March 2009

How to Sharpen Photos: An Introduction

We’ve received quite a bit of feedback from Post production readers asking us to look at the issue of sharpening photos. Sharpening is one of those everyday tasks that most photos can benefit from. In this post I’ll explain what sharpening is, when you should perform it and how to do it. The information here, although it is explained using Photoshop, is relevant to all photo editing programs.

Please click images to enlarge in this tutorial - it will illustrate much better the points being made with images at full size.

Sharpening does as its name suggests and sharpens the image making it look crisper and making the edges in the image more distinct.

In the darkroom the process is achieved by taking one negative and a slightly blurred positive image, sandwiching these together and making a very quick exposure of this sandwich. Then the exposure is completed using the negative. The resulting image has sharper and crisper edges than it would have had if the blurry (unsharp) mask image had not been used. The typical sharpening tool used in Photoshop and other graphics programs is named after this traditional darkroom process and is called the Unsharp mask.

In a graphics editor the Unsharp mask works by creating small halos along the edges in the photo. These halos enhance the contrast between the edges and the surrounding pixels making the edges look more obvious and giving the image a crisper and sharper look.

Here’s how to sharpen an image using the Unsharp mask:

Step 1

Sharpening should be done at the end of the editing process so finish doing all your edits to the image before you sharpen it.

Now create a flattened version of the image either by flattening or merging all the layers or press Ctrl + Alt + Shift + E (Command + Option + Shift + E on the Mac) to create a flattened layer at the top of the image. The Unsharp mask works only on the current layer so you need to have the image on a single layer for it to do its work.

Step 2

Choose Filter > Sharpen > Unsharp Mask. Set the Radius to somewhere between .5 and 1. This sets the width of the halos which are applied along the edges in the image – the smaller the radius, the smaller the halo and 0.5 – 1 is ideal – this is not always a situation where the more is better!

Set the Threshold to around 10. The Threshold value determines how edges are found – the higher the value, the more different adjacent pixels must be to be considered an edge so less of the image will be sharpened. A small value means that smaller differences in pixel values are considered an edge so more of the image is sharpened. The risk with a small Threshold value is that it can add noise to the image by enhancing edges in places where you don’t want to see them.

The Amount setting controls how much contrast is added to the edges – a higher value means more contrast and a more obvious sharpening. Start by setting this value to around 150.

Step 3

Take a look at your image and adjust the sliders from this starting point until you see more detail in the edges in the image but not so much that you see unattractive halos around the edges.

Typically, if you have an image with a lot of very fine detail you can use a very small radius value (so the halos are small) and a correspondingly high Amount value (so that the halos can be seen to sharpen the image). On the other hand, if you have an image without a lot of fine detail can use a larger radius say, 1 – 1.5 or more (which gives larger halos), and a smaller Amount setting because the halos will be bigger and more visible anyway.

Adjust the Threshold value so you get sharpening in the areas you are interested in being crisper but not so that it results in unwanted noise in the image.

This image is nicely sharpened – you can see the crisper edges.

This image is over sharpened – notice the unsightly halos around the edges.

Tips

It is generally advisable to view the image at 100% when you are sharpening it so you can see the effect on the image. You can do this by sizing the image to 100% before launching the Unsharp mask tool. Alternately, use the 100% preview in the Unsharp mask dialog –click on the preview to see the unaltered image so you can compare it with the preview..

When you are sharpening for printing you can generally sharpen more heavily than you should do for onscreen viewing.

There are other sharpening tools available in Photoshop CS2 and later which do an even better job of sharpening than the Unsharp mask. I’ll look at these tools in a future post. For now, regardless of which graphics editor you use, you should have an Unsharp mask tool and it should work in a similar way to the Photoshop Unsharp mask shown here.

Click here to View more...

The Orton Effect: Mimicking darkroom processes in Photoshop

Photoshop gives us tools we can use to create effects which previously could only be obtained in the darkroom using images which were captured specially. One such process is the Orton effect named after photographer Michael Orton. This process results in a somewhat surreal image which has a slightly out-of-focus look while retaining lots of edge detail.

In the darkroom this effect is created using two images one of which is slightly out of focus and both of which are slightly overexposed. Sandwiching these together and taking a print yields a photograph similar to the one above.

Thanks to Photoshop we can create this effect from a single well exposed image and create the overexposed and soft focus looks digitally.

Here is how to create this Orton effect on an image from your collection:

Step 1

Open the image, right-click the background layer in the layers palette and select Duplicate layer. With the duplicate layer selected choose Image > Apply Image, select the Screen blend mode and click Ok. This applies the image to itself in screen mode which is the same as creating an additional duplicate layer, setting this layer’s blend mode to Screen and then merging the two layers. The benefit to using Apply Image is that you do it all in one step.

Step 2

Duplicate this layer and set its blend mode to Multiply. This has the effect of cancelling out the lightening effect from applying the Screen mode.

Step 3

With this topmost layer still selected apply a blur to it using Filter > Blur > Gaussian Blur. Select the Preview checkbox so you can see the result on the image. Adjust the blur Radius to your choice of value – I used 4.5 but choose the best for your image. Notice that, if you create a very large small or very large blur, the effect all but disappears.

Step 4

If the image isn’t light enough, return to the middle layer and repeat Step 1 to apply the image to itself again in Screen mode.

Then, if desired, add some noise to the image to give it a grainy look. To do this, choose Filter > Noise > Add Noise. Disable the Monochrome checkbox, click Gaussian and adjust the amount till you get a slightly grainy feel to the image.

The result is a soft focus image which still has lovely detail in the edges and it is a process well suited to being used with portraits as well as landscapes and cityscapes.

Using Photoshop Elements?

The same effect can be achieved in Photoshop Elements but you will need to perform step 1 the long way. To do this, duplicate the Background layer twice, set the top layer’s Blend Mode to Screen then choose Layer > Merge Down to merge it to a single layer. There is no Apply Image command in Photoshop Elements.

Click here to View more...

How to Keep a Log of Your Work in Photoshop from Digital Photography School

How many times have you created a neat effect on an image using Photoshop and then wanted to duplicate the effect on another image? The problem is that unless you’ve taken notes about what you’ve done,

it is often difficult if not impossible to remember exactly the steps you took to get the final image.

While Photoshop has a History feature this is of limited use. One problem is that, by default, Photoshop only stores 20 history states so, if you’ve performed a lot of steps they may not all appear in the list. The second problem is that, even if you have configured Photoshop to store a large number of history states, all you see in the History panel is a brief description of what you did to the image such as Gaussian Blur, Apply Image, Blending Change and you don’t see the actual settings used.

The History panel in Photoshop lists the basics of what you’ve done but not the detail.

Here are some ways to improve on the basics and keep a log of your work:

Step 1

Before you start work on an image choose Edit > Preferences > General and select the History Log checkbox. You can select to save log items to the image Metadata, to a separate text file or to both. If you select either Text file or Both you’ll be prompted to enter a file name and a location to save the file to. Do this and click Save.

From the Edit Log Items dropdown list select Detailed. Sessions records only the time you spend working on a file, Concise records the Sessions information and the detail from the History palette and Detailed records the detail about the changes – it’s Detail you need.

Step 2

Now, when you work on an image, the detail is stored in the text file, the Metadata or both, depending on the setting you chose.

If you chose to store the data in a text file you can later open the text file with a word processor or a text editor such as Notepad on the PC.

If you chose to record the history in the image metadata choose File > File Info > History and you can read details of the edits you made to the image in the dialog. Use this information to perform the same steps on another image

Tip

To configure Photoshop to store more than the default 20 history states, choose Edit > Preferences > Performance and set the History States value to a higher number. You should note that this History information is available in the History palette and only while the image is still open – it is lost when the image is closed – unlike the Log data which is stored permanently.