RetouchPRO

Go Back   RetouchPRO > Technique > Photo Retouching
Register Blogs FAQ Site Nav Search Today's Posts Mark Forums Read


Photo Retouching "Improving" photos, post-production, correction, etc.

Curve of a curve of a curve...

Reply
 
Thread Tools
  #31  
Old 04-14-2015, 12:33 PM
skoobey skoobey is offline
Senior Member
 
Join Date: Jan 2012
Posts: 1,376
Re: Curve of a curve of a curve...

Quote:
Originally Posted by Doug Nelson View Post
By that logic images can't have shadows, either. That way madness lies.
It can be a shadow, if you're describing a shadow in the image, but calling the black dress a shadow, when it's just a dark tone ain't right. That same black dress can have shadows in it, or cast a shadow, though.
Reply With Quote top
  #32  
Old 04-14-2015, 01:56 PM
andrewrodney's Avatar
andrewrodney andrewrodney is offline
Senior Member
 
Join Date: May 2010
Location: Santa Fe
Posts: 1,091
Re: Curve of a curve of a curve...

Quote:
Originally Posted by skoobey View Post
It's like baking, adding to much salt, and then adding sugar to make it less salty won't result in the initial meal.
Excellent analogy.
Reply With Quote top
  #33  
Old 04-14-2015, 02:02 PM
andrewrodney's Avatar
andrewrodney andrewrodney is offline
Senior Member
 
Join Date: May 2010
Location: Santa Fe
Posts: 1,091
Re: Curve of a curve of a curve...

Quote:
Originally Posted by Doug Nelson View Post
It shall be known as a shibboleth, along with blurred skin, screen DPI, and sRGB, to differentiate the US from the THEM
Add another digital imaging urban legend I hear nearly every day: all images intended for printing have to be 300DPI. Not only is that value not necessarly correct or even necessary, our images are made of pixels, not dots. But whatever.
Reply With Quote top
  #34  
Old 04-14-2015, 04:16 PM
klev klev is offline
Senior Member
 
Join Date: Jun 2010
Posts: 1,109
Re: Curve of a curve of a curve...

Quote:
Originally Posted by Doug Nelson View Post
Obviously they don't cancel each other, as we both just demonstrated. But shouldn't they cancel out in theory? If +delta = -delta, shouldn't you end back up with the original value? So therefore any introduced difference is all on Photoshop?
I suggest consulting a book on numerical analysis and/or fixed point math, because even in theory it doesn't always work that way. As John pointed out it uses splines, which aren't exactly linear mappings. Even if we restricted this to operations that specifically use linear mappings, they aren't always invertible. You lose some amount of additional stability due to numerical rounding, but that's just an additional detail. An example of a linear mapping would be a conversion between color spaces, but even these aren't completely isomorphic, as they often contain different boundary conditions that are resolved by some sort of clamping, typically performed at each stage of computation.


Quote:
Originally Posted by Doug Nelson View Post
John:

So the inverse curve point to 64,32 would not be 64,96 but rather 32,64?

Using this curve gives similarly changed results.

It's impossible to know every step that occurs under the hood there, although I can make guesses. As I mentioned it doesn't have any symbolic utilities, as it's not mathematica. In theory
Reply With Quote top
  #35  
Old 04-14-2015, 04:30 PM
skoobey skoobey is offline
Senior Member
 
Join Date: Jan 2012
Posts: 1,376
Re: Curve of a curve of a curve...

Quote:
Originally Posted by andrewrodney View Post
Add another digital imaging urban legend I hear nearly every day: all images intended for printing have to be 300DPI. Not only is that value not necessarly correct or even necessary, our images are made of pixels, not dots. But whatever.
This reminds me when client called me panicking how the 20mpix files I've sent her are too small. Turns out she doesn't understand difference between DPI and resolution.
Reply With Quote top
Reply

  RetouchPRO > Technique > Photo Retouching


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to make a live curve in photoshop... Eedmonam Photo Retouching 14 04-26-2015 02:10 AM
Fair skin curve Matilda Photo Retouching 2 06-28-2013 09:14 PM
Position vacant - Curve Digital Ltd Noodles Classifieds 0 06-03-2013 07:13 AM
Robert Randall mglover92 Photo Retouching 20 03-03-2012 10:45 AM
Did you know this about the S curve? I didn't! Rexx Photo Restoration 15 04-11-2005 07:10 AM


All times are GMT -6. The time now is 02:55 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
SEO by vBSEO ©2011, Crawlability, Inc.
Copyright © 2016 Doug Nelson. All Rights Reserved