VFX I

3.7 Merging HDR


In this chapter, we will merge the rendered panorama layers in Photoshop to one HDR file

Import and Merge

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Exposure Brackets

We’ve rendered exposure layers in Autopano

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Select Merge

Photoshop > File > Automate > Merge to HDR

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Import the images

Browse to select the images

Disable Attempt to Automatically Align Source Images

Trap: If you’re prompted to set EV values manually, the layers weren’t rendered with EXIF metadata. Re-render as TIFF or JPEG, not PNG

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Merge step

This is the Merge interface to set color bit depth, exposure preview or even select which images are used

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Set 32 Bit Mode

Remove Ghosts: Can improve the result, but also create unwanted artifacts. Usually, leave disabled

Set White Point Preview: Set a preview exposure

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Merge Result

This is our HDR. It might feel low contrast with little saturation compared to the normal exposure shot. That’s fine, we are primarily interested in a high dynamic range for the Image Based Lighting


Check the HDR

Lighting will only work well with a true HDR. Make it a habit to always check the highlight values and their dynamic range with the 32-bit preview exposure

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Eyedropper to 32-bit

Get the Info box > Click on the Eyedropper

Change display values to 32-bit

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Checking Values

Hover over brightest highlights such as direct light sources

Values should be over 1, ideally much higher, here over 16, great!

Try different highlights. If you can’t find values over 1, it’s not a true 32-bit HDR

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32-bit Preview Options

View menu > 32-bit Preview Options

That’s the White Point Preview set earlier

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Preview Exposure

Lower the Exposure to the point that only the highlights stay bright. If the highlights darken linearly together with the image, the dynamic range is not good, or it’s is not a true HDR

Next: Find the exposure value closest to normal exposure. If that’s more than +/- 1, compensate later with a color correction

Move slider to 0. We want to save and export with no Preview Exposure


Save and Export

If the Preview Exposure was within margin and is now set to 0, we can move on to export the HDR

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Flip HDR

1. Save Photoshop file
Use a meaningful name, not just HDR_02.psd

2. Flip horizontally
Note: Not needed for Arnold
Image menu > Image Rotation > Flip Canvas Horizontal

3. Save Radiance file
Use a meaningful name, not just HDR_02.hdr