Tuesday, March 9, 2010

Expanded Depth of Field (Video Tutorial link below)

Early morning wildflowers
Canon 7D, EF 180mm f/3.5L, Induro C213, RRS BH-55

Depth of field (DOF), or the area of your image acceptably in focus, is a great tool for photographers.  Through our selection of aperture, focal length, and focal distance (this is a very complicated subject so we will limit to these three variables) we can control the DOF for all of our images.  knowing the viewer's eye is drawn to "in focus" areas of the image we can direct the viewer around the image as we prefer.  In general, landscape photographers prefer a deeper DOF in order to show the viewer the entire scene so they may "explore" in detail.  In contrast, the portrait photographer generally decreases DOF to highlight the subject.

Certain shooting scenarios, such as macro photography, deliver very limited DOF regardless of our aperture selection.  You have probably experienced this effect either when shooting or if you have seen a macro shot of a flower with only one portion of the entire subject in focus.  For most of photography's history, we have accepted limited DOF as a given.  A few years ago with the introduction of digital photography, powerful software tools allowed the photographer to overcome this limitation.

Software such as Adobe Photoshop CS4, gives us the power to combine multiple images (same subject but each with a different focal point/focal plane/DOF) into a single expanded DOF creation.  The video tutorial shows the process using Adobe Photoshop Lightroom and Adobe Photoshop CS4.

To capture the source images I recommend the following guidelines.

1) Shoot from a tripod! At Light we use Induro tripods and Really Right Stuff ballheads and L-brackets

2) Focus on the leading edge of the subject (the nearest part of the subject you want in focus.)

---Bull's Guaranteed Sharper Images ---
If your camera is equipped with Live View, use it!  Bring up the live view screen and then zoom in on the spot you want as the focal point (use the zoom button on the back of your camera with live view enabled and then scroll location with the multi function controller.)  Once you are zoomed in, fine tune your focus manually.  Using Live View and the 5X or 10X optical zoom and manual focus will give noticeably sharper images.  After focus is fine tuned, shoot from Live View.  This, of course, removes the problems associated with camera shake because of mirror movement/vibrations.  For those new to Live View, the mirror is already locked up.

3) Shoot the first image (use a cable release or the 2" timer option.)

4) Without moving the camera or changing composition, refocus deeper into the image.  In effect, you are stepping backwards.

5) Shoot again

6) Repeat steps 4 and 5 until you reach the trailing edge of the subject (the farthest part of the subject you want in focus.)

Now you have the required source files to use the Auto Align and Auto Blend functions of Photoshop CS4.  Follow the video tutorial from here (Blogger's difficult today so I just included the link.)


As always, any questions, comments, or concerns shoot me an email at Hal@LightWorkshops.com.

Fiat Lux!

4 comments:

  1. Great tutorial Hal! Thanks for sharing this technique.

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  2. Thank you Hal!

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  3. In a tutorial I saw some time ago the author suggests to move the whole camera forward or backwards on the rail instead of focusing by changing the distance between the lens and the sensor/film - By turning the lens on his helix or by changing the distances in the bellows
    For example if the DOF is 0.5mm move the whole rig - camera and bellows, backward 0.4mm or less after the first shot and so on.

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  4. I have found that technique does not work as well as leaving the camera stationary and changing only the focus point.
    -Bull

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