Lr on iOS - Color Noise in HDR vs. non-HDR Photos

[jepo13]

Dear All,

I have noted a strange behavior of Lr on iOS (iPhone XR): some times the HDR image has a lot more color noise in some areas than the non-HDR image (I opted for both versions to be stored) and at other times it's the converse (more color noise in the non-HDR image than in the HDR one). That this behavior oscillates randomly and that it's sometimes the non-HDR, direct-from-sensor image that has more color noise is baffling (me at least). Has anyone noticed this on an XR or some other iPhone model ? Is there anythiong to be done ?

Thanks for all suggestions and/or pointers !

[Charlie.D]

As you know, raw images have a lot more image data, and raw images need processing to appear like "normal" images.  Lightroom camera HDR images have 'Auto' settings applied, which I find usually is a good starting point.  LR Camera basic DNGs have just the basic Adobe Color profile applied with basic default adjustments (Whites +15, Blacks -5, Clarity +8)... in both scenarios, I sometimes still need to further adjust exposure or noise settings in Edit mode depending on how over/under-exposed the image is.  I have confirmed with Lightroom developers that the LR camera is simply ingesting the raw data the sensor/platform provides, and what's not corrected with the basic settings I just mentioned may indeed need manual effort to refine at times.  Personally, my approach is to capture in HDR mode by default, with 'Save unprocessed original' enabled in the in-camera options as I think you already know.  HDR tends to provide me the better image.

If you are seeing results that seem wrong, please feel free to share an example DNG image with us for the dev to investigate.  You can send that image to me in a direct message if you prefer.

[jepo13]

I'm perfectly OK with 'Auto' settings applied and with having to tweak various things by hand (this is why we use LrC, isn't it?). What I don't understand (without saying there's something wrong) is that sometimes there is more color noise in the unprocessed original than in the HDR and at other times there is more color noise in the HDR than in the unprocessed original. I expected more color noise to consistently appear in one (HDR) when shooting in consistent light and camera (iPhone) settings. It's the inconsistency that's bothering me. Do you also see this ? Does it bother you ?

[JohanElzenga · Accepted solution]

The explanation might be deghosting. I assume that Lightroom uses automatic deghosting when you shoot in HDR. Deghosting can lead to more noise in deghosted areas, because the darker shot was used exclusively in that area to avoid getting ghosts from the brighter exposures.

[Brady22014796b57p]

Im seeing a similar issue where some dark parts of the HDR really destroyed by noise. 

[JohanElzenga]

Well, I already gave you the most likely explanation. Deghosting does that.

[Brady22014796b57p]

Is there a way to controll it or simply move a stop up while shooting?

[JohanElzenga]

Why don't you try that stop yourself? You can't control deghosting.

[Brady22014796b57p]

Because in the iOS app you can't control the stops in rhe HDR. I wish you could control the AEB spread but it seems like it's only auto.

[Jao vdL]

This is correct. The cause is deghosting and the algorithm it uses for that. Could probably be better but yeah it takes the most underexposed image for that (and corresponding fastest shutter) so it stops motion in the area but also leads to a lot of noise.