VAE Decode (HDR)

An ordinary VAE Decode returns pixels in [0, 1]. That's fine if you're making a PNG and useless if you're making an EXR: the whole top of your image's range has been amputated, and a grade can only work with what's left. VAE Decode (HDR) is the decode half of Radiance's HDR pair, and the reason it exists is that values above 1.0 can survive the round trip.

The important detail is how. There are two paths through this node and picking the wrong one is the main way people get confused.

Two paths, and Auto picks between them

Sampler-safe is what you get after a sampler has touched the latent. This is essentially a normal decode, delivering the target colour space you asked for - sRGB for display, or linear light in a chosen gamut, or a camera log target (ARRI LogC4 means AWG4 plus the LogC4 curve; Sony S-Log3 means S-Gamut3.Cine). Nothing magic, just colour-managed.

Direct HDR is what you get when the latent came straight out of VAE Encode (HDR): the encode stamped the latent with metadata and a fingerprint, and if that fingerprint still matches, this node inverts the HDR coding exactly. Values above 1.0 come back as values above 1.0. If the latent is some other latent - say a sampler has reshuffled it past recognition - Direct HDR instead decodes it normally and runs the pixel SDR → HDR model to reconstruct clipped highlights, limited to the hdr_peak_nits mastering peak you set (1000 nits sits at 4.93 on the output scale, where SDR white is 1.0).

decode_mode = Auto (Recommended) figures out which one applies by checking that fingerprint. Leave it there unless you have a reason.

The controls that matter

samples and vae are required, plus target_space (12 options, default sRGB). Then, in rough priority:

• hdr_mode must match the encode setting. If you encoded with Compress (Log) and decode with Clip (SDR), you get whatever nonsense that implies. This is the number one mistake here.
• display_tonemap (Reinhard / ACES Filmic / None) is now the sole tonemap control in this node, independent of everything else. None means no tonemap at all - scene-linear values far above 1.0 pass straight through, which in ComfyUI's preview is guaranteed white-out. That's not a bug, it's documented behaviour for people feeding an OCIO-aware viewer.
• hdr_output skips the final [0, 1] clamp so the IMAGE tensor genuinely carries values above 1.0 and below 0.0. Turn it off when feeding SDR nodes.
• exposure_adjust (stops, post-decode) and hdr_scale_factor (linear gain, Direct HDR only, RGB only).
• decode_noise_scale - a real one, worth knowing. Compress (Log) expands values exponentially on the way back, which amplifies any residual VAE decoder artifact in flat highlights into visible grid patterns. This mixes a little Gaussian noise into the latent pre-decode to break that up. The tooltip publishes starting points per camera profile: 0.018 for LogC4 and S-Log3, 0.025 LogC3, up to 0.035 for Log3G10. It defaults to 0, so existing workflows don't shift.

For 4K work there are tile_size and overlap with Auto from VRAM, plus temporal_size/temporal_overlap for video - note the tooltip's warning that temporal_size counts latent frames, unlike ComfyUI's native tiled decode which counts pixel frames.

Outputs: image, and metadata, a JSON string naming the path that ran and whether the scale factor was applied. Read that string when something looks off; it answers the question you're about to ask on a forum.

Installing Radiance

Manager → search Radiance → install → restart → refresh. Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/fxtd-studios/radiance.git
cd radiance
python -m pip install -r requirements.txt

Windows portable: use python_embeded\python.exe. Radiance is GPL-3.0, ~147 visible nodes, and installs OpenEXR, OpenImageIO, OpenColorIO, diffusers and accelerate. If you use the Direct HDR reconstruction path on an ordinary latent, the SDR → HDR weights live in ComfyUI/models/radiance/ and download on first use - set RADIANCE_ALLOW_DOWNLOADS=0 to forbid that. Those weights are non-commercial only.

Troubleshooting

Everything is white. Either display_tonemap is None with real HDR values on the wire (expected), or hdr_mode doesn't match the encoder. Check metadata before anything else.

Highlights look like a halftone grid. Increase decode_noise_scale toward the tooltip value for your profile.

I get SDR values above 1.0 when I expected HDR. hdr_output is off, or the latent is sampler-touched and you're in practice on the sampler-safe path. That's by design.

Heads up about the pack in general. When the suite was announced, the top comment on the r/StableDiffusion thread criticised specific nodes for collapsing precision to 8-bit while advertising a 32-bit pipeline. The criticism was fair at launch and the project has tightened up considerably since - 3.5.0 is candid about what's heuristic and what isn't - but on a shot that matters, verify the round trip rather than trusting the feature list.