Blended Exposures for Photoshop Elements

January 5, 2003
Charles C. Lloyd (clloyd3@attbi.com)

 

The technique of "blended exposures" allows for constructing an image from two photographs with a resulting image that has better exposure across extremely bright and/or dark areas of the scene.  Several Photoshop tutorials exist on the web for doing this, which involve manual editing of a selection mask.  This is a tedious and error prone approach to this problem.  In this document, I describe a technique I picked up from "Gordon W" on dpreview.com (Sony Talk Forum).  Unfortunately, his procedure doesn't work in Photoshop Elements, so I also layout the recipe for doing this in a 'tricky' way in Photoshop Elements which is derived from a tutorial by Jay Arraich (http://www.arraich.com/elements/pse_rreal1.htm).

 

The full-blown Photoshop product supports the concept of layer masks which can be used to assist in blending one layer on top of another.  In a mask, a white pixel means the corresponding pixel in the layer’s image has an opacity of 100% while a black pixel in the mask results in a 0% opacity of the corresponding image pixel.  Mask pixels with gray color have an opacity equivalent to their gray value as a percentage of white. A mask can either be made by hand painting the mask with white, black and gray colors, or from the gray-scale pixels of a photographic image.

 

We can use this fact to help us copy the bright portions of a properly-exposed photo and leave the dark portions behind (actually just greatly diminished by their low opacity).  If we take a "dark" photo (one exposed for the brightest highlights will look dark overall) and make a mask from (the gray-scale version of) this photo, we can apply the mask to the photo itself and reveal only those portions of the photo which are properly exposed.

 

Unfortunately, PS Elements does not support layer masks directly, but with a special trick (provided by by Jay Arraich), we can force Elements to construct an image layer with a mask.

 

The following two recipes describe how to perform the equivalent blended exposures magic in both Photoshop Elements and Photoshop proper.

 

 

Note [01/03/03]: I have modified my own application of the procedure below. As it turns out, the use of the original image as the mask itself results in a less-than-satisfactory result. I have found it better to create the mask by hand painting in either white or black. Having opacity in the mask (ie grey values) is rarely useful as you generally want pixels from one area or another and not a mixture. I will fully update this document in the near future, although this procedure now more-closely resembles other tutorials on the net, and as such is redundant. In the short term, you can follow this procedure as a starting point and then clean up the result by painting in the mask with either black or white to get the appearance you desire.

Overall goal: add new “masked layer” containing properly exposed highlights from the dark image on top of the overexposed lights in the bright image.  The mask will only allow the brightest portions of the dark image to be seen.

 

 

Blended Exposures in PS Elements (with Jay Arriach’s layer mask technique):

 

1.    Open the dark image in Photoshop Elements

2.    Open Effects browser from Window->Effects

3.    Choose (single click) “Ripple Frame” effect

4.    Hold down the Option key (Alt on PC) and click “Apply”. Note:  you must hold the Option/Alt key until the effect command is complete.  Unfortunately, there's no indication that its complete, but its soon after the "Crop" progress bar goes away.

5.    Select the background layer (ie click the layer in the layer palette)

6.    Select all, copy

7.    Option-click (Alt-click on PC) on the mask thumbnail in the "ripple" layer to allow editing of the mask.

8.    Paste contents of clipboard to replace ripple frame mask with grey-scale version of your dark image. [You now have a masked layer which primarily shows the properly exposed highlights.]

9.    Open bright image

10.    Click the title bar of the dark image window to make it the active window again.

11.    Drag the newly created layer from the layers palette of the dark image and drop into the freshly-opened bright image window.

12.    In the bright image window, position the new layer on top of the existing one so all pixels line up (with move tool on and top layer selected, drag the image until it snaps into place)

13.  Adjust opacity to suit (75% often good)

 

 

Equivalent Blended Exposures in PS proper (based on tips from Gordon W.):

 

1.    Open bright image in Photoshop

2.    Open the dark image

3.    Select all, copy

4.    Close dark image

5.    Paste clipboard contents to create new, dark layer on top of bright layer.

6.    Ensure new, top layer is selected

7.    Choose from menu: Layer->Add Layer Mask->Reveal All

8.    Option-click (Alt-click on PC) on the mask thumbnail to allow editing of mask itself

9.    Paste clipboard contents into mask itself (clipboard should contain dark image still)

10.    Adjust opacity to suit (75% is often good)

 

 

With either Photoshop or Elements, you can now flatten the image or whatever else needs to be done.

 

Advanced handling:  Once you’re comfortable with the above approach, you may find that the mask doesn’t expose enough of the bright areas, and/or too much of the dark areas.  This results in a muted look to the picture and/or a glary look to the highlights.  This is because the mask itself doesn’t have enough contrast.

 

One of the major goals of these procedures is to avoid our getting involved with the tedious and error-prone job of painting on the mask.  So I have achieved fairly good success when this arises by applying the “Levels” command to the mask itself.  The Levels command is covered in many other tutorials, so I won’t rehash it here.  However, your goal should be to increase the contrast as much as you can without making it look like a “Threshold” image (no gray-scale pixels).  If you achieve a threshold look, the resulting mask is too harsh and the blended image will exhibit harsh transitions.

 

Once you have boosted the contrast, you may still have harsh transitions even without achieving the threshold look.  You can soften this a bit by applying a Gaussian blur to the mask itself.  Small radius values between 1-4 pixels are probably best.

 

Contact me:  If you have luck with these procedures, I’d be interested to know.  If you find a way to improve upon either these notes or the procedures themselves, I’ll be happy to incorporate your findings.

Examples: