Do you use flash outdoors on a nice day?

[HoppyUK]

I'm guessing the OP's flash was either left 'normal' or set to rear-sync. Therefore the camera defaulted to the sync speed.

@OP if shooting in daylight, you may well need a shutter speed faster than 1/200th (or whatever the flash sync speed of your camera is). In this case, set your flash to high speed sync, or whatever Nikon call it. This will reduce the effective power of your flash, so you won't be able to shoot at great distances, but it allows you to fill in when using faster shutter speeds.

I think that's the problem with the over exposed shots. The camera's max sync speed is too slow to balance with the daylight so you need to keep an eye on that and raise the f/number and/or reduce the ISO to keep it down.

You might still run out of options in bright light, which is where the high speed flash sync comes in (FP Flash in Nikon speak) but I don't think that's available with the pop-up flash - only with a separate gun.

There seems to be two quite different kinds of daylight flash being discussed here - the OP's fill-in flash for which the pop-up flash is usually very good, and strobist style off-camera technique where the flash is the main light source. That's much more difficult and needs loads more power.

 

[awp]

^^ Good shot Andy but way too complicated for the OP.

 

[kmiragaya]

Yes, to fill shadows unless I want to travel light

 

[tfboy]

The shots of the kid which are a little on the bright side shooting at f/1.8, with the camera on aperture priority, it's synching at 1/200s.

Not sure if the D90 supports it, but it's worth playing around with the FP setting. This allows shutter speeds far greater than 1/200s or 1/250s, so you can cut out the lighting of the sun somewhat. However, you do lose flash power as in FP mode, it's a short continuous burst rather than one burst as it can't sync at higher speeds. Only the SB900 (and maybe SB800) offer FP capabilities - you can't get it with the onboard even if the menu it set to FP.

First time I had my SB900, was shooting at f/1.8 and f/1.4 and completely forgot to set to FP. Now, I set it to that and it works brilliantly, albeit with its limited power

Also I'd suggest having a play on manual exposure. Set the SB900 to fill light mode on TTL and it'll fill in the subject without trying to lighten up the background anymore (which won't need lighting if it's in bright sunshine).