Introduction

With one of the most sophisticated focusing systems, the OM System OM-1 is capable of unprecedented AF performance.

Having an in-depth understanding on what the camera actually does in which mode guarantees peak performance.

In this article, I’ll explain all intricacies in detail.

Focusing System – General Information

Phase and contrast detection AF with full frame coverage
1.053 cross-type phase detection points
1.053 contrast detection points
AF working range from -5.5 to 19 EV (ISO approx. 100, with an f/2.8 lens)

Focus Modes

S-AF

When set to S-AF mode, the OM-1 utilizes contrast detection, which attempts to maximize the perceivable contrast of the subject under the active AF point. In order to do so, the OM-1 changes the focus distance of the lens back and forth rapidly, until maximum contrast is achieved.

+ Most precise focusing method

+ Chance of “false focus confirmation” very low

+ Low light does not impact accuracy

+ Lens focal length, lens sharpness/contrast at the largest aperture and subject distance do not impact accuracy

~ AF-speed is very lens-dependent

~ Some subject contrast is needed

- If the subject moves, the camera can fail to focus

C-AF

In C-AF mode, the OM-1 uses phase detection to achieve focus. This means that the image projected by the lens is split by on-sensor micro lenses located above the active cross-type phase detection pixel. The OM-1 then calculates the offset between the projected split images and drives the lens to the desired focus position to match the split images. As long as the AF is active, the camera will evaluate the subject distance and correct the focusing distance continuously.

+ Fastest focusing method

+ Subject movement does not hinder focus acquisition

+ Moving subjects stay in focus

~ AF-speed is lens-dependent

- Accuracy is impacted negatively by longer focal lengths, lack of lens sharpness/contrast at the largest aperture and long subject distances

- Low light does impact accuracy negatively

- Chance of “false focus confirmation” especially under the previously mentioned “low accuracy” scenarios

C-AF + TR

Just like in C-AF, the OM-1 uses phase detection with all the advantages and disadvantages that come with it. There is one major difference, though.

The OM-1 will register the color, shape and movement of the subject that is located under the AF target at the start of AF operation.
Then, as long as the AF is activated, the OM-1 will continue to follow the subject in the frame based on the color, shape and movement.
Depending on the AF Area Pointer, the camera will either display a green box (AF Area Pointer: On1) or multiple small target frames (AF Area Pointer: On2) which both will expand or contract if the subject size in the frame changes. The camera will automatically pick and activate a phase-detection point which covers the subject. If the subject leaves the frame or is no longer recognized, the camera will stop focus operation until the subject is detected again or focus operation is restarted.

+ Very convenient method for tracking subjects that move erratically in the frame

+ Can track subjects even if their appearance changes (e.g. person turning around during movement)

~ No specific focus point can be selected once C-AF + TR is active

- C-AF TR can loose the subject (especially in busy scenes or under challenging lighting scenarios)

OM System OM-1 - AF Area Pointer Selection (Off/On1/On2)

Autofocus Target Modes

The OM-1 offers a set of pre-defined AF target modes ranging from “Single Point” to “All”. Additionally, custom AF target modes can be set up (C1 to C4).

OM System OM-1 - configuring a Custom AF Target Area

Except when utilizing subject detection, the OM-1 chooses a focus point from within the selected group of AF targets automatically.

Based on practical observations, the OM-1 seems to pick a focus point based on the following criteria:

AF Mode set to C-AF

1) With center priority enabled, the OM-1 will attempt to utilize the central focus point of the selected target area first.

2) If this fails or when center priority is disabled, the OM-1 will utilize the AF pixel that detects the highest contrast or the AF pixel that detects the shortest subject to camera distance.

AF Mode set to S-AF

In S-AF, the OM-1 will utilize the AF pixel that detects the highest contrast or the one that detects the shortest subject distance.

Regardless of AF mode, you have to keep in mind that if the group of AF targets covers an area larger than the actual subject, there is a risk that the camera will focus on other objects in the fore- or background.

OM System OM-1 - C-AF Center Priority selection screen

OM System OM-1 - C-AF Center Priority indicator square

Subject Detection

Subject detection is not a separate focus method, but rather a support function that automatically selects an AF point.

When subject detection is activated, the OM-1 will analyze the frame looking for a predefined type of subject.

The following subjects categories are available and only one of them can be active at the same time:

Face- and Eye (People)
Cars and motorcycles
Planes and helicopters
Trains
Birds
Animals

OM System OM-1 - Face & Eye Detection options

OM System OM-1 - other Subject Detection modes

Once a subject that fits the selected category is detected, the camera automatically picks a suitable AF point. I’ll expand on how the camera selects the target later.

It is important to note that subject detection does not change the selected AF mode.

Subject Detection + S-AF

The camera will detect the subject, select an AF point (or multiple AF points) and focus once using contrast detection as soon as the AF is activated.

Use this mode only for still subjects.

Subject Detection + C-AF

The camera will detect the subject, select an AF point (or multiple AF points) and use phase detection to focus. As long as the AF is activated, the camera will repeat this cycle of detecting a subject and activating AF points, effectively tracking the subject as long as it is detected.

Subject Detection + C-AF + TR

When subject detection is used in conjunction with C-AF + TR, the camera will detect the subject and as soon as the AF is activated, the OM-1 will select an AF point. However, instead of continuously looking for the subject in the frame, as the camera would when using C-AF, the camera will follow the subject almost like in C-AF + TR mode – this means based on color, shape and movement.

Only when the AF operation is stopped by the photographer, the camera will start to use subject detection again.

OM System OM-1 - Subject Detection + C-AF + TR: note that there is no subject detection frame during AF operation

Subject Detection with C-AF or C-AF +TR?

Given the substantial difference when using C-AF or C-AF + TR in conjunction with subject detection, it can be quite difficult to decide which one is the best mode for moving subjects.

OM System recommends using subject detection predominantly in C-AF mode. By doing so, the powerful subject detection algorithms of the OM-1 unfold their full potential.

In my experience, there are only some situations where C-AF + TR in conjunction with subject detection is preferable. For example, when the subject turns around while using face detection and C-AF, the OM-1 will stop tracking and go back to the selected AF target until the face is detected again. In the same situation, with C-AF + TR selected, the OM-1 will stick to the subject’s head, no matter its orientation.

Face- and Eye Detection Specifics

When Face- and Eye Detection is active and multiple faces are in the frame, the OM-1 will pick one of them based on its size and its discernibility, the latter being heavily influenced by the focus position.

Once a face is prioritized, the OM-1 will memorize the face and keep focusing on it even when new faces enter the frame. Most remarkably, this is also the case when the view is obscured for a fraction of a second.

The photographer has two options to influence the camera’s decision:

Option 1: Face Selection
The function has to be assigned to a function button. By pressing the button, the camera will pick the face closest to the AF target. Additionally, while the button is pressed, the command dial can be used to cycle through all detected faces in the frame.

Option 2: Face Selection via Touch Screen
When the touch screen is set to the “Face Selection”-mode, tapping on a detected face prioritizes it.

Other Subject Detection Mode Specifics

In subject detection modes other than Face- and Eye Detection, the OM-1 will behave a little bit differently.

First, if subjects are too far away from the selected AF target, they won’t be detected. If there is only one subject in the frame, pick a big enough AF target or reposition the AF target closer to the subject.

Second, if multiple subjects are present, the camera will pick the subject based on the AF target position. Usually it is sufficient to roughly move the AF target over the desired subject. For best results, especially if the detected subjects are close together, use a small enough AF target and avoid overlapping with other subjects in the frame.

Closing Remarks

The complexity of the OM System OM-1’s focusing system can seem overwhelming at first – and the reason for out-of-focus images or poor AF performance is almost always due to a lack of understanding.

Always keep in mind what the camera actually does in which mode and you will realize the full potential of this remarkable high-end camera.

On YouTube

OM System OM-1 – Autofocus System Expert Guide