EV

Formula: \(EV = \log_2\frac{N^2}{t}\) N = aperture | t = shutter speed

• Also \(\frac{N^2}{t}=\frac{LS}{K}\) , S = ISO | L = Luminance | K = Reflected-light meter calibration constant
• The calculators for EV Equivalence used the formula \(EV=\log_2{\frac{100N^2}{St}}\)

I observed that for my smartphone with fixed aperture (f/1.79) and Shutter Speed and ISO set to Auto, when EV was set to +4.0, the ISO varied from 12799 to ~2000 as light increased, while the shutter speed remained at 1/14, and only changed to 1/20 under very bright light.

And as I changed the EV to -4.0 and pointed at the sun, the shutter speed was 1/10753 and increased as light decreased, while the ISO remained at 53. Even in total darkness, the shutter speed reached a maximum of 1/33 and ISO reached a maximum of 1489.

The calculations were not all that perfect, because at EV -4.0 the configuration was 1/25s | ISO1489. But by manually setting the shutter speed to 1/25s at EV -4.0, the ISO was 378. Similarly, manually setting the ISO to 320 or 400 kept the shutter speed at 1/136 or 1/130 respectively.

For the Ultra Wide Angle Lens (f/2.2), the minimum values for EV +4.0 under bright light was 1/3831s | ISO55 and the maximum value in darkness was 1/14s | ISO4000. The maximum values for EV -4.0 under darkness was 1/33s | ISO539

• Equivalent EV doesn't always result in the same image
  • e.g. Shutter speed can be slower causing water to have a ribbon like effect
  • e.g. Aperture can be adjusted to have a shallow/deeper depth of field (DoF)
  • More reads on equivalent EV: https://www.shutterbug.com/content/equivalent-exposure

Limits of my camera

f/1.79

EV -4.0

Under sunlight

• ISO 53 : 1/10753 (auto)
• ISO 50 : 1/10870 (manual lowest ISO)
• ISO 6200: 1/4000 (manual lowest shutter) [Doubt]

In the dark

• ISO 1489 : 1/25 (auto)
• ISO ???? : 1/33 (manual)

EV +4.0

Under sunlight

• ISO 4830 : 1/4000 (manual lowest shutter)

In the dark

• ISO 12799 : 1/14 (Auto)
• ISO 6200 : 1/4000 (manual lowest shutter)
• ISO 74 : 30s (manual highest shutter)
• ISO 50 : 1/8s (manual lowest ISO)
• ISO 6400 : 1/8s (manual highest ISO)