Photoshop advice - correcting perspective for compositing

I'm trying to correct for perspective (angling/distortion) in a composite. This is my first try at something like this; it's not too bad but not up to the standards of what I would want to show anybody else.

I don't normally do compositing, but it's a necessary technique for this set - that is, shrinking the subject in relation to their environment.

I incorrectly assumed that by positioning the camera in the same place with respect to a reference point in the background - that is, the same distance from the camera to the corner of the wall and the dock - that the compositing would be easy. Wrong! In retrospect, I think I should have framed the second photo so that the subjects looked as close as possible to my final vision - which would have meant getting farther away from the subjects. Oh well, it's definitely a learning experience.

Here are the two source images, and my bumbling attempts to get it to look passable.
- I'm using CS5
- Quick Selection and Refine Edge to copy the subjects out of the background
- Free Transform to shrink subjects
- Transform Perspective, Transform Skew to adjust to the best of my ability
- Magnetic lasso tool to separate the torso/head from the legs, and Free Transform to make the upper half slightly bigger
- Shadow painted on background (wife says the shadow is no good, as nothing else has a shadow)

I just had an idea, that I should do most of the placement and transforming BEFORE selecting and cutting - that way, I can line up the angles in the bricks and the dock.

Any other hints?

Here are the (almost) originals, though I have straightened and perspective-corrected the background before I try this again, so it doesn't exactly match.

IMAGE LINK: http://www.flickr.com …/nathancarter/6​053777665/

IMAGE LINK: http://www.flickr.com …/nathancarter/6​054326564/

IMAGE LINK: http://www.flickr.com …/nathancarter/6​053778031/

Hmm, the only thing that I'll toss out is that the people are way too small -- they look doll-size compared to the bottles.

Great, that was the point

Here are the others from the set (second one still needs work on the color):

IMAGE LINK: http://www.flickr.com …/nathancarter/6​047384421/

IMAGE LINK: http://www.flickr.com …/nathancarter/6​054297167/

So here are you two images with no fancy masking and that kinda thing. I'm guessing that you want to make them look miniature - otherwise, I agree with Tony. Note the perspective lines formed by the planks in the floor in both the background plate and the subject image. See how the perspective lines in the area of the background plate radiate to frame left, whereas you centered the subjects in the frame of your model shot.

Next time try shooting the subjects so that they are properly offset to camera left within the frame (as you said, more like what you envisioned in your final image) so that the view you get of your subjects will be visually consistent with their placement in the background plate. Also, you need to be careful with the low shot, as the effect of foreshortening will be accentuated. Again, you have to plan your model shot to capture the foreshortening that the low angle will generate in the comp.

Also, consider reading up on the vanishing point tool in Photoshop - although it may only be available in the extended version, i'm not sure. Also, try the perspective and lens correction tools to tweak your shot.

THe whole scene would be a lot easier to pull off if you just got a shrink ray. ("Squid launcher!")

Kirk

Here is one of THE classic examples of foreshortened perspective, Mantegna's Lamentation of Christ:

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The attachment posted by Kirk, shows part of the problem: The perspective is way off. That's the biggest problem IMO.
In your example: There's (way) too much feather on the selection, and the painted shadow doesn't match the lighting. Also: Set the shadow layer to "overlay".

Quick selection will probably do a pretty okay job on the selection, but refine edge won't work for the entire image with one setting.
I'd make a selection, mask, then duplicate a few times and tweak each mask (mask edge; it's the same as refine edge, but you can go back to alter settings) for a specific area (rug, hair, legs) to get an optimum mask in that specific area. (Actually, I probably wouldn't use quick selection and mask edge to begin with. More hassle then creating a good mask to start with. )

Quick and dirty, to show why the mask needs to be less feathered at the rug:

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

Thanks for all the advice. I wasn't really giving the masking my best effort in this test-run; I was more concerned with trying to adjust the perspective - assuming I would have to start from scratch at least once more. Still, thanks René for the masking tips, I'll give those different methods a shot. Your mask on the blanket definitely looks MUCH better than mine, though the edge around the hair and hat looks like it could use a bit of cleanup (feathering? removing the white matte? i dunno)

The Quick Selection and Refine Mask is what was covered in the Kelby class I took a couple weeks ago. I'm still only about half a notch above "utter novice" so that was the only method I know so far.

Kirk, I think I may see if the vanishing point tool helps me out - I do have CS5 Extended so I'll search for it.

I'll also plan on moving the subjects closer to the center of the background to reduce some of the difference in perspective. That standing bottle with the red neck can maybe go over to the (camera) left of the subjects, and the lying down bottles can help obscure where I chopped off the (camera) right edge of the blanket.

As for the foreshortening, I may give it just a little tiny bit of vertical perspective distortion to make the feet smaller, and just chalk the rest up to "Well, we can tell it was your first try, it was a good effort and at least you learned something."