Information about Metrics

FoCal IQ provides a lot of metrics - measurements of various aspects of the equipment.

The following sections give a brief explanation of the meaning of each metric.

Note: You can quickly jump to the appropriate section from the details pages by clicking on the help icon .

Adjustment for half of users

If you took all users of this particular camera with all lenses of the specified mount, then 50% of people would benefit from adjusting their cameras by at least the value indicated by this metric.

If the value is higher than around 2 units, it's likely you will get image quality improvements by calibrating the autofocus on your camera.

If the value is low - below around 2 units - then there is a 50% chance that you won't benefit hugely from autofocus calibration, or to look at it another way - there's a 50% chance you could benefit from calibration!

Adjustment Range of top 50%

Taking the best 50% of all calibrated cameras (best, in this case, meaning those requiring smaller focus adjustment), this metric shows the amount of focus adjustment variation across these cameras.

A smaller number indicates the likelihood of less requirement for calibration.

Top 50% Adjustment Limits

Again, taking the best 50% of all calibrated cameras, this metric shows the low- and high-ends of the required calibration range.

Unlike the Adjustment Range of top 50% above, this metric can show a skew of the data to one side or another. For example, if the range is -5.0 to +1.0, then you know that the majority of cameras requiring adjustment need a negative adjustment (i.e. an adjustment towards the user, indicating that the camera has a tendency to focus towards infinity).

Requiring No Adjustment

This metric shows the percentage of tested cameras that require zero focus adjustment - i.e. are perfect right out the box.

Requiring Small Adjustment

This metric shows the percentage of tested cameras that require a small focus adjustment. Within FoCal IQ, a small adjustment is defined as -1, or +1 adjustment units.

Requiring Visually Significant Adjustment

This metric shows the percentage of tested cameras that require a visually significant focus adjustment. We define this as an adjust of 2 focus adjustment units or more. An adjustment of 2 focus adjustment units produces a noticeable difference in image quality.

Calibrated Consistency of Focus

The Calibrated Consistency of Focus is a measure of how consistent repeated focus operations are, but only at focus adjustment settings close to the best result. This gives a clear indication of the focus consistency in a comparable scenario - a calibrated camera.

Consistency of Focus (Live View)

The Live View Consistency of Focus shows how repeatable focus operations are using Live View. As Live View typically requires less calibration than non-Live View (e.g. viewfinder autofocus on a DSLR), FoCal IQ accumulates all data obtained from Live View focus operations for this metric.

Representative Focus Accuracy

Within FoCal, the focus error can be calculated once a full calibration is completed. For a calibrated lens, FoCal determines a lens profile which can be used to calculate how a capture quality difference relates to a real-world focus error.

The Focus Error is shown in units of focus adjustment. A perfect camera would have a focus error of 0, so the smaller the value, the higher the score in FoCal IQ.

Handheld Stops Improvement

The Stabilisation Test within FoCal calculates the Stops Improvement by matching quality levels at different shutter speeds when the stabilisation system is active and disabled.

From this, we can calculate the number of stops benefit the stabilisation system is giving.

Average Quality Improvement (Handheld / Tripod)

The Average Quality Improvement is the sum of the average quality change across the shutter speed range.

This value can be negative, indicating that there is a higher chance the stabilisation system will degrade the image than improve it. This is typically only seen when the camera is mounted on a tripod.

Improved Shutter Speeds (Handheld)

This is the percentage of tested shutter speeds that show an improvement with the stabilisation system enabled while the camera is handheld.

Degraded Shutter Speeds (Tripod)

This is the percentage of tested shutter speeds that show an drop in quality with the stabilisation system enabled while the camera is on a tripod.

Ideally, there should be no degradation of the image quality when the stabilisation system is active, but some cameras can make quite a significant dent in the image quality if the stabilisation system is active while the camera is held very still.

Improvement Range

The Improvement Range shows the range of shutter speeds where an improvement in image quality is to be expected with the stabilisation system enabled.

This range may be indicated with a "-" at one end - for example "1/40s to -". This shows that the stabilisation system provides a benefit starting at 1/40s and continuing through the complete range of data in FoCal IQ (e.g. 2s), but may well extend beyond this.

Degraded Range

The Degraded Range shows the range of shutter speeds where an degradation in image quality is to be expected with the stabilisation system enabled.

This range may be indicated with a "-" at one end - for example "- to 1/40s". This shows that the stabilisation system actually makes the image quality worse from very short shutter speeds outside of the test data, continuing through to 1/40s.

Potential Hot Pixels

The FoCal Dust Analysis test not only detects dust, but can also detect stuck or Hot Pixels. This metric shows the average number of hot pixels detected in Dust Analysis test results uploaded.

Widest Affected Aperture

The Widest Affected Aperture is the typical widest aperture that is showing detectable dust spots.

Typical Spot Count

The Spot Count is the number of "high confidence" spots detected during a Dust Analysis test. FoCal considers a spot to be high confidence if it is detected across at least 3 apertures of the test data.

Typical Spot Size

The Spot Size is the typical size of spots on the sensor. The value is shown in millimeters, taking into account the pixel size of the camera sensor.

Typical Spot Max Opacity

The Typical Maximum Opacity is a measure of the darkness of the average spot on the sensor across all Dust Analysis tests. The Opacity is shown in percent, where 100% is a totally opaque black spot, and 0% would be undetectable.

Typical Impact

The Impact is a combined measure of the spot size, opacity and the number of apertures affected by this spot. A metric close to 100% suggests that this spot will be very noticeable in all shots.