Sharpening
The Adobe Photoshop Lightroom book 1.1 Update:
Sharpening and noise reduction
Capture sharpening for a sharp start
In this feature story I wanted to concentrate on the new sharpening and noise reduction controls in Lightroom 1.1. But before discussing the new sharpening controls, I should briefly explain the principle behind capture sharpening and the difference between this and output sharpening.
The Unsharp Mask filter in Photoshop has been around since the very earliest days of the program and has not really changed much since then. As Photoshop has matured our understanding of sharpening and how to best use the Unsharp Mask filter controls has improved and various techniques have evolved that cleverly use the Unsharp Mask filter to its best advantage. In his lifetime, author and Photoshop guru Bruce Fraser, did the industry a great service with his research into Photoshop sharpening. His recipes for optimum sharpening based on whether you were sharpening for input, i.e. ‘capture sharpening’, or sharpening for output, have done a lot to improve our understanding of how to apply the most appropriate level of sharpening at each step of the image editing and printing process. It is also fair to say that Bruce’s research and writing had an impact on the way some of the sharpening controls in Lightroom evolved. But more of this later.
Capture sharpening is all about adding sufficient sharpening to a photograph in order to correct for the inherent lack of sharpness that most digital images suffer from to a greater or lesser extent. If you shoot using raw mode, then your photographs will arrive untreated in Lightroom and they will most definitely need some degree of sharpening. If the photos you import have originated from a digital camera shot using the JPEG mode, then they will already have been sharpened in-camera. The Detail panel sharpening controls in Lightroom are therefore intended for use with photographs that are raw originals or non-raw files that have not been sharpened yet.
The main goal with input/capture sharpening is to correct for the lack of sharpness in an image. Capture sharpening is therefore something that you can evaluate on the monitor (providing you use the 1:1 view setting) and it is all about making the photograph look just sharp enough on the screen. You don’t want to over-sharpen at this stage, since that can lead to all sorts of problems later at the retouching stage in Photoshop.
Output sharpening is something that is always done at the end, just prior to making a print, and if you are familiar with the Lightroom Print module, you are aware of the sharpening options available there. But note that Lightroom does not allow you to see on the screen the effect of output sharpening. The print sharpen processing is hidden from view and the only way to evaluate print output sharpening is by judging the print. But I am getting ahead of myself here. This section is all about the capture sharpening and what’s new and special about the sharpening controls in Lightroom 1.1.
Sharpen preset settings
Perhaps the easiest way to get started is to use either of the two new Sharpen presets found in the Develop module Presets panel (Develop presets are also available via the Library module Quick Develop panel). These two presets can be a useful starting point when learning how to sharpen in Lightroom 1.1. All you have to do is decide which of these two settings is most applicable to the image you are about to sharpen.
Sharpen – Portraits
As you read the rest of this section it will become apparent what the individual sliders do and which combination of settings will work best with some photographs and not others. But to start with let’s look at the two preset settings found in the Lightroom Presets subfolder. Shown below is a 1:1 close-up view of a male portrait where naturally enough I chose to apply the Sharpen – Portraits preset. This combination of sharpening slider settings is the most appropriate to use for portraits male or female, or any photo where you wish to sharpen the important areas of detail such as the eyes and lips, but protect the smooth areas (like the skin) from being sharpened.
Sharpen – Landscapes
The other preset setting you can choose is Sharpen – Landscapes. This combination of sharpening slider settings is most appropriate for subjects that contain a lot of edge detail. You could include quite a wide range of subject types in this category. In the example shown below I used the Sharpen – Landscapes preset to sharpen an architectural scene. Basically you would use this particular preset whenever you needed to sharpen photographs that contained a lot of fine edges.
Getting to know what the sharpening sliders do
These two preset settings provide you with a great way to get started, make the most of the new sharpening settings and get improved sharpening without having to understand too much about how the sharpening in Lightroom 1.1 works or what the individual sliders do.
Sample sharpening image
To help explain how the individual sliders work, I have prepared a test image that has been carefully designed to try and show some of the key aspects of Lightroom 1.1 sharpening. You can access this image by clicking here to download a high quality JPEG version of the image file used here. This is the exact same size file as used in these demo screen shots.
This image was specially designed to demonstrate several key aspects of Lightroom sharpening. The eye and surrounding skin texture allows you to see the effects of portrait style sharpening where the objective is to sharpen detail like the eyelashes, but avoid sharpening the skin texture. Conversely, the patchy texture in the bottom right corner allows you to test the ability to sharpen smooth texture content where you do want to emphasize the texture detail. The high contrast detail content in the left hand section allows you to test the effects of sharpening on fine-detailed image content. And the crisscross lines have been added so as to highlight the effects of the Radius setting.
Evaluate at a 1:1 view
But first things first. When you go to the Detail panel to access the Sharpening slider controls, a warning triangle will appear if the photo you have selected is displayed at anything less than a 1:1 view. If you magnify the image view to 1:1 or higher, the triangle will disappear. Or, you might just want to click on the triangle itself – this acts as a direct route to a 1:1 view. In any case, the grayscale previews I’ll be discussing shortly won’t work unless you are viewing the image at 1:1 or higher.
Luminance targeted sharpening
The first thing to say about Lightroom sharpening is that the sharpening is only applied to the luminance information in a photograph. Lightroom always filters out the color content when it applies the sharpening. This is a good thing because sharpening the color information enhances any color artifacts and it is the luminance content that we really want to sharpen here. In the early days of Photoshop, people sometimes converted an RGB image to Lab mode and sharpen the Luminosity channel separately. This technique allowed you to sharpen the luminance information without sharpening the color content. More recently (from Photoshop 3.0 onwards), it has been easier (and less destructive) to sharpen in RGB mode and use the Luminosity blend mode to restrict the sharpening to the luminance information. Lightroom does a similar thing here: it filters out the color content when sharpening. For this reason it can be useful to inspect the image in luminance mode when working with the slider. You can do this by holding down the Option key (Mac), Alt key (PC) as you drag on the Amount sharpening sliders in the Detail panel. In addition to this you can hold down the same Option/Alt key to isolate the effect the other slider controls are having.
The sharpening effect sliders
Let’s start by looking at the sharpening effect controls: Amount and Radius. These two sliders control the how much sharpening is applied and how the sharpening is distributed. As I mentioned earlier, you can download this image and import it into Lightroom and copy the steps described here. Note that all these screen shots were taken while holding down the Option key (Mac), Alt key (PC) as I dragged on the slider controls.
Amount slider
1. The Amount slider is like a volume control. The more you apply, the more you sharpen the image. In this respect it works in a similar way to the Amount slider in the Unsharp Mask filter. The Amount range can go from zero (no sharpening) to 150 (maximum sharpening, where the slider scale goes into the red). The 150 setting goes well beyond the 0–100 range that was available previously, but there is a reason for this: you can use the sharpen suppression controls (described a little later) to dampen the effect of the sharpening. Although you are rarely going to need to set the sharpening as high as 150, the extra headroom is available should you need it. In this above example you can see what the image looks like using the default 25 sharpening.
2. As I increase the Amount sharpening to 100 you can see how all the detail in the image looks crisper. But used like this, the Amount slider is a fairly blunt instrument and it is the newly included ability to modify the distribution of the sharpening and filter out the edge halos that makes Lightroom 1.1 sharpening so special.
Radius slider
1. For this step and the next I held down the Option key (Mac), Alt key (PC) to isolate the effect that the Radius setting would have on the image. At the minimum Radius setting you can see that a small radius will have the greatest effect on the narrow edge detail such as the fence wire in the picture and very little effect on the soft edge detail such as the eye. Notice also the effect the small radius has on the crisscross lines.
2. When I take the Radius slider to the maximum setting notice how the halo width increases to the point where the halos have less real sharpening effect on the fine edge detail. The sharpening around the wire fence area looks kind of fuzzy, but at the wider setting there is more noticeable sharpening around the eyelashes of the eye and the eye pupil.
The suppression controls
The next two sharpening sliders act as dampening controls that modify the effect the Amount and Radius sharpening settings have on an image.
Detail slider
The Detail slider cleverly suppresses the halos effect and thereby allows you to concentrate sharpening on the edge areas. This in turn allows you to apply more sharpening with the Amount slider, adding sharpness to the edges, but without generating noticeable halos around them. A setting of zero will apply the most halo suppression and a setting of 100 will apply the least halo suppression.
1. In this step the Detail slider has been set to zero. I am holding down the Option/Alt key to preview the effect this slider setting adjustment is having in isolation. When the Detail slider is at this lowest setting nearly all of edge halos will be suppressed. The combination of a low Detail setting and a medium to high Radius setting will allow you to apply a strong sharpening effect to bring out details like the eye and eyelashes while suppressing the halos on the smooth skin tones.
2. When the Detail slider is raised to the maximum setting, all of the sharpening effect is allowed to filter through, unconstrained by the effect ‘Detail’ would otherwise have on the sharpening effect. When Detail is set to 100, you could say that the Amount and Radius sharpening settings are allowed to process the image with almost the same effect as the Unsharp Mask filter in Photoshop.
3. When the Detail slider is set to a midpoint value between these two extremes, we see how the Detail slider can be used to target the areas that need sharpening most. If you refer back to the sharpen preset used at the beginning, a lower setting of 20 is suitable for portrait sharpening because it will suppress the sharpening more so the smooth tone areas. A higher Detail setting will carry out less halo edge suppression and is therefore more suitable for emphasizing fine edge detail.
Interpreting the grayscale sharpening preview
This would be a good point for me to explain what the grayscale previews are actually showing us here. As I have already stated, if you hold down the Option/Alt key as you drag on the Amount slider, you see an accurate preview of the cumulative effect that all the sharpening sliders are having on the Luminosity information in an image. But when you Option/Alt drag on the Radius and Detail sliders you are seeing a rather different kind of preview, because with these you are able to preview the sharpening effect in isolation.
What does this mean? The more experienced Photoshop users will perhaps understand better if I explain that this is a little (but not exactly) like previewing a duplicate layer of the Background layer after you have just applied the High Pass filter. There is a Photoshop sharpening technique where you apply the High Pass filter to a duplicate of the Background layer to pick out the edge detail and set the duplicate blend layer to Overlay mode. The High Pass filter will turn most of the image a mid gray. When you set the layer to the Overlay blend mode, the mid gray areas will have no effect on the appearance of the photograph, while the lighter and darker areas in the layer will build up the edge contrast. The Radius and Detail Option/Alt mode previews are basically showing you the edge enhancement effect as if it were an isolated sharpening layer. And what these previews are showing you is the combination of the Amount, Radius and Detail slider settings in an isolated preview.
I’ll come on to the Masking slider adjustment next, but I should point out that the Option/Alt mode previews for the masking slider are showing you a mask that limits the sharpening adjustment. The best way to interpret this preview is to imagine the preview of the sharpening adjustments as being like a sharpening layer above the image and think of the masking preview as a layer mask that has been applied to that imaginary sharpening layer.
Masking slider
The Masking slider adjustment adds a final level of suppression control and was inspired by Bruce Fraser’s written work on his Photoshop sharpening techniques. If you want to read more about Bruce’s techniques for input and output sharpening plus his creative sharpening techniques, I highly recommend you check out Real World image sharpening with Adobe Photoshop CS2 (it is still just as valid if you are working with CS3). The basic concept of the masking control is that you use this slider to create a mask that is based on the image content that protects the areas you don’t want to have sharpened.
If you take the Masking slider all the way down to zero, no mask will be generated and the sharpening effect will be applied without any masking. As you increase the Masking setting more areas will be protected. The mask is generated based on the image content such that areas of the picture where there are high contrast edges will remain white (the sharpening effect is unmasked) and the flatter areas of the picture where there is smoother tone detail will turn black (the sharpening effect is masked). The image processing required to process the mask is quite intensive, so if you are using an older computer it may seem slow as the preview takes its time to update. But on a modern, fast computer you will hardly notice any time delay.
1. In this example, I set the Masking slider to 50 and held down the Option/Alt key to reveal the mask preview. Again, always remember that the Option/Alt previews will only work if the image is viewed at 1:1 or higher. At this midway setting you will notice how the flatter areas of the picture are just beginning to get some mask protection such as the skin tone areas around the eye.
2. As the Masking setting is increased to the maximum of 100 you can see how more of the flatter tone areas are now protected while the high contrast edges are preserved. At this extreme setting, Lightroom sharpening only applies to the areas shown in white. The black portions of the mask are completely protected and no sharpening will be applied in these areas.
Applying manual sharpening adjustments
Now that I have given you a run down on what the individual sharpening sliders do, let’s look at how you would use them in practice to sharpen an image.
1. In this first example I adjusted the Sharpening sliders to provide the optimum amount of sharpening for the fine detail areas. I applied a Radius of 0.7 to add small halos around the edge details and a Detail of 70 in order to limit the halo suppression. And I applied an Amount of 45 to make the fine edge detail nice and crisp. The Masking slider was set to zero, which meant that no mask was used to mask the sharpening effect.
2. In this second example I adjusted the Sharpening sliders to provide the optimum amount of sharpening for the soft edged detail around the eye. I applied a Radius of 1.5 to build wider halo edges around the eyelashes, but at the same time I used a Detail setting of 20 to suppress the edge halos. The Radius setting still has an effect on the sharpening, but the Detail slider is nicely suppressing the halo edge effect to produce a smoother looking sharpening effect. The Masking slider was taken all the way up to 85, so that I could target the sharpening on the areas that needed sharpening most, i.e. the details in the eye and eyelashes. You will note that the Amount was set to 33. This is a higher value than the previous default of 25, but this is because the sharpening is being substantially suppressed by the Detail and Masking sliders, so it is therefore necessary to apply a larger Amount setting.
Noise reduction
The noise reduction in Lightroom has undergone some improvements in this latest update. It may be hard to see what these changes are exactly, but if you compare the slider setting adjustments in Lightroom 1.1 with those in Lightroom 1.0 side by side in close up, you can definitely see quite a difference.
As with the Sharpening controls, you can only evaluate the effect the noise reduction sliders are having by viewing the image at a 1:1 view or higher. In this screen shot I have shown two versions of a close-up detail of a photograph that was shot using the Canon EOS 400D at an ISO setting of 1600. The left half of the content area shows the Noise Reduction in Lightroom 1.0 using a Luminance noise reduction of 33 and a Color noise reduction of 33. The right half of the content area shows how the close-up section will look when those exact same settings are applied in Lightroom 1.1.
When you compare the settings side there is a distinct improvement in the way Lightroom 1.1 handles the luminance and color noise. In particular you can see how Lightroom 1.1 does a much better job of reducing the white speckles in the shadows. The noise reduction in Lightroom 1.1 may not be as spectacular as Noise Ninja or Noiseware. But it is now considerably more effective than it was before.
________________________________
If you have found this extract useful and would like to read more then you will be pleased to know that Martin Evening, author of The Adobe Photoshop Lightroom Book, has also written a free Lightroom 1.1 PDF supplement update for readers of his book. The PDF is a compilation of all the Lightroom 1.1 update Lightroom-news stories, is 177 pages long and will soon be available for download via the Peachpit website (registration required). This is not a book revision, but a supplement to the original book in which Martin Evening desribes in detail all of the new features found in Lightroom 1.1. Martin writes: “I wanted to provide a free update for Lightroom 1.1 that would satisfy readers who had already bought the book as well as all those who hadn’t bought it yet but wanted to make sure they were up to speed on all the new program features”.
How to download the PDF supplement
The PDF update supplement will soon be available free for everyone to download. All you will have to do is visit the peachpit website at: www.peachpit.com/register. There you will need to create a new account by providing your email address, full name and a password to access the site. Once you have confirmed your account details proceed to the register page and enter the 10-digit ISBN number of the book. Please note that this PDF is not limited to those who are buying the book. Everyone will be welcome to register and download the PDF. Just copy and paste the following ISBN number: 0321385438 as shown below.
You will then be ready to download the PDF supplement after it is published. Watch out for further announcements on Lightroom-news for when the PDF is ready to download.
The Adobe Photoshop Lightroom Book by Martin Evening is available from Peachpit, Amazon, Barnes & Noble and all usual bookstore outlets.
Martin Evening has worked on the development of Adobe Photoshop as an alpha tester from the program’s earliest beginnings. The Adobe Photoshop Lightroom Book describes all of Lightroom’s features in detail, with photographers in mind. Photographers who routinely work with raw (and even jpg & tiff) images will find Lightroom–and The Adobe Photoshop Lightroom Book–an indispensable tool in their digital darkroom.
Lightroom-news has a free PDF download of Chapter 1. (click here to download-4.6MB PDF).