Most digital photographers have experimented with various panorama stitching techniques using either bundled software applications like Canon’s PhotoStitch or ArcSoft Panorama Maker, or the PhotoMerge tool in Adobe’s Photoshop and Photoshop Elements. These applications work well with images that can be overlapped seamlessly; shot sequences where nothing has moved between the shots.
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Most digital photographers have experimented with various panorama stitching techniques using either bundled software applications like Canon’s PhotoStitch or ArcSoft Panorama Maker, or the PhotoMerge tool in Adobe’s Photoshop and Photoshop Elements. These applications work well with images that can be overlapped seamlessly; shot sequences where nothing has moved between the shots. But what can you do if you’ve captured two sequential shots in which the subjects have moved a little? In this feature we’ll explain one of the simplest techniques you can use. Our sample images capture a group of Red-necked Avocets (Recurvirostra novaehollandiae), feeding in a shallow inland salt lake. They’re typically around 45cm tall and fairly shy, so you need a good telephoto lens to photograph them. These shots were taken with a Canon EOS 400D fitted with an EF 70-300mm f/4.5-5.6 DO IS USM lens, which was used at the 300mm focal length, providing the 35mm equivalent of a 480mm lens. Although the background is unchanged, the birds have moved between one shot and the next, making it impossible to stitch the images together with conventional software. However, using the layers function in Photoshop, we were able to produce a convincing merge by following the technique outlined below. Step 1: Open both images and check the size of each image file, making sure the Resolution of both images is set at 300 pixels/inch (for printing). Take note of the Width of each image (32.92cm in this example, circled in red).  Step 2: Select the left hand image and click on Image > Canvas Size.  In the dialog box that opens, set the Width in the New Size area to double the width of the original image, move the Anchor to the left side of the box and make sure White is selected as the Canvas extension colour.  Step 3: Click on the right hand image and Select > All. You’ll notice the ‘marching ants’ selection indicator around the border of the picture.  Now click on Edit > Copy to copy this image to the Clipboard. Then click on the left hand image file and select Edit > Paste. This pastes the copy of the right hand image into the centre of the canvas. Once this is done, you can close the right hand image file because all further work will be done on the prepared canvas.  Step 4: Select the Move tool from the left side toolbar and move the right hand image to the right until the non-moving areas in both images overlap. You should see a Layers dialog box on the right side of your workspace (circled). The top layer (which contains the right side image) is highlighted, indicating it as the active layer you will work on.  Adjust the Opacity of this layer until you can see the underlying layer beneath it and, using the Move tool, move the top layer over the bottom layer until the rocks in both layers overlap. (Enlarging the image can be helpful when positioning the top image.) Don’t worry about any white areas on the canvas; they will be cropped away later.  Step 5: Return the Opacity slider in the Layers palette to 100% and select the Eraser tool from the left side toolbar. Use the Brush drop-down box to set an appropriate brush diameter (which will depend on the resolution of the images) and set the Hardness slider to about 60%. The following settings should appear in the boxes beside the Brush setting box: Mode: Brush; Opacity: 100%; Flow: 100%.  Enlarge the image before starting to erase the unwanted areas. Then, using the Eraser brush, carefully ‘rub out’ the areas in the top layer that don’t match the layer underneath. You will probably need to adjust the brush Master Diameter several times, using a ‘broad’ brush for areas where you can work relatively quickly and a narrow brush where precision is required.  Step 6: When you have achieved your objective and the picture appears to be continuous, zoom out and flatten the image by clicking on Layer > Flatten Image. This will to merge both layers.  You can now tidy up any areas that haven’t matched quite perfectly with the Spot Healing Brush. Enlarge the area you wish to work on before you begin. Set the Diameter to a fairly small value and the Hardness to less than 50% for natural-looking blending. Finally, zoom out and crop the image.  
The final result.
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