Shouldn’t be a problem to implement, though I wonder the merit of adding haze using a dehaze tool. Personally, I would do the following in GIMP.
1 Output 2 images from RT: 1 without dehazing and the other with it.
2 Subtract the two and generate a new layer from that.
3 Add this difference to the image without dehazing.
Voila, you should have a more hazed image. You might need to fiddle around with the range and tones but it should work. (I haven’t verified it but you can!)
Thanks for the reply. What is the method for subtracting and adding images? I don’t use Gimp… I have an ancient version of PS. Any suggestions for that?
Sorry, I simply don’t have the time to demonstrate but what I will say is that Linear Dodge is definitely wrong because it doesn’t subtract or add all of the pixels in the same way. What you need is straightforward subtraction and addition.
1 Normal - Dehazed = Difference 2 Normal + Difference = Normal with more haze
Not sure if step 1 should be Dehazed - Normal instead. It depends on how PS orders its layers.
A long time ago, I liked adding some “haze” by simply applying a gaussian blur with large radius to a duplicate layer, and then play with blend mode and transparency. @porchard could you post an image we could play with?
Thanks @sguyader - that seems to get fairly close to what I was looking for. I tried this method some time ago, but I couldn’t have been using a large enough radius, because the results weren’t as good. The larger radius seems to to do a decent job. I still think that a negative dehaze would be a good feature to have in RT, though!
If you are really interested in having this feature considered for inclusion in some future RawTherapee versions it might be helpful to add it as an “enhancement” in the Github web-page:
In short, you need to create a new “issue” in this web-page and add your request. Needless to say, you need to have a personal account before adding this proposal on Github.
Only having this request on this forum might be less effective for your proposal in the long run…
I decided to verify my instructions above. I didn’t use GIMP since you don’t use it, only G’MIC for a strict subtraction and addition. Raw file was processed using RT with neutral profile and some lens corrections and raw tab tweaks.
Hint You can control the strength of the haze by multiplying the difference with a factor; i.e., controlling opacity or adding new layers to stack on top.
I’m in front of PS right now. Here are the steps to “reverse dehaze”.
Take the dehazed image. “Apply image” with original image, mode = subtract, offset = 127. Let’s call the result “diff” because it’s the offset difference between the two images.
Take the original (or copy thereof). Do Apply Image, using diff as the source, mode = subtract, offset = 127, opacity as desired.
I must admit I was very glad when local adjustments first appeared in RT …then proceeded to never actually use them so my experience with them is as is obvious quite minimal. Thanks for the feedback, I will check it out
kudos to the RT team. I cannot begin to understand the beauty of code you guys write; but I do appreciate that it exists. thank you!