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SPECIFICTION
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HDR Merge Master

github.com

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Spec score 7.5 #14 of 21 in HDR Software

What it is

HDR Merge Master is a free, GPL-3.0 open-source tool that uses Blender’s compositor to combine exposure brackets in batches. It outputs 32-bit OpenEXR or Radiance HDR files and creates tonemapped JPG previews alongside them. Multiple input folders can be added, with optional recursive subfolder processing and JSON batch import or export. Alignment choices include none, Hugin pre-alignment, and MTB alignment, depending on Blender version and mode. A headless command-line mode supports folder processing, JSON input, alignment, thread settings, and cleanup. Camera RAW processing requires RawTherapee, with adjacent PP3 profiles applied automatically. Documented workflows include Blender, RawTherapee, Hugin, Luminance HDR, and PTGui; a script can replace JPG paths with EXR paths in PTGui PTS projects. Blender 4.5 LTS and 5.1 LTS are actively tested, while older versions use a reduced-feature legacy script. The tool does not remove ghosting, so a steady tripod is advised.

Spec sheet

What it does
HDR Merge Master uses Blender’s compositor to merge exposure brackets in bulk into 32-bit EXR files.Read 3 Oct 2026 · github.com
Purpose
HDR Merge Master uses Blender's compositor to merge exposure brackets in bulk into 32-bit EXR files.Read 4 Oct 2026 · github.com
Integrations
The project documents optional use of Blender, RawTherapee, Hugin, Luminance HDR, and PTGui workflows.Read 3 Oct 2026 · github.com
License
The repository identifies its license as GPL-3.0.Read 4 Oct 2026 · github.com
Maker
The repository owner is Greg Zaal, whose GitHub profile lists South Africa.Read 3 Oct 2026 · github.com
Alignment
It offers no alignment, Hugin-based pre-alignment, or MTB alignment modes, with MTB as the default.Read 4 Oct 2026 · github.com
Automation
A headless command-line mode supports batch files, folder input, recursive processing, alignment options, thread counts, and cleanup.Read 4 Oct 2026 · github.com
Batch processing
Users can add multiple input folders and optionally process subfolders recursively.Read 3 Oct 2026 · github.com
Batching
The app supports multiple input folders, recursive processing, and batch lists that can be imported or exported as JSON.Read 4 Oct 2026 · github.com
Blender versions
Blender 4.5 LTS or 5.1 LTS are actively tested; older versions use a legacy script with reduced features.Read 3 Oct 2026 · github.com
Download
The installation instructions direct users to download the latest GitHub release and run hdr_merge_master.exe.Read 4 Oct 2026 · github.com
HDR output
The output format can be 32-bit OpenEXR or Radiance HDR.Read 3 Oct 2026 · github.com
HDRI workflow
The maker says Poly Haven uses the tool to merge exposure bracket sequences for HDRI creation.Read 4 Oct 2026 · github.com
Linux builds
The release notes state that Linux release binaries were added.Read 4 Oct 2026 · github.com
Notable limit
The tool does not perform ghost removal, and the README recommends using a steady tripod.Read 3 Oct 2026 · github.com
Notable limitation
The tool does not remove ghosting, and the maker advises using a steady tripod when shooting.Read 4 Oct 2026 · github.com
Other integrations
The workflow can use Hugin's align_image_stack for image alignment and includes a script to replace JPG paths with EXR paths in PTGui project files.Read 4 Oct 2026 · github.com
Output formats
Merged output can be 32-bit OpenEXR or Radiance HDR, and the app also creates tonemapped JPG previews.Read 4 Oct 2026 · github.com
Preview files
The tool creates tonemapped JPG previews alongside the merged HDR files.Read 3 Oct 2026 · github.com
PTGui workflow
An included script can replace JPG paths with EXR paths in a PTGui PTS project.Read 3 Oct 2026 · github.com
RAW processing
RAW input is supported when RawTherapee is installed and the RAW option is enabled.Read 4 Oct 2026 · github.com
Release downloads
The project distributes downloadable builds through GitHub Releases.Read 3 Oct 2026 · github.com
Requirements
The maker actively tests with Blender 4.5 LTS and Blender 5.1 LTS; older Blender versions use a legacy merge script with reduced features.Read 4 Oct 2026 · github.com
Who it is for
The README describes the intended workflow as creating HDRIs for stitching, then swapping JPG previews for EXR files before final export.Read 3 Oct 2026 · github.com

Strong points and limits

Strong points

  • Processes multiple folders recursively
  • Outputs OpenEXR and Radiance HDR
  • Creates tonemapped JPG previews
  • Offers command-line batch mode
  • Available for Windows, macOS, and Linux

Limits

  • Does not remove ghosting
  • RAW processing requires RawTherapee
  • Older Blender versions have reduced features
  • Steady tripod use is advised

Who it suits

It suits HDRI and bracketed-exposure workflows on Windows, macOS, or Linux, especially users already working with Blender and related imaging tools. Command-line batch processing is available for automated jobs.

Verdict

HDR Merge Master provides batch bracket merging, several alignment modes, HDR outputs, and automation options without a license charge. Its workflow depends on Blender versions and external tools, and ghost removal is outside its scope.

Where Specifiction places it

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