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Tools available for Maximizing Depth of Field, (DOF)

The picture above shows that the numbers on the measuring tape, closet to the camera are highlighted. That is what part of this picture is in focus! The rest of the image is out of focus

But what if we want the whole dish of mushrooms to be in focus, what are the tools or options we can use?

Your options are:

  1. Set a high f/ stop to increase your depth of field. If your goal is to have as sharp an image as possible, you may be concerned that if you use high f/ stops, it may start introducing diffraction thus working against your goals and lowering the sharpness of the image.
  2. Set a lower f/stop setting and use the lens focus ring to bring various parts of the item/scene being photographed into focus. Then using Lightroom, Photoshop or stacking applications like Helicon, as an example, stack the images to provide a single image with a very deep depth of field. The downside of this route of course is that you need to do as many steps as possible to ensure all areas of scene being shot is in focus else you will end up with areas that show circles of uncertainty, (out of focus areas that the software algorithms cannot solve).
  3. Use a slider that allows you to set the focus area as an example at the nearest point you want to be in focus and then, slide the camera/lens a little closer, take another shot, repeat till you have the furthest area you want in focus, imaged. This allows you to take many images and using a dedicated application like Helicon which is designed for this, bring the object from front to back, fully in focus. These sliders can come with stepper motors thus allowing as small a step as 3 micron which is needed if using a microscope lens or similar high magnification as an example.
  4. An alternative is to use a Shift/tilt lens or body to “lay” the focus plane along the area one wants in focus. With a medium f/stop like f/8 or f/11 and a bit of distance from the object to the lens, one can have a wide enough depth of field for the image

One of the tools we will use is a Depth of Field Calculator. There is a free version on the internet that we use called DOFMaster, http://www.dofmaster.com/dofjs.html . Check it out and download the apps if you find them beneficial.

The high f/ stop route! f/32

On the Left, 70mm-200mm lens, f/32, ISO 100, middle, 100mm Macro lens, f/32, ISO 100, on the right, 120mm large format lens, f/32, ISO 100.
200mm, (far left), 100mm, (center), 120mm/85mm large format/35mm

Click on images to blow up to full screen, Which one is the clearest??

Using the Focuser, images taken of front, medium and rear of bowl, then stack route!

We only did the two Canon lenses, (70-200mm at 200mm and the 100mm) as they have adjustable focusing rings on the lenses. The 70-200mm was done at f/11 to add a bit more DOF. Both were done with 3 images each, then stacked with Helicon stacking software.

Now we will compare two high image counts stacked together for each image. The 120mm Rodenstock lens image is a combination of 21 images in Helicon. The image on the right is the Canon 100mm Lens with a combination of 19 images stacked.

We could have gotten away with much less images due to the DOF at worst case being almost 1.6 inches for the 100mm and total distance from front of bowl to back is 10 inches. If we did each shot at 1 inch increments, 10, images would have sufficed for either lens.

Shootout!!

Now we will compare all 3 shots, first shot with single f/32 image, second shot with 3 x f/8 and third shot with 21 x f/8 images stacked. All these shot were done with the Canon 100mm lens.

first shot with single f/32 image, second shot with 3 x f/11mm, third shot with 21 images stacked

A second comparison is the 120mm Rodenstock large format lens with Tilt / Shift set at -5 degrees from plane using the Scheimpflug principle, ( https://en.wikipedia.org/wiki/Scheimpflug_principle ) versus the more complicated 19 image stack using the sliders.

Click on image to get full size

Finally, let's take a look at the stacking process. the following video is a series of 19 images plus the final stacked image.

Please let me know if you have any questions or comments.

Thanks, Bob

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