Sally Jane Photographic Art
Adobe Photoshop Tutorial
Getting Started with RAW
ACR Sharpening and Noise Reduction Tools
Sharpening in any digital editing program is a bit of a misleading term. There is no such thing as sharpening. If an image is poorly focused you simply cannot fix it...end of story. What these tools really do is increase the contrast along edges to within a very narrow band either side of the edge. This can make the edge seem more defined and can, if used subtly on an already sharp image, make the image appear crisper.
The tabbed window that contains the sharpening and noise reduction tools has two tiny triangles as its symbol on the tab and is the second tab in from the 'Basics' tab. You will see it contains 6 sliders separated into two sections. The top 4 are the sharpening settings and the bottom two are for noise reduction. Initially, when you click on this tab the window might display some values even though you haven't applied any yet. These values are taken from your camera. Most digital cameras allow you to predetermine a certain amount of in camera sharpening and even noise reduction at certain ISO settings. The settings you see here are the default settings that my Nikon D300 has. I could change them on the camera if I wished but as I only shoot in RAW it makes no difference as I can change them or remove them as required here.
For this tutorial I am going to use an image I took in a the Vasa Museum in Stockholm. This is a museum built to house a tudor ship that sank on it's maiden voyage. It was salvaged some years ago and restored and is now on display in a purpose built museum. The lighting is dim with only the vessel lit to add drama. The display is very effective but lousy for photographers. Luckily my Nikon D300 allows me to utilise some very high ISO settings which enabled me to take some shots hand held. Even so, the images still have a noise problem as you might expect but this is really only noticeable when I zoom in to 100% which on a 12 mega pixel image is rarely necessary. Here is a section of one of the shots zoomed in to 100%. You always need to have the preview image zoomed in this far before you make any changes in this window because unless you do you won't be able to see the effects of your settings properly. Although it is at 100% zoom in my ACR preview window on your screen it will be much smaller as it will have been resized to fit on this page. for this reason I have also included a cropped down version below that should be truly 100% in your browser window.
OK, so here is the image with all the default settings removed. No sharpening or noise reduction applied. Pretty noisy and not very crisp. There is a limit to what can be achieved here but remember this is a small section at full size so seen at a more normal size this will still be a viable image. Below you can see it full size as explained above. I will provide a detail like this under every image.
First lets look at Sharpening, for no other reason than it is at the top. It is worth noting, that if you intend to make further edits in Photoshop then it is probably not worth worrying about sharpening here. A better result can be achieved in Photoshop after all other edits have been completed. However, as most of my images don't get edited in Photoshop I generally apply a small amount of sharpening here just to give the image a bit more punch. It is also worth noting that the higher the resolution of your image the more effect these tools will appear to have. This is, as I have already said, a 12 mega pixel image, so the effects are quite subtle. That's fine by me as I like sharpening to be subtle. In my mind, if someone can tell you image has been sharpened digitally then it has been over done and ruined.
Because the effects are subtle and also because these are now web images I will take things to the extreme a bit or otherwise you won't see the effects. Here, in the two images above, I have taken the sharpening amount all the way up to 150 which is the max. I have left the Radius at 1. The lowest you can take the radius is .5 but I'll explain more about this next. There is not a huge amount of difference to bee seen but I think you can just about tell it's a bit crisper.
By moving the Radius slider all the way to the right to a max value of 3 the contrast along the edges has increased, see the two images below. The highlights in the rigging are broader. The radius sets the width either side of any detected edges that you want to effect. I like to keep this to 1 or .5 as any wider starts to look artificial in my opinion.
Now, in the images below, I will show you the effect of the Detail slider.
This is really popping this image but it has also increased the visibility of the noise. This is because the detail slider tells the program to include tiny details in the sharpening. The further you take the slider right the smaller the details are that will be sharpened. When take this far the program cannot distinguish between fine detail and noise so the noise is 'sharpened' or in reality, made more contrasty.
The last slider is Masking and this one is a bit of an anomaly as far as I am concerned. In the below two images I have moved the Masking slider all the way to the right with the Detail slider also still there.
It appears at first glance to have completely reversed the effects of the Detail slider but actually its done slightly more and has reversed some of the other effects too. It actually seems to be a bit of a backward step. If you drag your mouse over the bottom image you will see it flip back and fourth between Detail and Masking full on and Detail and Masking full off.
Remember, for this demon I have taken everything to the extreme and even with this if viewed at a normal size the total effect would be minimal. If you were to use the Unsharp Mask or Smart Sharpen features in Photoshop you could achieve much better and stringer results where required.
These next two sliders are useful to use in ACR. Yes you can deal with noise in Photoshop but better to do it here where the effects will always be reversible. Once again, the effectiveness of the sliders will depend upon the resolution of your image. The higher the resolution the less effect the sliders will have which is why noise reduction works better on RAW images taken from my 8 mega pixel Nikon Coolpix E8800 than they do with images taken from my 12 mega pixel Nikon D300 as shown here.
OK, I've reset the sharpening to what I think is reasonable for this image so now it is time to sort out that noise problem. The two sliders tackle different aspects of noise. The Luminance slider tackles greyscale noise which appears as dark and light speckles and accounts for most of the noise problems. The Color slider takes care of Chroma noise or phantom colour flecks. This image has a lot of both that you can easily see without my posting a larger view.
First I will show you what happens when I move the Luminance slider all the way to the right.
You can see that most of the speckling has gone but the spots of phantom colour remain.
Now lets see what happens if I return the Luminance slider to '0' and move the color slider all the way to the right.
The speckles have returned but the colored speckles have all gone.
Lastly, lets see what it looks like with both sliders taken up to their full strength.
The noise has almost been completely eradicated but at a cost. There is, and will always be with any noise reduction program, some loss of detail. Overall though, considering just how bad the noise was, the damage is not bad and when seen at a more normal size, is not even noticeable. To prove that, here, below, is the whole image in three different states. the first shows the image with all the settings for sharpening and noise reduction turned off, all sliders at '0'. The second image has all the settings at 100%, fully on. The last has the settings as I think suitable, Sharpening at '75', Radius '1', Detail and Masking at '0' luminance at 75% and Color at 25%. By clicking on any of these 3 images you can see the full resolution 12 mega pixel version in a separate tab but it might take a while for it to download depending on the speed of your internet connection.
The noise in this image can be seen even without seeing it full size.
Much clearer but a touch over sharpened. Notice how the spot lights in the top right hand corner seem like they don't quite belong. The rigging is a little harsh too but not bad.
Not a bad final result. Not perfect but still a good image for a hand held shot in very poor light.
In the next tutorial I will discuss the HSL/Grayscale tools.
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