Tanel

July 6, 2007

HDR imaging plugin has been requested by some people here, but as far as it is not available I thought I’d drop in a tutorial.

You can learn the backround of HDRI (high dynamic range imaging) here:

http://en.wikipedia....ki/Tone_mapping

http://en.wikipedia....mic_range_image

http://cambridgeinco...namic-range.htm

Technique described in my tutorial is entirely improvised, but it works well for me, giving a good amount of control over the process and results.

Some inspiration was provided by “The Layer Mask” technique described here. Since there is no layer mask in PdN yet, we will use two excellent plugins instead: Curves+ and Gaussian Blur+.

Particular curve shapes and blur amounts were selected to match my sample image. Take it as a rough guideline only; feel free to propose improvements! Below sample images are 16% size screenshots, actual processing was made on fullsize 6MP image.

I will blend three differently exposed images:

First image from the left is the original photo: camera was set to expose for highlights (spot metered from bright sky with +2 stops exposure compensation). Image was developed from raw file with no exposure compensation (note: raw file was developed to 8-bit tif-s with other software).

Second image was developed from the same raw file with exposure compensation of +1.3 stops to provide correct midtones.

Third image was developed from the same raw file with exposure compensation of +2.5 stops to provide correct shadows.

Obviously the dynamic range of the scene exceeds the capabilities of camera for a single jpg capture. But there are huge resources in the shadows with raw file (alternatively, in such static scene, the three separate images could have been shot using a tripod).

To blend a HDR image we will use highlights from the first (darkest) image, midtones from the second one and shadows from the third (brightest).

Note that in order to obtain natural look, the highlights should be kept on bright side and shadows on the dark side. Don’t overdo it by lifting all levels to the middle!

Preparation:

Open the images on layers and organize: dark image layer (first one in my sample) to the bottom, middle one to the middle, bright one to the top. Ensure all layers are checked.

Workflow:

Step1: tone mapping

In this step I will remove overexposed areas from bright images by turning those areas transparent. That will allow lower layers to show up on those areas.

a) Select the top layer (the brightest image).

Start Curves+ plugin from adjustments menu and apply a curve similar to the one shown below in order to remove midtones and highlights from top layer (Advanced mode, In: Luminosity, Out: Alpha) [download a sample curve to load into your Curves+: http://www.hot.ee/ta...r-curve_top.xml]

Note: this curve type adjusts transparency/opacity of pixels based on their brightness. You may find other curve shape to better match your images.

Select the middle layer.

Start Curves+ plugin from adjustments menu and apply a curve similar to the one shown below in order to remove highlights from middle layer (Advanced mode, In: Luminosity, Out: Alpha) [download sample curve to load into your Curves+: http://www.hot.ee/ta...r-curve_mid.xml]

At this point your image probably looks quite coarse and artificial. Don’t worry, we are not finished yet.

Step 2: smoothing the transparency blend

a) Select top layer and Open Gaussian Blur Channel plugin from Effects>Blurs menu. Dial in Alpha blur with amount of 10. Repeat (Ctrl+F) Alpha blur two times (total 3 times of Alpha blur on this layer).

Select middle layer and Open Gaussian Blur Channel plugin from Effects>Blurs menu. Run Alpha blur total 3 times on this layer as well.

Note: This step especially improves fine dark detail or sharp edges against bright backrounds (my sample image has a lot of those). You may find larger or smaller blur amount and repeat times more appropriate for different types of images.

We are almost there:

See how the layers look like on their own:

On the top layer (3rd image) only shadows are visible while transparent area (represented by the “checkerboard”) lets below layers to show up. On the middle layer shadows and midtones are visible but only midtones can show up through the top layer. From the bottom layer (1st image) only the brightest areas can show up through the middle and top layer.

Step 3: fine toning

Here you are actually free to run adjustments like levels, saturation, contrast etc to your own taste – either on each layer separately or globally after merging. In my example I preferred to reduce levels on top layer to give shadows more natural look and improve overall contrast.

When it looks fine, flatten image & save.

Done! This is the best result I could do this time, representing what I actually saw in this scene:

Endnote: you can also merge just two images instead of three – sometimes it’s enough. If you do so then ignore the middle layer part of from my tutorial (marked with “” in step1 and step2).

8)

June 24, 2007

Did you know that there is already a transparency adjustment plugin?

Yes BoltBait, I have tried it. Btw I even made some suggestions for that one, maybe you missed my post: http://paintdotnet.12.forumer.com/viewtopic.php?t=5222&start=15

June 24, 2007

Feature request: Transparency Adjustment

Hi,

is it possible to add transparency slider similar to saturation?

That would make great use in image blending: for masking out image areas based on hue - like skin tones, sky etc...

Thanks for great plugin anyway.

June 20, 2007

P.S. I think it's a great idea to create a tutorial on Curves...

Curves is universal tool, not PdN specific.

Simply google for RGB+curves+tutorial and here you go - 1st match, perfect tutorial:

http://www.cambridgeincolour.com/tutorials/photoshop-curves.htm

Same goes for Levels tool.

June 16, 2007

This is alien technology!

:shock:

June 16, 2007

No, the problem is not the alpha level, that calculates fine. The problem is when changing from alpha 0 to something else, the color of the pixel is undefined. I solved the problem in this plugin: http://paintdotnet.12.forumer.com/viewtopic.php?t=3285 by making the color of transparent pixels the secondary color. Maybe that would work here as well.

Note that color information is still there, if transparency has been achieved with Eraser tool (or even with your Transparency plugin). I would like to keep this image information intact (not replaced with single color). So that if you reduce transparency for Erased or Transparency'ed pixels then the "hidden" picture becomes back visible. The new Gaussian Blur Channel plugin works like this now and I like it.

Maybe you could fix this also in the Transparency plugin: so that if you use Transparency twice - first turned selection fully transparent then in 2nd run turn back to opaque, you would finsh up with the original picture. The "really empty" pixels in PdN are actually white, are'nt they (R=255, G=255, B=255, Alpha=0). So just treat those as white?

June 15, 2007

Well, I don't know if I did this right, but here ya go:

Wow, that was fast!

Thank you, it works well at first glance

One limitation that I haven't worked out yet... You can't blur onto a transparent pixel. I'm just not sure what to do in that case yet.

As a "dirty" workaround, maybe just replace alpha 0 with 0.01 or something in the code before blur calc? Or add 0.01 to everything...

June 14, 2007

Do you REALLY need to blur all three color channels separatly? (That would be a pain.)
Or, can you live with an Alpha Gaussian Blur? (That would be a snap.)

Alpha Blur is actually enough for me and I see real use for that. Leave out color channels if that's painful

I just imagined the further possibilities...

June 14, 2007

That may be a good idea. It would be nice to have it combined with my suggestion.

Sorry I missed your post about Advanced Gaussian Blur, although I searched before posting :oops:

Yes, my idea is almost the same, I should have shared it under your post.

As for the request, I can see how this would be useful,

What's your opinion, is it at least possible to build into a plugin?

June 13, 2007

Hello,

I'd like to have tool that applies blur to each color and alpha channel separately. Not sure if that is possible but worth to ask...

I am especially interested in alpha (transparency) blur which should be very useful in some image blending techniques. But why not include all color channels then.

Below is my sketch of possible UI, just to show the concept (I "borrowed" main part of this image from Illnab1024's Advanced Greyscale plugin UI).

Each slider changes amount of blur on it's dedicated (monochrome) color plane.

Possible enhancements could include drop-down option box for blur type (gaussian / fast / etc), and maybe even color space options (RGBa / Lab / ?)

Thanks,

Tanel

June 13, 2007

Wow, this plugin is hardcore :o

Thanks pyrochild, good job!

Awesome, really.

June 3, 2007

Thanks Ash! I didn't know that.

Learning something new every day

June 3, 2007

Thanks Ash! I didn't know that.

Learning something new every day

June 3, 2007

Ctrl+Shift+A is a convenient, one-hand-only shortcut key to reset to 100%.
... with a program that more often has scrolling horizontally than vertically...

The convention is that the mouse wheel scrolls up and down, and that modifier keys change that.

May I suggest few UI improvements, useful for images larger than screen:

#a) Mouse wheel scrolls horizontally when mouse pointer is held over horizontal scroll bar (Opera internet browser works like that).

# Ctrl+Mouse wheel click zooms to 100%, moving the mouse aiming point into the center of screen.

#c) Hold down mouse wheel to pan image (I really miss panning).

#d) F11 toggle full screen view (I really miss full screen view).

Hope it makes sense

June 3, 2007

Ctrl+Shift+A is a convenient, one-hand-only shortcut key to reset to 100%.
... with a program that more often has scrolling horizontally than vertically...

The convention is that the mouse wheel scrolls up and down, and that modifier keys change that.

May I suggest few UI improvements, useful for images larger than screen:

#a) Mouse wheel scrolls horizontally when mouse pointer is held over horizontal scroll bar (Opera internet browser works like that).

# Ctrl+Mouse wheel click zooms to 100%, moving the mouse aiming point into the center of screen.

#c) Hold down mouse wheel to pan image (I really miss panning).

#d) F11 toggle full screen view (I really miss full screen view).

Hope it makes sense

June 1, 2007

Features to come (eventually): CMYK, Alpha(Luminosity), dynamic histograms, Alpha(CMYK)

Feature request: Saturation Curve

Hi,

First, I have to say that Curves+ a wonderful plugin already, featuring many possible uses!

I just got an idea that could most easily fit into this plugin, and I have no coding skill to test the concept myself.

The concept is to implement a saturation transfer map, with axises scaling from 0, 0 (% of saturation) to 100, 100 (% of saturation).

By changing the curve, pixel's saturation would be transferred from initial saturation (%) to destinated saturation (%).

The only obstacle will probably be 0% saturated input pixels (pure black/grey/white), which cannot be lifted anywhere. But I think it can be worked around with a simple condition line in code, something like: IF(input<0.01% THEN do nothing, ELSE follow curve).

In my vision this plugin could be used for editing photos, for example lifting the color of dull landscape, while maintaining already-good color of blue sky.

I know that this kind of effect can be achieved with some other plugins around, but handy Curves+ would be my tool of choice any time!

Possibly I missed some nuances but basically, what do you think?

Here is a sketch of possible UI:

June 1, 2007