Noisy Sensors and 16-bit Workflow

[jbrembat]

I guess you are involved in the creation of this interesting program

My involvement is very marginal: some contribute to web site and to help.

I have downloaded the program, but it is unable to handle this large a file.

To give you the best answer, I asked to the authors:
1- 16 bit images are converted to 8 bit, the authors claim the results are very very similar
2- No more than 3 GB are available for a 32-bit Windows application. There is not a true limit to the image size, the limit is the memory operative system can allocate.
3- Last, but not least, why do you work on a stich? Denoising is the first (or second) operation to be performed on a photo

The "demo" text is annoying, but I guess this is a free trial.  How do I save?

If you purchase the product, "demo" is no more present and you can save.
 

It needs much improved documentation, though.

I'm interested on this point. What do you think is not clear?

Jacopo

[Jonathan Wienke]

3- Last, but not least, why do you work on a stich? Denoising is the first (or second) operation to be performed on a photo

I agree with this; you should do as much processing as possible (noise reduction, color corrections, tone curves, etc) before stitching. the only thing you should have to do after stitching is manual blending touch-up as needed to hide seams, and possibly a bit of sharpening to deal with interpolation softening.

[fike]

I agree with this; you should do as much processing as possible (noise reduction, color corrections, tone curves, etc) before stitching. the only thing you should have to do after stitching is manual blending touch-up as needed to hide seams, and possibly a bit of sharpening to deal with interpolation softening.

I understand your  point, but it is also a bracketed HDR stitch.  I have experimented with doing the HDR processing first and then stitching, but Photomatix does some odd things with the image dimensions (depending on the config) and it kills the metadata that the stitcher uses to configure itself.  More importantlu, it is difficult to see how exactly you want to process the HDR image parts when you can only see 1/10 parts of the whole image at a time.  As a result it can be difficult to get dark foreground and bright sky the way you want it in one shot.  

So, what I do is to use PTGui's HDR output or exposure fusion.  Then, if it is HDR,  I use Photomatix to process the output file.  

I am not sure about the file size restrictions being based on the memory available.  Many programs are able to handle these big images (pthotomatix and neat image for example).  I believe what they do is break the image into smaller parts and work on them individually.  

[jbrembat]

I understand your  point, but it is also a bracketed HDR stitch.  I have experimented with doing the HDR processing first and then stitching, but Photomatix does some odd things with the image dimensions (depending on the config) and it kills the metadata that the stitcher uses to configure itself.  More importantlu, it is difficult to see how exactly you want to process the HDR image parts when you can only see 1/10 parts of the whole image at a time.  As a result it can be difficult to get dark foreground and bright sky the way you want it in one shot.  

So, what I do is to use PTGui's HDR output or exposure fusion.  Then, if it is HDR,  I use Photomatix to process the output file.  

I am not sure about the file size restrictions being based on the memory available.  Many programs are able to handle these big images (pthotomatix and neat image for example).  I believe what they do is break the image into smaller parts and work on them individually.

This doesn't explain why you want to denoise the final image.
For HDR, you should get  noise reduction, so the problem should be mitigated.
Are you sure the effect you see is noise?

I'm not sure. You posted a color image with some noise on the red channel. But I don't understand if and how that image is related to panoramic HDR work.

Jacopo

[fike]

...For HDR, you should get  noise reduction, so the problem should be mitigated.
Are you sure the effect you see is noise?...

no, I am not sure it is noise.  That is the point of this whole thread.  It looks a bit like noise, so maybe it doesn't matter and noise reduction can help me.  

This image is made up of 33 images.  there were two rows.  5 images in the bottom row.  6 images in the top row.  Each of the 11 images was bracketed with three exposures.  I hope that clarifies.  Yes, I thought that HDR wouldn't have this sort of noise.  In color, the noise isn't too noticeable.  In B&W, the noise blossoms to be a bit distracting.

[jbrembat]

After reading your previous post, I found:

This image was taken at ISO 800 on a 50D

Do you use this ISO value?
If so, that may explain the noise. Your "zero" exposure level is underexposed (noisy).

If you take multiple exposures, you have to put ISO at low level (no or minimum amplification).
To get more light, the exposure have to be increased (you have to change shutter speed).

When you increase ISO, the signal is amplified, but the same thing is true for noise.

If you increase ISO, you get more noise. Noise may be acceptable for color image, but may be nasty on some channel (generally blue and/or red are more noisy).


Jacopo

[Guillermo Luijk]

When you increase ISO, the signal is amplified, but the same thing is true for noise.

If you increase ISO, you get more noise. Noise may be acceptable for color image, but may be nasty on some channel (generally blue and/or red are more noisy).

It all dependes on how much exposure time and aperture you can afford, or in other words it depends on how much light you can afford entering the camera.

If you are shooting on a tripod without exposure time limitations, it is clear that the lowest real ISO will produce the least visible noise in the final image.

But if you are handheld shooting in such low light conditions that you cannot get a proper RAW exposure at base ISO, raising ISO will reduce visible noise in the final image. The reason for this improvement is that ISO amplification only amplifies noise produced in the early stages before the ISO circuitry, but it does not amplify noise added afterwards (A/D converter).

Regarding the optimum mix of the RGB RAW channels to have a lowest noise B&W image, I did some calculations time ago and concluded that if a channel has a lower RAW exposure than other in the RAW file, there is always an optimal mix value depending on the RAW exposure of the channels to be mixed that will maximise SNR improvement. Of course this mix is independent of the desired channel combination to obtain the preferred contrast and luminance representation in the final B&W image, we are just talking about minimising visible noise in the final B&W image

Regards