Silverlog Flash
Flash Guide Number Calculator
Free · In-App Purchases · Designed for iPad. Not verified for macOS.
Calculate flash exposure from guide numbers. Work out the right aperture for any flash-to-subject distance, or find your maximum range.
Silverlog Flash calculates flash exposure using guide numbers — the fundamental relationship between flash power, distance and aperture.
HOW IT WORKS
Choose what to solve for and enter the other two values. Find the aperture for a given flash-to-subject distance, the maximum distance for a given aperture, or the guide number from a known distance and aperture. Adjust ISO to see how sensitivity affects your working range.
FEATURES
• Guide number to aperture calculation
• Guide number to maximum distance calculation
• Guide number from distance and aperture
• ISO adjustment
• Metric and imperial distance units
• Works offline — no internet connection needed
• Clean, focused interface
• Dark mode support
USEFUL FOR
• Manual flash photography without TTL
• Working out flash-to-subject distance for off-camera flash
• Understanding your flash's effective range at different apertures
• Film photographers using manual flash units
Part of the Silverlog photography toolkit. No account required. No data collected.
Ratings & Reviews
- This app has not received enough ratings or reviews to display an overview.
Fixed the "Nearest stop" hint when solving for aperture, which just repeated the answer rounded to one decimal place instead of naming the closest full stop (a GN 36 flash at 3m now correctly suggests f/11, not a repeat of f/12). Light and Dark now apply as soon as you choose them, and Settings shows the correct app version. Vibration on taps now works throughout the app.
New for tippers: Disco and ULTRA themes. ULTRA is a rainbow, spotlit, confetti-throwing mess — gloriously unhinged, and entirely optional. It stays still if Reduce Motion is on.
The developer, Simon Westgate, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Size
- 28.8 MB
- Category
- Photo & Video
- Compatibility
Requires iOS 15.1 or later.
- iPhone
Requires iOS 15.1 or later. - iPad
Requires iPadOS 15.1 or later. - iPod touch
Requires iOS 15.1 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Guardian Angel 9,99 €
- Legend 2,99 €
- Actual Saint 34,99 €
- Absolute Hero 5,99 €
- Nice One 0,99 €
- Provider
Simon Westgate
- Simon Westgate has identified itself as a trader for this app and confirmed that this product or service complies with European Union law.
- Address
27 Great Grove
Bushey
Hertfordshire
wd23 3bq
United Kingdom - Phone Number
+44 7957302258 - Email
simonwestgate@hotmail.com
- Copyright
- © SilverLog 2026