Measuring flash durations of speedlight and studio lighting and strobes

2012-01-19

It has been some time since I last delved into a technical article, but today we're delving into the world of flash durations. Despite extensive searching, I couldn't find any comprehensive resources offering real-world measurements of flash durations for speedlights, especially t.1 measurements.

Canon 580EX at full power
Canon 580EX at full power

Lights Tested

In this endeavor, I set out to measure the flash durations of various lights, including:

  • Canon 580EX
  • Nikon SB-24
  • Nikon SB-26
  • Nikon SB-28
  • Nikon SB-80DX
  • Yongnuo YN560
  • Cactus KF36 (Vivtar 285HV)

These speedlights employ IGBT triggered power control, resulting in shorter durations for lower power discharges. Additionally, I conducted tests on the following units:

  • Broncolor Flashman floor pack with Pulso 2 head (1800Ws symmetric)
  • Broncolor Impact 41 monolight
  • Godox 120 Ws
  • Alien Bee B400 160 Ws
  • Paul C Buff Einstein E640 (640 Ws), measured for constant color mode and action mode
  • A "Mystery" eBay light (400 Ws)

In the subsequent sections, I will present the results of these real-world measurements. Towards the end of the article, I will provide details on how these measurements were conducted.

Measurement Technique

For the measurement process, I constructed a basic circuit using a BPV11 phototransistor as the sensor. The output from this sensor was then read by an oscilloscope, and the t.1 interval was determined by setting two cursors to correspond to the respective t.1 amplitudes.

Circuit diagram with BPV11
Circuit diagram with BPV11

The selection of the resistor was made to ensure that the phototransistor consistently operated within its linear region, with collector current well within the maximum limits. The device never reached saturation. It possesses a response time between 5 to 6 microseconds for both turn-on and turn-off, which proved to be sufficiently fast for our measurements, staying within 5% accuracy for the swiftest measurements.

The t.1 (sometimes referred to as t0.1) was measured as depicted below:

t0.1 chart
t0.1 chart

Results

Flash Duration in Microseconds at Different Power Settings

Light1/11/21/41/81/161/321/641/1281/256
Canon 580EX4000.01088.0484.0266.0166.0105.671.650.4
Nikon SB-244322.01260.0732.0292.0192.0
Nikon SB-264088.0720.0368.0204.0128.092.072.0
Nikon SB-283780.01048.0496.0276.0158.4100.872.0
Nikon SB-80DX3888.0864.0408.0222.6135.290.463.245.6
Youngnuo YN5603200.0736.0356.0202.0124.079.254.843.4
Cactus KF36 / Vivatar 285HV3640.01504.0636.0188.8
Broncolor Flashman with Pulso 2 head (1600 Ws)5680.05888.07222.0
Broncolor Impact 41 Monolight4280.02500.01408.0
Godox 120 Ws2880.03480.03360.03520.0
Alien Bee B400 (160 Ws)824.0928.01032.01328.01120.01296.0
Paul C Buff Einstein E640 (640 Ws), constant color mode2560.0984.0592.0472.0396.0336.0296.0268.0236.0
Paul C Buff Einstein E640 (640 Ws), action mode2640.0624.0296.0162.0131.2116.8132.8128.8137.6
“Mystery” eBay light (400 Ws)7120.07920.08000.08080.09440.010160.0

Flash Duration in 1/s at Different Power Settings

Light1/11/21/41/81/161/321/641/1281/256
Canon 580EX25091920663759602494701396619841
Nikon SB-24231794136634255208
Nikon SB-2624513892717490278131087013889
Nikon SB-28265954201636236313992113889
Nikon SB-80DX2571157245144927396110621582321930
Youngnuo YN5603131359280949508065126261824823041
Cactus KF36 / Vivatar 285HV27566515725297
Broncolor Flashman with Pulso 2 head (1600 Ws)176170138
Broncolor Impact 41 Monolight234400710
Godox 120 Ws347287298284
Alien Bee B400 (160 Ws)12141078969753893772
Paul C Buff Einstein E640 (640 Ws), constant color mode39110161689211925252976337837314237
Paul C Buff Einstein E640 (640 Ws), action mode37916033378617376228562753077647267
“Mystery” eBay light (400 Ws)14012612512410698

Download Data

Sample Discharge Curves

Although I didn't save waveforms for every test, I did retain a couple for reference. Here are some examples to provide an understanding of the light output shape of the Canon 580EX at various power levels.

The vertical axis indicates linear irradiance at the sensor, with a doubling in height signifying twice the brightness (one stop). Please note that these plots are not to scale relative to each other.

Canon 580EX at full power
Canon 580EX at full power
Canon 580EX at full power minus one third
Canon 580EX at full power minus one third
Canon 580EX at 1/4 power
Canon 580EX at 1/4 power
Canon 580EX at 1/64 power
Canon 580EX at 1/64 power

Conclusion

This article may undergo updates as I continue to acquire additional gear for testing and expand the results list.