Image Sharpening with Lightroom
Although this article was developed for and is illustrated with Lightroom 3, the same techniques remain valid for the current version of Lightroom.
Lightroom 3 has a great workflow built from the ground up around photographers. It also has an excellent RAW converter which I now use for most of my work. One of the most impressive aspects of this converter for me is its sharpening and noise management capability.
The sharpening and noise reduction tools are located in the Details area which is found in the Develop module of Lightroom. The top part of the panel provides a view of any area of the active image at 100% magnification. This is supposed to be an aid to help you judge the effect of sharpening. In practice I find it much more effective to zoom in to 100% on the actual image.
To the top left of the detail panel is a small white square. This allows you to control where on the image the 100% preview is taken from. Simply click on the square and then click on the area of the image that you would like to preview in the panel.
Further down the detail panel you see the sharpening tools which at first glance might seem a little crude in comparison to all the options offered in Photoshop. As you will see later however there is a lot happening behind the scenes and these few sliders are remarkably powerful tools.
At the bottom of the details panel are the noise reduction tools. Lightroom splits noise into two types and provides separate tools for dealing with each. Color noise is seen as different coloured pixels in the image that give it a speckled appearance and can interfere with the colour. Luminance noise is a little like film grain and affects the sharpness of the image as well as giving smooth areas of tone (such as a clear sky) a course, gritty appearance.
Lightroom Sharpening Tools
Before deciding the best way to use the various tools it’s a good idea to understand the effect each one has on the image.
Amount Slider: This increases the amount of sharpening being applied to the image. When the slider is at 0 there is no sharpening and the other sliders become greyed out or inactive as shown above. At the other end of the scale is a value of 150 which is the maximum level of sharpening. If however you set all the other values set to their minimum values, increasing the Amount slider to the maximum has very little effect.
Radius Slider: Sharpening works by increasing the contrast along edges to make them more obvious to the eye. The wider this area of increased contrast the more obvious it becomes and the sharper the image might appear. The width of this area of increased contrast is determined by the Radius slider. The minimum value is 0.5 and the widest is 3.0. I have been told the values relate to pixel widths but I’m not sure how you get a value of less than 1 pixel.
If you are finding it hard to understand what is happening when you increase the Radius slider try this:
- Open an image and zoom in to 100% so you can see the detail
- Increase the Amount slider to 100
- Hold down the Alt key on the keyboard and whilst you are holding it down move Radius slider between its maximum and minimum values.
- You will see the main image changes to grey and show the edges that are being sharpened. As the value increases you will see the contrast edges get larger. You will often here the term halo used to describe these areas of increased sharpness as they appear like a halo around the edges in the image.
You are probably now wondering which radius value is best so shortly I will introduce you to my workflow which will help you achieve good results in most instances. Before this however here are some guidelines:
- For images containing lots of fine detail such as a landscape you will probably need to use a very small radius. This is to prevent the halos in the areas of detail interfering with each other which can actually reduce the sharpening effect.
- For images where there are areas of larger detail use a larger radius. An example might be a portrait where you wouldn’t want the pours of the skin to be emphasised but you might want the eyes to appear sharp. In these circumstances a larger radius will probably be best.
These are however just guidelines and each image will require unique treatment as well as adjusting the other images.
Detail Slider: This is a very clever slider that helps suppress the halos that were created by the Radius slider. This can help you better target the sharpening effect on your image. Move the slider to its maximum value of 100 and there is no suppression where as a value of 0 gives the maximum suppression. As with the Amount slider, you can hold down the Alt key as you move the slider in order to see what is actually going on. I have also included a screen grab below where the left half of the image shows the effect of a 0 setting and the right half a setting of 100.
As you can see, the difference is very marked. At 100 the edge around the rock is very obvious and I can also see the luminance noise starting to appear in the sky. Clearly this is not good as we don’t want to emphasise noise in the image.
Masking Slider: Is another control which limits how sharpening is applied by creating a mask from the image and applying sharpening through this. At a value of 0 there is no masking and every part of the image is sharpened. At a value of 100 the maximum amount of masking is applied and only the strongest (most obvious) edges are sharpened. Again holding down the Alt key as you move the slider allows you to see what is actually going on. In the screen shot below the left hand side of the image has a masking value of 37 where the right hand side has a masking value of 100.
You can clearly see the difference in masking. If you are unfamiliar with masking and what the image shows, the areas of black have no sharpening applied to them whilst the areas of whit do have sharpening applied. So if you are sharpening a portrait and see the skin pours being emphasised, the Masking slider can be used to prevent this by using a higher value.
Lightroom Sharpening Workflow
Here is the workflow I tend to use:
- Set the Luminance and Color noise reduction to 0. This assumes you have a low ISO image that contains little noise. The reason I set these to 0 before starting to sharpen is that they soften the image and prevent me from seeing accurately what is happening when I apply my sharpening. If however you have a noisy image shot at a high ISO you might want to apply a little noise reduction first so that your sharpening doesn’t just emphasise the nose.
- Zoom in to 100% on the image so you can see the impact of the changes you are making and pick an area with lots of detail that you want to target.
- Start by setting the Radius to 0.5, Detail to 100, Masking to 100 and finally Amount to 50. This gives a good starting position to understand how best to sharpen the image, especially for Landscapes which I tend to shoot most.
- Adjust the Radius to suit the type of image you are sharpening. With a detailed landscape image I tend to keep it between 0.5 and 1.0. With a Portrait or similar I will start at around 1.5. Try increasing and decreasing the radius until you achieve the best sharpness without problems becoming apparent in the image such as halos. Over time you will develop a feel for this but it does take practice. Don’t worry too much at this stage if you do start to see halos because you can hide them in the next step by reducing the Detail slider. It might be necessary to apply quite a lot of sharpening to bring out the best from an image before applying Detail and Masking adjustments to control any problems.
- At this point look around other areas of the image at 100%. You might find you have emphasised areas of noise in the image where you don’t want any e.g. the sky. If this is the case gradually increase the Masking slider until the noise is no longer visible but the detail in the image is still sharp.
- Now increase the amount further if need be to really emphasise the edges. At this point it’s likely you will start to notice the halos around the larger edges. Start to reduce the Detail slider to help suppress these so that they are no longer noticeable but the detail in the image is still sharpened.
- At this point you should have a nicely sharpened image. It is however worth just working your way around the sliders again to check you have a good combination. I should also point out that it’s not essential to get the image bitingly sharp at this point. Remember, all you are trying to achieve is a good conversion. You will need to sharpen it again once you have processed in order to prepare it for screen or print.
- Below is a before and after screenshot. The top half of the image is sharpened where the bottom half isn’t. It’s probably difficult to see on Internet samples but the difference is substantial.
Lightroom Noise Reduction
Whilst I have now sharpened my image I might still see traces of both luminance and colour noise. To resolve these problems I can use the noise reduction sliders.
Luminance Noise: You will see three sliders together which can be used to remove luminance noise (Luminance, Detail and Contrast). With the Detail slider set to 50 gradually increase the level of Luminance noise reduction until your problem areas are removed. If you find this causes areas containing lots of detail to soften you can increase the Detail setting to a higher value. Set this too high however and it can mask the effect of the noise reduction entirely. I find its best to look over the entire image and find an area where the Luminance Noise is a problem and has become obvious. I then concentrate on fixing this before returning to the key areas that I am trying to sharpen.
If you are wondering what the Contrast slider is for, so am I. I can only detect very slight impact on my images when I use it and I haven’t yet been able to find a comprehensive description that allows me to apply it effectively.
Color Noise: In this section there are two sliders, Color and Detail. Again find an area where colour noise is a problem and with the Detail slider set to 50 increase the Color Noise slider until the problem is corrected. If you have a particularly noisy image and you need to increase the noise reduction to quite high levels you may find colours start to bleed into each other. If this happens you can increase the Detail slider which should help reduce the problem.
Having made your adjustments to deal with image noise you might find that your image would once again benefit from further tweaking of the sharpening sliders. Equally however you might feel you have taken the overall image to the best level of sharpness possible but some areas could still benefit from being a little sharper. This is where the adjustment brush can help.
The adjustment brush is found at the top of the Develop module in Lightroom as shown is the screen shot below.
Selecting the adjustment brush will allow you to paint an adjustments to selected areas of your image, one of which is Sharpness.
When you paint increased sharpness on an area Lightroom applies additional sharpening to the areas you select using the same settings you created in the Detail tab. This can make a considerable difference to areas containing a lot of detail whilst avoiding areas that don’t need sharpening such as the sky.
I find the best way to do this is to paint the area that I want to adjust and then increase the sharpness until I am happy.
Whilst some areas might benefit from additional sharpening other areas such as the sky or a models skin in a portrait might benefit from less sharpening. Again the adjustment brush provides a great way to do this. Simply paint the area you want to selectively adjust and then move the sharpness setting to the left so that it is negative. This will reduce the sharpening in this area making it appear softer.
You now have the necessary tools with which to control the sharpening of your image in Lightroom. These are incredibly powerful but do take a little practice to become proficient.
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