High Dynamic Range Images - the Old-Fashioned Way
by Don Smith
On a recent outing with three of my good friends and talented photographers: Mike Hall, Pierre Steenberg and James Guillory, I had the good fortune to make a sunset image that has ended up becoming one of my favorites (and has garnered favorable responses on my photoblog). What originally had started out as an outing to hopefully shoot a moonrise at sunset, quickly morphed into Plan B (as is many times the case) as clouds to the east obscured the early rise of the nearly full moon. But as the old saying goes: "When life throws you a lemon…"
We were on location off San Juan Canyon Road in California’s San Benito County at an elevation of 2,000 feet (about 1100 feet below Fremont Peak which summits at 3169 feet and reveals a 360 degree panoramic view of the southern Santa Clara Valley, the Salinas Valley and the Santa Cruz / Monterey Bay). We were all captivated by the sea of fog which had rolled in off the Pacific Ocean – a common sight for the summer months. An inversion layer depressed the fog thus allowing the sun to set and cast its warm glow across is coldish-blue expanse.
As the sun began to near the horizon, I mentally visualized the shot. I had a descending set of hills in front of me (all part of the Gabilan Range), the wall of fog, and the setting sun and the colorful reddish-orange sky. A quick check of spot exposures via my camera’s meter showed an 11-stop range of light from deepest shadow to brightest highlight (which exactly matches human vision). My camera’s sensor, at best, could only capture 5 ½ - 6 stops of this light. Was the answer a 5-stop split neutral grad? I had in my bag three Singh-Ray Galen Rowell soft-edge split neutral density filters: a 2, 3 and 5 stop. My dilemma would be a very short window of time in which I could position the filter as the sun hit the horizon. I really needed a filter that Singh-Ray makes which is a reversed split neutral density (with the darkest part of the split positioned at the horizon line); however, I unfortunately did not have one in my bag.
Thus I thought about High Dynamic Range software. As you are aware if you read my articles or follow my blog, my favorite HDR software is Photomatix Pro 3.0. Unfortunately, experience has taught me that this is one of the few instances where that software has trouble blending the subtle exposure differences (at least to my liking). I have the sun, albeit shielded by a misty fog, and dark shadows along the hills in the foreground of the frame. Nonetheless, I decided to bracket my exposures and deal with the blends later in post-production.
When shooting images for HDR blend, it is important to be on a sturdy tripod, and make sure to bracket 1-stop exposures with the shutter speeds only. For this image, I bracketed 11-exposures starting with the sun, which I spot metered just before it hit the horizon. I determined 1/1000th would be my starting point on my Canon 100-400mmL lens at f/16 and 100 ISO. I took off my polarizer (a good idea when shooting towards the sun, especially with a zoom lens - thanks for the reminder Mike) to help prevent flare. Prime lenses are really the optimal choice when shooting towards the sun because they employ fewer internal lenses than zooms.
Now the fun began; the sun kissed the horizon and I bracketed fast. I have my shutter set to 1/3 stops, so I had to open three clicks per shutter. As quick as I could turn the dial, I’d fire a frame (holding my cable release in the other hand). For you techies out there, here were my 11 bracketed frames: 1/1,000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, and 1 second as my final frame. I had to work quick as the sun was moving fast. There is a way to set my Canon 1DsMKIII to automatically bracket up to 7 frames in one-stop sequence using the motor drive at 5 frames per second (this is a great option when dealing with fast moving clouds), but where I needed 11 frames, I chose the manual method. As a side note, I was able to make a single image capture of the sun seemingly melting into the fog (see my photoblog post) as a completely separate image. Here are the 11 bracketed images as they appear in RAW. Notice I cover the last frame with my hand to indicate the end of the sequence (I do this at the beginning os the sequence also).
Back at my computer the next morning, I picked 9 RAW images and went to work to determine if Photomatix could create an acceptable image. After three tries at various settings in the Detail Enhancer box with less than acceptable results, I decided to try it the old-fashioned way using Photoshop CS3 and layers and masks (this can be done in any version of Photoshop or any image editing software that supports layers and masks).
As I mentioned earlier, I captured all 11 frames in RAW format. I use the Adobe Camera Raw converter as my prime RAW editing tool, and started with the image of the sun (my highlight exposure). The only adjustment I made to all of my RAWs (except two – more on this later) was to change the color balance setting to 5500 Kelvin (daylight exposure) to warm the overall scene as it would appear at sunset. It is important when working with layers and masks to start with either with the highlight or shadow frame and then work in progression. When the first image was optimized in ACR, I opened it into Photoshop then went to work converting my second bracketed frame. Here is a critical concept to remember when converting images: as you bring a new image (layer) in to Photoshop, know what you want in terms of blend. I felt it was important in the second, third and fourth frame to make the transition of the sky appear natural as I moved away from the sun. The sky around the sun should appear slightly brighter than the sky further away from the sun, similar to how our eyes would interpret this scene in nature. I would place the newest frame on top because it would require the least amount of blending and would also allow my eye to gradually see the sky brightening. Remember, the correct exposure for the sun is now on the frame underneath the one you are looking at, so set you brush's opacity to a range of 30 -50 and blend it in accordingly. I feel using 100 opacity per brush is too heavy-handed as a starting point but this may work for you. Each click adds another percent of the opacity you set (it would take two clicks of 50% opacity to reach 100%).
To position one image on top of the other, click on (Control + A) to select all, (Control + C) to copy, then make the other image active by clicking on its top bar, and click (Control + V) to paste. You will now see in the layers box (F7) that you have two layers perfectly pin registered (this is why you can only do this using a tripod). What you just pasted will be the top layer. Now click the “b” key to select brush (I use a soft-edged) and tap either the right or left bracket key ([/]) to either enlarge or decrease the size of the brush. Lastly, click the “d” key to default your color swatches to black over white – black will be the key you want. Before you can use the brush to paint in and out, you must add a mask. You do this by simply clicking on the mask icon (white rectangle) at the bottom of the layer palette. A white mask should now appear on your upper layer. Black is the opposite of white, so with that color selected, you can now paint away any of the top image to reveal what is underneath. If you paint too much and need to add back, simply click the “x” key and white will now be over black. Remember, black turns off the effect, white brings it back.
In my example, I selected my second image to paste over my first image. I knew I wanted to work on the transition of the sun and sky so I simply set the opacity to 100% and sized my brush slightly smaller than the sun and clicked the brush over the sun and – voila – I had my original sun exposure back but with a one-stop lighter sky! I should also note that it is best to work on your ima
Now it’s time for frame three and working out further from the sun I expanded the transition of the sky even further. I won’t step you through each frame, but by now you should be getting the idea. By frame number five my sky was complete and it was time to start working on the fog. The only change I made here was to set my Kelvin temperature more towards 3000 K (by moving the slider to the left in ACR) to cool down the appearance of the fog. I only needed two frames to complete the look of the fog.
I still had frames 7-11 left to bring out detail in the hills. As it turned out, frame 11 was too bright, thus I discarded it. I did however utilize frames 7, 8 and 9 to bring out some muted detail in the rolling hills. Due to an atmospheric phenomenon called airlight (where diffuse scattered sunlight from air molecules cause distant objects to lose contrast), I wanted to make sure the hill closest to me remained the darkest and each successive hill became gradually lighter, again making it more truer to how our eye would perceive this scene.
Once the file is finished, save it as a master file (especially if you saved all the layers). I save all my masters in native Photoshop (.psd) format. Then go under the Layer menu and click on “Flatten” and save as a TIFF. I do not convert the image to 8-bit until I am certain all my editing has been completed. For this file, I still had a bit of work to do in Photoshop so I left it as a 16-bit file allowing me more color information to play with.
I realized the fog looked a little flat and not quite as blue as I had hoped, so I first opened a Hue/Saturation layer (by clicking on the half-circle icon at the bottom of the layer palette) and then refined my choice by clicking on the drop-down window and choosing “Blue,” then taking my cursor and moving over the fog, clicking again. This tells Photoshop that I just want to work on that specific shade of blue. Only at this point do I move the saturation slider to the right until the color of the fog looks correct to my eye.
To bump the contrast of the hills, I could use a Curves layer, but I opted for an easier choice. I opened the image into Nik’s new Viveza software, set a control point over the middle hill, and moved the contrast slider – simple!
Finished Image - 9-Layer Blend the Old-Fahioned Way!
Lastly I checked the image once again at 100% magnification for any dust spots I may have missed and I was done. I converted the image to 8-bit and saved as a TIFF. Any sharpening to the image will be determined by size and output. I do all of my sharpening with Nik Sharpener Pro software in the “advanced” mode.
Summary
One of the major pluses of working with blends is that every new frame you introduce has optimized exposure for the area you are working on. For example, the sky. Each frame I added and blended was the correct exposure for that particular area of the sky. The main bonus is that by working with the correct exposure, you will get the correct chroma (color) thus allowing for a natural saturation of color (no more underexposing to saturate color as we did with slide film). Go back to the contact sheet and look at how the sky drains of color with each successive frame as the sequence works towards correct exposure for the foreground. This is why spit grads were so important in days of shooting film. It prevented the chroma from being washed-out. But in the world of digital, you have total control! This in turns makes the image (and its color) appear more vibrant and true (under and overexposure changes the apparent look/density of the color). The chroma information has been recorded the way our eyes see it and is not limited by what the camera's sensor can capture. The other bonus of adding corretly exposed frames is there is no noise associated with this image because I did not have to lighten any portion of the image in post-production. Noise reveals itself in underexposed frames - especially in the blue channel.
Start to finish, this image took me about an hour; I think it was worth the effort. Photomatix can assemble HDR’s in minutes – thus its popularity amongst pros and amateurs alike. But when it doesn’t work, this is a great fallback method – just more time consuming. To learn this technique, you must practice. But it is the closet thing to painting that I can imagine. So find a scene that has a broad expanse of tones, bracket, and try it for yourself - I think you will be pleased with the results simply by doing it the "old-fashioned way."
If you have any questions about this or any other technique I teach here, please don’t hesitate to send me an e-mail. I also teach many of these methods in detail in my workshops and give hands-on experience. Just click on the Workshop tab to the left of this article for more information.