Bob’s HDR Workflow

On a few of the Flickr groups I belong to people have asked me to explain the technique I use to create (tone mapped) HDR photos. My technique is not unique, I’ve simply tried various tips others have shared and documented what seems to work best. There is no “correct” method, and you will develop your own work flow to create the “look” you are trying to achieve.

1. What is HDR?
HDR stands for High Dynamic Range. The term “Dynamic Range” is referring to how many shades of gray you can capture (and display) between absolute “white” and absolute “black”. When we add the color component we’re now adding how many hues of each color can be captured and displayed. The number of shades and color hues is affected by many factors that include (but not limited to) the photo format (JPG, TIFF, RAW) and your camera’s. True HDR, the image you see before you do the tone map operation, cannot be displayed on your PC because the photo’s dynamic range is beyond the capability of your PC’s video card.

To convert the HDR image to something we can view with awe, we must perform an operation called “tone mapping”. Tone mapping essentially compresses and combines all this graphic / color data down to an image format that a PC can handle. For the record we aren’t shooting HDR, we are actually tone mapping HDR images.

2. It’s all about exposure!
Throughout this explanation we will refer to increasing or decreasing the exposure in increments called ”E.V.”  E.V. is an abbreviation for Exposure Value. Traditionally we’d refer to exposure in “F-Stops”, but the term F stop only refers to a lens. When shooting HDR we want to shoot with a fixed aperture so the depth of field does not change. So, to increase or decrease the exposure we will be varying the shutter speed. If we were shooting at F5.6 and you were instructed to increase the exposure by 2 F stops, you would open the lens to F2.8 (F5.6 to F4 to F2.8). To decrease the exposure you’d close the lens, going from F5.6 to F11 (F5.6 to F8 to F11) and so on. Doubling the shutter speed (from 1/60 to 1/30) is a +1 EV adjustment.  A -1 EV adjustment would change 1/60 to 1/120 <1/125> and so on.

So the term EV refers to exposure changes using either F stop or an equivalent change in the shutter speed. Shooting at 1/60 second, a “+2 EV” will extend the exposure to 1/15 sec. A  “ -2 E.V.” exposure would decrease the exposure to 1/250 sec. and so on.

If you camera offers an Auto Bracket mode that can be combined with aperture priority, and you set it to + / – 1 EV, the camera would take three exposures 1/30, 1/60, and 1/125, where 0 EV would be 1/60th sec and so on. You would want to use aperture priority to force the camera to vary the shutter speed.

3. So how do I set my camera?

Because HDR photography combines several photos, it’s most important to have consistency with the photos that will comprise the final image. For this reason, you need to turn off as many of your cameras “auto” features as possible. No “auto” or “P” mode!

White Balance: Set to manual and do a manual white balance.

Focus: Critically, manually focus the image. If your camera offers a focus assist mode, use it.

Lens Aperture: If you shoot in a totally manual mode, set your lens aperture at about F8 – F11. You can also use aperture priority, selecting the same aperture.

ISO:  I prefer shooting at ISO 100 – 200, to keep the noise to a minimum. Cameras with larger image sensors can use higher ISO’s and maintain a good overall noise performance. Higher ISO’s can be used and noise reduction software can work wonders!

Shutter Release:  In order to minimize any camera movement it is highly recommended to use an external shutter release cable (if your camera supports this feature). If it doesn’t, most cameras offer a “self timer” Set it for the least setting, usually 2-3 seconds. Press the shutter and get your hands off the camera.

Mechanical Stability: You must use a tripod – the bigger, the heavier, THE BETTER! I sometimes hang a full 1 gallon paint can from the center of my tripod for added stability.

Image Enhancement Features: Any such features that your camera offers should be disabled.

RAW mode:  Generally, you can adjust a JPG image about + / – 1 EV. A RAW image allows for about + / – (2-3) EV. The only photos I regret taking were those I shot in JPG! Whenever possible, shoot in your camera’s RAW mode.  My camera allows me to capture RAW and JPG simultaneously. This allows me to really see how much better RAW mode really is.

Time: It’s more than a song by Pink Floyd … Shooting a good HDR photo requires time, don’t rush it. Including the setup time and tripod leveling  I’ve spent 15-20 minutes for just one tone mapped HDR shot – Don’t rush!

4.  How many photos do I really need to take?

 There is no simple answer, but generally more is better. Forget the techniques about creating a tone mapped HDR photo from one JPG image – this is a waste of time.  If that’s all you are willing to invest buy the Topaz Photoshop plug and create pseudo HDR. I’m not trying to be disrespectful, but it is, what it is.

First: The goal when shooting any scene in HDR is to properly expose the first image so that there is recognizable detail in the brightest component of your photo. This is generally lights or sun lit portions of the photo. Just make sure that the image is dark enough so that the brightest object is NOT burned out. Don’t be concerned if the image is predominately too dark.

Second: Once you’ve got the first shot you increase the exposure so that each subsequent exposure gets brighter and each subsequent shot adds some details from darker areas that are gradually getting brighter. Don’t worry about the real bright areas, these will be severely over exposed, but you’ve captured that detail in the first (darker) photos.

Third: You continue capturing photos until you see some detail in the darkest areas of your photo. In a church, this might be the darkness under the pews or some deep shadow areas.

Depending on the scene, this procedure might take you 3 shots or as many as 8-10. Most of my work usually takes 5-7 RAW shots.

5. So how do I make these exposures?

There are three methods I’ve used – please refer to this photo.

Method #1: My camera offers a “highlight feature.” If enabled, the brightest portions of a photo begin to “blink” from black to white, indicating that in these areas the exposure was too long and the details were lost (burned out).
• Set your camera to aperture priority mode (F8-F11) and take a test shot. Note the aperture and shutter settings.
• Go to manual mode and dial in these settings. Increase or decrease the shutter speed until the brightest component of the entire photo is not blinking. Don’t worry about how dark it looks. Note the settings. For argument sake, let’s say that this turns out to be F8 @ 1/125. This will be your 1st shot.
• Now you will take 1 shot (all @ F8 or whatever you decided to use) at 1/60, 1/30, 1/15 (continue with progressively longer if required) until the darkest areas of the scene you are shooting show detail. Usually you can do it in 4-5 shots. Any increase or decrease in exposure (using shutter speed should be done in 1 EV increments.
• That’s it – you’re done!

Method #2: If your camera does not have the highlight feature, you can also use the spot meter feature. Look into your camera’s exposure menus and set the exposure metering to “SPOT”. Spot metering will usually create a small “bulls-eye” in the EVF or on the LCD. Making this selection will instruct the camera to calculate the exposure on the exact object you sight the spot target on. Set your camera to aperture priority (say F8-F11) and sample at least 8-10 points in the scene, from brightest to darkest. Be sure to sight the bright lights, and the dark areas, like under pews. Write all the readings down. For the bright light you might see 1/500 or maybe even 1/1000, while the very dark areas will require 1/25 or longer. Note the shortest and the longest exposures and take at least 4-5 shots spanning the lowest and highest. You will be in manual mode, using a fixed aperture, and you’ll be adjusting the shutter speed. So your exposures will look something like 1/500, 1/250 1/125, 1/60. 1/30 (longer if required).

Method #3:  Using your cameras Auto Bracket mode. Most cameras only offer a total of 3 exposures, where you can select the amount the darker and lighter shots will be bracketed. If this is the only mode you have I suggest shooting one set at + / – 1 EV and another at + / – 2 E.V. If the camera was on a tripod you could actually get a total of 5 shots, bracketed from -2, -1,  0, +1 and +2 EV. Some cameras do allow many more auto bracketed shots such as my Panasonic Lumix which can go up to 7 shots. Auto bracket is the easiest way to shoot, but not necessarily the best. I’ve found, often that I discard the +2 EV shot as its too bright and really does not offer any additional detail. If used, it can detract from the overall image.

6. My Workflow

HDR photography can be as simple as combining a few photos using Photomatix, Photoshop or one of the many other HDR tone mapping software’s that are available. My primary workflow has expanded to now include several different pieces of software, some to simply automate the overall process.

 Step 1: Captured images (in RAW format) are imported into Adobe Light Room. “LR” provides an easy way to look at all my images in “strips” resembling strips of film negatives. But more important, I can make changes (such as white balance adjustments) to one photo, and have them equally applied to all or as many as I choose in a few clicks.

Step 2: I also use X-Rite’s  Color Checker Passport product. On location, I snap one RAW shot of this pocket sized color chart. Back at home it allows me to create a custom color profile for my camera and the specific lighting conditions I shot under and apply that color profile to all the shots using Light Room’s develop settings.

http://www.xritephoto.com/ph_product_overview.aspx?id=1257&tab=videos

 Step 3: The selected photos are automatically exported to Photomatix via their free Light Room plug-in.  This plug-in automatically exports the RAW images, as TIFF files, where Photomatix automatically combines them and process them into the HDR image ready to begin tone mapping.

 Step 4: Photomatix can do batch processing, though I prefer to do each tone mapped image individually.  I’ve noticed that there is a slight difference between Photomatix’s preview screen and the final rendered image. Once I obtain the final look I like, I save all the settings so I can  go back to these settings at a later date. At this stage in my work flow all images are saved in the 16 bit TIFF format. Each image usually is 70-75 MB in size.

 Step 5: Open the tone mapped TIFF file in Photoshop CS4 where I can do any global color correction. Since I’ve taken the time to color calibrate my system, I can come pretty close to “what I see is what will print.” I’ve found Costco’s photo printing to be both and excellent consistent quality and a very good price value. An 11 x14 print cost just $2.99, with 12×24 or 12×36 at only $4.99. Costco also provides printer profile for each printer in each store, so these are also installed into CS 4 as part of my photo proofing process.

 Step 6: Viveza 2, a CS4 plug-in is my Swiss army knife if I need to make any selective adjustments of color, contrast or brightness.  If I could only have one plug-in, this would be it!

 Step 7: Occasionally. I use a little known software called Focus Magic. FM can make minor focus corrections using pixel shifting. Especially in print, this can really increase the fine detail without adding noise.

 Step 8: Next, I look at my image at 100-150% to see if there is any objectionable noise (which is not uncommon with tone mapped images). If need be I apply noise reduction with Imagenomic’s Noiseware plug-in.

 Step 9: The final step is to save your file. I save mine both as a TIFF file and as a JPG. Since the TIFF files tend to get large, each shoot is saved to a separate CD or DVD. That’s it, you’re done!
7. HDR Software and other useful software I use.

Asking what the best HDR software is, is like asking what’s the best beer? It all depends what you like!

Photomatix is by far the most popular, and generally produces very good results. www.hdrsoft.com

 HDRMAX consistently produces a sharper end result, though it takes a bit of playing to get accustomed to the interface and what each control does. One of its advantages is that is displays each photo as a thumbnail that can be temporarily removed from the HDR process to see how it will change the end result. For reasons I cannot explain, HDR MAX seems to have problems with “woody” color tones, so I tend not to use it when the photo has lots of wood and wood tomes in it. All things considered,  it’s definitely worth a try. http://www.ariea.com/products/hdrmax/

Essential HDR is a very good package, reasonably priced, that concentrates on producing  natural looking tone mapped HDR images. The interface is clean and easy to use. If you are a fan of the cartoonish HDR look, skip this one.  http://www.imagingluminary.com/

Artizen HDR is another popular package, though in all honesty I have not used it too much. The attempts I’ve made to use it always seemed to produce exaggerated results with over saturated colors. There are many people who swear by it, so please give it a try.  http://www.supportingcomputers.net/

Noiseware  by Imagenomic is by far one of the best noise reduction software packages  I’ve used. I’ve found that it can remove a fair amount of noise, with the least reduction in fine detail. http://www.imagenomic.com/nwpg.aspx

Focus Magic is a little known software that can correct minor focus problems by using pixel manipulation.  Even when you critically focus an image, your camera’s sensor has some inherent focus error. When the correction is limited to 2-3 pixels, the fine detail in printed photos can really be enhanced without adding any visible noise. Focus magic is often the tweak you need when noise reduction slightly softened the final product. http://www.focusmagic.com/

I’ve saved the best, for last! Of all the plugins I use, Nik Software’s Viveza 2 is the most used software of my HDR tone mapping workflow. Viveza 2  simplifies the Photoshop concept of working in layers. It allows you to place an “anchor” and define a circular area around it. More important (in my opinion) is that it seamlessly blends the edge of the defined area into the rest of the image. You can adjust color, saturation, brightness, structure and other parameters In a few seconds.  Each anchor is created as a separate layer, so it can be easily deleted before you merge the layers in Photoshop. http://www.niksoftware.com/viveza/usa/entry.php?view=intro/usa_viveza2_announcement.shtml

7. HDR Books and Web Sites

I’ve read several HDR books. The one I find myself going back to, most often, is The HDRI Handbook by Christian Bloch. Some people complain that it gets too technical, but it’s the only book that teaches you the physics of digital photography and how HDR deals with many associated issues. Read it, one chapter at a time and digest it. There is a lot to learn if you are willing. http://www.hdrlabs.com/book/

 http://www.hdrlabs.com  is a great web site, but the person who runs it has a definite dislike for Internet Explorer 6 – you can’t access this site unless you are using the latest version of IE. I use FireFox, so it’s not a problem. This site offers monthly updated HDR topics that are always on the cutting edge. Bookmark it!