Hi folks, I bought a flashgun about 12 months ago now when I was asked to take some photo's indoors for a newspaper article. In my usual fashion, I equated "best" to "most-expensive" and so ended up with a Nikon SB-900, which has the usual half-inch thick manual with lots of information that I don't understand. As a consequence, after said article the flashgun went back into my kit pile never to see the light of day again. Until now... Having found a few articles on the web which explain flash usage in English rather than technobabble, I've dug it out for a little play. As an exercise I decided to see if I could "freeze water" by dropping water droplets into a bowl of water in a dim room. Please correct me if anything I say here is wrong - I only quarter understand what I'm doing here. So this is what I understand is the principle here: a). In a dimly lit room, the flash will be by far the biggest light source, and consequently the shutter can be open for as long as you want within reason - the exposure will principally occur when the flash fires. b). Flash doesn't have a brightness value. It is simply on or off - what varies is the length of time it is on for. Question: Could someone confirm this is right please? I would like a definite yes/no answer to this statement. Does the flash brightness vary or just the on-time? c). I am using the flash in TTL mode, or Through The Lens. As a consequence I don't set the power of the flash, I simply set an exposure modification value on the flash just like I would on the body, eg. +1ev. At exposure time, the flash fires twice, the first is used by the camera/flash system to determine how long to fire the light for the main exposure. Question: why doesn't this pre-flash expose the image? Which should leave me with a ghost of the drops which I don't see. d). Normally I stick the camera in Aperture priority mode, as I want to primarily control the depth of field in my pictures. Normally by fixing the aperture, the camera determines the exposure time for me based on the ambient light. However, now I've got two variables - the exposure time AND the light levels which can be varied with the flash. I cannot for the life of me work out what the body does in this situation (its a D300), but what I have read is that different bodies do different things when in this mode. Consequently, I'll stick to manual mode where the flash can then choose how long to illuminate the image for. Question: Is there anyway you can see how long it decided to flash for? Its not immediate obvious in the EXIF information, only the shutter exposure is present which in this setup is irrelevant. So onto the output. To kick off with, I chose to reduce the exposure on the flash (-3ev if my memory serves me correctly), my theory being I wanted to "freeze" the action, and therefore have the flash on for the minimum amount of time. I also used f16 aperture to help with focusing, as I needed a relatively large depth of field. (1) F16, 1/80th Obviously quite underexposed, as you would expect. Next up, trying the orange filter thing which came with the flash. Probably should have read the instructions on how to fit it, I squished it inbetween the pully-out-diffuser thingy. (2) F22, 1/80th Surprisingly orange! I didn't really expect such a large difference. So I wonder what the green filter does then? (3) F22, 1/80th Pretty green! Time to play with take the picture at varying points of the droplets impact. A well into oblivion? (4) F22, 1/80th Could be a water monster from a movie? (5) F22, 1/80th Impact! Speeding up the shutter exposure time should have no effect if my theory is correct. (6) F16, 1/200th Enough playing with the green filter, back to basics for a repeat of the impact picture, this time using a large aperture, which should give a faster exposure time and more frozen image? Of course at the expense of depth of field. (7) F8, 1/200th Must be getting tired, I'm seeing shapes in the images. A women in a dress anyone? (8) F13, 1/200th ... or how about a vertical snooker cue about to strike the ball? (9) F13, 1/200 Not sure I've moved on too far in understanding flash yet, but its a start. Still got fill-in-flash to get to grips with, and we haven't even mentioned forward or rear curtain sync yet Flash opens a whole new world of pain I would appreciate your input, particularly with respect to the three questions above. Thanks in advance.