Get Amazing Depth of Field with Focus Stacking

When we think about creating a photograph with everything in sharp focus from a few centimetres in front of the lens out to the horizon, we immediately think that we will need to ‘stop down’ to an incredibly small aperture and focus at the hyperfocal distance. Unfortunately, that means we will have to use extremely long time exposures to make up for the light lost with the small aperture, and who knows where the hyperfocal distance is anyway!?

You could invest heavily in a tilt/shift lens instead, but there is a way to use your current lenses to get this result. I am going to describe the procedure on the assumption that Photoshop is available to you, but there are inexpensive software packages available as well to perform what is referred to as focus stacking (Google it).

Before we get to the software, let’s outline the image capture procedure. The idea is to capture a number of images of the same scene (a tripod is a must for this), successively refocusing from closeup to infinity in small steps. The successive images must overlap in terms of focus. For this reason, it would be wise to use a fairly small aperture (like f/16, if the light allows), in aperture priority or manual mode, to give each shot as wide a depth of field as possible. Small focus steps will ensure the in-focus zones from one shot to the next overlap each other. This will require some experimentation with your lens. Take as many shots as you want. This will guarantee a good result, and the software will have no problem handling them.

Note that as you refocus, the size of the image changes slightly. For that reason, the first job of the software is to align all of the shots based on their content. Because each shot contains zones that are out of focus, the next job of the software is to blend the images together while removing the defocused zones from each.

When aligning the shots, the software creates a layered file comprised of each shot on a different layer (hence the ‘stacking’ term). To eliminate the defocused zones, it adds a mask to each layer which blocks out these zones individually.

So here are the steps I use in Photoshop. It is possible to align and blend all shots at once, but I found it gave me screwy results. Instead, I do the following:

1.       Open all of the shots in your sequence (at the same time to save time)

2.       Select File > Automate > Photomerge.

3.       Under Layout in the dialog box, select Collage. Under Source Files click Add Open Files. Uncheck the Blend Images Together box (I do this to avoid the aforementioned screwy results). The software creates a new, layered ‘Panorama’ file with content on all layers now aligned. Note that you will probably have to crop the edges where overlap did not occur.

4.       Highlight all layers using Shift-Click or Ctrl-Click. Select Edit > Auto-Blend Layers…, then check the Stack Images radio button and OK.

Now here’s where it can get a little tricky. If you zoom in to the resultant image and find some soft-focused areas, it means Photoshop didn’t quite get the masks right in that area. If you find a number of these areas, the fix will take time and patience. You can turn layers on and off by clicking the eyeball icon on each layer. With all layers turned off except one, you will clearly see where the mask on that visible layer has eliminated part of that layer (checkerboarded areas). By stepping this way through all layers, you will see where the trouble spots are. You may need to erase these areas from one mask (where Photoshop has left in a defocused area) and add to the mask on another layer where that area is in focus.

How do you subtract from or add to a mask? Click on that mask (the rightmost rectangle on a layer), select the Brush tool from the tool palette and choose the white patch from the bottom of the palette, and paint the image. You will see this reveals more of the image on that layer; in other words, it is removing part of the mask. To cover up part of the image on a layer (in this case, a defocused area for instance), use a black brush. Adjust the size and hardness of the brush to get the desired control. As I said, this can involve a lot of work.

First Image in Sequence

The sample images here show the first and last images in a stack sequence, and the resultant focus-stacked image. The actual number of images in the stack was 11, but the first and last images demonstrate how the background and foreground, respectively, are distinctly out of focus.  All shots were made at f/6.3, so each has a shallow depth of field. Despite that, the resultant image looks terrific.

Last Image in Sequence

Of course, if you have decent light you could avoid using focus stacking by using a very small aperture such as f/22 and focusing at hyperfocal distance. But this too requires skill in determining the right focus point.

Focus stacking may be too over-the-top for many, but if you are passionate about pushing your photography up a notch, your efforts will be greatly rewarded by trying it.

Focus-Stacked Final Image

The Photographer’s Workflow: Organizing your Images

Unlike the 35mm film days, we don’t think twice about taking reams of shots with our digital cameras. We’re only limited by the amount of camera memory we have. But what do we do with this plethora of photos? Organizing them into genres or collections of similar photos would help us find a particular image....maybe. Wouldn’t it be nice to type a word into an application and have all of the shots that pertain to it pop up on your computer? I have two words for you: keywording and Lightroom®.

For most of us, our image files end up in a big, ugly clump on our hard drive. Now, we have the task of deleting the junk and deciding from the remainder which ones are ‘maybes’ and which are keepers. I know - it’s difficult to make those decisions, and I can’t help you with that. But, once you whittle the pile down, you can start to organize it.

So what is a photographer’s workflow? Simply, this refers to what happens to your images between the moment you download them from camera to computer and the time you prepare them for email, website posting or printing.

Let’s back up to that first step: downloading from the camera. I use the utility software supplied on CD  by the camera manufacturer because it can automatically read each image’s metadata and store that image into a folder named with the date the shot was taken. At least now, we have some semblance of organization, but it’s only the beginning!

Enter Lightroom®, a software package from Adobe. For the purposes of this blog post, I am going to assume that the reader is not a power Photoshop® user, and that the image adjustment tools in Lightroom® are more than sufficient for tweaking the camera images. The workflow might go something like this:

1.       Import the ‘keeper’ image files into Lightroom®. These can be in a number of different formats, including RAW files. You may wish to import them into the default Catalog or create your own before importing. The Catalog stores all information about the images you import into it, including all changes you make, so they can be recalled later and undone step-by-step if you wish. The important thing to understand is that Lightroom® does not actually create a copy of the image when importing it, but rather stores only the location of the original file plus all changes you’ve made to it without changing the original.  In other words, it temporarily pulls in a virtual copy of your image and saves the changes you’ve made to it in the Catalog. The resultant Catalog file is much, much smaller than the total of all the original image sizes.

2.       Create keywords in the Library module for each image. There are two compelling reasons for  doing this:

a.       You can use Lightroom®’s search function to find all images that contain those keywords.

b.      If you sell prints or stock photos online, nobody will find your images unless you keyword profusely.

Within a Catalog, Lightroom® builds a keyword list from all the keywords you add to all the images in that Catalog. As you import new images into the Catalog, it gets easier to keyword them because you now have a list of keywords you can choose from.

What words should you use? Put yourself in the place of someone searching online for a photo like yours. Think of every word you might use in a search string. Include location, objects in the scene, weather conditions, season, genre (ie. Nature, people, architecture) and even the image orientation (portrait, landscape). Cover every possibility – the more words, the better the chance of being found.

3.       Tweak the images for best quality in the Develop module. While not supplying all the capabilities of Photoshop®, Lightroom® has an impressive array of tools to correct exposure, white balance, sharpness and noise. Other tools, such as split toning, allow some impressive creative adjustments to be made. If you’re not feeling particularly daring, you can select from a wide variety of special black and white or colour presets to give your image a different look. If you want to save various versions of the same image with different visual effects, you can create as many virtual copies of the same image as you like and apply different changes to each. The good news is that the keywords also get copied over to each virtual copy. This is probably the best reason to do your keywording before starting your image tweaking.

4.       Do something with your final images. I upload images to various sites for licensing stock images or selling prints on demand, so I like to Export jpeg files from Lightroom to a separate folder on my hard drive. Now I’ve created images that take up space on the drive, which may seem to work against the concept of using Lightroom®'s space-saving virtual copies, but sometimes it’s necessary. Otherwise, if you simply want to print what you’ve created in Lightroom®, you can go straight to the Print module without exporting a file. Or, if the website you use allows it, you can use the Web module to upload keyworded and tweaked images without increasing the footprint on your hard drive.

Once you’ve done all you’re going to do to an image, you can also create Collections within a Catalog. This allows you to store a virtual copy of a photo in a group of similar photos. For example, you may create separate collections for your Nature, Family and Travel photos. Just another way for you to find a photo if a keyword search isn’t helpful.

Crazy Composite

I've always had this scene in my mind whenever I've heard the song 'Crazy River' by Robbie Robertson, so I decided to build a composite image of my interpretation.

First, I shot an empty field toward sunset. Easy peasy. Because I wanted to give it a Louisiana bayou atmosphere, I figured it needed a big lazy moon. No problem - I had one on a slide. And stars came from a time exposure I shot weeks earlier. A bit of artistic license led to the meteor (or comet if you wish).

Robbie called for an abandoned '59 Chevy. Fat chance finding one of those, so I ordered a scale diecast model for $10 on Ebay. A bit of watercolour paint dabbed on it emulated the rust. To make it look like the car battery had been fiddled with to make the car radio work (so the occupant could listen to Little Willie John), I propped up the hood and lit up a yellow LED on the front seat to make it look like the dash was illuminated. A strobe with a blue filter emulated moonlight along the car's side.

The occupant lying in the back seat had to be created. I've never hired a model and wasn't about to for a personal project, so I was it. With a remote shutter trigger in hand, and side lit by an orange-filtered strobe, I became Robbie's character.

Using lots of layers and layer masks in Photoshop®, I built my composite using the field as a background. A deep blue photo filter layer converted the daylight field to a nighttime field. The masks were used for making the grass appear to be growing around the car and placing the appropriate parts of my body in the back seat. The burn tool added the car's shadow onto the grass. Matching the car to the surroundings was probably the trickiest part, involving a lot of edge smoothing using that layer's mask.

It took many hours to create, but was a great learning experience. One takeaway on big projects like this is to save your work as different (layered) files as you progress, so that you can always go back and rebuild if you really mess up.