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Blending Images In Photoshop For Increased Depth of Field


One of the most intriguing tools in Photoshop is layer alignment and blending. One practical use for these is macro photography – I have been experimenting with creating images that have depth of field that is nearly impossible to get in a single frame. (this post was originally written in Jan 09; updated Dec 09)

Why? Because a 105mm macro lens on a full-frame camera has depth of field of about 0.6mm at f/16 – in other words, a very, very thin slice. Combining multiple images with different focal points gives us – voila! ….a merged macro image that should be completely in focus.

Here’s how it’s done:

Use your camera of choice, preferably with a macro lens. Create the normal setup with the camera on a tripod. Set up or manage lighting, put the camera on aperture priority, and meter. I typically use mirror-up mode as well, and shoot with a remote. Shoot in RAW format if you can. (I used a Nikon D3 digital camera, and the new Nikkor 105mm Macro VR lens).

Typical aperture on these shots ranges from f/8 to f/16 in the 35mm class – higher f/stops tend to soften the image through diffusion error. Start at f/8 or f/11.

I usually work close to the lens’s minimum focusing distance.  I shoot several frames of the subject, changing the focal point to different parts of the subject, left to right and/or top to bottom. The camera must be absolutely still so that the frames will register with one another. If we could mark the focal points, they might look something like this:

Transfer the images to a folder on your computer. Open the folder with Bridge. Select the images you’ve captured (in this case four), press Command-R to open them in Adobe Camera RAW. You’ll see this screen:

Make your adjustments to the first picture only. Be conservative. Now click “select all” in the upper left corner of the dialogue, and then click “synchronize”. All of the RAW files will be updated.

Now click “Done” (blue arrow) in the lower right hand corner. Camera RAW will close and return to Adobe Bridge.

The four images will still be highlighted in Bridge. Go up to the main menu, choose Tools>Photoshop>Load Files Into Photoshop Layers.

The images will be loaded into a single Photoshop image with, of course, four layers. Open the layers dialogue and select all the layers.

Once this is completed (may take a while) go to the main menu, and click Edit>Auto-Align Layers. You’ll see a bigger dialogue, again just click Auto.

Once this is finished, go back to the Edit menu, click Edit>Auto-Blend Layers. Click on Stack Images, and Seamless Tones and Colors. Click OK.

Photoshop will launch into an analysis of all the layers, create layer masks to use the best portions of each layer, and blend the images. You should see an amazingly sharp image with significant depth of field. This is truly something new under the sun! Here’s an example:

flower red combo 1 copy final

My good friend photographer Ted Dayton told me about this, and I should add one of his points here: “take more pictures, with more focal points, than you think you need.” He’s right – once the images are blended, you’ll see the difference.

9 thoughts on “Blending Images In Photoshop For Increased Depth of Field”

  3. Hi David,

    Your information is fantastic and having just taken delivery of a new macro lens I was keen to try it. I have a 4GB RAM multimedia PC but the Auto Blend just won’t work due to lack of RAM?! I have googled the subject and have gone through preferences in CS4 and in advanced settings on the PC. I have more than Adobe’s suggested requirements, any ideas?
    Thanks.

    Judith

    Reply

    • Hi Judith,

      I don’t think that the RAM is the issue. I have a MacBook Pro with 4GB as well.
      Give this a try: set the exposure of the camera to manual only, and use manual focus. Shoot off a tripod; hand held doesn’t work all that well.

      Take your multiple frames, taking care to include multiple focal points. Be very careful that the camera *does not* move position, even the slightest, as this will trash the sequence and you’ll have to start over. (I kicked the tripod once just at the end of one of these – I think 10 frames or so).

      Give that a try. It’s nit-picky but worth the effort.

      David

      Reply

  4. Hi David,

    Thanks for your quick response, I am still sat at my PC trying to work this out. I have changed all the settings again and resized my 9 images, closed everything down that needn’t be running but I’m still getting the error message “not enough RAM” to auto blend, the alignment works fine and yes, I did use a tripod and focused on different areas, but just can’t finish the job in CS4. I will keep trying, but thanks for your help.

    Judith

    Reply

    • If you wish, you can send me the files and I can try it too. There’s a file drop box link on my web site – go to the Site Guide page, lower right you’ll see the link. I’m really curious about this. Up to you, of course.

      Reply

  5. Just what I was looking for! Thank you so much for explaining it so well! I’ll post the link to my image when I’m done (well, if anything good comes out !!)

    Reply

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