This post is the second in a series about image sharpening. You can read the first part , “What Is Image Sharpening?” here.
What is Capture Sharpening ?
Capture sharpening is the process of sharpening an image for your screen to fix the softening process your image has gone through in camera.
Why sharpen for capture?
When you take a picture with your lens and sensor softens the image. The camera doesn’t make the image out of focus but there is a slight blurring applied to the whole image. The image is blurred because, cameras capture information using three colour channels; Red Green and Blue. Sometimes the camera will apply a random colour to a pixel or on a smooth line and curve create an artefact called stepping. Manufacturers don’t want us to have an image full of digital artefacts; they want us to have nice pictures. Part of the reason for capture sharpening is to counter this blur.
Another reason is for your image to be sharp on screen and you can see all the details in the image.
How to sharpen for capture
Process with all software has a similar idea, to sharpen the image without creating new artefacts and halos (Halo – a highlighted area next to a darker contrasted edge)
Capture sharpening in my workflow comes after cropping, colour balance and basic light adjustments. No matter what software I am using I will view the image at 100% on an area of the image that is supposed to be sharp. Viewing the image so close allows me to see and judge the sharpening effect.
I will usually move the settings to the most extreme and then pull them back to a point where I believe the image is sharp. I would then raise the settings again slightly and then pull back to check I had it right the first time.
Capture Sharpening can be stream lined, once you have rough settings for a specific lens and camera you can create a preset. This preset can be used again and again with some slight tweaking.
How Much Should You Sharpen?
The amount of sharpening is specific to each image and each camera/lens combination used. There will be a general setting for the device with more sharpening being needed. A high frequency image (landscapes or images with a lot of details) compared to a low frequency image ( a portrait or an image with a small amount of detail)may need a little bit more capture sharpening. What you want is for the image to be sharp, strong, well defined edges, without creating distracting artefacts or halos.
How To Sharpen
In Picasa the Sharpening tool is quite simple, using only a single slider. Pulling the slider right sharpens the image. Pressing down the shift key allows you to make adjustments in smaller increments, enabling you to make a more precise adjustment. To zoom in at 100%, you can use the slider at the bottom of the application window or click 1:1. Using the procedure above, moving the slider to the extreme of the right and then slowly back to the left until the desired sharpening has been reached.
Lightroom and Adobe Camera Raw
Lightroom and Adobe Camera Raw (ACR) the raw convertor for Photoshop, use identical sharpening panels. Lightroom and ACR default settings for sharpening of raw files to; a radius of 1 detail of 25 and an amount of 25. Jpegs are not auto sharpened because Jpegs are normally sharpened in camera, if set to do so. With that said it is still worth checking your Jpeg files, and applying a small amount of sharpening.
Lightroom and ACR use four sliders that are meant to be used together;
Amount – The strength of contrast added to emphasise edges.
Radius – how far from an edge contrast is applied.
Detail – controls how much fine detail information is allowed to be sharpened.
Masking – lets you emphasis the sharpening of obvious edges.
The first two settings are the easiest to understand, whereas detail and masking are slightly more confusing at first.
Once you have sharpened your image, if the fine details are not sharp then instead of sharpening more you can change the detail setting sharpening to only sharpen small details more. This is good for landscape images when there are a lot of small details in the scene.
Masking on the other hand works in the opposite way. If once you have sharpened the image and small details are being sharpened too much, which you would prefer to be smooth, you can change the masking setting to apply the sharpening more to strong edges. The higher the setting the larger the edge needs to be to be sharpened. This is good for low frequency images such as portraits where you don’t want lots of small details sharpened.
To help you sharpen your image you can press Alt while making adjustments and you can preview the image with a greyscale or contrasted black and white viewing mode to see more accurately what and what is not being sharpened.
If you edit mainly in Photoshop, then Adobe Camera Raw would be where you would apply capture sharpening to raw images.
In Photoshop itself there are a plethora of ways to sharpen an image using different image modes, and filters. If you are sharpening images in Photoshop, the best files to be working with is Raw and Tiff files instead of Jpegs, as they are uncompressed files. If you are a beginner in Photoshop the best filter (IMHO) to use is the unsharp mask filter.
When working in Photoshop the best way to edit is with a smart object, this is a non-destructive editing method, especially when the image is saved as a Tiff or Psd file, as you can come back to the file in the future and make changes that otherwise you wouldn’t be able to make.
In unsharp mask you have three sliders to make your sharpening adjustment with.
Amount – controls the strength of the contrast applied to an edge.
Radius – how wide an area the contrast is applied to.
Threshold – sets how many pixels define an edge.
The best way to use this tool is to set the radius at about 300% with a radius of about 2 pixels. I then adjust the radius until halos and artefacts appear. I then adjust the threshold until low detail areas are smooth and noise artefacts and halos are reduced.
There is more sharpening to come
Once you have applied your capture sharpening you can carry on editing being able to see what is sharp and what is not, but this is not the end of sharpening. Capture sharpening is applied globally to an image sharpening the whole image. There may or will be areas that you want to sharpen some more. Be it a flower, adding some extra sharpening to the petals or a portrait, sharpening the eyes and mouth a little bit more. This is the next sharpening step called creative sharpening, which I will write about in my next post.
If there is any software I haven’t mentioned and you would like to know how to sharpen with, let me know in the comments section below and I will add this to the post. If you have any other questions, comments or just want to chat, you can also use the comment box as well. I look forward to hearing from you.
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