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Old Aug 31, 2010, 3:39 AM   #211
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The problem I found with denoising first is that you can lose too much fine detail in the dark areas. If you want to denoise first it's better to use something much more sophisticated like Topaz Denoise.

Clipping is minimal - when it stretches the local histograms there is no clipping. It then has a final step where it stretches the global histogram which expands the middle 99.8% of pixels to cover the full range. It's not an essential step but helps on some images which are heavily over or under exposed.

I'd disagree with one point about multiple EVs - if you can get the alignment perfect then they give less noise becuase the noise is effectively smoothed.

But I do think that single image HDR is the way forward - whatever software you use for it - we just need cameras which can capture a wider range in a single shot.
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Old Aug 31, 2010, 5:33 PM   #212
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This is the smoke stack monoliths of the skeletal remains of what was once Bethlehem Steel in Lackawana. The first is the original and the second with Martins Program.
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Old Sep 1, 2010, 1:27 AM   #213
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Quote:
Originally Posted by MartinSykes View Post
The problem I found with denoising first is that you can lose too much fine detail in the dark areas. If you want to denoise first it's better to use something much more sophisticated like Topaz Denoise.

Clipping is minimal - when it stretches the local histograms there is no clipping. It then has a final step where it stretches the global histogram which expands the middle 99.8% of pixels to cover the full range. It's not an essential step but helps on some images which are heavily over or under exposed.

I'd disagree with one point about multiple EVs - if you can get the alignment perfect then they give less noise becuase the noise is effectively smoothed.

But I do think that single image HDR is the way forward - whatever software you use for it - we just need cameras which can capture a wider range in a single shot.
Where I have dark areas in a photo I always remove the chroma noise first, which is very quick. Chroma noise is very obvious in the final image, especially in dark areas. I generally don't bother waiting around for a full noise removal. Full noise removal needs a lot of stuffing around, whichever of the various algorithms you choose. It always needs time to choose optimal parameters to avoid losing detail as you say.

I usually stretch the histogram to 99.9%, ie 0.1% clipping, to increase contrast. More care is need with people in the photo, to get good skin tones. 0.1% or .2% makes a very big difference compared to zero because histograms usually have a long thin tail in most images.

I posted an example way back (sunset over lake) where no one was able to get a better result with multiple exposures, compared to the single RAW. All the multiple exposure HDR attempts lost detail. A 10 micron (20 times the wavelength of light) movement of the camera will completely overlap 2 adjacent pixels. I find it hard to image keeping the camera, scene and image alignment accurate to this degree. Movement cannot improve an image, is can only degrade image quality.

For this reason, single images are always to be preferred over multiple images, except in the very rare circumstances that demand it. Even in these situations, thinking about the photo can be useful, such as by using gradient filters or infill flash with perhaps shorter exposures for example.
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Old Sep 26, 2010, 10:20 AM   #214
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v1.112 just uploaded features much better built-in noise reduction to the point where I don't automatically have to run it through Topaz in most cases. The new algorithm does a much better job of smoothing the noise while retaining the detail. Example 200% crop below shows v1.112 on the left and v1.11 on the right, both using 'soft' smoothing. It should be clear in the top example that the detail in the fabric is retained much better but the noise has been completely removed from the sheet of paper behind.

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Old Sep 26, 2010, 11:41 AM   #215
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I can only say amazing.
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Old Sep 26, 2010, 3:08 PM   #216
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Martin, just the program I was looking for. Thank You so much, it's great. Keep up the great work
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Old Sep 26, 2010, 5:52 PM   #217
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Excellent work, Martin. I'm impressed.

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Old Sep 28, 2010, 12:00 AM   #218
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The top of the cheek and bridge of the nose look as though the noise removal has been taken too far. There's an interesting tutorial I saw somewhere that shows how adding a bit of white noise back in, can make the picture look more realistic after noise removal.
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Old Sep 28, 2010, 2:26 AM   #219
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It's been further improved in 1.14 to leave more detail in. I'm finding it works better than topaz in some situations because it uses the information from the original image to smooth the final one whereas topaz only has the final image to work with. I'll have a look at adding uniform noise back in as well though thanks.
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Old Sep 29, 2010, 8:20 AM   #220
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I've made a start on some online documentation. It's accessible from a link on the main page: http://www.autohdr.co.uk

I'll link it into the next version of the program. C&C on the help pages welcome.

Edit: v1.116 released with better extraction of details and better handling of noise. Forgot to link to the help. doh!
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