More from my tabletop education, this time on expanding depth of field through a subject. One way is to close down the aperture to a small size (more than f/16) but this diminishes the sharpness which can be noticeable in a close-up composition. The other way is to make many images, each one focused on a different point on the subject and then stitch them all together to give a deeper depth of field.
Keep in mind your lens has only one focal point that exists as a plane parallel to the sensor (or film). Depth of field is the distance in front of and behind the single point of focus where our eyes don’t notice a change in focus. It’s technically defined as the circle of confusion. Think of a point that is perfectly focused by your lens. As you move the point of focus back and forth the original point will start looking blurred or out of focus (confused, as it were). The depth of field is simply the bounds between which a change in focus doesn’t make the point look blurred. Depth of field is a function of lens construction and aperture size, which is why sharper lenses with wide depths of field are usually more expensive.
Anyway, here’s an image I made using the second method – many images stitched together. One issue with this technique is it’s almost impossible to do out in the natural world – nothing sits still for long enough!
ISO 100, 1/250 sec., f/8
This was made from 11 individual images, each one focused on a different part of the flower. I started with the deepest part of the bloom and worked my way out to the edges of the petals. In Photoshop there is a command that will auto-align the set of images (to make sure everything lines up and there are no ghost lines in the final image) and then auto-merge all the images together. I guess the command was designed to look for “in focus” areas because that’s what gets selected from each image to make up the final image.
It’s almost unrealistically in focus. Our eyes don’t see it like this unless in a photograph so initially it looks odd but our brains quickly adapt. Cameras don’t see it this way, either. The macro lens I used to make this, at the distance I was from the bloom, has a depth of field measured in millimeters, even with the aperture fully closed down to f/22. A single image focused on the stamens (those yellow fluffy balls) would show the edges of the petals and back of the blossom as blurred.
Sometimes a picture is worth more than we can imagine when it shows us something we can’t normally see.
