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How to kill noise without a ninja
Ok so I get occasional emails from other microstock shooters (or those looking to get into it) frustrated about the whole ‘noise’ thing. So I figured I’d put together a bit of a piece on how I personally go about combating it. This piece wont focus on any of the third party plugins, like noise ninja or neat image as I don’t personally use them. All tools here can be found straight in photoshop.
Before we enter photoshop though noise managing starts with the capture. Always shoot on the lowest ISO you can, 99% of the time this should be 100 or 200, note that it’s not worth doing the extended range thing my canon 5D (and probably other cameras) as that isn’t using the sensor at it’s optimal setting and only results in more noise than 100 ( I believe it even says this in the Canon manual). If shooting in low light is going to be at all a possibility then a tripod should be carried and used rather than bumping the iso up. Exposure should be to the right side of the histogram, if you’re not quite sure what this means then look up your camera manual for information on using the histogram. Basically what you are looking for is the brightest exposure you can get without blowing the highlights in any area that you would normally want detail in. By that I mean that if you have the sun in frame, or are shooting an object on a white background, or have other light sources (eg street lights etc) in frame then you will always blow the highlights there, where you don’t want to be blowing highlights is in skin tones of people or any object in frame that is part of the composition (unless you have very good reason to do so and are doing it deliberately). You can tell blown highlights on the LCD review screen by the blinking areas. Now your image might look a little bright and washed out at this stage in capture, so long as the detail in the highlights is there that is ok, you will bring that down in post.
It’s always better to try to darken images in post than lighten them. Lightening a dark area in post will always result in a massive noise increase, where as darkening an area will not. You can darken the whole image by using the curves function of photoshop or parts of it by using the burn tool.
Now lets assume that you have an image that has more or less the contrast & brightness settings that you want, even if you used iso100 and a good exposure you will still have noise in it. It is most identifiable in large, mid to darker areas of minimal detail, the most common area being skies. Here is where I am going to use the reduce noise filter in photoshop. Now before we use this filter we should make sure that all other post work has already been done. Contrast enhancements, colour shifts, dodging and burning, all these processes introduce noise into the photo, so do everything else first.
First step is to flatten the image if you have used multiple layers, if you wish to retain the layers for possible future editing later on then you can always duplicate all the current layers, reorder them and then merge the duplicate set of layers.
So now you have one layer that is your finished photo (but too noisy!) we aren’t going to run the filter straight on it though as when you use the reduce noise filter it also reduces detail and we don’t want that! So what we do is duplicate the layer and run reduce noise (filers-noise-reduce noise) on the top layer, you should run it at the highest possible setting, that would be strength-10, conserve details-0, sharpen details-0, the colour noise is slightly dependant on the image but I normally have that cranked up to full also. Now we are going to use a layer mask to undo the noise filtration in the areas we want. Simply click the little mask button down at the bottom of the layer palette and you’ll have a layer mask over the top (filtered) image. This is currently all white, which means the entire top layer is what we are seeing. All you do now is paint on that mask with a black brush in the areas that you want that top layer to be invisible and the unfiltered “detail” layer underneath to show through. Right now we are quite literally painting back in the detail. For this areas like eyes, lips, hair, clothing, objects in focus should all be painted back in. Anything that is in focus and has any sort of detail or texture that needs to be seen. You don’t have to worry so much about noise in areas of detail as even though it is technically there it is exceptionally hard to pick up - unless it is a VERY VERY noisy picture, in which case the round steel filing cabinet is probably the best place for it. Skin is a hard one, sometimes you want the smoothing effect that the reduce noise filter applies but often it ends up looking unnatural. Often I will paint back in the skin with a 50% opacity brush (or adjust the opacity to suit) this means that half the top layer will show through stuck over the detail layer underneath, this often gives a slight smoothing effect to the skin without loosing too much detail, you can still see pores and it still looks like skin.
Remember to play with brush sizes, opacity & flow (and know the difference between these two), even use the fade tool (edit-fade brush stroke) when a paint stroke lets back in just a little too much detail.
The above is the standard way I use to defeat noise in about 80% of the shots I edit. Every now and then I can’t be bothered with all this and will just play around with the settings in the reduce noise filter, usually the “conserve detail” slider. But in most shots this gives a less than perfect result, there always seems to be bits of noise that it lets through as it thinks it is detail and bits of detail that it eradicates because it thinks it is noise. But by all means do play with these sliders and learn what they do. Sometimes the perfect result comes a little easier by combining the layer technique with some slight tweaking of the “conserve detail” & “remove colour noise” sliders.
Also every now and then you’ll find that the image is so noisy (especially after some heavy post processing) that the reduce noise filter isn’t enough, even on max settings. This normally means you’ve passed the point of no return and need to either ditch the shot or re-edit with less wacky PS work. But you can save the occasional image by just blasting it twice with the reduce noise filter (obviously in conjunction with the layer technique). Other useful tools for ridding yourself of noise in specific areas are the blur & smudge tools, smudge being a much stronger effect than blur. Just be careful with the smudge tool in that if you do a large area with a large brush size you could be waiting a long time for the computer to process what you just did. My normal technique with the smudge tool is to choose a strength of around perhaps 20-40% and go over the offending area in a wiggly crosshatch fashion. If you go back and forth only one way and you’ll end up with nasty streaks.
Every now and then if I have a large area of sky I might even select it (with lasso, magic wand etc) give the selection a generous feather (select-modify-feather), copy and paste it to a new layer over the top of the old one (ctrl-C then ctrl-V), lock the transparency (there’s a little icon on the top of the layers palette that does this, just mouse over the icons and they’ll tell you which one it is) and then run a beefy Gaussian blur on it.
In short there are many ways to combat noise in photoshop but I’ve only gone over the latter ones briefly as to be honest I don’t use them very much at all. In most cases the reduce noise filter on full is more then enough to get rid of any noise you have, and masking back in the areas of detail gives you the best of both worlds, noiseless patches of sky & uniform colour along with sharp detail in the areas that need it.