The merged 32-bit HDR file shows next to the bracketed photos you selected for the merge. If you don't see it, click above the filmstrip and check All Photographs.

This error normally happens when using version 4.0 of Lightroom. Upgrading to version 4.1 or higher should solve the issue, as support for 32-bit TIFF file was added in Lightroom 4.1.

If you restarted Lightroom after installation and the "Merge to 32-bit" item does not show under File > Plug-in Extras, then it is likely because Lightroom is looking for the plug-in in another place than where you installed it. This could happen if Lightroom was installed by a different user account than the one you used to install the plug-in for example, but might also depend on other factors specific to your Lightroom installation.

It is possible to manually instruct Lightroom to install plug-ins from a different location. You can install the plugin manually as follows:

1. Choose File > Plug-in Manager.
2. On the Plug-in Manager dialog, click on the Add button on the bottom left.

3. Browse to the location where you installed or downloaded the plugin. The plugin name is MergeTo32bitHDR.lrplugin. This is a folder on Windows, and a file on Mac.

   If you are on Windows and installed the plugin with the Photomatix Pro installer, the plugin would be in this folder:

   Windows 8, Windows 7 or Windows Vista:

   • C:\Users\<UserName>\AppData\Roaming\Adobe\Lightroom\Modules

   Windows XP:

   • C:\Documents and Settings\<UserName>\Application Data\Adobe\Lightroom\Modules

         Where <UserName> is your account name on the computer.

   If you are on Mac OS X, you will find the plugin in the place where you downloaded it. The plugin is named MergeTo32bitHDR.lrplugin and is located inside the MergeTo32bitHDR1.2 folder.

4. Click on the Add Plug-in button and select MergeTo32bitHDR.lrplugin.

1. After installation, restart Lightroom if you are on Windows (or used the installer on Mac).
2. Select bracketed photos from either the Filmstrip or the Grid.
3. Right-click to invoke the contextual menu.
4. Select Export and then Merge to 32-bit.
5. Select the desired option and click on the Merge button.
6. In case the merged image does not show once the merge has completed, click above the filmstrip and check All Photographs.

If you bought a license of Photomatix Pro before the Merge to 32-bit Plug-in was released, i.e. before August 2012, you are entitled to a free license key for the plug-in. You can retrieve it from this page.