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Tutorial: HDR 101

Adobe Photomerge Exposure

The new Adobe Photoshop Elements 8 [QuickPrice Check] features a couple of new functions that make an upgrade well worth the money. Today I want to take a look at their Photomerge Exposure function that takes two or more pictures taken at different exposure settings and merge them into a single one with optimal exposure setting.

Photographers will immediately recognize this as High Dynamic Range (HDR) — the real kind, not the eye-popping headache-inducing candy version.

It is difficult for cameras to record a picture where detail is preserved in both the highlights as well as the shadows. If we meter for the highlights (e.g. the bright sky, to capture the rich blue color), then the shadows are usually underexposed and are too dark. If we meter for the shadows (to preserve interesting details), then the highlights are overexposed, i.e. “blown.”

How do pros do it? Here’s the secret. They capture two or more pictures of the same scene, metering for the different parts of the scene where they want to preserve detail. Then, in post processing, they use an image editing software, such as Photoshop, to merge the photos with different exposures together [hence, the name “Photomerge Exposure”] into a single image where detail is preserved in the high, mid and low tones! In other words, they obtain a perfectly exposed picture that will have your friends wonder “What camera did you use to get such nice shots? Mine always comes out too bright or too dark.”

Step-by-step instructions:

Step-by-step instructions follow.

STEP 1 – BRACKET YOUR EXPOSURES

Here are 3 pictures I took at the Centre Island Farm using the camera’s Auto Bracketing function to expose them at -1 EV, 0 EV and +1 EV.

+1 EV to preserve detail in the shadows (low tones)

+1 EV to preserve detail in the shadows (low tones)

0 EV (mid tones)

0 EV (mid tones)

-1 EV to preserve detail in the highlights (high tones)

-1 EV to preserve detail in the highlights (high tones)

[Note: Click on any image for a larger version.]

If your camera has an Auto Exposure Bracket (AEB) function, use it. I set mine to +/-1 EV when the scene has very dark shadows and very bright highlights. Otherwise, use less range, such as +/- 1/3 EV or +/- 2/3 EV.

If your camera does not have AEB, but has Exposure Compensation, then dial in the exposure compensation manually. It’s the same thing.

If you have a very difficult scene (as far as the lighting is concerned), then you may choose to meter manually for each area you want to preserve detail in and take as many exposures as you believe you need.

You optimally want your camera on a tripod so the 3 shots register perfectly.

An Area AF function with AF Spot metering is very helpful here, allowing you to keep the camera pointing on the scene, but moving the AF Area frame to the exact spot on the scene you want the camera to meter on.

Avoid scenes where there is movement, such as people moving.

STEP 2 – OPEN IN PSE8

Once you have transferred the pictures from your camera to your computer, open them up in Photoshop Elements 8.

Step 2- Open in PSE8

Step 2- Open in PSE8

Notice how I arranged the 3 pictures in order of high tone, mid tone and low tone. Not sure what algorithm is being used in PSE8, but I find that when I arrange them like that, and leaving the low tone as the selected and last one, Photomerge does a better job and takes all three images into consideration. Any other order and PSE8 merges only two of them. You may want to experiment a bit and see what works best for you.

STEP 3 – RUN PHOTOMERGE EXPOSURE

Now go to File – New – Photomerge Exposure and let PSE8 do its magic.

Step 3 - Run Photomerge Exposure

Step 3 - Run Photomerge Exposure

If it can, it will automatically merge the shots and display the resulting merged image. If it can’t for some reason, it will ask you to do it manually.

STEP 4 – ADJUST TO LIKING

Step 4 - Adjust to Liking

Step 4 - Adjust to Liking

Notice the sliders in the right column, allowing you to vary Highlight Details, Shadows and Saturation to your liking.

STEP 5 – MANUAL MERGE

If you want to, you can also take full control and do the merge manually. Click on the Manual tab in the right column.

Step 5 - Manual Merge

Step 5 - Manual Merge

STEP 6 – MANUAL MERGE: SELECT BACKGROUND IMAGE

Step 6 - Manual Merge: Select Background Image

Step 6 - Manual Merge: Select Background Image

All you need to do is to drag the image you want to use as the background. I select the low tone image here.

STEP 7 – MANUAL MERGE: SELECT DETAIL TO MERGE

Step 7 - Manual Merge: Select Detail to Merge

Step 7 - Manual Merge: Select Detail to Merge

Selecting which part of the image (the high tone image in my case) to merge into your background (the low tone image) is now a simple matter of “painting” or identifying it. Just a bar as I’ve done here is enough for PSE8 to know to extract the barn door and fence posts from the high tone image and merge them into the low tone image.

STEP 8 – DONE!

Photomerge Exposure - Done!

Photomerge Exposure - Done!

And here’s the result! I sharpened my output.


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