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How to Create a Magnified Inset with Photoshop

Learn how to highlight a specific area within an image and present it as a magnified insert on the main image.

In this tutorial you will learn how to use Photoshop to create a magnified insert of an area of interest on the image itself. It uses a combination of layers and the transform tool to bring an area of interest to life. Essential software needed: Photoshop CS2 or above, that has the ability to use layers.

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Video tutorial

Getting started: prerequisites

Before you start, you will benefit greatly from having a decent high resolution image of the general area you are interested in. In this example I will use the 2 pane mosaic of NGC7822 and the very small and faint Abell 1 planetary nebula that I noticed in the frame. I wanted to show its location as well as give an indication of how small it was.

You’ll also need Adobe Photoshop, version CS2 or later, so you have the ability to use layers.

Step 1: Open your image

Select your image of interest in Photoshop [PS]. This will open up the image and create it as a layer in the layers palette on the right hand side called Background.

Step 2: Rename the Background layer

Firstly, double click the Background layer in the layers palette on the right of the screen. This will bring up the New layer box where you should type in the name Original and then click OK.

Step 3: Select your area of interest

Within your image, there’s an area of interest that you want to highlight. You are selecting this area in this step so that you can use it as a reference for the size and location of the area of interest within the main image.

Use the marquee tool on the left hand side of the menu to select the shape that you want to area outline to be. In this case I have selected a circle. Move your mouse to the area, hold down the left mouse button, and select the area. You will see a dashed line showing the area of selection.

Place your mouse cursor within the selection and right click. This brings up the box shown and you want to move your cursor to Layer via copy, and click on it. This will create another layer on the right hand side that will contain just that area of selection.

Step 4: Rename the new layer

You are going to rename the new layer created above to small detail.

Note: These named layers are used in order to prevent confusion, when you can easily do the process you won’t need to rename these layers.

The layer is renamed by double clicking on it, and renaming it to small detail on the new layer box that opens.

Step 5: Duplicate the small detail layer

Right click on the small detail layer. That brings up a further menu box. At this point select and click on Duplicate layer and the layer box comes up again. Name this new layer as large detail and click OK.

You will now have three layers in the layers palette.

Step 6: Create group and organise the layers

We are now going to create a group containing the original and small detail layers. This is so that we can alter the size of both of these by the same scale.

Now we need to organise the layers accordingly. The group can be dragged and dropped around the layers palette as can the individual layers. You want to have your palette arranged in the following way: large detail above the group containing the original and small detail layers.

Step 7: Free transform (resize) the group

In this step you are effectively shrinking the layers in group 1 so that the large detail layer will be larger in size than the original selection.

Highlight group 1 in the layers palette by clicking on it. Then go to Edit->Free transform. Click on Free transform.

You will get a menu across the top where you need to do the following. Click on the lock between the W and H percentage. This will keep the scale the same for both width and height. I put 40% into this and it immediately shrinks the background accordingly.

In order for the transformation to be permanent, click on the move tool in the top of the left hand menu and you will be given a box to confirm if you want the transform applied. Confirm that and that transformation is complete.

Step 8: Create a border around the areas of interest

Double click on the small detail layer and ensure that it is highlighted in blue. From there the layer style box will be displayed and you want to double click on Stroke at the bottom of the box.

Now, select the pixel width (size) of the edge of the selection. Also double click on the Colour box and the Select stroke colour window allows you to choose any colour you like for the outline. In this case I have selected red.

Once these selections have been made, click on OK in both the Select stroke colour and Layer style windows. Now you can see that your selected area of interest has an edge around it.

Step 9: Copy the edge for the large detail layer

Now you want to copy the same edging for the large detail layer. Right click on the effects layer in small detail and you get a menu box. Click on Copy Layer style.

Now right click on the large detail layer, and that will become blue as well as the menu popping up again. Click this time on Paste Layer style. This will paste the same layer style into the large detail layer and you will see an equal red edge appear on the larger inset selection.

Step 10: Move the large inset to the background image

Coming towards the end of this process we are now going to move the larger selection into place on the original image.

Click on the move tool on the left hand menu. Now holding down your left mouse button, hover over the large selection and move it to wherever you want to place it on the finished original image.

Step 11: Create the guide lines between the two selections

Now we have 2 outlined selections, the first is the reference point in the main image. The second is an apparent magnified view of the selection that has been placed in a suitable place for comparison. We need to draw lines to visually aid the comparison of the two selections.

To do this create a new layer at the bottom left. This layer will be placed at the top of the layers palette above the other layers. For ease I like to move this in between the large detail layer and the group 1 layer. This is done as a simple drag and drop placing it between the two.

Ensure this new layer is highlighted. Click on the line tool in the left menu. The top menu displayed can be changed in the following way.

Here you are selecting the following.

  • Width (weight) of the line in pixels
  • Style of the line (I use no style in this case to keep it simple)
  • Colour of the lines (I prefer to keep them the same as the selection edges)

You may need to enlarge the area you are working on to get the lines in the best place. Draw lines from the edges of the small circle to the outer edges of the larger circle.

Step 12: Crop and flatten

Just to finish off this image you need to crop and flatten the image. Select the crop tool on the left menu and crop the selection around the original image. Press enter or return on your keyboard and the crop will be done.

All you need to do now is flatten the image so that all of the layers are compressed. Click on Layer->Flatten Image.

Now you have your main image, with an area of interest highlighted within the image as a reference and a larger highlighted selection showing greater detail that is easily seen and compared to the overall image.

Another style of inset magnification

There is no reason to keep the inset inside the image! See this example:

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About the author

Sara Wager

Sara Wager is a UK expat. She started imaging when she moved to Spain and it has now seemingly become a way of life! Initially enjoying general photography, she had an article published in a US photography magazine, but stuck firmly to astro imaging and its hardships in every sense.

She is an APOD recipient, winner of the International Astronomy Show 2015, and winner of Astrophotography Website of 2015 in Spain and Europe.

Sara has a home observatory in her garden and has had many published images, some competition wins and written articles for astronomy magazines. She is passionate about what she does as well as feeling a sense of responsibility for passing on help to others.

See more of Sara's work on her website.

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