What is Reddit's opinion of LEE Stopper Exposure Guide?

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I apologize for neglecting to mention this in my previous comment: I use the Lee Stopper Exposure Guide (Android / iOS) to calculate my shutter speed when I make long exposure images.

This app is very easy to use:

• Once you determine your exposure (before you attach your ND filter), make note of what your shutter speed is. We'll call this your "normal shutter speed".
• Tap the top menu to choose the density of your filter.
• Turn the left wheel to select your normal shutter speed.
• Read the adjusted shutter speed from the right hand wheel. Use this.

Once you have your adjusted shutter speed, just attach your ND filter and dial in that adjusted shutter speed. If your adjusted shutter speed is longer than 30 seconds, put your camera in BULB mode, attach a remote shutter release, and use the built-in timer on the app as your stopwatch.

Lately I've been using the LEE Stopper exposure app. It has a calculator for shutter speeds when you use ND filters (it has settings for 6, 10, and 15 stops) and also functions as a timer for those settings as well.

Found it!