Measuring flash durations of speedlight and studio lighting and strobes
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.
I decided I would measure the flash durations of various lights. These include:
- Canon 580EX
- Nikon SB-24
- Nikon SB-26
- Nikon SB-28
- Nikon SB-80DX
- Yongnuo YN560
- Cactus KF36 (Vivtar 285HV)
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.
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.
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:
Duration in microseconds at different power settings
|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|
1/s at different power settings
|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|
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.
This article might be updated later as I get my hands on more gear to test and add to the result list.