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Photoshop

Expand Dynamic Range from a Single Raw

by Tim Dempsey on February 7, 2009

Surf Hotel Block Island

There are plenty of occasions when I simply don’t have the tripod, or perhaps even the time, to set up the perfect HDR. I have had this image on my hard drive since August, and I hadn’t yet uncovered the techniques that would transform the raw file into a better reflection of what the scene had ‘recorded’ in my memory.

Surf Hotel, Block Island, Rhode Island

Here’s the “after” [by "after" I mean after the image has been recorded on the sensor. In my lexicon, "before" is what I saw and persists in my imagination, i.e. like the image above].

There are several issues we will address one at a time.

First, the shadows on the porch. This porch has a fantastic compass rose painted on the surface, and one of those sky-blue ceilings (to keep the bees away, I’m told). As captured by the sensor, the compass rose looks like a weather-worn indoor outdoor remnant from railroad salvage, and the ceiling is just too muddy. I also find that wood features like shingles, the decking, and the white fence love the effect of the LucisArt or Topaz Adjust filters.

Surf Hotel, Block Island

In this case I worked with Topaz Adjust. But first I had to isolate the sea, bluffs, sky and clouds from the hotel structure, so I turned to the Polygonal Lasso Tool in Photoshop, and created this selection, which I hastened to save as a channel. I won’t go into details (experiment! try! err!), but the Refine Edge dialog is essential, and is an option introduced in CS3 and available when any selection tool is active.

I tweeked the “Adaptive Exposure” slider, and its “Regions” slider to .4, and 14 for this project. I also boosted the “Highlight” slider to .06 in order to protect that beautiful railing.

The “Details” settings were: “Strength” 1.8; “Boost” 1.1. This enhances local contrast, giving the wood surfaces the texture that I think of when remembering New England cottage style buildings.

I “stamped” the layers to consolidate the work so far: (Ctrl-Alt-Shift-E).

Second fix is the sea, sky, clouds, and bluffs in the distance. In the original RAW file, they simply lack the saturation and richness I remember from the moment I pressed the shutter release.

Surf Hotel, Block IslandThis one was an easy fix — and I’ve used this loads of times since I first experimented with it. I grabbed my selection (highlighted it on the channels panel, clicked on “load channel as selection”, then went to my new top “stamped” layer, and clicked on the “Create Mask” icon in the layers panel. This creates a mask and applies the current selection — the area outside that selection is masked “out,” the selection area is now available for adjustment.

After experimenting, I found that simply applying the “multiply” blend mode did the trick. It restored the vibrance I remembered without introducing the extreme pixel damage of heavy saturation adjustments.

Surf Hotel, Block IslandFinal tweek: adjust that horizon line to make the final composition look just right.

So: If you have an extra $6,000,000, this is a great real estate opportunity! If not, you can see why Block Island is one of my favorite places by checking out the BI sets on my Flickr photostream.

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Rachel at 35

by Tim Dempsey on January 29, 2009

Rachel at 35, originally uploaded by TimDD.

We celebrated with Rachel and her mother on Rachel’s 35th. This was a simple on-camera flash shot, bounced off the ceiling; significant surface blur and a good half-hour of brushing to bring the key details back. We’re going to gallery-wrap this one for Rachel’s mother, Susan.

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Processing High Dynamic Range Images: Tutorial

by Tim Dempsey on March 5, 2008


I’ve had a number of requests and inquiries about processing technique, so I decided to put together a mini-tutorial on some of my most commonly used tools and techniques using this picture as the example. This will be a long post… but I hope worth the read.

First, start with great subject matter ;-) . This is Frank Lloyd Wright’s winter home and residential architecture school, Taliesin West, in Scottsdale, Arizona. Let’s look at how we got to this result given the original images.

Frank Lloyd Wright, Taliesin West

At right, the original image.

The exposure details are: ISO 100, f/4.0, 1/1250. While the picture is decent, there is a huge black void just right of center (the building’s kitchen), and there is detail lost in the studio area to the left (large white canvas areas).

Also, the sky lacks drama: it’s a bit flat.

The picture doesn’t adequately express the impact of the building material — rock from the immediate vicinity of the building mixed with concrete. There isn’t enough contrast or texture to accurately reflect the experience of these materials in this building at the time I was there.

Second Exposure: Overexposed One Stop.

Here’s exposure two. Same ISO, same f-stop, 1/640th. I see a dramatic difference in shadow detail available, which PhotoMatix will take advantage of nicely for us.

However note that with only three exposures, and hand-helds at that (I was on a tour, and unable to take my time for setup), we still need some help on those pesky shadow areas. In an ideal situation, I would have had the tripod, and make seven exposures (at f/4, three each at one stop intervals below and above the “middle” exposure setting.

More on this later.

Exposure 3: Underexpose one full EV

Here’s exposure three. This one is f/4.0, but at 1/2500th. This will provide loads of data for the highlight areas which are quite void of information in the original exposure.

There’s nice depth in the Arizona sky as well.

I also find the foreground detail and water tone useful for the finished project.

Photomatix Settings

Here is a snapshot of the PhotoMatix settings. PhotoMatix is an excellent tool for generating high dynamic range images from multiple exposures. It includes a number of adjustments, and in this on I boosted the saturation a bit (which is almost always necessary, given the trade offs HDR software makes). I also selected “very high” light smoothing, which means this blended image will have few of the artifacts I personally find annoying when I’m going for a realistic, as opposed to some kind of scifi, effect.

With this image I am definitely looking for more realism.

In the original, I generated the HDR in 16-bit depth (just because I want to retain as much data as I can as long as I can).

Time for PhotoShop.

Photoshop, TIFF loaded

If you click on any of these embedded images, you can see larger renditions for details. This is the TIF, created by PhotoMatix, loaded into Photoshop.

As you can see, I created three additional layers to produce the final image. This first is a layer I will create to address sharpness, texture, and contrast issues using the LucisArt “Exposure” filter.

The second additional layer uses the gradient tool to create more drama in the sky.

The third deals with what I find is a distraction in the foreground — the stone deck surrounding the pool.

LucisArt settings

Here is the LucisArt tool with the final settings I chose to use for this image. [Note: the LucisArt filter only works in 8-bit depth mode]. As you can see, the tool has two “adjustments” in the “Exposure” filter. The round shapes along the bottom seem to determine the pixel radius at which the tool operates for a given filter application, while the slider (set here at 50) seems to control the “power” of the filter effect. I am making all of this up, however, as I have not consulted any documentation at any time. Play with the tool on your own images: you’ll find what degrees of impact you are comfortable with.

LucisArt has a dramatic impact on your image — and it can be a bit scary. But fear not, for we shall use a mask, our brush tool, and opacity settings to ensure we get enough, and not too much, impact on our finished image from this tool.

And look at the improvement in those very dark shadows! Loads of detail to enrich the final image. And LucisArt helped dramatically in a problem area caused by hand-holding the three original exposures. PhotoMatix attempts to align the image — but does so around subject matter at the center of the image. LucisArt Exposure has had a “sharpen / unsharp mask” effect on some of the “fuzzy areas” of the original HDR — especially in the tree at right.

On the negative impact side, it is easy to see the “pixel damage” that the LucisArt filter has done to the sky. I almost always mask the sky from the LucisArt filter for this reason. That is, I mask out areas of the original image that need the detail and integrity of the original, and use the mask and brush tools to allow the magic of the LucisArt filter to effect the final image where appropriate.

In this case, after applying the filter (clicking on the big “check mark” in the LucisArt tool), I immediately did an “alt-click” on the mask icon in the layers palette to create the mask. This masked the entire new layer from LucisArt, leaving my original image showing.

I then took up the brush tool at 300 pixels and 70% opacity, and started to paint away there areas of the LucisArt-filtered image that I wanted in the final image.

Play around with the brush and these masks on your own: you’ll get the hang of it quickly. With layers and the ability to switch between foreground and background brush color, you can do and undo to your heart’s and your image’s content. I played around for quite some time, but there were a couple of interesting learnings here.

1) LucisArt Exposure is perfect for bringing out contrast and texture on surfaces like the concrete and stone, the redwood beams and trusses, and the vegetation on the mountains behind Taliesin. I allowed lots of the LucisArt filtered image to come through in those areas.

2) I thought that the filter did too much damage to the water in the pool. So I switched the brush color from background to foreground, and restored that area to the original. There are cases where I’ll even import one of the original exposures, and create a mask to bring some aspect of one of the original frames into the finished product. Perhaps I’ll do a tutorial on that some day too.

3) I determined that the foreground stone needed a bit more texture — in fact I did a final pass to ensure that all stone surfaces I could find were in the 60-70% opacity range providing great texture from the LucisArt filter layer. I toned down the grass a bit, since it looked a bit too beard-like with full texture from the filter.

If you look at the enlarged image, you can see the effect of these brush strokes on the mask for the background copy layer. There the mask is white, I have allowed all of the LucisArt-filtered layer to show through, where you see gray, it is partial opacity. Where the mask is black, the original data shows through in the final image.

Final gradient added to desert sky.

Still not entirely satisfied: I want to ensure that the clear focus is on the main building. This will involve creating a new layer to place a gradient in the sky, and a new layer to place a gradient over the foreground stone and the pool.

The gradient tool took me a while to understand, but in this case I did this:

1) Created the new layer by clicking on the new layer icon in the layers palette (Layer 1 in this snapshot). I selected the gradient tool, and the “foreground to transparent” option. I set the blending mode of this layer to “Overlay,” which adds contrast. I then mouse clicked and dragged from the top edge of the sky down to the top of the building, and released the mouse button. The gradient was created as you see it here — all I had to do was adjust the opacity, in this case to 65%.

2) Created the final layer by clicking on the new layer icon in the layers palette (Layer 2 in this snapshot). I selected the gradient tool, again using “foreground to transparent” option. And again set the blending mode to “Overlay.” But this time I started in the lower left corner of the image, and click-dragged toward the fountain in the middle of the triangular pool. I added another click-drag from the lower right toward the fountain, but not as long. Set the opacity to 65% to achieve the focus on the building that I was after in this project.

I would love to receive feedback on this tutorial, either here as comments, in Flickr mail, or you can email me at “tim at synopshots dot com.” Thanks.

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