampled from 10 MP at ISO 1600 automatically becomes ISO 27!

1600 / 10MP * 0.167MP = 27

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alehel · 04-07-2009, 09:34 AM

Hmm, you learn something every day.

PhotoGator · 04-07-2009, 11:44 AM

Is it possible I ma getting more noise in RAW than jpeg? I looked at some older images I shot when I first got the K200 this summer... no noise to speak of. Now with RAW my shadows seem to all have noise starting at ISO 200 and up. I was surprised at ISO200. I could see maybe 400 and up.

Could I have accidently reset something in my menu to increase noise. It is killing my photos. Thanks for your advice.

RBellavance · 04-07-2009, 12:03 PM

I apply "wavelet denoising" to the K10D RAW images I process in UFRaw. Typical thresholds are 50 for ISO 800, and 75 for ISO 1600.

I normally do not use any noise reducting at ISO 400 and lower, but may do so if I significantly push exposure during processing.

I routinely use ISO800 without hesitation. ISO 1600 is still only for "emergencies". When I get to the point where it is needed, I usually start using flash.

**Marc Sabatella** · 04-07-2009, 12:14 PM

Originally Posted by PhotoGator

Is it possible I ma getting more noise in RAW than jpeg? I looked at some older images I shot when I first got the K200 this summer... no noise to speak of. Now with RAW my shadows seem to all have noise starting at ISO 200 and up. I was surprised at ISO200. I could see maybe 400 and up.

The camera does noise reduction on JPEG, unless you have it turned off. For RAW, there is no in-camera NR, so you have to do it yourself in PP. You should always be able to get better results that way, but you do have to actually do the work.

*Canada_Rockies* · 04-07-2009, 10:44 PM

I turn off NR. I am with the group that would rather keep the detail. I am also with the group that compares digital noise to film grain, and frankly find that there is no noise. Relatively speaking, of course. How many out there have pushed Tri-X to 1600 (or 3200 I tried once)? Might as well paint a picture with golf balls.

*OregonJim* · 04-07-2009, 11:03 PM

Originally Posted by falconeye

You already did do noise reduction by downsampling your image.

A 500 x 334 (0.167 MP) image downsampled from 10 MP at ISO 1600 automatically becomes ISO 27!

1600 / 10MP * 0.167MP = 27

How does that do noise reduction? Seems to me that the signal/noise ratio remains constant (less noise but equally less image).

*OregonJim* · 04-07-2009, 11:31 PM

Originally Posted by Canada_Rockies

How many out there have pushed Tri-X to 1600 (or 3200 I tried once)? Might as well paint a picture with golf balls.

Never tried 3200, but 1600 plenty of times. You must have used D-76 to get golf-ball sized grain. Microdol-X is better - only half-dollar sized grain.

*Canada_Rockies* · 04-08-2009, 01:04 AM

Originally Posted by OregonJim

Never tried 3200, but 1600 plenty of times. You must have used D-76 to get golf-ball sized grain. Microdol-X is better - only half-dollar sized grain.

This was so long ago that Tri-X was only rated at ASA 160.

*christinelandon* · 04-08-2009, 01:48 AM

Good one, Albert!

Personally, I turn on in-camera NR only for ISO 1600, which I almost never use. I think I've only cleaned up a couple of noisy images in Photoshop in the past four years. I don't really photograph much on "the dark side," I suppose.

*falconeye* · 04-08-2009, 04:18 AM

Originally Posted by OregonJim

How does that do noise reduction? Seems to me that the signal/noise ratio remains constant (less noise but equally less image).

The correct answer would have to be three pages long (because it introduces a satisfactory definition of "image noise" which involves computing a signal/noise over spatial frequency curve). And then you are correct.

The short answer is that everybody confuses "noise" with "random fluctuations of the pixel's rgb values), i.e., "pixel noise".

And this pixel noise is of course reduced. Because you average multiple original pixels into one final one, thereby eliminating most of their fluctuations. The Poisson formula tells you exactly by how much. Quoting a shift in ISO is easier to handle for most people, though.