Comments on: Nonlinear Curve Adjustments and Histograms http://blog.epicedits.com/2010/02/12/nonlinear-curve-adjustments-and-histograms/ A Resource and Community for Photography Enthusiasts Tue, 07 Sep 2010 02:27:23 +0000 hourly 1 http://wordpress.org/?v=3.0 By: My Camera World http://blog.epicedits.com/2010/02/12/nonlinear-curve-adjustments-and-histograms/comment-page-1/#comment-140332 My Camera World Sat, 13 Feb 2010 14:06:11 +0000 http://blog.epicedits.com/?p=3689#comment-140332 Here is another tip in using curves to adjust a local spot. I first open a curves dialog box and focus on just the area I want to change and make the changes. This will at times change similar tones in other parts of the image but that will be corrected with a mask. I then add another curves on top of this one (just temporary) and make this more extreme in changes. Makes mask edges easier to detect. I now mask of the best I can using many tools such as wand, or Colour channels and sometimes I will even bring in an ACR copy of image with changes made to make it easier to extra a mask. Example I will in this copy make the sky over-brighten (lighten blue) and darken edges near sky (if green darken yellow and green). Then I use wand to select. With the curves at extreme settings I now work the rough edges of the mask and blur for best effect. It doesn’t look right at the moment but when I remove this extreme curve the normal curve with mask looks almost perfect. I always use the extreme curve to check edges and it amplifies any problems that are barely visible at normal curve settings and therefore hard to get right. Niels Henriksen Here is another tip in using curves to adjust a local spot.

I first open a curves dialog box and focus on just the area I want to change and make the changes. This will at times change similar tones in other parts of the image but that will be corrected with a mask.

I then add another curves on top of this one (just temporary) and make this more extreme in changes. Makes mask edges easier to detect.

I now mask of the best I can using many tools such as wand, or Colour channels and sometimes I will even bring in an ACR copy of image with changes made to make it easier to extra a mask.

Example I will in this copy make the sky over-brighten (lighten blue) and darken edges near sky (if green darken yellow and green). Then I use wand to select.

With the curves at extreme settings I now work the rough edges of the mask and blur for best effect. It doesn’t look right at the moment but when I remove this extreme curve the normal curve with mask looks almost perfect.

I always use the extreme curve to check edges and it amplifies any problems that are barely visible at normal curve settings and therefore hard to get right.

Niels Henriksen

]]> By: Brian Auer http://blog.epicedits.com/2010/02/12/nonlinear-curve-adjustments-and-histograms/comment-page-1/#comment-140303 Brian Auer Sat, 13 Feb 2010 06:48:42 +0000 http://blog.epicedits.com/?p=3689#comment-140303 @Niels: Great tips! I'm thinking of wrapping this mini-series up with a post about tips, tricks, and things to avoid when dealing with curves. The trick you mention is definitely worth reiterating. @Janne: Absolutely! There's usually more than one way to accomplish the same task with the available tools. One benefit of applying a levels adjustment prior to a curves adjustment is that you have more range to work with in the curves. This is generally beneficial, but I figured I would show the various capabilities of the curve dialog in this series. Maybe we should have started the discussion with levels, eh? ;) @Niels: Great tips! I’m thinking of wrapping this mini-series up with a post about tips, tricks, and things to avoid when dealing with curves. The trick you mention is definitely worth reiterating.

@Janne: Absolutely! There’s usually more than one way to accomplish the same task with the available tools. One benefit of applying a levels adjustment prior to a curves adjustment is that you have more range to work with in the curves. This is generally beneficial, but I figured I would show the various capabilities of the curve dialog in this series. Maybe we should have started the discussion with levels, eh? ;)

]]> By: Janne http://blog.epicedits.com/2010/02/12/nonlinear-curve-adjustments-and-histograms/comment-page-1/#comment-140300 Janne Sat, 13 Feb 2010 06:28:17 +0000 http://blog.epicedits.com/?p=3689#comment-140300 It's perhaps worth noting that "single bend curves" like the ones you show are essentially the same as "gamma adjustment". In Gimp there's a very convenient "edit these settings as a curve" button in the Colors->Levels dialog. You can set the black point and white point, and the gamma there, then do fine adjustments of the resulting curve in the Curves tool. It’s perhaps worth noting that “single bend curves” like the ones you show are essentially the same as “gamma adjustment”.

In Gimp there’s a very convenient “edit these settings as a curve” button in the Colors->Levels dialog. You can set the black point and white point, and the gamma there, then do fine adjustments of the resulting curve in the Curves tool.

]]> By: My Camera World http://blog.epicedits.com/2010/02/12/nonlinear-curve-adjustments-and-histograms/comment-page-1/#comment-140256 My Camera World Fri, 12 Feb 2010 21:43:05 +0000 http://blog.epicedits.com/?p=3689#comment-140256 This method allows better control on specific tonal sections within the image as opposed to the nonlinear, which affects almost the whole range. One thing I like to do is with the curves dialog box is to use mouse over the image and by left-clicking I can see where on the curve the particular tone lies. An then when I want to adjust it, I use Alt key and left-click to set a specific spot from the image as a control point on the curves. I may then add some points outside this range to lock changes, while I manipulate between the 2 set points. Niels Henriksen This method allows better control on specific tonal sections within the image as opposed to the nonlinear, which affects almost the whole range.

One thing I like to do is with the curves dialog box is to use mouse over the image and by left-clicking I can see where on the curve the particular tone lies. An then when I want to adjust it, I use Alt key and left-click to set a specific spot from the image as a control point on the curves. I may then add some points outside this range to lock changes, while I manipulate between the 2 set points.

Niels Henriksen

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