B&W Photo Enhancement.
December 21, 2007 7:39 PM Subscribe
I need to enhance facial detail in a 70 year old B&W 120 negative. The negative is both underexposed and out of focus. I am using PS Elements 3.0. I also have Photoshop 7. I will be using a Canoscan 8400F scanner. I can go to a local pro and have the negative scanned on his Epson V750 for $$$$$ if needed. What are good texts that can explain the mechanics of image enhancement? Any advantage in upgrading Elements? My computer does not have an internet connection and I do not need any of the net connected features that seem to be the reasons for upgrading Elements. I can also live with the 3.0 poor cataloging.
Don't get your hopes up too far. There are limits to what can be accomplished with post processing. You won't be able to recreate an image as it would have been if the camera had been properly focused.
This google search turns up several pages which may be of use to you. This one looks particularly decent.
But this kind of filter can only work with what is present, making things you may not be able to discern visible, and making things you can see more visible. Information that is lost, or was never captured, is gone forever. (Getting it back turns out to be isomorphic to inventing perpetual motion. Papa Shannon showed that it violates the Laws of Thermodynamics.)
To give you an example I just created, this is what you wish the original photo was like, right? Nice and sharp, lots of detail. Unfortunately, this is what you actually have. Perhaps not quite that blurred, but that's the general way it looks.
Information has been lost in that second one. There's no way to get it back. The easy way to tell that is to compare the sizes of those two PNG files. PNG is lossless and compressed. The resulting file is within a few percent of having an entropy of 1 because it uses Huffman encoding, which is very good. (That's why when you put a PNG file inside a ZIP it doesn't compress much; it's already compressed.)
The first file has a size of 96K. The second one is 34K.
It's possible to apply an unsharp mask to the second image, but the result is really rather disappointing: light, heavy.
They don't look like the original, and it's impossible to recreate the original from the second image.
posted by Steven C. Den Beste at 9:24 PM on December 21, 2007
This google search turns up several pages which may be of use to you. This one looks particularly decent.
But this kind of filter can only work with what is present, making things you may not be able to discern visible, and making things you can see more visible. Information that is lost, or was never captured, is gone forever. (Getting it back turns out to be isomorphic to inventing perpetual motion. Papa Shannon showed that it violates the Laws of Thermodynamics.)
To give you an example I just created, this is what you wish the original photo was like, right? Nice and sharp, lots of detail. Unfortunately, this is what you actually have. Perhaps not quite that blurred, but that's the general way it looks.
Information has been lost in that second one. There's no way to get it back. The easy way to tell that is to compare the sizes of those two PNG files. PNG is lossless and compressed. The resulting file is within a few percent of having an entropy of 1 because it uses Huffman encoding, which is very good. (That's why when you put a PNG file inside a ZIP it doesn't compress much; it's already compressed.)
The first file has a size of 96K. The second one is 34K.
It's possible to apply an unsharp mask to the second image, but the result is really rather disappointing: light, heavy.
They don't look like the original, and it's impossible to recreate the original from the second image.
posted by Steven C. Den Beste at 9:24 PM on December 21, 2007
Try out nik sharpener pro 2.0 for PS - I highly recommend it (for reducing blur and enhancing details). It won't get you super far, but its about as good as you can get without redoing it by hand (another option).
posted by lrodman at 11:29 PM on December 21, 2007
posted by lrodman at 11:29 PM on December 21, 2007
The mechanics of facial detail enhancement in this kind of scenario basically refers to a touch-up artist painting in the missing detail - the information is not in the photograph, so to get significant results those details have to be added. If you have other photos of the subject, you'll have a better idea of what to touch them up to look like, but otherwise, you make them look how you want them to look. Artistic license and all that. Photoshop is the tool to use for this.
What you see in the movies ("computer enhancing" pulling more detail out of thin air) is 98% fantasy.
posted by -harlequin- at 12:35 AM on December 22, 2007
What you see in the movies ("computer enhancing" pulling more detail out of thin air) is 98% fantasy.
posted by -harlequin- at 12:35 AM on December 22, 2007
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Underexposed just makes the final image grainy, or blotchy if it is very underexposed.
Out-of-focus is a real problem though. You can spend a few happy hours messing with the adjustments of the various sharpening filters to try to make something not-too-awful.
Estimate how out-of-focus a point is (does a point in the image look like it became an 8-pixel diameter blob) and use that in the unsharp masking filter. (Or if photoshop has a sharpening filter with a settable kernel (the kernel may be a small image, or, echh, a matrix of numbers), use the blob as a kernel). Don't like it? Change the blob a little.
After a while, your idea of 'good enough' should be so degraded you will be delighted with the results :)
posted by hexatron at 8:59 PM on December 21, 2007