hm..... i dun really know too..... i have always thought of getting the travel lens and the prime lens.... but after a trip to the bird park, found that my kit lens does not give good bokeh at anything less than full tele and the shutter speed is not acceptable when the birds are in a shade and i am at full tele....
totally confused as to which i need more too..... more zoom or faster lens to replace my kit lens FIRST.... :embrass:
I do think that if you get the superzoom (18-250), you aren't gonna improve on the bird shots' shutter speed, because even though you have more reach, the maximum aperture is a VERY sad f/6.3 at the long end.
The solution is to pump your ISO, which may lead to undesirable noise.
Bokeh isn't gonna improve much because the max aperture of the superzoom is also quite similar to your kit lens at equivalent focal lengths (or so I should think). You'd be better off getting a wide aperture prime or wide aperture walkabout zoom lens (such as the Tamron 17-50 f/2.8)
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bringing the travel lens and flash is good if indoor shot but what if the subject is not easily illuminated by your flash, e.g. hiding under some leaves (like bird) or in a place where no flash is allowed (maybe have to lug around a tripod...)? mmm... furthermore, it doesn't give good bokeh at anything less than 50mm too, rite? so tight corner portrait shooting will be out....
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There are a few solutions to this, as I mentioned earlier. You can either pump the ISO, or get a lens with a wide maximum aperture.
Depth of field is affected by three things (of which you can alter two at the moment):
1) Medium (sensor/film plane size)
2) Focus distance (closer you focus, thinner DOF, and vice versa; notice how macro subjects usually have razor thin DOF because they're so close?)
3) Aperture size (the wider you open it up, e.g. f/1.8, f/2, f/2.8, the thinner the DOF, compared to f/11 or f/16)
