Friday, July 14, 2017

An Easy Photoshop Trick for Blending Exposures

Our eyes are amazing creations and in most cases, far superior to a film or digital camera.  Our eyes are able to look around a scene and dynamically adjust based on subject matter. This trait accounts for many of our commonly understood advantages over cameras. For example, our eyes can compensate as we focus on regions of varying brightness, can look around to encompass a broader angle of view, or can alternately focus on objects at a variety of distances.

Cameras capture a single still image.  Some adjustment to the image can be done after capture with photo editing software, but that is limited by the camera technology.  If areas of our photo are too bright (blown out) or too dark then no information will be available in those areas, no matter how much we try to fix the image.

Our eyes are more akin to a video camera — not a still camera.  Our eyes and brain work together to compile relevant snapshots to form a mental image. What we really see is our mind's reconstruction of objects based on input provided by the eyes — not the actual light received by our eyes. As a result, we can see into dark and light areas of a scene at the same time.

There are techniques for overcoming the limitations of our digital cameras to try and simulate what our eyes see.  One of the most popular is High Dynamic Range or HDR.  Even our cell phones can do HDR now.  However, the result can look unrealistic or even cartoonish.  Recently I have been using image masking in Photoshop that can produce more realistic results.

Warning - this works in Photoshop.  If you don't have Photoshop you may not be interested.  If you are, please read on.

1. Make a series of photos using exposure bracketing.  You want the darkest shot to have no blown highlights and the brightest shot to have no underexposed areas.   I set my camera up to take 5 exposures at - 2 2/3, -1 1/3, 0, +1 1/3, and +2 2/3 EV.  Most DSLRs support bracketing. You may have to find and read your manual to make this work.  You should have your camera on a steady tripod to make sure the images line up.


-2 2/3 EV


-1 1./3 EV

0 EV

+1 1/3 EV


+2 2/3 EV

2. Load the five images into Lightroom.  You can use other photo editing tools.  Lightroom is what I use.

3. Pick enough of the bracketed shots to cover the dynamic range by looking at the histograms. The histogram on the darkest one should not be touching the right side.  The histogram on the brightest should not be touching the left side. 

First Shot

Third Shot

Use control-click in Lightroom to select those images and any in between.

4. In Lightroom, choose the Photo menu, Edit in and Open As Layers In Photoshop...  This will launch Photoshop and bring the images in as individual layers.

5. Drag the layers around to put the brightest on top and the darkest on the bottom.


6. Click the eye icon to the left of the layer to turn off all but the bottom two layers.  In this example, I only have 3 layers.

7. Click the second to the bottom layer, then click the Add Layer Mask icon.

\

8. With the layer mask on the second to the bottom layer selected, go to the Image menu and select Apply Image.
A dialog box will appear.  Click the Invert box and click OK.

Photoshop will create a layer mask for you that masks out the brightest parts of the top image. You can click the eye icon on the second to the last layer to turn in on/off to see the effect.

9. Turn on the next layer up by clicking on the eye icon and then repeating steps 7 and 8.  Do this for each layer.

I will sometimes paint in some additional masking on some layers to brighten or darken areas of the photo.

The resulting image will be low contrast and will appear flat and uninteresting.  You'll fix this in Lightroom.

10. You can save the image as is with the layers or flatten the layers before saving.  I flatten the layers this to make the files a little smaller and save space.  Close the file in Photoshop.  It will appear in Lightroom along with the originals.

11. Use Lightroom Tone sliders to darken the backs, lighten the whites and add some contrast.   Be careful to not reintroduce blown highlights or dark shadows. At this point, you can do what ever additional edits you want.  In this example I used the Vertical Transform slider to correct some of the perspective distortion, and added a little clarity.

This example does not have extreme contrast to deal with.  I have used this technique in some extreme situations, such as the sunset example below.

Exposed for the sunset sky

A little brighter

Exposed for the flowers in the foreground

End Result

I hope this is helpful for a few people who use Photoshop.  There are other techniques, such as Luminosity Masking, which are even more powerful but are much too complicated to explain here.  I have found I can use Image Masking in most cases.

1 comment:

  1. Very informative and it looks like a lot of steps.

    ReplyDelete