Focus Stacking for Greater Depth-of-Field

This morning I went to a local park, Berry Springs, to shoot some macro images of dragonflies, butterflies and insects.  Since I had sent the Canon 7D off to Canon Professional Services for a check and cleaning, that left me with the new Canon 5D Mark III to shoot with so I opted to go with my typical dragonfly setup that consists of the Mark III, (1) 25mm Canon extension tube, (1) 12mm Canon extension tube and the Canon 100-400 f/4.5-5.6 L lens.

An extension tube merely moves the camera’s mirror further away from the lens thus increasing your magnification (which is what we want for macro photography) and decreasing your minimum focusing distance (which is also what we want); however, it also reduces the amount of light falling on the camera sensor (which is what we don’t want, but have to live with).  Therefore, we must either add light through the use of flash (which is what I normally do) and/or we must increase our ISO (I try not to do and generally shoot at ISO 400 or 800) or we must decrease shutter speed and/or our f-stop (aperture).  I have found that for this setup (see photo below) a tripod is required at all times for sharp images.  I generally shoot in the neighborhood of 1/250 @ f/11 to f/14 for dragonflies, large butterflies, and other large insects to maintain sufficient depth of field.  This is because as we move toward an object our depth of field decreases at the same aperture.

Dragonfly Equipment Setup

Dragonfly Equipment Setup

Today I came across many large Yellow-and-Black Argiope spiders and wanted to practice my focus stacking in Adobe Photoshop CC.  I came across a nice looking subject and set up my tripod where the spider was at about a 45 degree angle from the front element of the lens (this isn’t important but just know that I would need focus stacking much more at this angle than if the spider were at a 90 degree angle to the lens).  I always shoot macro in manual exposure mode so I can control my settings.  I wanted to take three (3) consecutive shots with varying focal points to ensure that all eight (8) legs of the spider would ultimately be in sharp focus.  When shooting any images that you plan to “stitch” or “stack” together such as a Panoramic or a focus stacked image, you want to make sure your exposure remains consistent for every image.  This will only change if you plan to add High Dynamic Range (HDR) processing to the mix.  In addition, I focus almost exclusively in manual and on the Canon 100-400 I turn off image stabilization as it has a tendency to “jump” at times.  I believe this is due to the older IS technology in the lens.

I took a shot to make sure my settings of 1/160 @ f/16, ISO 800 and flash exposure compensation of -1 1/3 were spot on.  With a subject like this, if we have our flash set too brightly, we will easily blow out (lose details) on the body of the spider due to the pale yellow/whites and the dark background.  I set up for the first image with focus locked in on the closest front leg and part of the body nearest the camera.  If you click on the image, you can see that the legs furthest away from the camera are blurry due to the narrow depth of field even at f/16.

Focal Point #1

Focal Point #1

I took a second shot with the focal point being the eyes and body of the spider.

Focal Point #2

Focal Point #2

I then focused on the legs furthest from the camera and took a 3rd shot.

Focal Point #3

Focal Point #3

When shooting a series of images in the field where I know I will be stacking or stitching them together, I often take a shot of my hand at the beginning and end of the sequence to help me remember which images I wanted to sequence so that when I upload my images into Lightroom I can easily find them.  This makes it easy to see a series in the film strip at the bottom of Lightroom’s workspace since I know any images found between images of my hand are intended for that purpose.

Once all my files have been uploaded to Lightroom, I can then make a few edits such as lens corrections, sharpening/noise reduction, and other such adjustments.  The key is that I want each of the three images to have the EXACT same settings before going into Photoshop for the image stacking itself.  I select all three images in Lightrooms filmstrip at the bottom and then right click to open the contextual menu.  I then select Edit In ⇒ Open as Layers in Photoshop… (see image below).

Open as Layers in Photoshop

Open as Layers in Photoshop

Once I had my images loaded as layers in Photoshop, I made sure all three were selected (of course, if I had 5 images to stack, I would select all 5 layers).  I selected them by clicking on one layer then while holding the Shift key, I clicked on the last layer and all layers were highlighted as in the image below.

Selecting the Layers

Now, despite the fact I was using a tripod, there was still a bit of movement from one image to the next due to a slight breeze this morning which resulted in a slight change from image to image.  The image below shows the slight blur due to the images not being exactly aligned.

Images Need Aligning

Images Need Aligning

Because the layers didn’t line up exactly (and I highly recommend checking this before you stack your images), I decided to Auto-Align them in Photshop.  To run this function, I simply selected Edit ⇒ Auto-Align Layers…

Auto-Align Layers

Auto-Align Layers

After selecting Auto-Align a box will open and then I chose Auto as the projection type and allowed Photoshop to align the layers.  The other modes are for various types of Panoramic images.  I also made sure that neither the vignette or geometric distortion box was checked.  Once I had done that, I clicked OK.

Auto-Align Layers Box

Auto-Align Layers Box

After aligning the images and ensuring they lined up well, I was ready to blend the images to combine the sharpest part of each image.  Now, honestly, how Photoshop does this is pure magic!!  I won’t even attempt to explain the how, just know it works and it is really quite easy in terms of what you have to do.  Again I went to the Main Menu and selected Edit ⇒ Auto-Blend Layers…

Auto-Blend Layers...

Auto-Blend Layers…

This opens up another dialog box that looks like this:

Auto-Blend Options

Auto-Blend Options

As you can see, my options are limited to either Panorama or Stack Images and for my purposes, I selected Stack Images and then clicked OK.  I saw the Photoshop blending progress bar and waited while the magic happened.

Auto Blending Progress

Auto-Blend Progress Bar

Once the blending was complete, my image was done and all that was left was to save the image to a new name and new format.  Now, Lightroom handles RAW file formats but when we blend layers in Photoshop we can’t keep the images in a RAW format.  Our choice, to maintain the most quality and to have a chance to go back and edit the layers separately, is to either save the image in TIFF or PSD format and check the Save Layers options.  Yes, this does create a larger file and requires more memory, but memory is cheap.  For my purposes, I chose to save as a TIFF file and I renamed the image to Focus Stacked Spider.

Save Image as TIFF

Save Image as TIFF

We can then close the image in Photoshop and if we return to Lightroom we will notice that our image has now appeared in our Lightroom filmstrip.  Now, to make sure our images reappear in Lightroom where we expect them, it is important to make sure that the Save As to Original Folder preference is checked in Photoshop.  This option can be found under Photoshop ⇒ Preferences ⇒ File Handling…

Photoshop Save As Preference

Photoshop Save As Preference

If the box for this option is not checked, I recommend doing so.  Otherwise, unless you pay special attention to where you saved the image, you may have to do some searching and hunting for the image.  In the image below you can see our TIFF file back in Lightroom (note the file name in upper left).  I didn’t have to do anything special to get the image back in Lightroom because I opened the files from within Lightroom to focus stack them.  Now, had I opened the files from Photoshop without going through Lightroom, the file would not have appeared in Lightroom without me having to import the file as a new image.

Back in Lightroom

Back in Lightroom

I prefer to do all the editing I can within Lightroom and use Photoshop only for those functions which are not available in Lightroom.  Once back in Lightroom, I wanted to crop the image from a horizontal to vertical composition.  I applied some clarity and vibrance edits and some further sharpening and noise reduction.

Clarity, Vibrance & Sharpening/NR

Clarity, Vibrance & Sharpening/NR

I felt after that the image was ready.  Here is the final image.

Final Image

Final Image

I will be offering some macro workshops in the summer of 2015 so watch for those announcements to come.  Feel free to let me know if you have any questions on image stacking.

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