I know this is really a photography
thread but I thought I'd share this PS trick that I just worked out. A really good way of changing the sky or background in a pic - without having to cut it out manually.
Here's my original pic - I took it when I was on a barge trip for a week last month. Just 2 of the guys waiting to open a lock. Nothing special - nice bland sky.
This is the pic with the settings altered so the sky looks more interesting - just a bit more contrast and saturation but obviously everything else is too dark.
So, open both images in PS and put them in the same image.
This is where it gets interesting. Make sure you only have the 'light sky' image visible - the background in this example - and then click the channels tab above the layer palette. You then get something like this. You can select to show just one colour at a time - you want to pick the one with the most contrast between the foreground and the background - in this case it is the blue channel. Then select>all>edit>copy merged and then click the RGB tab again and go back to the layers.
Now, make a layer mask for the second layer (forgot to screencap that bit, but just make a blank layer mask on the dark sky layer) and then go back to the channels tab.
Click the eye thing beside the 'layer 1 mask' channel and then edit>paste and it will look something like this:
Now go back to the regular layers palette and you should have something like this. You can see that the layer mask is now in the shape of the image that you pasted.
Then just have a fiddle with the settings of the layer mask - I increased the contrast to make it more black and white and then filled in some of the lower area that wasn't completely black - the white in the foreground was affected by the mask - and that's it. A new sky and you can't really see the join.
Final image - bit more interesting than the original IMO.
You can also use to to draw in a completely different sky.
That ones a bit extreme so you can almost see an edge but you get the idea.
Shopping at The Leftorium since 1977.