Reducing haze or mist using PWP

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mark_hay
Posts: 26
Joined: August 22nd, 2009, 4:05 am

Reducing haze or mist using PWP

Postby mark_hay » October 15th, 2016, 1:32 pm

Hi All
- what PWP steps could be used please on photos which have mild amounts of haze or mist to make the scene a bit sharper? (I am using RAW followed by processing in Canon DPP software.)
- I am aware that Canon software (DPP) offers Picture Styles - one of which is called "Clear" - it seems to increase contrast dramatically/too much to remove mist nicely.
- I have included small jpegs for Clear and Neutral picturestyles.
Thanks, Mark.

- More detail from Canon on Picturestyles is available here http://www.canon.co.jp/imaging/pictures ... clear.html )

- There is also mention of Adobe Light Room having Dehaze feature - https://helpx.adobe.com/lightroom/how-t ... ehaze.html
Attachments
IMG_2251clear.JPG
Canon Picturestyle Clear
IMG_2251clear.JPG (244.4 KiB) Viewed 1633 times
IMG_2251neutral.JPG
Canon Picturestyle Neutral
IMG_2251neutral.JPG (296.09 KiB) Viewed 1634 times

jsachs
Posts: 780
Joined: January 22nd, 2009, 11:03 pm

Re: Reducing haze or mist using PWP

Postby jsachs » October 15th, 2016, 3:56 pm

Several programs have recently come out with a dehaze feature - I have used the one in Lightroom and also the similar Clear View feature in DxO Optics. The two of them work somewhat differently from each other and seem to produce unnatural-looking results a lot of the time, especially if you apply them heavily. There is an extensive literature on this topic, but I have yet to see an algorithm that is reasonably easy to implement and that does not produce artifacts in one situation or another. There is no straightforward way to do this with Picture Window's existing commands since a correct implementation involves determining a depth map of the scene and figuring out what color the haze is and how it builds up with distance. All of the algorithms amplify noise, saturation and contrast in areas where there is a lot of haze since you are subtracting off the haze color and then scaling the result up to recover the scene brightness. To get around this problem, they usually stop trying to remove haze when it gets too thick. There are also problems when a nearby object such as a tree overlaps distant objects since the haze removal must be applied differently based on the distance and it is tricky to create an accurate enough distance map. Scenes where the depth increases gradually are easier to correct. I played with some code briefly, but it looked like it was going to be a lot of work to get something that well all the time.
Jonathan Sachs
Digital Light & Color

ksinkel
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Joined: April 2nd, 2009, 11:58 am
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Re: Reducing haze or mist using PWP

Postby ksinkel » October 15th, 2016, 4:25 pm

I tried to reproduce the anti-haze filter using PWP Brightness curve and saturation. It's not an exact match, but I think it is instructive.

First I loaded your before image and brought up the brightness curve. Notice that the histogram is zero at the very extreme left. This means that there are essentially no blacks -- your blackest areas are actually a dark gray. This reads as haze in the photograph. To correct this, just move the left point of the histogram to where the blacks start. (I also made a similar adjustment at the white end.)

Your image is also low contrast. You can increase apparent contrast by applying the S-curve. The tradeoff is that you will lose shadow and highlight detail. And in fact your output image loses all detail in the shadow areas. How much shadow detail you are willing to lose for improved contrast is a creative choice and depends on the image. I adjusted the curve to match the Nikon results as closely as possible. However I think if this were my image, I would back off a little bit to show more detail in the shadows.

Finally I also boosted the saturation by about 20%.

Here is the histogram and my final image:

20140804_Curve.jpg
20140804_Curve.jpg (82.54 KiB) Viewed 1607 times


20140804_Curve.jpg
20140804_Curve.jpg (82.54 KiB) Viewed 1607 times
Attachments
20140804after.jpg
20140804after.jpg (299.97 KiB) Viewed 1608 times
Kiril Sinkel
Digital Light & Color

den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

Re: Reducing haze or mist using PWP

Postby den » October 15th, 2016, 5:42 pm

...

Perhaps this approach will help achieve a preference PWP Composite-Blend of an overly dramatic image version [high contrast] with its more natural verson [normal contrast] where:

Img1 = IMG_2551neutral.jpg

Img2 = IMG_2551clear.jpg

Step1: lower-left Apply Add a Mask-BrightnessCurve StepStair: 0-0, 50-0, 50-100, 100-100; to Img1 and leave the Mask Tool 'active' [do not close]...

Step2: open the Composite-Blend transform where Input = Img1 and Input Amount Mask = the 'active' mask of Step1; Overlay = Img2... ...Note: to make the posted images 1:1 register, a 4-point Alignment was used as Img1 and Img2 had differring pixel dimensions but essentially identical scene content...
ScrnVw_1_Composite-Blend_with_Mask.jpg
ScrnVw_1_Composite-Blend_with_Mask.jpg (77.72 KiB) Viewed 1590 times

Step3: adjust Input Amount Mask black and white and Overlay Amount sliders to preference while monitoring an updating Preview... ...click OK or Apply... ...OK or Close the Mask Tool...
ScrnVw_2_resulting_Preview.jpg
ScrnVw_2_resulting_Preview.jpg (96.05 KiB) Viewed 1590 times

This is an adaptation of the theory/discussion described in the Tips Section here: http://www.dl-c.com/board/viewtopic.php?f=5&t=1020

...have fun...
...den...

MarkT
Posts: 83
Joined: April 24th, 2009, 2:07 pm

Re: Reducing haze or mist using PWP

Postby MarkT » October 16th, 2016, 8:31 am

I've had some success with foggy, hazy images by using the Filter Transformation:

filter_operation-1.jpg
filter_operation-1.jpg (179.17 KiB) Viewed 1540 times


Basically filter the image with itself, and use a mask, if necessary, to preserve some details from the original.

den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

Re: Reducing haze or mist using PWP

Postby den » October 16th, 2016, 2:39 pm

...

Yet another possibility using a favored nature Landscape USM Local Contrast Enhance transform to: (1) enhance large radius major edges; (2) control transform Amounts applied above and below 50% HSV-V tones; and importantly (3) limit Local Contrast Enhancement primarily to the 'dark' half of edges without generating 'white' half halos...

The suggested transform settings and mask [a Blur=2 was added following the applied curve (shown)]...
IMG_2551neutral_USM-LCE_transform-mask.jpg
IMG_2551neutral_USM-LCE_transform-mask.jpg (89.42 KiB) Viewed 1506 times

The resulting Preview with added small detail Sharpening and slight increase in HSV-S saturation...
IMG_2551neutral_USM-LCE_Preview.jpg
IMG_2551neutral_USM-LCE_Preview.jpg (96.95 KiB) Viewed 1500 times

Just exploring possibilities...
...den...

JenniferB
Posts: 1
Joined: November 16th, 2016, 10:32 pm
What is the make/model of your primary camera?: Canon 70D

Re: Reducing haze or mist using PWP

Postby JenniferB » November 17th, 2016, 7:28 am

In a hazy picture the red channel often contains the most detail, so I created this version by replacing the HSL L channel with the red channel. (Specifically, by using Color->Extract Channels to get R, H, and S followed by Gray->Combine Channels.) It isn't meant to be a final version, just a better place to start your adjustments from.
Attachments
L replaced with red.jpg
L replaced with red.jpg (107.6 KiB) Viewed 1301 times

Robert Schleif
Posts: 63
Joined: May 1st, 2009, 8:28 pm

Re: Reducing haze or mist using PWP

Postby Robert Schleif » November 28th, 2016, 9:38 pm

JenniferB's method works because the longer wavelengths of red light are less scattered by the particles in the haze than the blue wavelengths. This is the reason that red filters reduce haze in black and white photography. Replacing the intensity channel with the red channel works both in HSV and HSL with very little difference in the result.

mark_hay
Posts: 26
Joined: August 22nd, 2009, 4:05 am

Re: Reducing haze or mist using PWP

Postby mark_hay » February 12th, 2017, 6:20 pm

I would like to thank everyone for their help.
At last I had some free time and I have used the method provided by Jennifer and got pleasing results of the Grand Canyon with reduced haze.

This was by using Color->Extract Channels to get R, H, and S followed by Gray->Combine Channels.
(I did find that I needed to be in 24bit color to do this - using 48 bit color resulted in some extreme colors arising.)

Thanks, Mark.

doug
Posts: 81
Joined: April 24th, 2009, 10:06 am
What is the make/model of your primary camera?: Nikon D-500
Location: Toledo, Ohio USA

Re: Reducing haze or mist using PWP

Postby doug » February 13th, 2017, 9:48 am

Finally! A new post that relates to using PWP to solve particular image adjustment issues and not its new status as freeware.

I am retired (10 years now), but not yet dead. Similarly PWP may be entering a well deserved retirement phase. But it too is far from dead.

After getting used to and appreciating it's "under the hood" (as DEN has put it) approach, I intend to use it as my go-to editor for a long time. Friends, I hope we can keep this board and the sharing of questions and tips as active as in the past.

Doug Haag


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