Unexpected Photographic Tools

Sometimes great photographic tools come in surprising packages. Take for example the Stanley Fat Max Laser Distance Meter. This is a device that projects a red laser and then measures the distance to whatever the laser dot falls on. So how is this a photographic tool? Well, consider for a moment how the plane of focus factors into depth of field. For any focal plane there is a certain amount of the image in front of that plane that is in focus and a certain amount behind it that is in focus. Just how much is easily calculated with a depth of field scale or an iPhone application like I use.

Stanley Fat Max Laser Distance Meter

In my large format days it was easy to stop the aperture way down and know that you would have huge depth of field. Diffraction was there but was not objectionable due to the large size of the film. On my digital SLR with cropped sensor diffraction becomes an issue at much larger apertures and some of my lenses do not stop down more than f/16. This makes it more critical than ever to be aware of what will be in focus and be able to select the plane of focus more acurately.

Here's where the laser distance meter comes in. Just aim the laser at the farthest point you need to have in focus and then at the nearest point that is critical. Now with a depth of field chart you can easily pick the distance to focus on and the required aperture.

Here's an example.

With this scene my tripod was set as far back as possible. One leg was on the stairs to my right and one leg was against the door to elevator behind me. At 17mm I was only able to see the center third of the scene. However my intention was to capture this image in slices with a 50mm lens and then stitch them all together.

County Building

According to my Depth of Field calculator, at 17mm and f/11, the hyperfocal distance works out to 4ft 3in. Focused at that distance everything from just over 2 ft to infinity would be clear and sharp.

DOF for 17mm

At 50mm this changes significantly. A 50mm lens focused at 4ft 3in with an aperuture of f/11 would have all of 1 foot in focus. That is no where near what I needed for this image but guessing at what I needed was a bad idea. On this particular lens the minimum aperture is f/32. I could have stopped down and hoped for the best. But where would I focus?

DOF for 50mm

I used the Fat Max to measure the distance to the far wall as 35ft 4in and the railing closest to me at 5ft 9in. Using a Depth of Field calculator I quickly found that I would need f/32 focused at exactly 9ft 8in to have both the raling and the wall in focus. Not 9ft 6in. Not 9ft 10in. But 9ft 8in on the nose. Pacing this distacne off would just not be accurate enough. But using the laser distance meter I was able to select a point exactly 9ft 8in from the camera and lock focus on it. Actually I used my camera bag and set it on the floor then measured from the camera to the bag. Moved the bag and measured again until I had exactly 9ft 8in.

If I had lost a bit of focus on the background the image would not have suffered as much as if I lost focus on the foreground. But the only way to know where to focus to maximize DOF was with a DOF calculator and a measureing device.