Advanced HDR Editing – Tutorial

When we’re working with tonemapped HDR images, sometimes additional editing is needed or desired.  Why?  Well, if we look at HDR as a way to expand dynamic range and as a way to give us a better starting point; rather than looking at HDR as an endpoint, then it makes sense that additional tweaking may be something we want to do.  In addition to that, the HDR process can sometimes do funny things with colours that we don’t want.  I wrote about HDR being a starting point in an earlier blog post,“The Great HDR Debate” .

What we’re going to look at in this tutorial are a couple methods to work with tonemapped HDR images to give us a the final image we want.  One approach is going to involve layer masks and the other is going to use layer blending modes.  The layer mask adjustment is going to build on my earlier layer mask tutorial.

Earlier this summer I shot some interiors of a well known cathedral in Toronto – St. Michael’s Catholic Cathedral.  My intent when I went into the church was to build on the ‘artistic architectural’ project.  It’s a terrific space with wonderful stained glass and architectural features.  The painting on the ceiling is magnificent.

The shot below is the tonemapped HDR.  This is almost what I wanted.  I wanted a darker overall look but still showing detail and I got pretty close to that.  The one area I wasn’t completely happy with was the stained glass window.  Even using HDR, in order to get the detail I wanted in the rest of the shot, the window ended up being a bit too bright.  Various burning approaches didn’t give me what I wanted so I decided to go the layer mask route.

Tonemapped original (click for larger version)

This next image is the one that was used to create the layer mask.

Mask layer (click for larger version)

With the tonemapped image open, I selected one of the darker images from the bracketed set – in this case it happened to be the darkest overall exposure – that had a better exposure for the stained glass.  Opening that image in PS, I selected the entire image (Ctrl + A or Select>All from the menus), copied the image (Ctrl +C or Edit>Copy) activated the tonemapped image by clicking on it and pasted the dark image on top as a new layer (Ctrl + V or Edit>Paste).  This places the darker image on its own layer above the tonemapped background layer.  Now, I don’t want the entire dark image, only the stained glass.  I could have used the layer blending options and worked with the layer blending sliders by double clicking the top layer, moving the shadow slider for the top layer to the right, using Alt + clicking on the triangle to split it then moving the split slider a little further to the right (see the Blended Exposures tutorial for more information on this blending method).  And I did try this but still didn’t quite get the look I wanted, so I decided to go with a layer mask.

With the top (dark) layer active, go to Layer>Layer Mask>Hide All.  I chose Hide All in this case because I only wanted the small area of the window to be painted in so using a Hide All mask I could just work on that area.  Make sure white and black are active as your foreground/background colours on the tool palette and select White as your brush colour.  With the image zoomed at 100% (or more if you want greater precision) I chose a soft edged brush that was the size of the panes in the window.  With the brush set to a low opacity (about 25%) I started painting in the window area.  A soft edged brush helps to feather the effect at the edges so if you happen to paint over the edge by accident it won’t be as effected.  If you do paint in an area you don’t want, switch the foreground colour to Black and paint the mask back into that section.  Using a low brush opacity allows you to more carefully build up the effect of the mask in some areas vs. others.  It takes a bit more time because you have to paint over some areas multiple times, but the end result is generally preferable.  Using a lower brush opacity and painting more in some areas than others, you can effectively feather the mask as you go.  The image below is the result after painting in the stained glass window of the layer mask.

Image with masked window layer (click for larger version)

The brightness of the window is toned down now to a point where I’m happy with it.  If I wanted to tone it down further, at this point I could create a Dodge/Burn layer and very lightly burn the window in a bit more.  Alternatively I could import this image into Lightroom and use the Brightness Adjustment Brush set to a low (around 15%) opacity and a negative brightness to effectively burn the window in more.  The Brightness Adjustment Brush in Lightroom is a terrific tool for dodging and burning.  The next image shows the layer stack, the top layer being masked out and showing only the window area having been painted back in.

PS layer stack (click for larger version)

Next we’re going to look at using different layer blending modes to help adjust for colours that may not come out exactly as we want in the HDR merging process.

Below is an image of Spiral Gorge in Watkins Glen State Park.  The exposure isn’t bad but I’d like a bit more detail in some of the areas of the vertical rock wall at the back but don’t want to blow out the exposure of the water which, in this shot, is just about at that point.  Could I dodge some of the rock wall area?  Probably but in doing so I risk bringing out noise as well.  To get the overall exposure I wanted, I decided to shoot it for HDR.  In the HDR merge and tonemapping, the colours were affected and the result was far too magenta/purple.  I did really like how the swirling leaves came out.

Tonemapped HDR (click for larger version)

After playing around with the colours to try to get them where they should be, I decided to try using one of the original files with the layer Blend Mode set to Color.  By doing this, only the colour of the layer is applied but the detail and texture of the Background layer isn’t affected.  The colours in the original image (below) were too blue/silver in the rocks but the reds, yellows and greens were good.  I figured I could get a result I was looking for by combining the two.

Colour layer (click for larger version)

I copied this single image layer and pasted it into my tonemapped HDR then set the Blend Mode of this top layer to Color.  After that, the Opacity of this colour blend layer got dropped to 60%.  Dropping the Opacity allowed some of the colour from both layers to show and gave me close to the colour balance I was looking for.  It was still a little too purple/magenta and the reds/yellows weren’t quite as vibrant as I wanted.  From here, I created a Hue/Saturation adjustment layer on top of the Background layer and adjusted the Magenta channel to suit, decreasing Saturation and increasing Lightness.  Next I increased Saturation slightly on both the Red and Yellow channels.  Getting closer.  Next I created a Hue/Saturation layer on top of the colour blend layer.  On this H/S layer I increased the Saturation slightly of the Reds, Yellows and Greens, adjusted the Hue of the Greens a bit and the Lightness of the Reds, Greens and Yellows.  I also dropped the saturation of Magenta and reduced Lightness slightly.  The end result is below.

Blended image (click for larger version)

The layer stack for this image is shown here in this final screen capture.

PS layer stack (click for larger version)



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