Moon Over Piedras Blancas Bluffs ©Renee Besta
There are a ton of HDR tutorials on the internet. There are very few that frame them through the lens of printing. This week we start a three part series from Renee Besta on HDR and printing. A start to finish encyclopedic tutorial on how to print great HDR photographs.
Originally developed for use in the movie industry, HDRI (high dynamic range imaging or just HDR) was once a well-kept secret in Hollywood’s CG artist community. Now a much more mature technology, HDR has found its rightful place in digital photography, resolving the age-old film photography dilemma of whether to expose for the highlights or shadows. HDR allows photographers to capture the full range of luminosity in a scene, despite great differences in tonality. From bright sunlight to the deepest shadow details, HDR captures it all. With so much tonal information available in an image, the bar has been raised to new heights, yielding stunning images and prints.
HDR has been in my arsenal of tools since 2007, shortly after I discovered a wonderful book by Emmy award-winning visual effects artist Christian Bloch, The HDRI Handbook. In his book, Mr. Bloch states that HDR is akin to a digital negative on steroids, and with that I concur. Coupled with the inspirational images of Photoshop guru/instructor Ben Willmore, an entirely new world was opened up as I was able to capture all tonal values present in a scene. My photographs could now convey those scenes as I experienced them, without compromise.
Over the past four years, HDR software and related plug-ins have greatly improved, bringing with them a steep learning curve, ever-increasing computer hardware requirements, and many choices. The plethora of HDR information available on the web is enough to make the average photographer’s head spin, with conflicting opinions on how best to merge, tone map, and post-process images. But before we can begin to talk about the printing process, it is necessary to take many steps back and be sure we are adhering to best practices for HDR shooting/processing and color management. Producing the highest quality fine art prints begins with a properly processed image file.
I realize many of you are advanced photographers; however, it has been my experience as a fine art printer and instructor that even the best photographers may be unaware of basic information necessary to produce prints that really pop. Since you have taken time to read this article, I presume you are interested in taking your images and prints to the next level, and are willing to put in the time necessary.
In this series, we will cover everything you need to know from camera settings and color management, to post-processing and printing tips. I will attempt to simplify things by walking you through the necessary steps to produce superb prints from your HDR images. For the purpose of this article, I assume you own a digital SLR camera, are using an image editing program such as Photoshop, Lightroom, or Aperture, and are somewhat familiar with HDR processing software.
Although there are now many fine software programs available to merge and tone map HDR images, I will be focusing on Photomatix Pro by HDRsoft, as it remains a staple for many HDRtists. Photomatix has been around a very long time, has a great reputation, and is still very popular. Other popular options include Photoshop CS5’s built-in HDR Pro, Nik Software’s HDR Efex Pro, and Unified Color’s HDR Express/HDR Expose. Whatever software you choose, the basic principles remain the same. Once certain terms and settings are clarified and put into practice, you’ll be making images and prints like a champ. So, let’s get started!
Proper Camera HDR Color Spaces and Settings
Before the shutter button is even pressed, we need to step back and be certain the camera’s settings are optimized for HDR shooting. Here are some important points to keep in mind:
- For best results, shoot in Camera Raw mode. This will enable you to capture the most tonal (or brightness) values in a scene by keeping the image in 16-bit mode and avoid having the camera make any processing decisions. Raw files include 1 to 2 EVs (exposure values or stops) more at each end of the exposure, so they contain much more tonal information than jpegs. This is why the Recovery slider in Photoshop Camera Raw or Lightroom is so efficient in regaining lost highlight information. Something not possible with jpegs.
- If shooting jpegs, please be aware that by nature jpegs are compressed 8-bit files, which translate to 256 tonal values. Eight bits is 2^8 which equals 256 values, ranging from 0 (black) to 255 (white), not even close to what the human eye can see. In contrast, 16-bit files contain over 65,000 tonal values; however, one of those bits is used for something else, so Photoshop can only use 15 bits. That still gives us 2^15 which equals 32,768 values, a whopping amount.
Since the point of HDR is to capture as much tonal information as possible, shooting jpegs defeats this purpose. Not to mention the fact that in 16-bit mode you have much more leeway when editing your images because you are starting with many more tonal values. Keeping an image in 16-bit will reduce banding and posterization. If you have ever applied adjustment layers such as Curves in Photoshop to an 8-bit image, you probably noticed the resulting ‘combing‘ in the histogram. This translates to lost information, and is represented by the white vertical lines. Below is an 8-bit HDR tone mapped image with no adjustments applied yet in Photoshop CS5:
Below is the same 8-bit image with a slight Curves adjustment applied. Notice the combing in the histogram (seen as vertical white lines):
Can you bracket and tone map jpegs? Of course, but for the purpose of this article, we are aiming for best practices that will result in the highest quality prints. Heck, there are now apps for the iPhone that allow you to make ‘HDR’ images. Pseudo-HDR images can be produced from a single shot and then given that ‘HDR look’ with various plug-in software. Some HDR software companies emphasize the option to shoot in jpeg. Nothing wrong with that as it has its place; however, keep in mind that these companies are trying to sell their software to the largest, most diverse group of photographers, and are not necessarily aiming for best practices or high quality print output. In today’s digital world, most images end up being posted on the web, yet never printed. Thus the plethora of 8-bit sRGB images floating around. This is a fact lamented by many and discussed by respected photographer, printer, instructor, and writer David Ulrich in “Are You a Craftsman Dedicated to Mastery?”
- All digital SLRs allow you to select a color space, with the choices being either sRGB or Adobe RGB. We will discuss the merits and meanings of various color spaces later, but for now select Adobe RGB, which will give you the greatest color gamut. On my Nikon, this menu can be found under Shooting Menu > Optimize Image > Custom > Color Mode. Check your user manual for details. Please be aware that this only has an effect if you are shooting jpegs, as the camera will apply that color space and compress your image down to 8-bit. Note that if shooting in Camera Raw, this setting is irrelevant, as no on-board software processing is done by the camera. However, as you may need to shoot jpegs from time to time, it is best to set the color space to Adobe RGB and leave it there. We will talk more about color working spaces later.
- When shooting HDR, it is important that the camera be as stable as possible (on a sturdy tripod) and that the images are shot in quick succession. Otherwise you run the risk of misregistration, blurring, and ghosting (moving objects in the scene) when merging the files. Use a cable release to reduce camera shake and always shoot in aperture priority mode, varying only the shutter speed. After focusing the camera, switch from autofocus to manual focus mode; if not, you run the risk that the camera will change the focus between exposures. (This is particularly important in scenes with low light, as the camera may attempt to refocus between the bracketed shots.) If your lens has image stabilization, turn it off when using a tripod.
- Shoot at the lowest possible ISO to avoid noise (HDR software will exaggerate noise), and enable your camera’s continuous shooting mode. To further avoid shake, use the mirror lockup mode or enable the exposure delay mode on your camera.
- Enable your camera’s autobracket mode, which allows you to select how many images will be shot automatically in a sequence and at which exposure intervals. Each digital SLR has its own limitations when it comes to autobracketing, so refer to your user manual for details. Professional high-end cameras may enable you to shoot up to nine bracketed shots at the EV interval of your choice, while others are limited to three shots at 1 or 2 EV intervals. Obviously the contrast in the scene determines how many exposures are necessary, so there is never a definite number. But I have found that shooting a minimum of 5 shots in 1 EV intervals gives me good results. This amounts to 2 over, 1 normal (as metered), and 2 under, a good starting point. For a scene with more contrast, I may shoot nine images, 4 over, 1 normal, and 4 under. There is varied opinion on whether to shoot 1 or 2 stops apart, with most tutorials recommending +2, normal (as metered), and -2 as a starting point. While this will often work just fine, I have sometimes found that 2 stops apart in exposure may be too much, depending on the contrast of the scene. Image details may end up being compromised, resulting in increased noise and artifacts. In general, the more images I feed Photomatix Pro, the better results I get. Hey, this is a digital camera, so extra shots are free! Simply stop and think when you’ll be photographing a particular location again. If the answer is not in a long time, then shooting more images is the way to go. Shortcuts do not pay off.
- Here’s a tip for overcoming the limitations of your camera’s built-in autobracketing feature: add exposure compensation to the mix. My Nikon only allows me to shoot 3 exposures, although I can choose the EV intervals I want up to +/-2. When encountering a scene with great contrast, such as the inside of a building with bright light through the windows, many more exposures are required. Thus I set up autobracketing and take my three usual shots at 1 or 2 EVs apart, then dial in exposure compensation on top of that and shoot another three to nine images, depending on what is needed. That way I am covered.
Alternately, shoot in manual mode at a fixed aperture. Meter for the darkest and lightest areas in the scene, which will provide you with the shutter speeds necessary to cover the complete tonal range. Then begin by shooting for the highlights (underexposed shots) and keep adjusting the shutter speed until you have covered the shadow areas (overexposed shots).
The best solution, though, is to purchase an intervalometer such as the Promote Control by Promote Systems. This wonderful device allows you to program how many bracketed shots you want and at what EVs. It is an advanced remote control that works with most digital SLRs. It is also excellent for noctography (night photography), allowing you to enjoy a hot cup of coffee while the Promote does its thing.
- It is important to note that only by viewing the histogram on your camera’s LCD can you verify that you have taken enough shots to cover the entire tonal range of a scene. Be sure there is no clipping in the shadows or highlights. In particular, be sure you have not clipped the highlights by making certain there are no ‘blinkies‘ on the histogram in the underexposed shots. Blinkies refer to the flashing that occurs when reviewing your images on the LCD; the areas with highlight clipping flash on and off. It is very important when shooting HDR that the shadows are not blocked up nor the highlights blown out. If care is not taken, the HDR software will try and create details where none exist, thus causing much noise, ugly gray skies, and other artifacts. All of this adds up to one unattractive print. When shooting outside under bright sun, it can be difficult to read the histogram on the camera’s LCD. In that case, try to shade it with your hands or a hat, or purchase a loupe from Hoodman.
- Finally, I recommend you change the order the bracketed images are shot in to make things easier when later reviewing your images. I set up my Nikon to first shoot the underexposed images, then the normal one, followed by the overexposed images. This order makes most sense when viewing the bracketed shots in Lightroom or Bridge, as there is less confusion as to when one sequence of shots ends and the next begins. Refer to your manual for directions.
Photoshop and Camera Raw Color Settings
Before you begin processing your images, whether HDR or not, it’s important to be certain the proper color settings are enabled in Photoshop. I have come across many clients who were having trouble with prints, only to discover they were working with ‘untagged’ images – those without a color space assigned – or had recently upgraded to a new version of Photoshop and did not redefine the default color settings. Let’s review the color settings in Photoshop. For whatever reason, the powers-that-be at Adobe set the default Photoshop Color Settings to North American General Purpose 2, even though this is not optimal for photographers unless the images are intended for the web or commercial printing. Begin by going to the Edit menu, then down to Color Settings.
The Color Settings dialog box will then open, and the default settings will be shown unless you have already changed them. If you cannot see all the options, click on the More Options button on the right. Here is what the default settings look like right out of the box:
Note the Description box at the bottom. It states that these settings are intended for screen and print (meaning 4-color CMYK commercial printing, not RGB inkjet printing). In addition, the profile warnings are disabled. As digital photographers and inkjet printers, we are most concerned about the RGB settings, color management policies, and rendering intent. In order to obtain the widest possible color gamut from our images, and therefore our prints, we need to change these settings and save them as our new default. Please refer to the screenshot below demonstrating the settings I use:
Starting from the top under Working Spaces, change the RGB to ProPhoto RGB and the Gray to Gray Gamma 2.2. More on this in a moment. Under Color Management Policies, keep the defaults for each color mode to Preserve Embedded Profiles, then check all the boxes under Profile Mismatches and Missing Profiles. These policies establish how Photoshop handles images whose profiles don’t match your preferred color working space, or images with untagged or missing profiles. If there are mismatches when opening an image, you will receive an alert and be given the option to use the embedded profile, convert it to your default working space, or discard it. This serves as a safety net; otherwise you may not be aware what color space you are working in upon opening an image.
Under Conversion Options, Intent, there are basically two appropriate choices for photography: perceptual and relative colorimetric. Simply put, rendering intents are various ways of handling colors that are out-of-gamut – colors present in an image (source) that a printer (destination) cannot faithfully reproduce. The perceptual rendering intent will shift (compress) the colors in an image in an attempt to preserve ‘visually pleasing’ relationships, thus remapping colors that Photoshop thinks are out of gamut. However, with today’s advanced printer technologies, some colors that overlap into the ProPhoto RGB space can now be printed on certain papers. Thus, the relative rendering intent is my first choice. (I would recommend when printing to experiment with both rendering intents.) When you are finished, be sure to click on the Save button and give your new default color settings a name.
RGB Color Space
A word about RGB color spaces – it is preferable to use the widest possible color gamut, which today means ProPhoto RGB, developed by Kodak. The prior gold standard, Adobe RGB (1998), works fine, but you may lose vital color information in your HDR image and therefore your print. Be aware that Camera Raw’s (and therefore Lightroom’s) default color space is ProPhoto RGB, so why use anything less? The sRGB color space, also referred to as standard or small RGB, was developed by a team led by Michael Stokes at Hewlett-Packard in conjunction with Microsoft, and is the smallest color space intended for web use. (Trivia: the ‘s’ in sRGB stands for Stokes.) This smaller space is used so that images can be properly displayed on an assortment of monitors and in browsers with varying color gamuts. Since most people do not own high-end pro quality graphics displays, this prevents images from looking washed out or like a science fiction movie when posted on the web.
Keep in mind that the goal is to always keep your images as 16-bit tiff or psd files in ProPhoto RGB. You can always export copies as 8-bit jpegs in sRGB for other purposes, such as the web or projection on a screen. Let’s take a look at just how different these color spaces are. The diagram below was made by color expert Jeff Schewe and can be found in the 2004 Adobe whitepaper, “A Color Managed Raw Workflow –From Camera to Final Print,” which he co-wrote with the late, great Bruce Fraser:
It is obvious in examining this diagram that ProPhoto RGB is a much larger color space than Adobe RGB, while sRGB is quite limiting. This is particularly important when shooting HDR, as the resulting 32-bit merged file (from the bracketed shots), even when tone mapped down to 16-bit, produces colors and tonal values that were at one time impossible to render, much less print. The circle marked as ‘2200 matte paper’ refers to results achievable using Epson’s much older Stylus Photo 2200 printer on standard matte paper. It is important to note that there are certain colors that can be printed with this older printer that fall outside both the sRGB color space and the Adobe RGB color space. Since this is so, imagine what current printers can render.
With today’s technological advances, cameras and printers are no longer limited to the sRGB space. For example, Epson’s newer line of printers, the 4900, 7900, and 9900, utilize ten Ultrachrome HDR pigment inks – including green and orange – and can print colors that extend into the ProPhoto RGB space. Thus the importance of starting out with the highest possible color gamut and staying in it. There is just no reason to handicap your images at birth, so to speak. You can always make copies in 8-bit in lower color spaces. In addition, newer professional fine art papers such as the lines made by Breathing Color allow your vision to be seared into print. Not only has printing technology greatly advanced, so have paper manufacturing and coating technologies.
Keeping Your Files Looking Their Best
Another issue may arise when exporting your image files from HDR software, Camera Raw, Lightroom, or Aperture into Photoshop or plug-in software for further processing. It is critical that the file be exported as a 16-bit tiff in the ProPhoto RGB color space and not downgraded at this point. Why a tiff? Simply because most HDR processing software (with the exception of Photoshop) uses tiff or jpeg file formats upon export. The psd format is an Adobe proprietary one. So unless you are using Photoshop’s Merge to HDR feature, your exported 16-bit tone mapped HDR file will most likely be a tiff. There are exceptions to this, such as Unified Color’s HDR Express/HDR Expose software, which allows you to work in a 32-bit floating point environment instead of downgrading to 16-bit.
While it may seem obvious how to keep your files at their best, there are some photographers unaware of how to do this; thus they unknowingly downgrade their images immediately after export from Photomatix, Lightroom or other HDR software. Let’s first take a look at the Camera Raw dialog box. In the screenshot below, notice the colored text at the bottom center that looks like a hyperlink. If you click on this link, it opens a dialog box that allows you to choose your output settings.
Be certain this is set for ProPhoto RGB and 16-bit (see below). The resolution does not matter at this point and can be changed later in Photoshop. However, do not choose to up- or downsize your image relative to its native pixel count. I keep mine at 300 ppi (pixels per inch) so it is resolution-ready for small prints (more on this later). Once a choice is made, it becomes the default for each image you open unless you click on the link and change it. So be sure to always check the link before opening your image in Photoshop.
If using Lightroom, you most likely exported the Raw HDR bracketed images from Lightroom into the HDR processing software of your choice. Once the tone mapped HDR file is sent back into Lightroom, it should be a 16-bit tiff (unless you selected 8-bit jpeg or 8-bit tiff). When exporting your images from Lightroom for editing in another program, the same concept applies. Go to Photo > Edit In > and choose the destination software. You will then be presented with a dialog box of options. In most cases, you will want to ‘Edit a Copy with Lightroom Adjustments,’ not the original. Again, keep the file in 16-bit ProPhoto RGB. If you can’t see the file options, click on the Copy File Options triangle to open it. Once the tone mapped HDR image is downgraded to 8-bit or a lesser color space, information has been irretrievably lost in the exported file. However, you can always go back and re-export the original tone mapped file, but then any post-processing you did after exporting will be lost (unless you wish to use the 8-bit edited file in another color space). Refer to the sample screenshots below:
If you are trying to work with the HDR tone mapped file in Camera Raw and find you can’t open your tiff or jpeg, you need to change your file handling preferences within Photoshop. To do this on a Mac, go to Photoshop > Preferences > File Handling; in Windows, go to Edit > Preferences > File Handling:
Then, under File Compatibility, click on Camera Raw Preferences:
Once inside, look at the bottom under jpeg and tiff handling, and use the drop-down menus to choose Automatically open all supported jpegs (or tiffs). I usually have these disabled, as I prefer to use Lightroom as my Raw editor and don’t want exported tiffs or jpegs sent into Photoshop’s Camera Raw.
Getting to Know Your Image Profile
I am often asked how to quickly verify the color working space and bit depth of an image without going through the usual menus. One easy method I use immediately tells me, upon opening an image in Photoshop, what those parameters are so I can breathe easy. Some photographers are not aware that at the bottom of each document window in Photoshop, a drop-down menu exists that allows you to set your preferences as to what data is displayed. Look at the bottom lower left of the document window, just to the right of the currently displayed document view size, and you will see a small arrow. Click and hold this arrow, and a drop-down menu will appear where you can select your preference. By default, Photoshop sets this to Document Sizes. The option I use is Document Profile, which shows my copyright status, the color working space, and bit depth. See below:
If you are having problems getting to the document window, press the F key repeatedly to change screen modes in Photoshop until it appears.
This was part one of the three part series on How to print HDR photographs — Camera Settings and Color Management. Next will be Monitors and Post-Processing, followed by Printing Tips — Prints that really pop.