Measure Exposure with the Pocket Light Meter App

Owned by Joachim Strand (Unlicensed)
Last updated: Jul 19, 2016
3 min read

Below is a quick guide on how to set your exposure using the Pocket Light Meter app. While not as accurate as a proper light meter (Minolta/Spectra Cine available in the store) the Pocket Light Meter App is a decent alternative.

Free on iOS and reasonably priced for Android.

Being a Spot Meter (reading light REFLECTED off the subject) measurements MUST BE taken from a gray card to attain a proper reading.

Know This!

Before you start using the Pocket Light Meter (or any other light meter for that matter) you must know the following information:

  1. The Shutter Speed your camera is set to.

  2. The ISO or Gain Setting your camera is set to (see below for a guide to setting the ISO/Gain in your camera).

ISO or Gain

Here's a rough guide to setting camera ISO:
100 or 200 ISOsunny and bright daylight
400 ISOcloudy days or indoors
800 ISOindoors without lights
1600+ ISOreally low light situations
If camera only has Gain settings, see conversion table below
-3dbequivalent toISO 100
0dbequivalent toISO 200
+3dbequivalent toISO 400
+6dbequivalent toISO 800
+12dbequivalent to

ISO 1600

+18dbequivalent toISO 2400

 

Please note that the higher the ISO/Gain the more grain you introduce into your picture.

Lock the Shutter Speed:

Tap the T section of the control panel.

From the pop-up menu select Shutter Speed value equivalent or close to the shutter speed set in your camera (default is set to 1/50). As this is an American app using NTSC shutter speeds, set to value nearest your camera shutter speed. so if camera is set to 1/50 set to 1/60.

 

Ensure there is a Lock Icon on the Shutter Speed Selection

Lock the ISO setting:

Tap the ISO section of the Control Panel.

From the Pop-Up menu, select the value nearest the ISO/Gain setting of your camera.

Ensure there is a Lock Icon on the ISO Selection

 

Put your gray card in the Key Light (or use another typical Mid-Tone value: average blue sky, latin/asian skin tone. Caucasian skin tone is one stop over mid-tone, so set camera to one stop UNDER your readout).

Aim phone camera at gray card. Tap on phone screen where you want to take measurement from.

Read the f/stop - this is your mid-tone value: correct exposure for the point you just measured.

 

Set camera to measured f/stop.

Exposure Range

Your Exposure Range will be roughly 2-3 stops either side of your mid-tone so make the necessary adjustments to ensure there is no clipping/under exposure in your shot.

Press HOLD to freeze the Readout.

 

Press HOLD again to unfreeze and take another reading.

Press LOG to take a snapshot of your readout.

In the pop-up you can note down log information.

 

Tap 'Add' to save your Log Note

The Log Note is saved to your phone's Picture folder.

A very thorough How-To video on using a light meter 

Light Meters in the Digital Age