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Author Topic: Brightening/Correcting Underexposed Images  (Read 3839 times)

helpful

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Re: Brightening/Correcting Underexposed Images
« Reply #15 on: June 07, 2012, 05:38:54 PM »
Another example of HDR:

First image is original
Second image is Picasa's best attempt at HDR
Third image is HDR applied with the new technique.
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Re: Brightening/Correcting Underexposed Images
« Reply #15 on: June 07, 2012, 05:38:54 PM »

Tammy

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Re: Brightening/Correcting Underexposed Images
« Reply #16 on: June 09, 2012, 01:39:32 PM »
Sorry i'm not posting an image for you to use but I just wanted to let you know that I think your method/software is truly going to be amazing! Even just for use to extract more accurate color/detail/dynamic range from your typically exposed photos.

Any idea on how long we might be looking at till it may be in product stage?
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NotABunny

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Re: Brightening/Correcting Underexposed Images
« Reply #17 on: June 09, 2012, 02:12:25 PM »
I don't understand why you show us photos processed with Picasa.

Here is one of your above photos recovered with 2 sliders in Lightroom 4.1: exposure +1, shadows +80
« Last Edit: June 09, 2012, 02:17:46 PM by NotABunny »

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Re: Brightening/Correcting Underexposed Images
« Reply #18 on: June 10, 2012, 10:19:27 PM »
I don't understand why you show us photos processed with Picasa.

Here is one of your above photos recovered with 2 sliders in Lightroom 4.1: exposure +1, shadows +80

That's very good. I think the colors are a little better with my method. Also, I was just taking a screen shot of Matlab. I will upload the original corrected image for comparison. I have Matlab only in my office, unfortunately, and it's very slow to remote desktop to it.

Other methods can definitely push exposure. I do have Lightroom and the full suite of Photoshop + a lot more from Adobe (not CS 6 yet, however), but I used Picasa because really Google does have good software, and I am not sure how many people on this forum really have all the expensive tools that they should have. Picasa, although free, has many state of the art methods built in, and a much faster database than Lightroom. I have three computers with almost a million photos on each one from the past decade or so, and the rate of pictures needing to be stored is increasing all the time, and I couldn't survive without the speed of Picasa.

However, I think my method, based on true color curves, rather than shifting the histogram, is better. As you know, the histogram becomes choppy when doing these exposure adjustments.

I will also look at the histogram after I upload the original corrected image, and see whether it is less damaged than the histogram from Lightroom after doing the +1 exposure and +80 shadows.

Thanks for taking the time to help with my project!!
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Re: Brightening/Correcting Underexposed Images
« Reply #19 on: June 10, 2012, 10:28:13 PM »
Sorry i'm not posting an image for you to use but I just wanted to let you know that I think your method/software is truly going to be amazing! Even just for use to extract more accurate color/detail/dynamic range from your typically exposed photos.

Any idea on how long we might be looking at till it may be in product stage?

The easiest form for me to let people use it would be through a web page, i.e., uploading an image and then having it processed--being able to select the relative brightness or darkness multiplier; or being able to specify how many stops of + and - exposure to recapture in the HDR processing option.

I am working right now on porting it from Matlab to a C program using libjpeg for compressing and decompressing JPEG images.

Did anyone know that JPEG actually supports all sorts of color curves, and 16-bit per channel color depth all the way up to 64 bit color depth, and that is per channel??

The 8-bit "baseline" JPEGs that everyone is using are just the tip of the ice berg.

JPEGs are truly marvelous because they erase only data that is invisible to the human eye at first (separating the image into chroma and luminance channels), and then erasing more and more data until an 8x8 pixel grid is reduced to a single data point, which is obviously visible to the human eye.

It would be a miracle if cameras started to use gamma curves with JPEG images that had 16-bit color channels plus an extra 16-bit luminance channel. There would be no limit to the processing options then, just a limit to the sensors (16-bits of luminance could store 64,000+ levels of brightness without ANY noise or affect on color accuracy). And it would all fit into 64-bit data value sizes, which is a perfect match for new 64-bit computers (actually 64-bit systems were adopted by mainstream users almost 10 years ago). And the JPEG image compression method would give people the option to store it all at 10:1 compression or greater if they wanted to, without losing any visible information.

And then there would be no more proprietary RAW image formats.


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Re: Brightening/Correcting Underexposed Images
« Reply #20 on: June 10, 2012, 10:45:35 PM »
OK, compare this to the other one from Lightroom (attached). It's actually brightened even more (look at the arm and the sky), and yet there are less visual artifacts. Look at the doghouse, for instance in the dark doorway. Lightroom fails big there.

There are way more blotches in the Lightroom version. I'm sure you could eliminate them by extra post processing / retouching. But my algorithm just keeps colors the way they are... black stays black, green green, etc.

I toggled back and forth between the Lightroom result and my result in this post, and the Lightroom image screams damage from intense post processing all over it, and the one in this post looks more subdued and more like an original. (The artifacts around the legs are actually the result from too much sharpening applied in the original, and they are showing up the same in both the lightroom and my result.)

The sky looks a little less saturated after the HDR effect, but that was partly because I brightened the whole image more, including the sky, and just because I have applied absolutely no other processing to the image.
« Last Edit: June 10, 2012, 10:55:24 PM by helpful »
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Re: Brightening/Correcting Underexposed Images
« Reply #20 on: June 10, 2012, 10:45:35 PM »