HDR processing adds lots of noise to image

[PeterAit]

I am using HDR Expose 3 to process a stack of 3 bracketed images taken at ISO 400 with an EM-1. In the darkest area of the image, the original frames show essentially no noise while the merged image shows horrid noise. I've not encountered this before - any ideas?

[kirkt]

I have noticed this change with HDR Expose3 as well.  I have no idea why this occurs, but it completely defeats the purpose of HDR.  I would file a bug ticket or contact Unified Color.  They, however, are not the most responsive folks.

What version/build of Expose3 are you using?

kirk

[Bart_van_der_Wolf]

I am using HDR Expose 3 to process a stack of 3 bracketed images taken at ISO 400 with an EM-1. In the darkest area of the image, the original frames show essentially no noise while the merged image shows horrid noise. I've not encountered this before - any ideas?

Hi Peter,

I don't know it this is an issue with HDR Expose, but anyway bracketing is best done at base ISO. Maybe there is more noise in the Raw data of the (by definition) under-exposed ISO 400 image than you think. Bracketing at e.g. ISO 100, will reduce the noise to 50%, which maybe just what Expose wants/needs.

Cheers,
Bart
 

[Peterretep]

I was thinking that increased noise is a typical by product of HDR processing. I use a little HDR, very little, and when I do I often find more noise in the dark areas than what my original converted tif files had. I use Photomatix and generally use it to produce an image as natural looking as possible.

Peter

[PeterAit]

Hi Peter,

I don't know it this is an issue with HDR Expose, but anyway bracketing is best done at base ISO. Maybe there is more noise in the Raw data of the (by definition) under-exposed ISO 400 image than you think. Bracketing at e.g. ISO 100, will reduce the noise to 50%, which maybe just what Expose wants/needs.

Cheers,
Bart

Bart, thanks but I am not sure I buy this. First of all, my underexposed ISO 400 image has almost no noise in this region (a dark part of the photo) while the merged image has blatant horrible noise - it is not a subtle increase! Also, is seems that the merge process would take this part of the final image from the "overexposed" frame, not the underexposed frame.

I agree with using the lowest ISO possible, but sometimes one must compromise in order to get sufficient DOF and a useable shutter speed (I am hand-holding the camera).

[EduPerez]

Some HDR software tends to raise the shadows, resulting in noise amplification; is this the case?

[Hans Kruse]

I am using HDR Expose 3 to process a stack of 3 bracketed images taken at ISO 400 with an EM-1. In the darkest area of the image, the original frames show essentially no noise while the merged image shows horrid noise. I've not encountered this before - any ideas?

Is the reason that you use the HDR software to create the HDR look or simply to extend the dynamic range? If it is the latter I would recommend to use base ISO in the camera. If you edit in Lightroom and have Photoshop as well you could use the blending method I suggested i this thread http://forum.luminous-landscape.com/index.php?topic=96947.0
In my opinion this gives a better result than any HDR programs I have tried and used.

[Jimbo57]

Is the reason that you use the HDR software to create the HDR look or simply to extend the dynamic range?

That is the pertinent question.

In my own case (using Nik HDR Efex Pro - but other software should be similar), I only use HDR for the latter purpose and never for the former.

If, however, you do go for the "HDR look", then it is not so much that noise is "created" but rather that existing noise is accentuated, perhaps to an extend that is is much more noticeable.

[Hans Kruse]

That is the pertinent question.

In my own case (using Nik HDR Efex Pro - but other software should be similar), I only use HDR for the latter purpose and never for the former.

If, however, you do go for the "HDR look", then it is not so much that noise is "created" but rather that existing noise is accentuated, perhaps to an extend that is is much more noticeable.

So I assume by that you mean that there is more noise noticeable than in the most exposed image that is blended into the HDR image. HDR programs have in my experience a tendency to do many things that you don't really want. Therefore I have abandoned all HDR programs and only use the blending method described in Photoshop. It's just as easy to do as to do the merge in HDR and there are no extra HDR program sliders to deal with.

[PeterAit]

Yes, that's right. I have pretty much solved the noise issue as follows:

1) Process all the exposures in LR applying modest sharpening and noise reduction only, same for all images.
2) Export as TIFFs.
3) Use HD Expose to blend the TIFFs.
4) Use HDR Expose's own NR tool to further tamp down the noise.

But now I am having some other idssues such as halos. I think I'll try your PS method.

[Bart_van_der_Wolf]

Yes, that's right. I have pretty much solved the noise issue as follows:

1) Process all the exposures in LR applying modest sharpening and noise reduction only, same for all images.
2) Export as TIFFs.
3) Use HD Expose to blend the TIFFs.
4) Use HDR Expose's own NR tool to further tamp down the noise.

But now I am having some other idssues such as halos. I think I'll try your PS method.

Just one caution against TIFF input to HDR Expose, which is a pity because that also prohibits chromatic aberration removal with other tools. When I tried it, TIFFs as input gave significantly more noisy results than Raw conversions by HDR Expose. Don't know if that's still the case, because I don't use it for HDRI, I use SNS-HDR instead. HDR Expose does do a decent job, but I don't like the dark 'halo' at the bottom of clouds.

Cheers,
Bart

[texshooter]

Therefore I have abandoned all HDR programs and only use the blending method described in Photoshop.

Absolutely!  My baptism into HDR was using Photomatix then HDR Expose (better), following the techniques of Serge Ramelli and Trey Ratcliff. But then I stumbled upon Sean Bagshaw's videos and learned HDR programs are not only unnecessary but inferior to the old tried-and-true PS blending methods (unless you're after that radioactive look). Photomatix is so... dare I say...

[kirkt]

If you do not need the full 32bit data to accomplish your task, then exposure blending, and staying in the realm of LDR throughout the process, is probably a simpler way of combining exposures.

If you are going to relight your scene or do extensive color grading or effects, then it is probably advantageous to merge multiple exposures to a full 32bit dataset and tone map to gently compressed, low contrast 16bit LDR file for further processing.  Part of the problem comes when trying to create a "final" image in an HDR program.

kirk

[Misirlou]

I get the least noise by extracting tiffs from the raw files via DXO, often using their PRIME noise reduction engine. Then I process the HDRs in any of several different tools, depending on the type of image I'm dealing with. The newest version of Photomatx seems to be the best of them all for handling ghosts. And it's not hard to find settings that keep the noise down to a low enough level to be no problem in prints. But, there are so many variables in that workflow that I find it difficult to repeat my own work, much less explain to anyone else how to do it.

Let's see what the new HDR tools in LR 6 can do.

[Hans Kruse]

I get the least noise by extracting tiffs from the raw files via DXO, often using their PRIME noise reduction engine. Then I process the HDRs in any of several different tools, depending on the type of image I'm dealing with. The newest version of Photomatx seems to be the best of them all for handling ghosts. And it's not hard to find settings that keep the noise down to a low enough level to be no problem in prints. But, there are so many variables in that workflow that I find it difficult to repeat my own work, much less explain to anyone else how to do it.

Let's see what the new HDR tools in LR 6 can do.

Given that Adobe would have to write a new merge process for Lightroom for the 32 bit merge that is not based on Photoshop functions directly, it would make sense that it would be an improved HDR merge we will see. I haven't been too impressed with the Photoshop 32 bit merge. I look forward to see it and try it out. I assume it also would keep track of which exposures (original or virtual copies) that went into the merge which would be really nice too. Also I hope Lightroom would give a warning in case one of the exposures that is part of a merge would be deleted or removed from the catalog.