Measuring flash durations of speedlight and studio lighting and strobes

19 January, 20126 min readPhotography, Electronics

It’s been a while since I’ve written a technical article. But today I’m going to talk about flash durations. After a bit of wild searching on the internet, I couldn’t really find any good resources showing actual real-world measurements of flash durations of speedlights, especially t.1 measurements.

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

Lights Tested

I decided I would measure the flash durations of various lights. These include:

These speedlights above are have IGBT triggered power control which result in shorter durations for lower power discharges. I also performed tests on these units:

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

Here are the results of the real world measurements made. Later in the article, I’ll describe, how I performed the measurements. I’ve added some results of a few mains powered strobes for reference.

Measurement technique

I built up a basic little circuit using a BPV11 phototransistor as the sensor. The output was then read by an oscilloscope and the t.1 interval determined by setting two cursors to correlate to the respective t.1 amplitudes.

flash duration circuit

The resistor was chosen so that the transistor always operated within its linear region, and collector current was within the maximum limits allowed. The device never reaches saturation. It measures light between 620 to 980 nm, peaking at 850nm and has a turn on and turn off response time between 5 to 6 microseconds each (plenty fast enough for our measurements, within 5% for the fastest measurements).

The t.1 (sometimes called t0.1) is measured as below:

t chart diagram

Results

Duration in microseconds at different power settings

Light 1/1 1/2 1/4 1/8 1/16 1/32 1/64 1/128 1/256
Canon 580EX 4000.0 1088.0 484.0 266.0 166.0 105.6 71.6 50.4
Nikon SB-24 4322.0 1260.0 732.0 292.0 192.0
Nikon SB-26 4088.0 720.0 368.0 204.0 128.0 92.0 72.0
Nikon SB-28 3780.0 1048.0 496.0 276.0 158.4 100.8 72.0
Nikon SB-80DX 3888.0 864.0 408.0 222.6 135.2 90.4 63.2 45.6
Youngnuo YN560 3200.0 736.0 356.0 202.0 124.0 79.2 54.8 43.4
Cactus KF36 / Vivatar 285HV 3640.0 1504.0 636.0 188.8
Broncolor Flashman with Pulso 2 head (1600 Ws) 5680.0 5888.0 7222.0
Broncolor Impact 41 Monolight 4280.0 2500.0 1408.0
Godox 120 Ws 2880.0 3480.0 3360.0 3520.0
Alien Bee B400 (160 Ws) 824.0 928.0 1032.0 1328.0 1120.0 1296.0
Paul C Buff Einstein E640 (640 Ws), constant color mode 2560.0 984.0 592.0 472.0 396.0 336.0 296.0 268.0 236.0
Paul C Buff Einstein E640 (640 Ws), action mode 2640.0 624.0 296.0 162.0 131.2 116.8 132.8 128.8 137.6
“Mystery” eBay light (400 Ws) 7120.0 7920.0 8000.0 8080.0 9440.0 10160.0

Duration in 1/s at different power settings

Light 1/1 1/2 1/4 1/8 1/16 1/32 1/64 1/128 1/256
Canon 580EX 250 919 2066 3759 6024 9470 13966 19841
Nikon SB-24 231 794 1366 3425 5208
Nikon SB-26 245 1389 2717 4902 7813 10870 13889
Nikon SB-28 265 954 2016 3623 6313 9921 13889
Nikon SB-80DX 257 1157 2451 4492 7396 11062 15823 21930
Youngnuo YN560 313 1359 2809 4950 8065 12626 18248 23041
Cactus KF36 / Vivatar 285HV 275 665 1572 5297
Broncolor Flashman with Pulso 2 head (1600 Ws) 176 170 138
Broncolor Impact 41 Monolight 234 400 710
Godox 120 Ws 347 287 298 284
Alien Bee B400 (160 Ws) 1214 1078 969 753 893 772
Paul C Buff Einstein E640 (640 Ws), constant color mode 391 1016 1689 2119 2525 2976 3378 3731 4237
Paul C Buff Einstein E640 (640 Ws), action mode 379 1603 3378 6173 7622 8562 7530 7764 7267
“Mystery” eBay light (400 Ws) 140 126 125 124 106 98

Download data

Sample discharges curves

I didn’t save the waveforms for each test. But I did keep a couple for reference. Here are some of them, just as an example to see the shape of light output of the 580EX at different power levels.

The vertical axis is linear to the irradiance at the sensor, so something that is twice as high means it was twice as bright (one stop). From one image to another in the plots below, they are not to scale.

580ex full power
Canon 580EX at full power

580ex 1 minus third
Canon 580EX at full power minus one third

580ex quarter power
Canon 580EX at 1/4 power

580ex 64 power
Canon 580EX at 1/64 power

Final Words

This article might be updated later as I get my hands on more gear to test and add to the result list.

© Andy Gock 2009−2019