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02-19-2007, 08:51 PM   #1
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smc Takumar RAW balance

I'm really pleased with the sharpness of my old m42 smc Takumar 55mm f2.0 lens.

The problem is everything is pretty flat using this lens. Are there profiles for these old lenses or perhaps just a guideline of what curve adjustments work best when converting from RAW?

I'm extremely color deficient so, while I can get it close, it will take me a while to do so.

02-19-2007, 10:33 PM   #2
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Tom,

Probably no public profiles.

There are a couple of methods for matching colors-well it's actually one method with two implementations. It's in a book called Real World Camera RAW-I'll get you the full citation if you want.

Basically you shoot a standard reference target called the ColorChecker from MacBeth saving the image as RAW. Then working from the 'known values of the gray patches you repeatedly adjust the exposure and tint sliders in ACR until you get a close match.

You repeat this procedure with the green, red and blue patches adjusting the color sliders as you repeatedly re-convert from RAW. It may take two or three iterations. And several hours.

Tom Fors of Chromoholics(sp) has a java script that runs in PScs1 and 2 that uses a nth order simplex optimization routine and does the same thing in about 90 minutes on the typical p4 machine @2.3-3Ghz clock speed. The script may need some tweaking to run with ACR3.6 and 3.7. For 3.6 it needs two additional lines of code; haven't looked into 3.7 yet.

These will get you the most accurate colors possible assuming you use one of the four PS working spaces.

There are an endless series of PS tweaks that you can use to 'boost' color. Two that have found general acceptance are a straight RGB curves adjustment-basically changing the response from straight line to a lazy or gentle 's' shape. And then in L-a-b space to directly steepen the a and b channels via the same curves type dialog followed by an L channel sharpening.

Less effective is a direct saturation bump or hue shift. Books by Kelby, Evening, Eismann, Fraser and others contain all the gory details-I can provide those references if you like.
02-20-2007, 12:31 AM   #3
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Original Poster
QuoteOriginally posted by jfdavis58 Quote
Tom,

Probably no public profiles.

There are a couple of methods for matching colors-well it's actually one method with two implementations. It's in a book called Real World Camera RAW-I'll get you the full citation if you want.
Thank you. That's exactly what I'm looking for.

How long is the passage? If it's more than a two or three paragraphs, I prefer to buy the book.
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