Light Counter is a precision light integrator system for ultraviolet printing processes. The system is designed by a photographer for photographers. It works simply and quickly, with a strong emphasis on ease of use.

LC3+ Light Integrator
LC3+ Light Integrator

This guide is intended to help you to quickly start using your new LC3 Light Integrator.

Table Of Contents

Two Important Concepts: Measurement-based Exposures and ‘Units’

Measurement-based Exposures

Printing exposures are usually based on time, measured from the moment the lights are switched on to whenever they are switched off. Time-based exposures are easy to measure, but inaccurate because the intensity of all light sources varies over time, especially when the lights are warming up.

Light integrators allow photographers to make measurement-based exposures. These are based upon measurements of the actual intensity of light over the entire exposure. Measurement-based exposures are more accurate than time-based exposures, but require specialised equipment.

The Light Controller system uses a state of the art microprocessor, custom-designed digital sensor circuits and advanced software to bring measurement-based exposures within the reach of all photographers. The system was originally designed for platinum/palladium printing but will work for any ultraviolet-based printing process.

Measuring UV with ‘Units’

The light integrator measures UV intensity in micro-Watts per centimeter squared (µW/cm2), but this is pretty meaningless to most photographers. Calibration allows the light integrator to convert this raw measurement into things called ‘units’. These are much easier to use when printing.

After calibration, one ‘unit’ is about one second of exposure when the lights are at full power.

The light integrator does the necessary calculations and adjustments automatically, ensuring that your prints get the same exposure regardless of how the light intensity varies during exposure. You can even switch off your lights for a while during an exposure, and the light integrator will sort it out.

If the system has not yet been calibrated, then it will report the raw sensor measurement as units. For example, if the uncalibrated system measures 200 µW/cm2 then it will report this as 200 units.

‘Units’ are calibrated to a specific light source, so they are not comparable between exposure units. A 300 unit exposure under a low intensity light source is not the same as a 300 unit exposure under a high intensity light source. And because ‘units’ are an arbitrary measure, they are not comparable across systems made by different manufacturers.

System Devices

Light Counter is designed as a flexible system. The basic configuration has a light integrator and a single UV sensor. Advanced users can add additional peripheral devices to support their specific needs.

The system devices are:

  • The Light Integrator – “the brains” of the system. It controls the exposure, and all peripheral sensors and devices
  • UV Light Sensors – provide factory-calibrated measurement of the ultraviolet light source
  • Temperature Sensors – allow monitoring of the temperature inside the UV exposure unit
  • Visible Light Sensors – extend the systems capabilities to non-UV processes such as silver gelatine
  • Power Controller – allows the light source to be automatically switched on and off by the light integrator
  • Data Logger – records exposure information to an SD card for further analysis in a spreadsheet such as Microsoft Excel; also enables firmware upgrades to the light integrator
  • Remote Control – allows control of exposures (start and pause) using a remote button

The Light Integrator

The light integrator is “the brains” of the system. It controls the exposure, and all peripheral sensors and devices.

During exposure, the light integrator continually measures UV intensity, and automatically adjusts the exposure time to allow for lamp warm-up and any fluctuations in the power supply.

LC3+ Light Integrator
LC3+ Light Integrator

The LC3+ light integrator has a large 4.3” TFT display with a capacitive touch screen (using the same technology as your mobile phone or tablet computer). This allows incredibly easy set-up and control. It supports up to four sensors (UV or temperature), so you can monitor exposure in every part of your UV printing unit. It stores up to eight exposure presets and four programs, for fast switching between your favourite printing variations.

The LC3+ features an automated calibration process, ensuring that your exposures are consistent even if you move the sensors.

The LC3+ supports a power controller device that will switch your UV light source on and off as required. The system also works without the power controller, of course: you just have to switch the light source on and off yourself.

The LC3+ supports a data logger device that records exposure details to an SD card for further analysis in a spreadsheet such as Microsoft Excel. The data logger also enables firmware upgrades to the light integrator.

UV Sensors

Two versions of the UV sensor are available. The standard version has a 365nm narrowband filter to optimise the sensor for iron-based printing processes. A broadband version without the filter is available by request.

Second Generation UV Sensor

The second generation UV sensors are factory-calibrated using a standard light source to ensure that all sensors have comparable readings. This is important because the inherent variability between sensors can be significant (sometimes as high as 25%).

Up to four UV sensors can be connected to the LC3 light integrator, allowing the entire printing area to be monitored during exposure.

First generation UV sensors designed for the LC2 light integrator continue to work with the LC3 light integrator, albeit without the advanced features introduced with the second generation sensor.

Temperature Sensors

The temperature sensor monitors the temperature inside your UV printing unit. This allows you to be confident that you are not over-heating your prints during exposure. Temperature sensors can also be used to verify that cooling systems are working effectively in all parts of the exposure unit.

First generation temperature sensors designed for the LC2 light integrator continue to work with the LC3 light integrator.

Visible Light Sensor

The LC3+ supports a visible light sensor as well as UV sensors. This allows it to work for non-UV processes such as silver gelatin.

Note that only one type of light sensor can be connected at a time. If UV and visible light sensors are connected, the visible light sensor is ignored.

Power Controller

The power controller is an add-on device that allows the light integrator to switch the UV light source on and off. This brings extra convenience and a small increase in exposure accuracy.

Two versions of the power controller are available. The standard power controller can switch loads up to 5A, which is approximately 1100W in Europe, and 550W in the USA. This is sufficient for most photographers’ UV light sources.

Standard Power Controller

The professional power controller has double the capacity: 10A which is about 2200W in Europe and 1100W in the USA. This is designed for high intensity professional light sources, especially high power LED systems.

Data Logger

LC3+ Data Logger
LC3+ Data Logger

The data logger has two purposes:

  1. To record exposure data onto an SD card for further analysis in a spreadsheet. The data is stored as a simple CSV file
  2. To allow firmware upgrades to the LC3+ light integrator

The data logger plugs into any of the light integrator’s device connectors.

Remote Control

LC3+ Remote Control
LC3+ Remote Control

The remote control allows you to start and pause the exposure when you are at a distance from the light integrator. It has a button for starting/pausing the exposure, a small display to show progress through the exposure, and a backlight switch.

Press and hold the remote control button to start an exposure. This takes the light integrator to its normal confirmation display. This is a safety feature to avoid accidentally starting exposures. From the confirmation screen, press the button a second time to start the exposure.

Once an exposure is underway, pressing the remote control button pauses and resumes the exposure.

The remote control plugs into any of the light integrator’s device connectors.

Connecting your LC3+ Light Integrator

There are three types of connector on the back of the light integrator:

  • A standard barrel connector for the power supply
  • A 2.5mm stereo jack plug connector for the power controller
  • Four USB-A connectors for the sensors

Connecting the Sensors

Attach the sensors to the USB connectors on the light integrator using the supplied cables. It does not matter which USB connectors the sensors are attached to.

LC3 Light Integrator Rear Connectors

During system start-up the light integrator will work out which sensors are attached and show this on the start-up display. This information can also be found by touching the Customer Support button.

The UV sensors should be placed near to the printing area pointing directly at the light source. It is important that they are fixed in a stable position: screwing them to the exposure unit wall is a good option.

The included USB cables are 1m long. The system has been tested with 2m and 5m USB cables, but whether longer cables work for you will depend on your environment. Long cables act like giant aerials, and electromagnetic interference can cause the sensors to work unpredictably. It is best to use the shortest cables possible.

Do not use multiple USB cables connected together. Do not use ‘active’ USB extension cables.

Attaching the Power Controller

The power controller is attached to the light integrator using a standard 2.5mm stereo jack plug cable.

The power controller has two mains electrical connectors, both standard ‘kettle’ type connectors (technically called ‘C13’ and C14’ connectors). The C13 connector (standard ‘kettle’) is used for the mains electricity supply. The C14 (‘kettle extension’) is used to connect the light source.

C13 (right) and C14 (left) Cables

The standard power controller is rated for a 5A load. The professional power controller is rated for a 10A load. Do not exceed these limits.

Connecting the Power

The supplied power adapter has connectors for North America, Europe, United Kingdom, Australia and China. Select the correct connector for your region. There is an on/off switch beside the light integrator power connector.

The first generation LC2 light integrator can be powered straight off a standard USB power adapter, but the big display used in the LC3 requires more current than USB can typically provide. If you wish to experiment with powering the system from USB, then please contact Ian Leake Studio. A suitable power cable is available on request.

Using the Light Integrator

After boot-up, the light integrator shows its ‘home‘ screen. From here you can access all light integrator functions.

Please note the colour of the touch buttons on the screens. Yellow buttons are activated immediately when they are touched. The darker orange buttons require a one second long touch to activate. This is a safety feature to protect from accidentally starting/stopping exposures or triggering other high impact functions.

The Home Screen

LC3+ Light Integrator
LC3+ Light Integrator

Exposure information is shown on the left:

  • The large digits show the exposure target, either in units or time depending upon the selected preset. This is updated during the exposure to count down to zero, when the exposure is complete
  • The second line the selected program or preset
  • The third line shows the current intensity of UV light being detected. This will be 0.0 units/second unless there is an ongoing exposure
  • The fourth line shows the current exposure duration
  • If a climate sensor is attached the fifth line shows the temperature and humidity, depending upon the specific sensor attached

There are four touch buttons on the right: Presets, Programs, Settings, Start Exposure. These buttons default to showing icons, but can be set to showing text if you prefer.

LC3+ Presets Icon
LC3+ Programs Icon
LC3+ Settings Icon
LC3+ Start Exposure Icon
Start Exposure

If the LC3+ is set to work in ‘dark mode’ then the screen colours are inverted. This is helpful when working in a darkroom under low lights.

LC3+ Dark Mode
LC3+ Dark Mode

Presets Screen

LC3+ Presets
LC3+ Presets

The presets screen has eight preset ‘slots’ which can be set to measurement-based exposures, time-based exposures or manual exposures.

LC3+ Home Icon
LC3+ Edit Icon

To select a preset, simply touch the preset button, which will change from blue to orange to show it is selected, and then press the ‘home’ button.

To select a preset, simply touch the preset button, which will change from blue to orange to show it is selected, and then press the ‘edit’ button. On the preset editing screen you can set the preset value.

LC3+ Preset Editing
LC3+ Preset Editing

If the preset is set to measurement-based exposures, then the last blue button on the top row shows the label Units. To change to a time-based exposure, touch the button; it will then display Time and additional buttons will appear that allow you to set hours, minutes and seconds. To set manual exposure, simply set a preset value of 0.

LC3+ Cancel Icon
LC3+ Cancel Icon
LC3+ Confirm Icon
LC3+ Confirm Icon

Programs Screen

LC3+ Programs
LC3+ Programs

The LC3+ has four program slots. A program is a series of exposures chained together. They are designed to help you to make test strips, and also for dodging and burning when printing from traditional negatives.

‘Test Strips’ programs have the following parameters:

  • The base exposure (either measurement-based or time-based)
  • Whether the test strip exposures increase above the base exposure, decrease from base exposure downwards, or bracket the base exposure
  • Whether the individual steps are in whole, 1/2, 1/3 or 1/4 stop increments
  • How many steps in the program – either 3, 5, 7, 9, 11 or 13

The picture below shows a configured Test Strips program which has 7 steps, each of 1/2 stop, decreasing from a base exposure of 300 units. The text at the bottom of the screen shows the total exposure each step will receive.

Important: When working with test strips, we normally cover each strip in turn with a sheet of board. To enable that type of working, during the exposure, the light integrator exposes for the gap between the two steps not the whole step. So the program shown below exposes as follows:

  1. 37.5 units
  2. +15.5 units (so this strip receives a total of 53 units)
  3. +22.0 units (so this strip receives a total of 75 units)
  4. +31.1 units (so this strip receives a total of 106.1 units)
  5. +43.9 units (so this strip receives a total of 150 units)
  6. +62.1 units (so this strip receives a total of 212.1 units)
  7. +87.9 units (so this strip receives a total of 300 units)
LC3+ Program Test Strips
LC3+ Program Test Strips

‘Series’ programs have the following parameters:

  • The base exposure (either measurement-based or time-based)
  • Up to three additional exposures

The picture below shows a configured Series program which has a base exposure of 300 units, followed by:

  1. +150 units (for a total exposure of 450 units)
  2. +250 units (for a total exposure of 700 units)
  3. +50 units (for a total exposure of 750 units)
LC3+ Program Series
LC3+ Program Series

The LC3+ can be set to either pause the exposure between each step or to simply beep and continue. Most people will prefer the former, but if you are using a light source that has a significant cool-down time then you will most likely prefer the latter.

Settings Screen

LC3+ Settings
LC3+ Settings

The settings screen shows the configuration settings:

  • Integration speed – either ‘Most Precise’ or ‘Fastest’
  • Display brightness – either ‘Brightest’, ‘Bright’, ‘Dim’ or ‘Dimmest’
  • Temperature units – either ‘Centigrade’ or ‘Fahrenheit’
  • A setting to define whether programs pause between individual steps or simply beep and continue (see Programs above)
  • Whether to show ‘Icon Menus’ or ‘Text Menus’
  • Whether to work in ‘Light Mode’ or ‘Dark Mode’
  • Humidity units – either ‘Relative Humidity’ or ‘Absolute Humidity’

Touch the appropriate button to cycle through the setting values.

When set to ‘standard’ integration time, the light integrator takes a single highly accurate reading every second. When set to ‘fast’ integration time, the light integrator sacrifices a bit of precision in order to take six quick measurements every second. The former is most suitable for long exposure times, and the latter is most suitable for short exposures.

The buttons on the right of the settings page:

  • Home – returns you to the home page
  • Data Logger – see below
  • Diagnostics and Customer Support
  • Calibration – takes you to the sensor calibration page
LC3+ Home Icon
LC3+ Data Logger Icon
Data Logger

LC3+ Information Icon
Diagnostics and Customer Support
LC3+ Calibrate Icon
Sensor Calibration

The Data Logger icon only appears if the data logger is attached. This takes you to the data logger settings page. From there you can set the date and time, format SD cards, and start the firmware upgrade process.

  • Calibrate – which starts the calibration process
  • Reset – which triggers a factory reset
  • Customer Support – which shows a page of troubleshooting information
  • Home – which returns the light integrator to its home screen


Calibration does two things:

  1. It converts the raw UV measurements into ‘units’
  2. It helps to eliminate measurement errors due to placement of the sensors

The second point is important. All light sensors are highly sensitive to the distance from the light source they are measuring, plus their orientation to the light source. Turning a sensor by just 10 to 15 degrees can have a significant effect on its measurements. Calibration helps to eliminate this.

The calibration process determines a ‘Calibration Value’ that is used to adjust the sensor measurements so that 1 unit is roughly one second exposure when the lights are at full power. A calibration value of 1.000 simply means the LC3+ is uncalibrated.

First fix the sensor in your preferred position (see above).

From the home page touch Settings, Calibrate then Confirm.

LC3+ Calibration

You can also manually set a calibration value by touching the Edit button.

LC3+ Settings Icon
return to Settings
LC3+ Edit Icon
Edit the Calibration Value
LC3+ Confirm Icon
Start Automatic Calibration

Calibration has two stages:

  1. Waiting for the sensors to detect UV light
  2. Waiting for all attached sensors to report stable UV light intensity. This may take a few minutes for light sources that have a long warm-up time
  3. Measuring the sensors for one minute
  4. Calculating a new calibration value

The light integrator beeps once calibration is completed, and returns to the home page

If you interrupt the calibration process using the ‘Stop’ button then the calibration process will be halted.

Important: Do not recalibrate every time you use the light integrator. You only need to recalibrate if you change your sensor configuration or the light integrator itself.

Automatic Exposure

To start an automatic exposure:

  1. Choose a suitable exposure preset or program
  2. Touch the Start Exposure button from the home screen
  3. Then touch the Confirm button

If a power controller is attached, the LC3+ switches on the UV light source, and immediately starts measuring UV light. Once the exposure is complete, it switches off the power controller and beeps to indicate reaching the end of the exposure. If you do not have a power controller attached, then switch off the lights manually when the light integrator beeps.

Migrating from an Earlier Model

Migrating from an LC3 Light Integrator

LC3 light integrators can be upgraded to the LC3+ by using a back-to-base upgrade service (here). All LC3 devices are 100% compatible with the LC3+.

Migrating from an LC2 Light Integrator

The LC2 and LC3/LC3+ devices run on different hardware. Although there is no direct upgrade path, I offer LC2 customers a preferential deal when buying a new LC3+ (here). Please contact me for further information.

The main differences between the LC2 (first generation) and LC3/LC3+ (second generation) light integrators are:

  • Changing to a large touch-screen display
  • Support for multiple sensors
  • Support for exposure presets
  • Improved calibration process for greater precision
  • A host of usability enhancements

The LC2 (first generation) and LC3 (second generation) light integrators use the same definition for ‘units’ so their exposures will be broadly comparable (assuming both systems are calibrated using the same exposure unit). Many people will see no difference between the two.

However, given the improved calibration process and more precise sensors, so it is possible that there may be a slight difference between your new LC3+ exposures and your old LC2 exposures. It is recommended to make some test prints to verify your exposures before making critical prints.

It is not strictly necessary to place the new LC3 sensors in the same place as the old LC2 sensor, although doing this will make troubleshooting easier.

Product Safety Notices

  1. Electrical safety. Light Counter devices use low voltage power supplies, and are in general very safe to use. However two components use mains electricity and require normal common-sense precautions. These are the power adapter (only use the supplied adapter) and the power controller device (this switches the mains supply to your light source, so do not open the device with mains cables attached)
  2. More electrical safety. The standard power controller is rated for a 5A load. The professional power controller is rated for a 10A load. Both may work with higher loads, but prolonged usage may damage the device or in worst be a fire risk. If in doubt consult a qualified electrician
  3. If any device gets wet, immediately switch off the power supply. Allow the device to dry out before reconnecting
  4. Devices contain static-sensitive components. Opening them will void the warranty
  5. Only attach cables when the power supply is disconnected
  6. Do not connect the sensors or light integrator USB connectors to a computer. The system uses USB cables for convenience and low cost, but does not use the USB protocol. Connecting a computer to these devices may damage the computer and the device

Neither Ian Leake nor Ian Leake Studio accepts any liability to any person or entity with respect to loss or damage caused or alleged to have been caused directly or indirectly by use or misuse of this system.

Customer Support

If you need any assistance then please contact me. It would be helpful to attach a photo of the Diagnostics and Customer Support screens with your email.