Focus Stacking is a technique where you take multiple images focused at incremental points through the depth of the scene. These images are then stacked using special software applications and merged into a resulting single image. The resulting image has the entire scene in sharp focus (a very deep depth-of-field)
You can use software to tether your camera to a computer and use software like Helicon Remote and Helicon focus to create such images. In the field however, this computer and camera combination may not be practical. If you have a Canon DSLR camera that supports Live Viiew you are in luck. The Promote Control provides focus stacking functionality in a small unit (5 by 2.5 inch unit that is a little over 1 inch thick. It weighs 5.5 ounces).
Here is how to set up the Promote Control and your camera
- Using the “Mode” key, set the Promote Control to the “Focus Stacking” mode.
- Using the supplied USB cable connect your camera to the Promote Control. You do not need the Shutter cable for focus stacking.
- Once the connection is established, turn on your camera.
- Set the camera and lens to autofocus. Do not use AI Servo or AI Focus.
- Set the camera to single shot mode
- Disable Mirror Lock-up
- Set the image preview duration to 2 seconds or less
- Turn off “Face Detection Live Mode”. You can use “Live Mode” or “Quick Mode” this applies to cameras that have a Live View specific “AF Mode” setting (Canon 5D Mark III and Canon 6D)
- On the Promote Control change the “Step” setting from “None/Reset” to “Small”. Medium and Large steps are also available and you will need to test which one is most suitable for the scene you are capturing. The focal length of the lens is also a factor that needs to be considered.
At this point your camera’s live view will become active
- Set the aperture to the desired setting – it is better to use wider apertures and high shutter speeds rather than narrow apertures. The stack will address the depth-of-field that you wish to obtain.
- Use the manual focusing ring of your lens to focus on the near point of focus in your scene. This will be the starting point of your focus stack.
The Promote Control shows a focusing range as follows
The first number indicates beginning of the focus stacking, while the second number indicates the end.
- Using the “Up” and “Down” keys on the face of the Promote Control, drive the lens focusing mechanism so as to get to the place in the scene where you want the focus stack to end.
The display should read as follows:
+000…+008 (Or a number greater than +001)
The “Frames” setting is a calculated value that shows how many images will be taken based on the step value and the lens travel from the beginning point to the end point of focus. You have the option to reduce the number of frames if you feel that the resulting focus stacking sequence will be too gradual.
The number of “Frames” can be adjusted by selecting the reading and changed using the “Up” and “Down” keys. You will need to return to the “Focus Stacking” mode before pressing “Start” to capture the sequence of images.
The Promote Control will retract your lens to focus on the starting point of focus in your scene, take an image and step the nest point. This process will continue till all the frames have been captured.
You can then bring the sequence of images to be stacked and merged into a single frame using one of many software applications.
I highly recommend Helicon Focus from HeliconSoft – here is the link to license the software http://www.heliconsoft.com
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- If you adjust the focus ring on the lens after the focusing range on the Promote Control has been established, you need to do the following:
Change “Step” to “none/Reset” and then repeat the set-up process from the beginning. Not following this will result is a poor sequence of images that will not stack to your satisfaction.
- If you change your “Step” size setting on the Promote Control after establishing the focusing range, the focus range settings will revert to +000…+000 and you will have to repeat the set-up from the beginning.
You can download a PDF version of this tip – Promote Control – Focus Stack