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Author Topic: Synthetic HDR  (Read 25402 times)
st326
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« Reply #40 on: March 31, 2007, 01:16:52 AM »
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The mathematics of lower quantization errors might be clear to you, but this issue won't be resolved for me in practical terms until you can provide a RAW file that will open in ACR and preferrably RSP as well. I don't suppose you could borrow a Canon 5D and take a shot of a particularly contrasty scene, could you?   
[attachment=2209:attachment]  [attachment=2210:attachment]
[{POST_SNAPBACK}][/a]

OK,

[a href=\"http://findatlantis.com/untitled_508.dng]http://findatlantis.com/untitled_508.dng[/url]

Knock yourself out! :-)
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Ray
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« Reply #41 on: March 31, 2007, 01:58:26 AM »
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OK,

http://findatlantis.com/untitled_508.dng

Knock yourself out! :-)
[a href=\"index.php?act=findpost&pid=109827\"][{POST_SNAPBACK}][/a]

I suppose I've got the role of Devil's Advocate here   . It'll take a while to download through my 56k modem, so don't expect a quick reply   .
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Forsh
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« Reply #42 on: March 31, 2007, 02:23:57 AM »
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I have been using this method for a few months to extract all of the exposure I can out of single shots, then tonemapping them back. I call it "HDR Lite"  
I am heading back to Okinawa Japan.
I extract the full exposure to an exr, then tonemap it back to a 16-bit TIFF

Examples:


Peace prayer park



Bise Okinawa
« Last Edit: April 15, 2009, 06:15:22 AM by Forsh » Logged

Futenma Shrine My HDR Photography from Okinawa Japan.  | okinawa japan Other from Okinawa Japan. So what do you do? You don't want create a scene as they can call upon their members beating you down with their home made reflectors in nanoseconds, and creating an international incident over a pix of the rare Zebra butterfly is probably not a great idea.
st326
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« Reply #43 on: March 31, 2007, 02:33:19 AM »
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I have been using this method for a few months to extract all of the exposure I can out of single shots, then tonemapping them back. I call it "HDR Lite"   

I extract the full exposure to an exr, then tonemap it back to a 16-bit TIFF


[a href=\"index.php?act=findpost&pid=109832\"][{POST_SNAPBACK}][/a]

Very impressive images -- really striking. You have something there.
« Last Edit: March 31, 2007, 02:34:27 AM by st326 » Logged
Ray
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« Reply #44 on: March 31, 2007, 08:48:00 AM »
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Sarah,
I thought you were going to send me the RAW of the first image so I could see how good I could make the shadows.

The image you sent me is quite nice; a bit like the moon really. Maybe not   .

There are no noisy shadows despite the image being underexposed by a couple of stops, so that's a testament to the high dynamic range of your camera.

So what's the procedure here? I send you my attempt at a reasonable rendition using standard procedures of selection, levels and curves (and a bit of local contrast enhancement) and you send me your tone-mapped version? Right?

[attachment=2211:attachment]  [attachment=2212:attachment]
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Tim Gray
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« Reply #45 on: March 31, 2007, 12:15:16 PM »
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I'm with Ray here.  There is no clipping in this image - just under exposed.  I'm not seeing where the standard PS tools and techniques are falling short.

[attachment=2213:attachment]
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st326
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« Reply #46 on: March 31, 2007, 02:58:04 PM »
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I'm with Ray here.  There is no clipping in this image - just under exposed.  I'm not seeing where the standard PS tools and techniques are falling short.

[attachment=2213:attachment]
[a href=\"index.php?act=findpost&pid=109887\"][{POST_SNAPBACK}][/a]

I'm with you *and* Ray. It's the wrong image.   It was late, what can I say other than mea culpa...

(The image I did put up was the first of a series of shots before I'd got the exposure adjusted -- I always use manual exposure, and don't bother with a light meter when I'm shooting digital, just under/over clipping indication, and I typically don't make any attempt to place the mid tones where they would be in a final print either, so my raw images look a bit weird to people who aren't used to working the way I do. The location was Arizona, it's the painted desert, but it looks weird because there was snow on the ground. I could probably claim it was Mars or Titan, but no, just Arizona. :-) )
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st326
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« Reply #47 on: March 31, 2007, 03:45:27 PM »
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I'm with you *and* Ray. It's the wrong image.   It was late, what can I say other than mea culpa...

(The image I did put up was the first of a series of shots before I'd got the exposure adjusted -- I always use manual exposure, and don't bother with a light meter when I'm shooting digital, just under/over clipping indication, and I typically don't make any attempt to place the mid tones where they would be in a final print either, so my raw images look a bit weird to people who aren't used to working the way I do. The location was Arizona, it's the painted desert, but it looks weird because there was snow on the ground. I could probably claim it was Mars or Titan, but no, just Arizona. :-) )
[a href=\"index.php?act=findpost&pid=109913\"][{POST_SNAPBACK}][/a]

OK, it's up there now. Same link as before (I had two images with the same name and picked up the wrong one -- that'll teach me to reset the counter).

In other news, the plugin is coming along. It builds and installs in Photoshop CS2, but doesn't actually do anything much yet. The algorithm is relatively simple, so it should be fairly straightforward from here (actually, creating a plugin and getting it to load is a major pain and rather more of the job than it really should be). Initially there will only be a Windows version because I don't actually own a Mac suitable for doing the port, but I think I can probably borrow one temporarily if there is any interest in having a Mac version.
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Tim Gray
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« Reply #48 on: March 31, 2007, 04:32:17 PM »
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fun...

converted in LR and traditional PS stuff (nothing third party)  
2 tiffs processed from original
masked with ctrl alt ~

[attachment=2214:attachment]
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st326
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« Reply #49 on: March 31, 2007, 09:42:53 PM »
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The plugin is now available at

http://findatlantis.com/wiki/index.php/Synthetic_HDR

It basically does what I intended in the first place, and gives far, far better results than the do-it-yourself Photoshop approach. The plugin version has no effect on the overall tonality of the image, nor does it require to know anything about the black level (it actually works across the entire tonal range). It also uses round convolution kernels, so the square-edged artifacts in the old images are also now entirely gone.

I'm currently working on the web pages for it, but it's already up there for download if anyone wants to play with an early alpha-test version. I'll post some example images shortly -- I'm quite pleased with the results I've seen so far.

Tweaking the controls:

The Amount box, in effect, sets the dividing line between the source image, which is kept sacrosanct and unaltered, and the deeper bit depth information that is calculated on the fly. Small settings of Amount favour the source image, higher settings favour the generated data. The plugin automatically selects between 3x3, 5x5 and 7x7 convolution kernels on a per-pixel basis.

The noise reduction settings basically do despeckling on what comes out of the main algorithm. The best approach seems to be to set Amount to a point where you just see a small amount of 'salt and pepper' noise with noise reduction off, then use the same value again with noise reduction set to strong. What it does is kind-of analogous to median filtering, but isn't actually implemented anything like it.

In a future version, rather than a hard dividing line between interpolated and source image data, there will probably be a softer-kneed transfer curve which should make this kind of artifact far less visible.

Caveats:

0. This is alpha test software. Expect a few rough edges. I didn't start coding it until last night, so this really is a first-chance-to-see.

1. The preview image is currently pretty much useless and not really indicative of what you'll get, so don't pay much attention to it.

2. Currently, it doesn't affect the outer two rows of pixels around the image. This is fiddlier to fix than it sounds, so I decided to leave it for the next release because it doesn't really get in the way of experimentation.

3. Selection masks are currently ignored -- the plugin affects the entire image.

4. It only currently works properly for 16-bit images.
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st326
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« Reply #50 on: March 31, 2007, 10:13:37 PM »
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fun...

converted in LR and traditional PS stuff (nothing third party) 
2 tiffs processed from original
masked with ctrl alt ~

[attachment=2214:attachment]
[a href=\"index.php?act=findpost&pid=109925\"][{POST_SNAPBACK}][/a]

Looks like a pretty decent job there, Tim.
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st326
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« Reply #51 on: March 31, 2007, 11:54:45 PM »
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Sample output from the plugin

It's important to state that the plugin does not give equivalent results to the Photoshop method mentioned elsewhere in these pages -- rather, it goes to extremes to exactly preserve the tonality of the original image. For example, here's an original image, straight from the camera:



Running the plugin over it (with settings Amount = 50%, Noise Reduction = Strong), you get:



There are no prizes for pointing out that there is no appreciable difference between the two. This is the general idea -- the algorithm has near-negligible effect on the tonality or detail present in the original image. However, if you look into the shadow areas (with the brightness and contrast enhanced with Levels) you see what the plugin has actually done:



Unmodified image, 100% crop from the bottom right corner



Result from the Synthetic HDR plugin, same 100% crop and Levels adjustments

Whilst the original image shows unacceptable levels of noise and posterisation (at least to my eyes, your mileage is welcome to vary), the synthetic HDR image looks more like a deeper dynamic range version of the same image, with a little film-like grain. This effect covers the whole image through all tones, not just the shadow areas.


Relationship to 'traditional' HDR

The intent of the Synthetic HDR plugin is a little different to the HDR photography community, though it's certainly possible to borrow techniques in both directions. The main aim of synthetic HDR is to give images more usable dynamic range, allowing greater manipulation of contrast in post-processing than would normally be the case. It is certainly possible to borrow traditional HDR techniques like tone mapping, however:



Tone mapped image created by applying local adaptation in CS2

Though this image isn't particularly to my taste aesthetically, it does show off the smooth shadow detail pretty well.
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Ray
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« Reply #52 on: April 01, 2007, 03:06:13 AM »
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Thanks for sharing your plug-in, Sarah. I'll give it a try but I'm already getting the impression that whilst there is a perceptible reduction in noise in the shadows, it's pretty small. Shall we say, of pixel-peeping proportions.

Below are 2 crops side by side. The second has been converted in PS3 with luminance smoothing set at 80. The first is your original tone-mapped image. I applied a small and equal amount of sharpening with Focus Magic to both images.

The question is, if I use your plug-in on the conversion with luminance smoothing, will the noise reduction be more significant?
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st326
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« Reply #53 on: April 01, 2007, 03:14:57 AM »
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Thanks for sharing your plug-in, Sarah. I'll give it a try but I'm already getting the impression that whilst there is a perceptible reduction in noise in the shadows, it's pretty small. Shall we say, of pixel-peeping proportions.

Below are 2 crops side by side. The second has been converted in PS3 with luminance smoothing set at 80. The first is your original tone-mapped image. I applied a small and equal amount of sharpening with Focus Magic to both images.

The question is, if I use your plug-in on the conversion with luminance smoothing, will the noise reduction be more significant?
[a href=\"index.php?act=findpost&pid=109997\"][{POST_SNAPBACK}][/a]

I don't know, try it.

Yes, the plugin's effect is subtle. Thats basically the idea -- it doesn't have anything like the level of artifacts of most denoising algorithms, and those that it does have look relatively pleasant. It also has (almost) no effect whatsoever on detail, particularly around edges, which is pretty much exactly what the standard algorithms all screw up on.

It actually works on the entire tonal range, not just in the shadows, though that's less obvious in this test image. Actually, I don't want it's effect to be obvious, ever -- I just want images to look extremely smooth and stand up to plenty of contrast tweaking in postproduction, without having nasty digital-looking artifacts from overenthusiastic median filtering.

Forget the original tone-mapped image, it's way inferior to the result from the plugin. Feel free to use the plugin to make your own, or give me a prod and I'll send you a full res image that you can take a look at.
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Ray
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« Reply #54 on: April 01, 2007, 04:59:30 AM »
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Forget the original tone-mapped image, it's way inferior to the result from the plugin.
[a href=\"index.php?act=findpost&pid=110000\"][{POST_SNAPBACK}][/a]


In that case, I won't bother displaying the crops that have almost identical shadow noise. (I think the image I tried to attach to the previous post might have been too big).

I've downloaded your plug-in but where do I put it? Copying and pasting into the plug-ins folder doesn't seem to do anything.
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st326
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« Reply #55 on: April 01, 2007, 05:01:57 AM »
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In that case, I won't bother displaying the crops that have almost identical shadow noise. (I think the image I tried to attach to the previous post might have been too big).

I've downloaded your plug-in but where do I put it? Copying and pasting into the plug-ins folder doesn't seem to do anything.
[a href=\"index.php?act=findpost&pid=110003\"][{POST_SNAPBACK}][/a]

What version of PS are you using and on what operating system? It's built with the CS2 SDK, so I've no idea what other version(s) it might run with, if any. It could be that you're missing something that's there on mine. Also, you have to completely exit PS and then start it again in order to have it check for plugins.
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Ray
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« Reply #56 on: April 01, 2007, 05:13:12 AM »
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What version of PS are you using and on what operating system? It's built with the CS2 SDK, so I've no idea what other version(s) it might run with, if any. It could be that you're missing something that's there on mine. Also, you have to completely exit PS and then start it again in order to have it check for plugins.
[a href=\"index.php?act=findpost&pid=110004\"][{POST_SNAPBACK}][/a]

I've got a CS2 and CS3 versions on my Win XP x64 machine and CS2 on a 32 bit computer. The trouble is, this plug-in file of yours doesn't look like the usual plug-in format. If I paste it into the plug-ins folder, where am I supposed to find it when I open PS?
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st326
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« Reply #57 on: April 01, 2007, 01:59:48 PM »
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I've got a CS2 and CS3 versions on my Win XP x64 machine and CS2 on a 32 bit computer. The trouble is, this plug-in file of yours doesn't look like the usual plug-in format. If I paste it into the plug-ins folder, where am I supposed to find it when I open PS?
[a href=\"index.php?act=findpost&pid=110006\"][{POST_SNAPBACK}][/a]

You have unzipped it from the zip archive, yes? You should get a file synhdr.8bf inside, that's all you need. It's a 32-bit executable.

When you open PS, you (should) see a 'FindAtlantis' entry down toward the bottom of your Filters menu. It's in there, or should be anyway.
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Ray
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« Reply #58 on: April 01, 2007, 04:12:22 PM »
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You have unzipped it from the zip archive, yes? You should get a file synhdr.8bf inside, that's all you need. It's a 32-bit executable.
[{POST_SNAPBACK}][/a]

Ah! A zip file. When you wrote, the plug-in is available at [a href=\"http://findatlantis.com/wiki/index.php/Synthetic_HDR]http://findatlantis.com/wiki/index.php/Synthetic_HDR[/url] , I thought that was the plug-in. It seems I just downloaded your 14kb Wiki page.

You see, I'm not all that conversant with computers   . Thanks for your trouble. I now see the plug-in at the bottom of the filters menu. I'll try it out on a few noisy high ISO images.
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bjanes
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« Reply #59 on: April 02, 2007, 01:27:17 PM »
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I have been using this method for a few months to extract all of the exposure I can out of single shots, then tonemapping them back. I call it "HDR Lite"   

I extract the full exposure to an exr, then tonemap it back to a 16-bit TIFF

Examples:

Forsh,

Your examples are striking, and I especially like the first image of the young woman. What software do you use to extract the full exposure to the exr and to do the tone mapping?

Bill
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