Tuesday, November 5, 2013

Focus Stacking

Focus Stacking or Extended Depth-of-Field

Here is a trick for digital shooters that will increase depth-of-field. The technique is called focus stacking or extended depth-of-field and this is an easy software solution to a common issue in photography. This is not to say that it is always necessary to have nearly unlimited depth-of-field. Sometimes a nice soft out-of-focus background is essential such as in portraits or wildlife photography. There are other times when it is more aesthetically pleasing to have a photo where nearly everything is in focus. 

Start by taking a series of photos with the center of focus beginning in the foreground and extending through the picture. It is necessary to overlap the areas of focus so that areas between sharp points of focus are not out of focus. 

Here I have a bed of tulips and I have taken 6 photos and each photo has a different focus point until I have enough images so that there are no areas that are out-of-focus.You may want to use a system that indicates that these are sequential photos for a focus stack.  I use a photo of my fingers at the end of the shots that indicates the number of shots in the sequence. You may also want to work fairly quickly in case there is something that may move in the image.

It may be difficult to discern the center of focus in these low-resolution images, but believe me, there are different focus points throughout the image.  Once the normal processing for exposure, saturation, and contrast, etc. are done you can save these files for stacking. I save as a .psd file if I am going to print later. 

Using Photoshop CS6 I can now begin the process of stacking the images. In Photoshop go to File>Scripts>Load Files Into Stack. A dialogue box will open and you can either choose to load open files or browse to the images.  You will then see each image added as a layer. Click and Shift+Click so that all layers are selected. Now go to Edit>Auto-Align Layers. A dialogue box will open and you can just select Auto. Then select Edit>Auto Blend Layers and choose Stack and check Seamless Tones and Colors and Photoshop does the rest. When Photoshop finishes the stacking you can now flatten the layers and finish processing by sharpening and any cleanup or cropping as needed. 

There are other software programs such as Helicon Focus© that will do the same thing and you can even get into layers and masks to do this manually in Photoshop. However, it has been my experience that the latest version of Photoshop does a wonderful job and this is a great skill to have in your digital toolbox. 

Try it out. In the digital world what do you have to lose?