It will probably take me a month to absorb this. Right now I'm busy
trying to recover my print sizing screw ups for my daughter's collage
project. My brain must have been elsewhere when I sized them.
Chuck Norcutt
Fernando Gonzalez Gentile wrote:
> You've answered a question I hadn't yet imagined :-)
>
> Well, this is what's been puzzling me:
>
> I've been doing USM and LCE the way I learned here.
> After you posted the link
> <http://www.luminous-landscape.com/tutorials/high-pass-sharpening.shtml>,
> I went a little further and found something which seemed obvious:
> making the sharpening in the luminance channel only - maybe everyone
> did so and I hadn't noticed.
> Take into account I use film only, and my 'noise' standard is that of
> the 4000ED - nonetheless either DFine or NeatImage 'find' it noisy,
> specially if I play with NikonScan curves to balance color and contrast,
> or use Nikon Scan UnsharpMask.
>
> Found this very clever
> <http://www.luminous-landscape.com/tutorials/instant_photoshop.shtml>:
> "Go to *Image / Mode / Lab Color* and then *Window / Show Channels*. In
> the *Channels *palette select the *Lightness channel*. Now choose
> *Filter / Sharpen / Unsharp Mask*."
>
> _ and I felt happy for a couple of days, until found this thread:
> <http://www.luminous-landscape.com/forum/lofiversion/index.php/t28753.html>
>
> Wow - if there's trouble when going to sRGB from Adobe RGB '98 (
> "conversion *intents*" ) - it should be worse when going from RGB to
> Lab, and coming back to RGB !!!.
> Thanks to Ken, I had scanned another Velvia 50 cactus and nailed in the
> green, but sharpened in Lab. Found nothing too wrong, ignorance still
> bliss, I hadn't found that thread yet. Maybe you could make the effort
> and glimpse for a second or two this huge Flickr file - I won't feel bad
> if you refuse:
> small: <http://www.flickr.com/photos/fernando_gonzalez_gentile/3096675514/>
> large:
> <http://www.flickr.com/photos/fernando_gonzalez_gentile/3096675514/sizes/o/>
> (tripod mounted 65-116, 135/4,5 @8, maybe 1:10x, OM 2n on Auto mode
> +1/3, Velvia 50, perceptual intent conversion to sRGB, NeatImage).
>
> OK, despite it looks right for me, the rationale of a round trip to Lab
> is confusing. I don't completely understand Lab, and feel too lazy to
> read Dan Margulis books (http://en.wikipedia.org/wiki/Dan_Margulis).
>
> Months ago, Chuck posted another tutorial - which I found one of the
> most useful:
> Found in <http://www.cambridgeincolour.com/tutorials/unsharp-mask.htm>
> this advice:
>
> _Remedies_: Color shifts can be avoided entirely by performing the
> unsharp mask within the "lightness" channel in LAB mode.
> **A better technique, which avoids converting between _color spaces
> <http://www.cambridgeincolour.com/tutorials/color-spaces.htm>_ and
> minimizes posterization
> <http://www.cambridgeincolour.com/tutorials/posterization.htm>, is to**:
> 1) Create a duplicate layer
> 2) Sharpen this layer like normal using the unsharp mask
> 3) Blend sharpened layer with the original using "luminosity" mode in
> the layers window
>
> Tried it two days ago on a .jpg out my 720SW - it works nice too.
>
> What I now feel reluctant to use is the traditional USM - I'm beared
> towards 'sharpeining' in the Luminance channel - so:
>
> 1- the 'high pass' technique - is or is not related to Luminance
> channel: seems so.
> 2- Lab .... ?
> 3- Blending sharpened layer using Luminosity Mode ... subtle sharpening
> and have two sliders to play with, which I didn't understand yet.
>
> Last:
> 1- what if I do nothing in NikonScan, except ICE, and work anything in CS3.
> 2- *when* in the workflow do I apply Luminance sharpening. If I have
> amusing color shifts while USMasking this was a non issue ... but this
> is getting more complex, isn't it ?
>
> TIA
>
> Fernando
>
>
> Chuck Norcutt wrote:
>> I hope that answered the question you haven't yet asked. :-)
>>
>> Chuck Norcutt
>>
>
>
>
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