A fill-in flash? Maybe that's why I felt that the colour is rather dull? Lack of vibrance? Just somehow felt that everything else is there but something is missing... So should I use the built-in flash for this? Will it cause shadow due to the lens?
the flash is to make some parts of the dragonfly - like eyes and thorax - brighter, and not nec to make the colour less dull. I think the colours are quite acurrate but maybe a little flat. For that you do some S curve tweaking and if still nec tweak with Hue/Saturation. The flash may or may not help to make more vibrant colours.
I see. I'm not so proficient with S curve tweaking. I'll try to take a few shots with flash the next time I attempt this. Sometimes I find that the build in flash tend to over expose the image, even if I used FEC of -2.