Technical Guide

Exposure Modes and Exposure Meter

This guide explains how to use the Exposure Modes and Exposure Meter available in Cinema P3 Pro Camera.
In particular, it provides information about the ISO Priority and Shutter Priority exposure modes that are available when using the 'Video' and 'Creative Modes'.

Contents
1 Exposure Modes
   1.1 Introduction
   1.2 Center and Spot
   1.3 Manual
   1.4 ISO Priority
   1.5 Shutter Priority
2 The Exposure Meter
   2.1 Description
   2.2 Key Elements
   2.3 Metering Modes
   2.4 Exposure Meter Settings

1 Exposure Modes

1.1 Introduction

Cinema P3 Pro Camera has 5 Exposure Modes for video capture:

  • Center
  • Spot
  • Manual
  • ISO Priority
  • Shutter Priority

The Exposure Modes are accessed from the 'Camera Settings' menu.

The blue text lists the key properties of the Exposure mode.
Tap the text for more detailed information.

1.2 Center and Spot

Center (C) and Spot (S) are the standard automatic exposure modes available in iOS.

They are simple for users who want to 'point and shoot'.
The camera reacts very quickly to changes in exposure, and ISO and SS are set automatically.

A manual Bias control is used to make adjustments to the exposure.

In Center mode, the exposure point of interest is in the centre of the screen.
In Spot mode, the exposure point of interest is indicated by a Spot, which can be repositioned manually.

1.3 Manual

Manual (M) exposure mode provides manual control of ISO and SS.

SS (Shutter Speed) is adjusted using the Shutter Angle control.
Shutter Angle is a way of setting the shutter speed relative to the frame rate.

ISO is adjusted using the ISO control.

(For cinematic video, a shutter angle of 180 degrees is often used as it produces a desirable amount of motion blur.
180 degrees produces a shutter speed that is half the frame rate.
e.g. for a frame rate of 30 frames per second, the shutter speed is 1/60 second.)

1.4 ISO Priority

ISO Priority (IP) is a mode that controls SS and ISO automatically.
It sets exposure by adjusting shutter speed, prioritising the lowest possible ISO.

ISO Priority mode targets a different middle grey level compared to the Spot and Center modes, and reacts to light level changes more slowly.

Manual Adjustments to the automatic settings are made using a Bias control and Max Shutter Angle control.

The Max SA control is displayed by tapping the 'SS' button and is used to set the Maximum Shutter Angle.
Typically, a value of 180 degrees is used, but can be varied between 10 and 340 degrees. The minimum shutter angle can be set in the Exposure Meter Settings (see section 2.4 below) to prevent fast shutter speeds.

The Exposure Meter will automatically adjust the camera's shutter speed between the minimum and the maximum Shutter Angle.

The Exposure Bias control is used to make adjustments to the automatic exposure.
It is displayed when the 'Bias' button is pressed.

It does this by adjusting the Exposure Meter's target value.
Adjusting bias from -2 to +2 will offset the Exposure Meter's target value from -20% to +20%.
The 'Exposure Bias' control is displayed when the 'Bias' button is selected.

1.5 Shutter Priority

SS Priority (SP) is a mode with automatic control of ISO and manual control of Shutter Speed.

The Manual SA control is used to adjust shutter angle to a specific value.
It is displayed when the 'SS' button is pressed.

The Exposure Bias control is used to make adjustments to the automatic exposure.
It is displayed when the 'Bias' button is pressed.

Shutter Priority mode targets a different middle grey level compared to the Spot and Center modes, and reacts to light level changes more slowly.

ISO Priority and Shutter Priority are for intended for more advanced users that require automatic operation with some manual control. These modes may require the use of ND (Neutral Density) filters to reduce the light entering the camera when used in bright conditions.

2. The Exposure Meter

2.1 Description

The Exposure Meter is a tool that assists setting exposure by indicating scene light level and average luma level.

The Exposure Meter is always displayed when using the 'ISO Priority' and 'Shutter Priority' exposure modes. In these modes, the Exposure Meter provides three methods of 'metering' to determine how automatic exposure is set.

The Exposure Meter is displayed to the left of the Bias, SS or ISO controls.
The image below shows the Exposure Meter displayed next to the Bias Control.

2.2 Key Elements

The key elements of the Exposure Meter are described below.

Exposure Mode
The Exposure Mode is displayed at the top.

Metering Mode
In IP and SP modes, a graphic indicates the Metering Mode.
The example above indicates Matrix metering mode.

Light Level Meter
- The blue needle indicates the amount of light reaching the camera.
- When the needle is pointing to the left, very little light is reaching the camera, and high ISO and slower shutter speeds are required.
- When the needle is pointing to the right a lot of light is entering the camera, and low ISO and fast shutter speeds are required.
- The ideal position for the needle is in the middle region, which corresponds to low ISO and low shutter speeds.

Exposure Meter Scale and Target Value
- The scale indicates luma values from 0 to 100%.
- The Exposure Meter samples over 200 points from the image and displays the measured value using
the yellow metering needle. The needle positition represents the average luma measured by the meter.
- A target value for the meter is indicated by the wider horizontal line located at 40% on the scale.
- The Exposure Meter adjusts ISO and SS so that the average luma level sits at the target value.
- The bias control can be used to offset the target value of the exposure meter. Adjusting the bias +/-2 will change the target value +/-20%. i.e. range from 20% to 60%.

2.3 Metering Modes

When using ISO Priority and Shutter Priority exposure modes, the Exposure Meter provides three metering modes:
Spot, Centre Weighted and Matrix.

When you tap the Exposure Meter, it reveals three buttons which are used to select a metering mode.
The selected mode is highlighted in yellow.

Matrix Metering

In matrix metering mode, the Exposure Meter samples 225 evenly distributed points from the image to measure the average luma value.

Center Weighted Metering

Center Weighted metering mode, samples the whole image, with additional weight given to the center of the image.

Spot Metering

In spot metering mode, a spot is displayed which can be manually positioned on the screen.
The Exposure Meter only samples points inside the spot to measure the average luma value.

2.4 Exposure Meter Settings

The Exposure Meter has settings to adjust how metering operates in ISO Prority and Shutter Priority modes.

Tap "Exposure Meter" from the Camera Settings menu to access the 'Exposure Meter' settings menu.



Show Exposure Meter determines when the Exposure Meter is displayed.
When the switch is 'ON', the Exposure Meter is displayed in all Exposure Modes.
When the switch is 'OFF', the Exposure Meter is only displayed in 'ISO Priority' and 'Shutter Priority' Exposure Modes.

Adjustment Speed sets how quickly the Exposure Meter responds to changes in light levels in ISO Priority and Shutter Priority exposure modes.

Maximum ISO is used to set an upper limit for ISO in the ISO Priority and Shutter Priority exposure modes.
When Auto is selected, the ISO will operature within the full range of ISO values supported by the camera.

Show Center Weight displays the location of the center weight on screen when using center weighted metering mode. This Center Weight position can be moved to adjust the region of the image that receives additional weight.

Max Shutter Angle is used to set a lower limit for Shutter Angle in ISO Priority Exposure Mode. This can be used to prevent fast shutter speeds.