Digital Blending [Tutorial]

Started Jul 23, 2005 | Discussions thread
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yirmon Senior Member • Posts: 1,930
Digital Blending [Tutorial]

In the past whenever I’ve had to blend two exposures in photoshop I’ve simply used a layer mask and painted the areas in by hand. However, a recent image I was working on contained a lot of small areas of blown highlights. I knew that if I was to paint back these areas manually it would be very difficult, not to mention time consuming. So that got me thinking… why not use a luminosity mask to do the work for me?

Luminosity masks are explained well in this article here: .

To quote the essentials: “A luminosity mask uses the brightness values in an image as a mask… White areas are selected, black areas are unselected, and grey areas are partially selected.”

So I thought I’d put together a quick tutorial of this technique and see what you think of it. I’ve always looked for a method to make digital blending a little easier and more automated so hopefully this helps. If you’ve got any suggestions to improve the method let me/us know. I’d also be interested in hearing how this compares to the HDR function in CS2 (I’ve only got CS at the moment!)


The purpose of digital blending is simply to increase the dynamic range of the shot. So here are the two pictures I’ll be blending. The first is exposed for the shadows, and the second for the highlights. While I was quite happy with the exposure of the first shot, there were a number of small tricky areas which were blown out.

=== THE BASICS ===

1. Open both images in photoshop.

2. Copy (Ctrl+A) and paste (Ctrl+V) the darker image on top of the lighter image.

TIP: to help you align the images correctly, set the top layer’s blending mode to ‘difference’.

3. Make sure the darker image layer is selected and press Ctrl+Alt+' (i.e. the button to the left of 1 on the keyboard). This selects the luminosity mask.

4. Click on the ‘Add Layer Mask’ button while the selection is active.

5. And that’s it! It’s really that simple. You should now see what has happened with the layer mask – it’s masking out the dark areas of the darker image, while retaining the highlight details.


This is the bit that I like about this technique. There are a few ways to fine tune how the images are blended.

i) While the layer mask is selected press Ctrl+L to bring up the levels dialogue box. Play about with all three sliders and see what happens:

Move the left hand slider (black point) to the right to lighten the shadow areas.

Move the right hand slider (white point) to the left to darken the highlight areas.

Move the middle slider (mid point) to the left to darken - or to the right to lighten - the midtones.

ii) Manually paint the layer mask in areas you’re unhappy with. Use a black brush to reveal the lighter image, and a white brush to reveal the darker image.

iii) Change the opacity of the darker image.

Here’s the final image with a little tweaking and some more PP.

I’ve only really tried this technique on this image, and very quickly on a couple more. So let me know what you think of it, and if it works for you!
Here's another I've quickly tried the technique on:



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