Moving active autofocus area

Birds in bushfire smoke

 

Autofocus for interchangeable lens cameras was invented in the late 1980's. One of the many challenges facing AF engineers was finding a way to move the active AF area from one position to another. In 2008 mirrorless interchangeable lens cameras arrived on the scene. These enable autofocus right on the imaging sensor. They can therefore be designed to allow AF anywhere on the frame.

In the early days of autofocus Some cameras could only AF in the center. This led to the strategy of "focus and recompose" which some people still use.

Eye control AF was used by Canon in several SLR models in the film era. I had one of these for a time. The technology worked but was prone to focussing on a point adjacent to the one desired and there were issues with calibration. So this feature was soon discontinued. I suspect one of the complicating factors was the way our eyes actually work. When we look at something our eyes are always scanning in little skips. They do not rest on one spot for more than a fraction of a second. So, I do not anticipate a return to eye control any time soon.

Touch screens It seems every kind of device these days has a touch/swipe screen. Even motor vehicles have them, creating a highly dangerous source of driver distraction.

The distracted photographer is unlikely to kill anyone but touch screens on cameras face a problem similar to that on cars. Just as the car driver should be looking out the front windscreen at the road ahead, the photographer needs to look through the viewfinder at the subject ahead. In each case having to attend to a touch screen is a distraction from the main task. There are also simple physical problems. It is effectively impossible to get a finger onto the screen with the eye to the viewfinder. Panasonic has a feature called Touch Pad AF. This allows the operator to move AF area by touching the screen while looking through the EVF. I found it impossible to use effectively although I have had feedback from one reader that he was able to make the feature work on the Panasonic GX7 with it's EVF at the top left corner. The touch screen works quite well on a tripod mounted camera as you don't have to hold the thing as well as access the screen.

Hard user interface modules (UIM's). Some cameras have a complicated rigmarole by which the AF area is moved up/down by the front dial and left/right the rear dial. Or maybe it was the other way around, I forget. I once had a Canon SLR which used this system. There was a great deal of button pushing and dial turning. It was so clumsy I gave up and used focus (with the center area) and recompose.

Many cameras these days use a 4 way controller located on the lower part of the control panel on the right side of the camera for AF area movement. This works quite well if set up properly so the AF area moves immediately when one quadrant of the controller is pressed. However this arrangement does require the user to release grip with the right hand in order to operate the 4way controller. This is not a tragedy but some method not requiring the right hand to change grip would be better.

Some high spec Nikon cameras use a kind of mini 4 way controller a little higher up on the control panel. This is more accessible and therefore an improvement. Some Canon cameras use a "Joystick" in a very similar location, again an improvement over the standard 4 way controller.

 

The JOG lever is the UIM nearest the EVF. It is larger and more prominent than the regular buttons. It needs to have a highly textured profile to make it easy to move in any direction with the thumb. Below and to the right of the JOG lever is a "return to center" button.  Above and to the right of the JOG lever is the AF ON button.
The top photo shows the hand/thumb  position required to operate the JOG lever. The lower photo shows that to operate the 4 Way controller the user's hold on the camera with the right hand must be partly released.

 

The JOG lever This is a generic term for the Canon Joystick. If optimally designed and positioned this should provide the best ergonomic solution to the problem. The JOG lever is always on. This means it moves the AF area immediately when pushed up/down or left/right. It is operated by the right thumb. The best position is such that the distal pad of the thumb falls directly onto the lever when it swings to the left from the basic hold position.

In my work with mockups this has led to an issue which could be a problem. Every time I go through the exercise of locating UIM's on one of my mockups the best position for the JOG lever ends up right on the top right corner of the monitor screen. If the JOG lever were to be placed there it would necessitate chopping off the top right corner of the monitor screen housing. I don't know if there is some engineering reason why this should not occur, but I suppose it might clip off the top right corner of the preview or review image in some aspect ratios. Some users might be sanguine about this others might not.

In the event I have located the JOG lever on my recent mockups 10mm above the position I regard as ideal. This is probably satisfactory for most users but some with small hands or short thumbs might have to shift grip slightly to get their thumb far enough over the top of the lever to tbe able to operate it.

Not withstanding these concerns I think the JOG lever is the optimum solution if it can be well implemented. It can also undertake selection and other duties in Setup, Prepare and Review phases of use.