LC5 User Manual

 The LC5 Light Integrator and Darkroom Timer is the heart of the Light Counter system. It contains an advanced microcontroller that helps you manage your exposures with unparalleled precision. The system is designed by a photographer for photographers. It works simply and quickly, with a strong emphasis on ease of use.

Simple exposures can be defined in calibrated "units of light" (usually abbreviated to just "units") or in times, with both accurate to a fraction of a second. You can save your most commonly used exposures in the eight presets available.

More complex exposures can be configured as programs of multiple exposures. There are four programs available, which can each be configured on one of three ways:

  • Automatically calculate test strips — e.g. seven half-stop steps increasing from 10 seconds, or three 0.3-stop steps bracketed around 12 units of light
  • Run a series of up to ten timed or units of light exposures
  • Run a series of up to ten f-stop based exposures — ideal for darkroom workers who use f-stop printing

The LC5 is controlled and programmed using a large 4.3" touch screen. There are no fiddly buttons, switches and command codes to learn. Just touch the screen and go! It also has a micro SD slot for firmware upgrades, saving and loading device configurations, and recording detailed exposure measurements for data analysis.

This guide is intended to help you to quickly start using your new LC5 Light Integrator.

Latest update: 21st July 2022 for firmware v5.0.16.

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

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 inherently 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 or visible light-based printing process.

Measuring Light with ‘Units of Light’

The light integrator measures light 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. If the lights are a little bit dim, then the light integrator will record less than one unit. If they are a bit bright, then it will record more than one unit. In this way variability in the light source is accounted for, and ceases to be an issue when printing.

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.

But Can I Still Use Timed Exposures?

Of course! The LC5 includes a multi-step darkroom timer, accurate to 0.1 seconds. This is especially useful for silver gelatin printing with an enlarger. This is described in the section on programs.

System Devices

Light Counter is designed as a flexible system. The basic configuration has a light integrator and a single light 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
  • Visible Light Sensors – extend the systems capabilities to non-UV processes such as silver gelatin
  • Temperature Sensors - allow monitoring of the light source temperature during printing
  • Environment Sensors – allow monitoring of the temperature and humidity
  • Smart Power Controller – allows the light source to be automatically switched on and off by 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 light intensity, and automatically adjusts the exposure time to allow for lamp warm-up and any fluctuations in the power supply.

LC5 Light Integrator and Darkroom Timer

Light Counter LC5

The LC5 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 light, visible light, temperature or temperature and humidity) so you can monitor exposure in every part of your printing unit. It stores up to eight exposure presets and four programs, for fast switching between your favourite printing variations.

The LC5 features an automated calibration process, ensuring that your exposures are consistent even if you move the sensors.

The LC5 supports a smart 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 LC5 includes a built in 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, and backing-up your configuration settings.

The LC5 supports a remote control that allows you to switch on, pause and resume exposures from a distance.

UV Light 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 also available.

UV Sensor

Up to four UV sensors can be connected to the LC5 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 LC5 light integrator, albeit without the advanced features introduced with the second generation sensor.

Visible Light Sensors

The LC5 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.

Temperature and Environment Sensors

The temperature and environment sensor both monitor the temperature inside your UV printing unit. This allows you to be confident that you are not over-heating your prints during exposure. They can also be used to verify that cooling systems are working effectively in all parts of the exposure unit. The more expensive environment sensors also record the ambient humidity.

Temperature Sensor

First generation temperature sensors designed for the LC2 light integrator continue to work with the LC5 light integrator.

Smart Power Controller

The Smart Power Controller is an add-on device that allows the light integrator to switch the light source or enlarger on and off. This brings extra convenience and a small increase in exposure accuracy.

On the front panel is an LED indicator that shows whether the power controller is active, and an override switch that allows you to switch the power on and off manually.

The smart power controller is rated for 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.

Smart Power Controller

A PCB-only version of the smart power controller is available for fixing within another device, such as a light unit. This can be used to control downstream power supplies or bespoke lighting systems. The PCB-only version does not have an LED indicator or override switch. It is intended for installation by a qualified electrician.

Smart Power Controller for Internal Use


An adapter is available to convert an old-style power controller with a 2.5mm jack plug into a smart power controller.

The LC5 can control up to three smart power controllers. All switch on and off at the same time.

Built-in Data Logger

The data logger has three 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 LC5 light integrator
  3. To allow the user to save and restore configuration settings

Remote Control

Remote Control

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

Press and hold the remote control button for a second 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 LC5 Light Integrator

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

  • A standard barrel connector for the power supply
  • A set of USB-A connectors for the sensors and other devices

There is also a slot for the micro SD card used by the data logger.

Important: The LC5 does not support "plug and play" behaviour. If you want to add or remove a peripheral then you must first switch off the light integrator. Only switch it on again since all cables are connected.

Connecting the Sensors

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

Light Counter LC5

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 Diagnostics button in Settings.

The UV light 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 visible light sensor should be attached inside the enlarger head, or on the printing frame if sun-printing.

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 the supplied USB cable cable. The connector is on the front panel of the smart power controller.

Smart Power Controller

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

Smart Power Controller

The smart power controller is rated for a 10A load. Do not exceed this limit. 10A is approximately 1100W in the US and 2200W in Europe and the rest of the world.

If you need to control a more powerful light source, then use a secondary control circuit, such as an industrial relay. Use the smart power controller to switch the industrial relay, and thus ensure that the device is not overloaded.

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 LC5 can also be powered from high power battery packs used for charging laptops and tablets. Not all battery packs are able to power the LC5, and some experimentation may be required. 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.

The Home Screen

The Home Screen

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
  • If a light sensor is attached then the second line shows the current (or most recent) light intensity
  • The next line shows the current exposure duration
  • If a temperature or environment sensor is attached, then the fourth line shows the temperature and humidity

There are four touch buttons on the right: Edit Exposure, Exposure Programs, Settings, Start Exposure. These buttons default to showing icons, but can be set to show text labels if you prefer (in the settings screen).

  Edit Exposure
Exposure Programs
Start Exposure

If the LC5 is set to work in ‘dark mode’ then the screen colours are inverted. This is helpful when working in a darkroom under low lights. There is also a safe light mode for silver gelatin workers.

Editing an Exposure

An exposure can be set to use either units of light or time. This is configured by pressing the yellow "Change to Units" or "Change to Time" button.


Edit Units

Edit Exposure in Units

The LC5 can manage units exposures up to 99,999.9 units. Once calibrated this represents almost 28 hours of light (remember, when calibrated, one unit is approximately equal to one second under full power). 

Edit Exposure Time

Edit Exposure in Time

The LC5 can control timed exposures up to 9 hours, 59 minutes and 59 seconds.

Using Presets

Printers often have standard exposures that they use. The LC5 supports eight presets for standard exposures. These can be accessed by touching the Load preset button on the exposure editing screen. Presets can be configured in either units of light or times.

 Load Preset Load Preset


Manage Presets

Manage Presets

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 edit 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.

Using Programs

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.

The LC5 supports up to four programs. These can be accessed by touching the Programs button from the Home screen.

A program can be configured as either:

  • Test Strips – which are an automatically calculated series of exposures based upon a baseline exposure and a step size in stops
  • Series – which are a user-defined series of exposures in either units of light or time
  • F-stops – which are a user-defined series of exposures based upon stops relative to the baseline

Test Strips Programs have the following parameters:

  • The baseline exposure (in either units of light or time)
  • Whether the test strip exposures increasing from the baseline exposure, decreasing from baseline, or bracketing the baseline
  • The step size in 1/10 of a stop
  • The number of steps – either 3, 5, 7, 9, 11 or 13

Test Strips Increasing from the Baseline

Test Strips Increasing from the Baseline


Test Strips Decreasing from the Baseline

Test Strips Decreasing from the Baseline

Test Strips Bracketing the Baseline

Test Strips Bracketing the Baseline

In each case, the calculated exposures can be checked by using the Preview menu button. This shows shows the incremental exposure given by each step in the test strip.



When working with test strips, the program assumes that you cover each strip in turn after the exposure. For example, the program shown above (seven half-stop steps increasing from 10.0 seconds) exposes as follows:

  1. 10.0 seconds
  2. +4.1 seconds (so this strip receives a total of 14.1 seconds)
  3. +5.9 seconds (so this strip receives a total of 20 seconds)
  4. +8.3 seconds (so this strip receives a total of 28.3 seconds)
  5. +11.7 seconds (so this strip receives a total of 40 seconds)
  6. +16.6 seconds (so this strip receives a total of 56.6 seconds)
  7. +23.4 seconds (so this strip receives a total of 1 minute and 20 seconds)

Series Programs have the following parameters:

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

The series may be in either units of light or time. All exposures in the series must have the same mode.

F-stops Programs are similar to series programs, except that each step is a number of stops based upon the baseline exposure. These are designed for people who want to do f-stop printing.

The LC5 can be set to either pause the exposure between each step or to simply beep and continue into the next step. 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. This is configured in the settings screen.

Settings Screen

Settings Screen


The settings screen shows the configuration settings:

  • Integration Mode – either ‘Precise’ or ‘Fastest’
  • Display Brightness – either ‘Brightest’, ‘Bright’, ‘Dim’ or ‘Dimmest’
  • Display Mode – either 'Light', 'Dark' or 'Safe'
  • Temperature units – either ‘Centigrade’ or ‘Fahrenheit’
  • Humidity units – either ‘Relative Humidity’ or ‘Absolute Humidity’
  • 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’

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 (UV sensors) or 0.1 second (visible light sensors). When set to ‘fast’ integration time, the light integrator sacrifices a bit of precision in order to take several quick measurements in that interval. The former setting is most suitable for long exposure times, and the latter is most suitable for short exposures.

Several settings are only activated when a suitable sensor is attached.

The buttons on the right of the settings screen are:

  Return to the home screen
System Settings Additional system settings
Sensor Calibration – only visible if a light sensor is connected


The System Settings screen is used for less regularly used functions. From here you can upgrade the firmware, save and load settings, change the screen rotation, and reset the light integrator to factory default settings.

The settings load and save buttons are not visible on LC3+ and LC4+ light integrators. This is because these use an external data logger which does not support these functions.

Old LC3+ and LC4+ devices with a connected external data logger will show a menu button for setting the data logger's date and time.

Set Date and Time Set Date and Time – only visible on LC3+ and LC4+ devices with an attached external data logger


Warning: A factory reset will erase all settings, presets and programs. There is no way to recover these afterwards.

Sensor Calibration

Calibration does two things:

  1. It converts the raw light 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 LC5 is uncalibrated.

Many light sources continue to emit light for a short time after the power is cut. This 'afterglow' is measured once calibration is completed. It is shown in both units of light in seconds.

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

From the home page touch Settings, Calibrate, then Confirm.

Sensor Calibration - Default Values

Sensor Calibration - Default Values

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

The buttons on the right of the calibration screen are:

  Return to the settings screen
Manually edit the calibration value
Start automatic calibration


Calibration has five stages:

  1. Waiting for the sensors to detect light
  2. Waiting for all attached sensors to report stable 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
  5. Measuring any afterglow once the lights have been switched off

The light integrator beeps once calibration is completed, and displays the results of the calibration.

Completed Calibration

Completed Calibration

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.

Calibration for Jon Cone's 1000 System

Jon Cone's light units are configured with a system intended to give portable exposure settings. The goal is that an exposure of, say, 450 units on one light unit produces the same on another.

To calibrate for the 1000 System, first follow the standard calibration process described above, and then press the 1000 System button. The calibration value will then be converted to the appropriate value for the 1000 System.

1000 System 1000 System – convert from standard calibration to the 1000 system



Please be ware that the 1000 System calibration feature has been temporarily disabled until a bug has been fixed.

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 LC5 switches on the light source, and immediately starts measuring 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.

You can pause, resume and cancel an exposure at any time.

If you are running a program, then the light integrator will either pause at the end of each step or beep and continue straight into the next step. This is controlled by the system setting described above.

If you use the remote control to start an exposure, then it requires a one second long press to start, but shorter presses will pause and resume the exposure. This is a safety feature to avoid accidentally starting an exposure by inadvertently pressing the remote control button.

Manual Exposures

To start a manual exposure, simply set an exposure of zero units or time. Manual exposures are started in the same way as automatic exposures, but stay running until you stope them.

Split-Grade Printing

Multiple programs are particularly useful when doing silver gelatin split-grade printing with an enlarger. You can keep one program dedicated to the grade 0/00 exposures, another for the grade 5 exposures, and still have two programs left for the various test strips and experiments you make while working on the print.

Migrating from an Earlier Model

Migrating from an LC3, LC3+ or LC4 Light Integrator

The LC5 firmware can also be loaded onto older LC3 and LC4 light integrators, which then become LC3+ and LC4+ devices. Doing this requires an external data logger or a "back to base" upgrade. After the upgrade, all features described in this manual are available except for those that rely on the LC5's internal data logger.

LC3 and LC4 Peripheral Compatibility

  • All sensors work on the LC5
  • Remote Controls work on the LC5
  • External Data Loggers do not work on the LC5 because it has an internal data logger
  • LC4 smart power controllers work on the LC5
  • Old-style power controllers with a jack plug cable do not work on the LC5 without an adapter

If you have any questions about compatibility and upgrades, then please contact Ian Leake Studio for support.

Migrating from an LC2 Light Integrator

The LC2 and LC5 devices run on substantially different hardware. Although there is no direct upgrade path, I offer LC2 customers a preferential deal when buying a new LC5. Please contact me for further information.

The main differences between the LC2 (first generation) and LC5 light integrators are:

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

The LC2 and LC5 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, it is possible that there may be a slight difference between your new LC5 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 LC5 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 smart power controller is rated for a 10A load. Do not exceed this load. 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.


All Light Counter kits, devices, and sensors are covered by a global repair-or-replace warranty. If a component fails within a year of delivery, then just ship it back to me and I will repair or replace the item free of charge.

Please note that the following actions will invalidate the warranty:

  • Do not connect a computer to the sensor USB ports. These use standard USB cables for reasons of cost and convenience, but they do not use the USB protocol. Connecting a computer may damage the device or your computer
  • Do not open the device enclosure. The devices contain static-sensitive components. Opening the enclosure and touching components may damage them
  • Do not overload the power controller with high power lights. The smart power controller is rated for a maximum 10A load. If you are unsure then please consult a qualified electrician

Customer Support

If you need any assistance then please contact Ian Leake Studio by email or by using the contact form on this web site.