Archive for the ‘post-processing’ Category

Tips for dealing with High ISO Noise in Capture NX

Monday, July 28th, 2008


When working in low light, shoot in RAW and err on the side of overexposure.

If you have to shoot using high ISOs, the best way to prevent noise from building up in the shadow areas of your image is to make sure not to underexpose. If you shoot in RAW, you will be able to recover mild blown highlights (but don’t go crazy — there are limits to what you can get back with RAW) quite cleanly, but if you try to recover detail from the shadow areas, noise will eat your lunch.

If you’re using Capure NX 2, the easiest way to recover the highlights is to use “highlight protection” in the quick fix menu. In NX 1.x, you can reduce the exposure compensation, then tweak the levels and curves to make sure you don’t bring down the midtones.

Turn off in-camera sharpening and noise reduction

In-camera sharpening is not very intelligent. Either turn it off in-camera, or else turn it off in Capture NX before you begin editing. In-camera noise reduction is both dumb and slow, so definitely turn that off in-camera.

Think locally, act locally,

Sharpening and noise reduction are not mutually exclusive, but they’re close. When you reduce noise, you reduce sharpness. When you sharpen an image, you sharpen the noise. You can ameliorate this somewhat by tweaking the settings — increasing the “sharpness” slider in noise reduction, and careful application of high pass sharpening (and avoiding unsharp mask if possible) will both make it easier for you to have both sharpness and noise reduction in the same area.

But it’s not likely that you need every inch of your image to be sharp, and it’s not likely that every inch of the image needs the same degree of noise reduction. So, apply both your sharpening and your noise reduction locally, where each is needed most. This is easier in Capture NX 2, because selection control points allow you to work quickly to isolate the areas you need to effect. Just drop selection points at full opacity in the areas you want sharp and partially or totally reduced points where the image is supposed to be soft. Similarly for noise reduction.

Of course, sometimes you’re going to have a lot of noise in areas you need sharp — it can’t always be avoided.

If you don’t have NX 2 yet, you can perform the same localization by masking the areas in question manually. This will be much, much, much easier if you have a Wacom tablet. It gets tedious very quickly is you use a mouse.

Intensify the highlights and shadows

If your image contains dark shadow area where detail is going to be lost anyway, or where the detail is really noisy, consider using control points or an LCH adjustment to shove those areas closer to pure black. Also brighten the lighter areas where noise should be at its minimum already.

Convert to black and white

Noise looks better in black and white. use the BW conversion menu, play with the filter settings, find what works best for your image.

Convert to black and white, even in color

Bear with me. Even if you’re going to want a color image as your finished output, you may want to make a trip to the BW conversion menu. Try converting to black and white and playing with the opacity settings. Often a conversion with partial screen or multiply opacity can help emphasize the areas of an image you want sharp, especially if you figure out what color filter setting to use.

Convert to black and white, again

I’ve found that in some situatuions, it’s helpful to do a blue-filtered BW conversion applied with partial screen opacity, followed by a second black and white conversion applied normally or as an overlay, with green filter setting. Sometimes this helps brighten and clarify an image without increasing noise.

Not sure exactly under what conditions this works best; I’m still experimenting.

Desturate the noise

Dishes @ ISO 1600

Here’s another area where Capture NX really shines. If you’re going to keep the image in color, one way to make noise more pleasing without actually having to reduce it is to drop a control point into some of the noisy areas, crank the saturation to 0, and then drop control points into areas that are relatively noise-free but otherwise similarly colored. The effect will be overall reduced saturation and a possible change in color balance, but if done correctly, it also renders the noise less noticeable and more like film grain.

Color Noise

Friday, May 16th, 2008

I like grain. I’m hardly unique in this — grain has a long and noble history in photography. One of the awesome things about shooting film is the weirdly satisfying look and feel of film grain.

Cigarettes and Coffee

Nose to the Water

Good-looking grain makes it possible to shoot at very high speeds and still get usable results for many applications, and in many cases, it’s a critical part of the image.

Digital doesn’t have grain, it has “noise.” In addition to sounding much less awesome than grain, noise also, sadly, does not look as awesome, mainly because it’s garishly colored. I don’t have an example of this, so I won’t post one, but I’m sure you know what I mean.

There are two obvious approaches here. The most obvious one is noise reduction. I find that I use less and less of this as time goes by. Sometimes it’s really needed, and sometimes it really works, but sadly, those times don’t necessarily coincide, and when noise reduction goes wrong, the resulting muddy softness is even more irritating than noise. I could probably invest a lot of time and energy in getting better at noise reduction and sharpening, and at some point I will have to do that, but in the time, I’m trying to cut back on it.

The second obvious approach, which I use maybe a little too much, is black and white conversion. Black and white conversion of digital noise doesn’t result in film-like grain, quite, but for many applications it’s fairly close, and fairly pleasant, even when shooting at ISOs that are far higher than what’s really advisable.


This approach works well in a lot of situations, especially in low-light conditions where colors often become boring and/or ugly, anyway. And, indeed, in any situation in which the important visual information is to do with contrast and tonality rather than color (and this is many, if not most, images), black and white is probably a better choice, anyway.

But, sometimes color is important. For shots in which you have objects with similar tones but very different hues, a black and white rendition will be quite boring, and quite possibly misleading. And if one of the goals of an image is to accurately depict reality, and the subject is known by the audience to be colorful, a black and white image will often fail horribly.

So, what I do now to deal with color noise in digital files, when I want to preserve color in a scene, is to desaturate the noise.

Olympus XA

I do this using Capture NX, which is a program of odd strengths and weaknesses — the strength in this case being its inclusion of Nik Software’s U-Point technology, which is lately being marketed as a Photoshop/Aperture plugin called Viveza.

The points, called “Control Points” in NX, are little dots placed in areas of the image, each sporting an area of sliders for brightness, contrast, saturation, RGB, etc. You use the sliders to tell NX what to do to parts of an image, within a certain radius, that match the part you dropped the point in. A few more points placed in different areas, either to make other changes or to protect from changes by surrounding points, and you’ve (hopefully) got your image just how you want it. It’s a profoundly better way to do local edits than layer masking, and by comparison, burning and dodging in the darkroom is a tremendous burden.


The trick is to place a control point in an area of intense noise, and then completely or nearly completely desaturation it. Then place a second control point in a nearby area of the same overall color, but without so much noise. This will result in some overall desaturation, but mainly it will reduce the color noise, leaving you with a grainy speckling, but none of those annoying red, green, etc. dots — and the overall effect is much more pleasing.