Merge to HDR using Photoshop CS2.pdf

Merge to HDR using Photoshop CS2 - by Robert Berdan

Merge to HDR (high dynamic range) involves taking several shots of the same scene using a camera

mounted on a tripod and varying the exposures. For example you might set your camera EV to -4, -3, -2,

-1, 0, + 1, +2, +3, +4, F-stops to create a series of 9 exposures from the same spot braket in full 1 F-stop

values. You only need do this with scenes that have very wide dynamic ranges that exceed 8.5 F-stops

for example interior of home with large windows where you want to show both the inside and outside.

Another example would be shooting directly into the sun. Velvia slide film has a dynamic range of about

5.5 F-stops, most digital cameras about 8.5 stops. To merge multiple images varying in exposure here

are the steps for Photoshop CS2. The technique can be applied to .jpg or RAW files.

1. Choose File>Automate>Merge to HDR or in Bridge choose Tools>Photoshop>Merge to HDR (jump to

step 3 if using Bridge)

2. In the Merge to HDR dialog box, click Browse, select the images and click OK.

3. Click OK again when you see the menu with each image on the left and the main window with the full

32 bit dynamic range photo. Note this image will appear flat because it exceeds the display capabilities of

most monitors.

4. To convert from 32 bit to 16 bit Select Image>mode>16 bit and you will see the following pop up menu.

5. You have several controls

Exposure and Gamma – let you manually adjust brightness and contrast of the HDR image

Highlight Compression - compresses the highlight values in the HDR images so they fall within the

luminance values range of 8 or 16 bits per channel image file. No further image adjustments are

necessary; this method is automatic.

Equalize Histogram - compress the dynamic range of the HDR image while trying to preserve some

contrast – no further adjustments are necessary.

Local Adaptation – Adjusts the tonality of the HDR image by calculating the amount of correction

necessary for local brightness regions throughout the image.

Optional Click the arrow to view Toning Curve and Histogram

You can 1) Choose exposure and Gamma – move the exposure slider to adjust the gain and move the

gamma slider to adjust contrast (do neither with the images I supply).

2) chose Local Adaptation, move the Radius slide to specify the size of the local brightness

regions (set to 88 px) set threshold slide to 23.15 with these images. This specifies how far apart

two pixels tonal values must be before they are no longer part of the same brightness region. You

can also use the toning curve to make adjustments – pull it up or down.

The resulting image may be too dark or too light - use your basic workflow 1) adjust tonal levels. 2) Boost

the Hue & Saturation.3) Adjust shadow\highlights 4) Burn & Dodge 5) Use unsharp Mask -6) Change the

image to 8 bit mode Image > Mode> 8bits per channel and save as a .tif file.

This images is the result of combining 9 separate exposures. A neutral density grad filter darkened the sky but

resulted in burned out highlights in regions where the river reflected the sun’s light. The HDR image was able to

capture detail in the water and in the clouds around the sun.

BW image taken with a 2 F-stop neutral density hard edge grad filter, note the lack of detail in the river.