Light is a strange thing
It’s amazing how light works. Light travels, bounces, diffuses, reflects, attenuates, in so many different ways that it becomes really complicated to guess how a picture is going to come out. Sometimes I used just one light with one diffuser and things were already complicated. Moving either of them a couple of centimeters made the photo change so much. Light is a matter of inches. I decided to take some test shots using flashes to understand better how they spread light.
When I bought, years ago, the Nikon SB-910 speedlight I remember trying to understand every detail in the owner’s manual. I went into all the options and tried to see what differences it would make changing from one setup to another. I’ve always been very analytic, which is important when understanding how a device works and getting the most out of it. However, suddenly I realized that the best thing to do was to play with the speedlight. See if you get the picture you want by modifying small things and learn from the experience. So I did this, again and again.
Analysing the illumination patterns
But the left side of my brain wanted to analyse the different illumination patterns of the Nikon SB-910. There are three modes: standard, even and center weighted.
The difference between standard and even modes is that the falloff in even mode is lesser on the borders of the light beam. This is one of the reasons Nikon recommends you use this illumination pattern for group photography. The light would be more even across everyone in the picture.
The center weighted, however, is more suitable for portraits because falloff is greater in this pattern which won’t matter on most occasions. The SB-910 concentrates more light in the center of the beam.
Below there is a comparison among the three illumination patterns at 24 mm.
If we think about the illumination pattern as a cone of light whose vertex is the speedlight, with an angle you can open and close, you would go from a greater angle (even) to a narrower one (center weighted) which passes through the middle (standard).
Zoom head position
Illumination patterns are a coarse manipulation of angle of the cone of light. To modify it finely the Nikon SB-910 allows you to change the zoom head position from 12mm to 200mm. You read correctly, it can pack light zoomed into 200mm.
The zoom head position is the main feature of the SB-910 which I wanted to analyse. I thought I could position it parallel to a white wall and take pictures perpendicular to the wall. This way I would be able to photograph the profile of the light coming out of the SB-910 for every value in the whole range of the zoom head position. Below you can see the comparison among all the possible zoom head position values for the standard illumination pattern.
I shot all the images manually at 1/250, f7.1, ISO 100 to obtain clear light patterns over a dark wall. I could have used other settings and obviously the images would have ended up brighter or darker on the furthest side from the speedlight. This is why you shouldn’t pay too much attention to the distance the light reaches in the images but more to the shape and angle of the profiles on the wall. I also converted all images to black and white so they’re clearer to see.
You can see all the images in the next slideshow:
