Can some one explain me why ?

[yb98]

I have a canon S30 but I post this question here because I think I have more chances to have an answer here. I want to take a shot by night with a person in the foreground and some city lights in the background. As I want to have the "star" effect on the background lights, I use the smallest aperture I have on my S30 (f4.5) when in tele mode. Of course, I also use the flash. The problem is :

1. if I use a short exposition time (about 0.8 sec) the personn is well focused and sharp but the background is of course too dark.

2. if I use a higher exposition time (4 sec) then the background is nice but the personn is blurred even if the personn doesn't move at all.

Is there any possibility to have a nice background and a nice foreground ?
Else why not ? is it because on my S30 the flash can be activated only on the first curtain ?

Yacine.

[cloudless]

If you use a small aperture you must accept longer shutter time. And it would be extremely difficult to ask someone to stay steady for over one second. My suggestion is to give up the star effect, open the aperture wide, then use slow sync and set the shutter to about 1 second. Such that both the background and foreground will be well exposed.

[PacAce]

....Or you can take two pictures and merge them together. One exposed for the foreground subject and the other exposed to get the start effect you want.

...Or you can forget about the star effect and take a normal picture. Then use PS to add in the star effect later.

...Or you can try using the "star effect" filter and see if that works any better.

[PacAce]

...I use the smallest aperture I have on my S30 (f4.5) when in tele mode

The smallest aperture you have is f/4.5???? Don't you mean the biggest aperture you have is f/4.5? The smallest aperture the S30 has is f/8.

[IndyJeff]

yb I am not familiar with your camera but to get that star effect you use a special filter that screws onto your lens.

Cokin filters (http://www.geocities.com/cokinfiltersystem/stars.htm)

You can get different filters which add different amounts of points to the lights.
I have one and have used it for wedding shot a couple of times. Great effect.

[yb98]

sorry, yes I mean f/8

I was just wondering if the flash was in the second curtain, if the result will be the same...?