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How to Do Masking For Sky or Window Replacement

June 10th, 2008

Doing quick Photoshop masks for sky replacement or window replacement on interior shots is a frequent need that real estate photographers have.

The crux of creating such masks is that the mask edges are never clean and simple. Like the image in my demonstration video, the mask between the sky and the foreground can be complicated with lacy trees and branches. Same for interiors with plants and other complicated objects in front of the window. How do you create masks like this without spending hours in Photoshop?

As everything in Photoshop, here are many ways to do this but here I show you my favorite one since it is so fast and easy. It may look daunting at first but if you look carefully you’ll see there are just three simple steps. The lacy trees along the skyline make this image harder than most. With this approach on many images that have mostly hard edges along the skyline you can just increase the contrast of the mask and quickly get a perfect mask. With this example you can’t do that because of the delicateness of the trees along the skyline… believe me, I tried.

I’m still working on improving the quality of these screen capture videos. Phil Meadows and I are thinking about doing a whole series of post-processing videos. What subjects would you like to see in this area?

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16 Responses to “How to Do Masking For Sky or Window Replacement”

  • […] Source and Read More: photographyforrealestate.net […]

  • Awsome technique. I think it’s going to save me hours a week! Thanks for this and all the other info on this site!

  • Nice tutorial Larry. It’s a slightly different way of blue-channel masking than I was doing before, but seems to work very well. I think i’ll be using this one in future for those pesky selections!

    Tufuse is also very good for this type of thing, using Jeremy’s tutorial. I think it depends on what is being done though.

  • Thanks Larry for taking the time. This is one area I haven’t got my head around yet as I try to master the transition from iPhoto to PE4, to LR and now PE 6 (not to mention PT Lens!!). Huge learning curves!! Lynda.com looking like getting a new customer!
    I have previously used the Magic Extractor in PE4 and then cutting and pasting from my “sky library”, but there seems so many ways to replace a sky.

  • I cannot view the video.. Its no longer active is the message I get online.. Any suggestions?

  • Good stuff larry very Useful.
    I saw a similar thing in an old book by Design Graphics.

    Its a few years old but awesome tips by some of the retouching worlds best Ben Wilmore etc .Studio Skills for 7 and CS
    Its still available I strongly recommend it.The images are not realestate but the techniques are excellent exactly what you need, its very well put together and simple to follow.
    Have a look Larry .

  • Great tut, thanks for that! You might add your Feather Radius settings and that you can “create a selection” after using the pen tool (around roof of house) and then chose Select > Modify > Contract to size it down by Pixel size if alignment is a little big, great lesson though I learned a few new tricks thanks!

  • I learned stuff! Thanks Larry.

  • @Con – I’m not sure what the problem might be. Yours is the only report I gotten with troubles viewing the video. Have you tried different browsers? Can you view other youtube videos? I just tried it a it works OK for me with Firefox and Safari.

  • Great tutorial Larry! I’ll be able to use that in lots of situations including sky replacement. I’m curious however, in this particular example would you have found using Viveza faster and just as effective?

  • @David – Viveza could darken, lighten the sky or make it a color but in this situation I had a nicely exposed sky with clouds that I wanted to put in over the poorly exposed sky. So Viveza wouldn’t help with that. Also, after you practice this technique a few times it is ridiculously fast. When the skyline is sharp and high contrast the mask doesn’t require refining like this lacy one did.

  • hi larry! i was in a tight situation just now editing some pics. the light was very contrasted and i couldn’t get good detail on both sky and house, so i started looking for this tutorial and quickly found it!

    it’s amazing, in just minutes i got the result i wanted. a very quick and effective solution to my problem! the selection was perfectly done, it looks very natural.
    thanks!!

  • Sylvia- Yes, for complicated selections like trees on a skyline this approach is hard to beat!

  • Hi Larry–

    I would love to see a multi-strobe/ambient blending tutorial. I know the basics but I’d like to learn the finer steps.

    Cheers.

  • Hi Larry,
    I’ve used your technique and some other variations with pretty good success; some more than others. Good masking results can sometimes be a challenge, especially if you are pressed for time.

    I just received notification of a new Photoshop plugin tool from Topaz Labs that I wanted to make you aware of; which may prove quite useful to our community of real estate photographers…

    Product details can be viewed at: http://www.topazlabs.com/remask/

    You can get a free 30 day trial of any of their products. I have yet to test this one thoroughly, however, I have used several of their other products and can recommend them very highly.

    Give it a try and let me know what you think.

    Regards,
    David

  • This may help. After copying the blue channel, select all (ctrl-a), copy (ctrl-c), then paste (ctrl-v). All on the blue channel. This places a copy of the blue channel over itself, you will not see any change. BUT THE TRICK IS – go to Edit->Fade which is now available because of the first steps. Don’t do do anything in between these steps or you will loose the fade command. In the fade dialog, change the blending to multiply. Then OK. The blacks and grays will be much darker and the lights much lighter, just what you want (more contrast). This is a very quick operation and gives you a much better starting point. You could continue as you have for the rest of the video but I have a couple of more ‘enhancements’ that you might light to try.

    After the fade-multiply trick, run the levels (ctrl-l) command (not an adjustment layer, not available on channels). Move the black an white points inward slightly. This further strengthens the blacks and whites. This may be too advanced because how much to move the sliders comes from lots of experience. Move them in too much and you destroy the gray transitional edges around the trees and sky that you prize so much – not good. Play with it if you like.

    When making a selection, instead of painting in with white or black, use the fill command shortcuts. Make sure that black and white are selected on your color picker (ctrl-d). Alt-backspace will fill the foreground color, ctr-backspace the background color. This is quicker and you don’t risk missing any areas.

    Finally, if you have like the edge of the roof (dark gray) against the sky (near white), paint with a brush set to Hard Mix (not available when you made the video), and set to around 50% opacity. If you paint with white, anything above mid gray will turn to white leaving anything below mid gray alone. Black works the same, makes grays black and leaves lights alone. Don’t do this on your transitional edges (sky and leaves) or you will destroy the transition and good effect. Works great for cleaning up hard edges.

    Finally finally, when all done, the mask may be too sharp, especially around the hard edges. This gives the cut out and pasted on effect. Soften your mask by selecting it (click on the mask icon, layers pallet to make the mask selected). Then run Gaussian blur at around 1 pic +/-. Have the image at 100%, the image is visible but the mask is selected. Visually judge the edges till you get a good effect with the Gaussian blur. Hint: if the mask in not too good to start with, a larger GB may save it, good enough for government work. The large radius blurring tip usually only works when you are masking the image over a darker version of itself – not a totally new sky.

    I mask on almost every image somewhere along the workflow. If you learn these tips, they do not take very long to execute and give good results.

    Larry

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