What exactly does it change, and why does it lead to increased noise?
Well what the RGB curve does it that it allowes you contoll manulay the settings of blue/red/green of the entire image in a combination (if i m not mistaken) well i dont get alot of noise when i play with my RGB curves from the image i have taken, but when the iamge has been resized and the download you will loose detail because there are just less pixels on the image the more pixels to create one spot the less noise you will have, does that make any sense?
Well for highlighting the boat what i did is that i copied the layer once again, and then i made the image a tad lighter, and then added a layer mask to remove all the other parts of the image so the boat would appear only light. Then i played with the selective colours of this layer and just looked at what the changes made to the boat, it will affect the entire image but that didnt really matter as i was only going to apply it to the boat. So i played with the sliders till i was happy with it. Then for le grand final i first merged all the layers (ctrl+shift+e) and then copied the layer again (ctrl+j) and then i applied Filters>sharpen>unsharped mask then again i played with the streng and radious, only focusing on the main boat again because that is the only place i wanted to the effect, then i ok:ed it and applied a layer mask again and painting back in the sharpening where i wanted it
i think the great thing about photoshop in general is the idea of layer mask they are really your key to creaitng a certain effect on a specific part of the image.
A note to bring out the clouds a bit i use the high pass filter (filters>others>high pass) and just play around with this a bit till your happy and then playing around with the opacity of the high pass filter layer, for incrase or decreased effect!
No problem my freind, i enjoy this and from working on diffrent types of images i broaden my knowledge on the software. I can bring back the light down from the sky if i want to, but i guess i just missed that part
was focusing on another part of the image!