A lot of people have asked me what various types of speedlight modifiers do and I always try to explain. However, if you're like me, visual educational tools sometimes speak more clearly than words.
So, I put an SB-800 on a light stand, and placed various light modifiers on the flash to show a visual representation of what each modifier does. I chose an aperture and shutter speed combo that would give me a decent overall exposure to illustrate my point and I used that same combination for each shot.
These photos, by no means, represent my best work! =) They are for educational purposes only.
The first shot, is the SB-800 zoomed to 28mm ...the calendar is on the wall for a frame of reference ...you will also notice that in these frames, the light fall-off is not as abrupt on the left side due to the fact it is a corner of the room, so I'm actually getting a little reflected light from the wall...
The second shot, zoomed to 105mm ...notice the light spread is somewhat smaller and appears hotter in the center
The third shot is with a 36" white, shoot-thru umbrella. This shot really isn't as a good a representation as the rest due to the fact that the umbrella takes up quite a bit of the frame and some of the light is reflected back towards the camera, but it should give you an idea of its apparent light size
The fourth shot is with a slip-on Stofen diffuser. This is one of the most common types of speedlight diffusers
The fifth shot is with a Lumiquest SB III, one of my favorite light modifiers
Coming up sixth on the list is, a Honl 1/4" speed grid. I've just started using these so this experiment was helpful to me.
Lucky number seven is, a Honl 1/8" speed grid. Notice that the light pattern is a bit tighter (smaller) than the 1/4" grid.
And last, but not least, is the Honl 8" Snoot. I've used this little guy quite a bit, and really love the effect I get. This shot was taken in broad daylight. I dropped the ambient by several stops to get a darker background, then lit the model with a snooted speedlight.
This is only a few of the light modifiers that are available for speed lights but are some of the most used. I hope this post will help you to have a better understanding of what these types of modifiers do, and if you have any questions, just give a shout!
::All of these shots were taken with a Nikon D300 at f/11 1/250 sec. ISO 100. The flash was about 4 feet away from the wall, at 1/8 power and triggered with CLS.