They are essentially two images sharing a theme or having something in common, placed together to form one image. These are of two types:
There is no rule that you have to create a diptych using images that have something in common, many times images that have nothing in common or don't look great on their own, can look attractive when viewed together.
The possibilities are endless, you can get really creative in making them. Here are a few examples where they can be useful:
As an example here, lets create a horizontal diptych by taking two images of 500px width and 750px height.
Step 1 - Creating the canvas: First lets calculate the size of the canvas.
Width: Let's add the widths of the two images, in this case - it is 500px + 500px = 1000px. We need a little bit of padding around the images So, lets add 5px at the beginning + 5 px between the images in the centre + 5 px at the end. This makes the total width =1000 px + 5*3px = 1015px.
Height: For the height, we just have to add the padding at the top + height of the images + padding at the bottom = 5px + 750px + 5px = 760px.
Now we have the width and height, lets create a canvas of size 1015 px * 760 px. To do this go to Click File --> New --> Enter 1015px for width and 760px for height --> Click OK
Step 2 - Place the first Image: Click File --> Place --> Browse location for Image 1 - Once the image is placed on the canvas, move it around and adjust its position towards the left, while allowing space for the padding.
Step 3 - Place the 2nd Image: Click File --> Place --> Browse location for Image 2 - Once the image is placed on the canvas, move it around and adjust its position towards the right, again while allowing space for the padding.
Step 4 - Save the image: Click File --> Save for Web --> Name the file and click save - That's it, its really simple to create diptychs.
Diptychs are essentially nothing but 2-image collages. Isn't it? Using a similar technique, you can create 3-image collages that are called triptychs (like the post cover photo). You can get really creative in experimenting with the orientation, position and size of these images to form a variety of collages. Its all about just pulling and placing the images onto the canvas in a cohesive way that forms a collage.