Having purchased a new flash which only works in manual, I found myself having to refresh my memory on the workings of speedlights. I had taken an 8 week course on flash photography back in 2012 but did not have much opportunity to use what I had learned and have forgotten most of what I learnt on the course. So I’m finding myself working through some tutorials again.
I have always been pretty darn hopeless with maths so as soon as numbers get thrown at me I become very flustered. I was watching the video below on flash guide numbers and started to do the prescribed calculation on the computer calculator. Now apparently my Yongnuo YN660 has a guide number of 217 – nowhere in the manual does this number state whether it is feet or metres. Makes a difference, right? On the video the presenter explains that one has to divide the guide number by the distance and this will give you the aperture to use. The example he had was that his flash was zoomed at 105mm, had a GN of 112 and light source was 10 feet away from subject giving him an aperture of f11. Sounds simple enough. Well for the life of me I kept on getting an aperture setting f66 which couldn’t possibly be right. I really don’t know what I was calculating – maybe I threw the zoom figure into the mix, I really don’t have a clue.
Anyway today I decided to tackle this again. Went online and searched for a few sites to find the guide number of this flash and came across a site that stated the GN was 66 metres, and another which stated the GN was 217 feet. So I threw all the numbers into an Excel spreadsheet and punched in the formulas. Aha – the picture is looking a little better now. At 3 metres, full power my aperture should be f22. Now I can plug in the aperture settings for 1/2, 1/4, 1/8 power and on.
I also read a couple of Neil van Niekerk’s postings- one on dragging the shutter– balancing flash and ambient light.
- For ambient exposure there are three controls:
- shutter speed
- For flash exposure there are four controls:
- distance (light source to subject – closer = brighter)
- power (increase/decrease – affects exposure)
There are two common denominators when we compare the two types of exposure: aperture and ISO. This means shutter speed becomes an independent control for available light source. The shutter speed won’t affect anything because the flash is instantaneous, while the ambient light is continuous.
The other video tutorial I watched again was Neil van Niekerk explaining how he used his “Black Foamie Thing” light modifier. I had made one of these for myself years ago but never actually got around to using it. Written explanations are on this page. I tried it out last Friday and seem to be getting the hang of it but want to get a little more comfortable with it before I post some images.
Adorama TV (2016) Flash Guide Number – OnSet ep. 70 [user-generated content online] Creat. Adorama TV. 1 February, 2016. 4 min 48 secs. Available at: https://www.youtube.com/watch?v=2TtEoxhE9n4 (Accessed 30 January, 2017)
van Niekerk, N. (n.d.) Dragging the Shutter [online] Neil van Niekerk Tangents Photography Blog. Available at: http://neilvn.com/tangents/flash-photography-techniques/dragging-the-shutter/ [Accessed 30 January, 2017]
van Niekerk, N. (n.d.) Video tutorial – Using the ‘black foamie thing’ [online] Neil van Niekerk Tangents Photography Blog. Available at http://neilvn.com/tangents/flash-photography-techniques/bouncing-flash/ [Accessed 30 January, 2017]