Hue Saturation Transformation

Moderator: jsachs

Post Reply
rfuerman
Posts: 59
Joined: April 27th, 2009, 7:27 am
What is the make/model of your primary camera?: sony rx100iii
Location: philadelphia

Hue Saturation Transformation

Post by rfuerman »

Hello.
1) Select Hue Saturation Transformation | select [Show Affected Region] button and the preview display is black. Suggest that the [Select Input + Preview] button should be default view.
2) Select Hue Saturation Transformation | select [Show Affected Region] button and select an area to adjust. [OK] button. Resulting image is the preview window with the [Show Affected Region] button area, that is, much of the image is black because it is not the affected region. Most folks will expect to see adjusted input image when they select [OK] button. Works as expected if deselect the [Show Affected Region] button.
3) Working image has an area of mostly blown out color that I want to adjust.
a) use cursor to select affected region. Other areas of image also very light, so they are selected, also. Saturation, brightness & hue sliders work as expected on affected regions.
b) create a mask to select only the bright area I want to adjust. Select [Show Affected Region] button and mask corresponds to affected area, as expected. Saturation, brightness & hue sliders do NOT adjust the affected, masked region, however.
For me, I think generally it would be easier to use a mask with this tool.
Thank you.
jsachs
Posts: 3692
Joined: January 22nd, 2009, 11:03 pm

Re: Hue Saturation Transformation

Post by jsachs »

I think you may not be using the latest version as I believe I fixed 1 and 2 in the 6-July update.
Jonathan Sachs
Digital Light & Color
rfuerman
Posts: 59
Joined: April 27th, 2009, 7:27 am
What is the make/model of your primary camera?: sony rx100iii
Location: philadelphia

Re: Hue Saturation Transformation

Post by rfuerman »

Aha - you found a way to make me take the update to v309.
3b) With mask to set affected region, I'm not seeing any change with Saturation, brightness & hue sliders. Set both mask amt sliders to 100% and still no change.
3c) Adjust histogram while mask is selected and this does not change affected region. Would histogram change masked part of image, or entire image? If mask is used to select affected region, should histogram be disabled?
4) Hue Saturation 'reset' removes the mask. You can reset mask from mask dialog and the 'amount mask' has a reset option, or adjust both mask amt sliders to 100%. Suggest that transform resets should not remove mask.
jsachs
Posts: 3692
Joined: January 22nd, 2009, 11:03 pm

Re: Hue Saturation Transformation

Post by jsachs »

The Show Affected Region checkbox applies only to those pixels selected by the color and brightness histograms. For these selected pixels, the sliders do show changes and the region changes when you change the selections in the histograms. The mask is ignored as far as Show Affected Region is concerned -- it is used primarily to either scale back the overall effects of the transformation or to exclude some parts from being changed, for example if you only wanted to change colors in the sky. Show Affected Region blacks (or whites) out the unaffected regions and over the entire output image which is then blended back with the input image according to the mask. If you want to see the areas affected by the mask, you can use the Mask dialog box with a color mask overlay. If you invert the mask temporarily, it will hide all but the affected region.

I have been considering for some time adding a Reset all but Mask(s) command to all transformations with one or more mask. Reset can, if you have saved your defaults in a file, restore the saved masks along with the other settings, so making Reset not reset masks would break this feature.
Jonathan Sachs
Digital Light & Color
rfuerman
Posts: 59
Joined: April 27th, 2009, 7:27 am
What is the make/model of your primary camera?: sony rx100iii
Location: philadelphia

Re: Hue Saturation Transformation

Post by rfuerman »

"The Show Affected Region checkbox applies only to those pixels selected by the color and brightness histograms."
That is not what I see. My image has a rectangular area with partially 'blown out' highlights. I want to bump the colors as much as possible in the blown out area. Select Hue & Saturation transform | create mask over the b/o area. Now select the [x] show affected region box. The mask area is covered by the black out region, that is, the mask = affected region. The affected region is *not* selected by histogram. This implies to me that changing the hue, saturation sliders should affect the mask/affected region of the image. But the sliders do not change anything (because the histogram is not set?). So when you say "The mask is ignored as far as Show Affected Region is concerned" then the mask should *not* be covered by the affected region color. But that is not what I am trying to do. I want the mask = affected region.

"Show Affected Region blacks (or whites) out the unaffected regions and over the entire output image which is then blended back with the input image according to the mask." I think you mean to say "Show Affected Region blacks (or whites) out the affected regions"? And I do not understand the 'blended back' part of this sentence.

5) Select Hue & Saturation transform | create mask over the b/o area. Select [x] show affected region and the affected region = mask area. This is what I would expect.
Keep mask; clear [ ] show affected region and adjust histogram for some part of image. Select [x] show affected region and the mask area is still completely blacked out; no effect on unmasked image. I would expect the histogram to affect the masked, affected region, only. That is likely what happens, except the mask already selected the entire region, so histogram has no effect. Is that what is happening?
Adjust mask amt slider to 50% and the affected region = 50%, as expected, but still do not see any histogram impact. Change the histogram does not seem to change the affected region (= mask area in this case).
Seems to me that the mask is not compatible with the histogram selection. Should histogram apply to masked area, only, or to entire image when mask is selected? User can use brightness mask or color range mask to get same affect as histogram in a masked area, no? [ ] show affected region could also be disabled because affected region = mask area. If user uses histogram to select the affected area, what happens to affected area if user then adds a mask to the transform? Does histogram apply to entire image or is it limited to mask area? Haven't tried this!

---> You are using the histogram to mask the hue saturation transform, but there is already a robust mask routine to do this. I can't think of any other transform that has a built in mask routine.

I second motion to add the 'Reset all but mask(s)' option.
jsachs
Posts: 3692
Joined: January 22nd, 2009, 11:03 pm

Re: Hue Saturation Transformation

Post by jsachs »

I'm not sure how I can explain this any more clearly, but try reading this as you seem to be focused on a model of how transformations work that is different from how they actually work.

In Hue-Saturation, the so-called Affected Region is defined solely by the selection in the color histogram and not by the mask -- the mask is only used to blend parts of the input image back into the result. If you don't make a selection by the hue-saturation histogram, there is no affected region and the sliders have no effect which is what you are seeing. The Brightness histogram settings are just used to limit the range of values selected by the hue-saturation histogram and do not select anything. The purpose of the mask for this transformation is, for example, to restrict the changes defined by the hue-saturation histogram to a specific part of the image in case there are regions in the Affected Region that you do not want to modify.

To make this transformation work more or less the way you are trying to use it, you can select the entire hue-saturation histogram by clicking and dragging a circle that encloses the entire histogram. Then the sliders will apply to all the colors within the masked area, but the Affected Region will be the entire image.

If you are not going to use the histograms to specify which pixels to modify, it sounds like you should perhaps be using Levels and Color or Adjust instead of Hue Saturation which is a tool for adjusting images based on their hue and saturation. Hue Saturation is similar to Selective Color Correction which is another alternative that may work better for what you are trying to do. Again, you need to create control points in the color wheel first to indicate which colors to change and how you want to change their hue, saturation and brightness and then use the mask, if necessary, to avoid changing parts of the image you did not intend to change.

The way Amount masks work for is the same for all transformations -- they take the effects of the transformation applied to the entire image and blend back in part of the input image. Where the mask is white you get the transformed image and where it is black you get the input image. This in effect restricts the application of the transformation to just the areas selected by the mask. The mask is only applied after the transformation has been applied to the entire input image, so it does not enter into the computation of the transformed pixels until the very end.
Jonathan Sachs
Digital Light & Color
Post Reply