Going from HDR DNG from Lightroom to EXR in Affinity Photo

[Seamaster84]

Hi

 

I’m having some difficulty converting files exported from Lightroom. 

With the latest versions of Lightroom mobile you can make full 32bit HDR files with your iPhone.

 

However, Lightroom can only export those files as DNG files...

 

I want to use the photo’s in a 3D rendering application where the data in those files are being used to light 3D objects and scenes. 

Therefore I need the full range that’s inside of the DNG. 

 

That’s why I want to use the Affinity Photo to open the DNG file and save it out as an 32bits floating point EXR file. 

 

Iv’e been trying many ways to get this to work but I just keep getting clamped values in the resulting file. 

 

 

Could anyone help me out?

 

 

 

Thanks!

[James Ritson]

Hey Seamaster, I've just tried to emulate your approach using Lightroom CC Classic by creating an HDR Merge, choosing not to tone in Camera Raw, then exporting as original (which does indeed export it as a DNG).

 

In Affinity Photo, you can change the RAW Development from 16-bit to 32-bit unbounded by using the assistant (the little suit icon on the top toolbar), but this change only applies to images opened afterwards. This isn't a problem, simply:

1. Open Affinity Photo with no document open
2. Click the suit (Assistant icon)
3. Click Develop Assistant at the bottom of the dialog
4. Set RAW output format to RGB (32bit HDR)
5. Open your DNG file

The 32-bit output option will avoid clipping or rounding the pixel values in the DNG file. I've attached a screenshot to show my result and the visible highlight detail from scrubbing the 32-bit exposure preview slider.

 

From a technical standpoint, the DNG exported from Lightroom will be in half-float, but you'll be temporarily importing and working in 32-bit within Photo. On the OpenEXR export dialog, you can always click the More option and set the Image pixels format to 16-bit (HALF) to save on file size  

 

Is there a feature that's tying you to do the merge in Lightroom mobile, e.g. does it stitch HDR 360x180 panoramas? (You mentioned using HDRIs) - If it's a single scene, I just wonder whether it would be easier to do the HDR merge in Photo (uncheck Tone Map on the dialog) and export straight to OpenEXR?

 

Hope that helps!