Discover High Dynamic Range (HDR) Imaging
An Excerpt from Improve Your Photography: 50 Essential Digital Photography Tips & Techniques
HDR represents a major development in the past few years for new techniques for digital photographers. I rate this pretty high, up there with the advent of RAW image file formats, full frame digital SLRs, Lightroom and Aperture.
As digital photographers, we’ve seen leaps in technology for a few years now. 10 years ago, it was the advent of the digital camera. Soon after, we were able to purchase 5MP compact digital cameras for under $1000 U.S.! Then a few years later, we saw the first digital SLRs hit the market that were around the same price. The Nikon D70 and the original Canon Digital Rebel really fueled the digital SLR proliferation, putting feature-packed tools in the hands of the budding photographer at a decent price point. Today, we’re even getting full HD quality video out of our digital SLRs, with quality that challenges $40,000 cinematic movie cameras! Live LCD image review are now becoming standard equipment. We’ve come a long way.
In the last decade, software has also advanced. Photoshop is currently in its 11th or 12th version. Camera Raw is now a standard file format for capturing images. There are many highly respectable third-party image-editing add-on’s for Photoshop, Elements, Aperture and Lightroom. We’ve also seen a new trend in the past few years that is remarkable. High Dynamic Range (HDR) imaging has become a reality for the digital photographer.
What is High Dynamic Range (HDR)?
HDR is actually a simple concept, but somewhat tricky (until now) to implement for digital images. HDR is a number of images, taken at different exposures that when combined in software, contain an entire dynamic range of the scene, elements from the extreme shadows to the extreme highlights, and everything in between. Got all that?
Think of your typical single image metered with your digital camera. Your digital camera can meter a scene the best it technically can, typically in the range of 4 to 9 f/stops. Our own eyes and brain view a scene, and can interpret approximately 9 to 14 f/stops! That’s quite a difference, one that you have no doubt experienced. This is the primary reason, as you recall, that you often shoot scenes that appear to you straightforward, but when you view them on your computer or LCD screen, the image lacks detail in shadow areas, or has blown out highlights in the lighter areas of the image.
An HDR image, when shot and processed properly, will give you detail in a much larger dynamic range than a normal photograph can present.
Factoid: A typical digital SLR camera can read a dynamic range of 4 to 10 f/stops (EV range). Our eyes and brain can see 9 to 14 f/stops (EV range)
Overview of the HDR Process
Creating HDR images takes a few things that your currently may not be doing. First, if you aren’t, you should be bracketing your exposures when you’re out in the field taking photographs. Second, you’ll need some additional software, I recommend Photomatix Pro. Photoshop or Elements does not have the capability of fully processing HDR images, hence, the additional software need. Photomatix is the most popular.
With those thoughts in mind, lets look a the process:
- Shoot bracketed exposures: Bracketing is a technique photo geeks like me used to do back when shooting in
the film days. Back then (a mere 10 years ago), we didn’t have LCD screens on our cameras where we could view the results of taking a photograph, or view a histogram. Bracketing entails taking multiple photo’s of the same scene, using different exposures. That would mean shooting in Aperture priority mode, and setting your cameras autobracketing setting to taking 3 images, one at the metered exposure, one -1/3 to 2 stops, and the other +1/3 to 2 stops, depending on your taste. When shooting transparency film (slides), we had a limited dynamic range to work with, so I always bracketed my shots at 2/3rds of a stop. For HDR images, I actually prefer setting my autobracketing to 2 stops. - Process your multiple (bracketed) exposures in Photomatix Pro. This isn’t a Photomatix Pro tutorial, but, choose the Merge to HDR option. Photomatix Pro will automatically create a 32 bit HDR file.
- Tone Map the HDR Image. This is where Photoshop (at least not yet) can completely process an HDR image. Tone mapping transforms the image file to where the entire dynamic range of the exposures you provided are mapped in the image.
- Save the image. I choose TIF as the format to save my HDR tone mapped images in Photomatix Pro.
- Open the new tone mapped image in Photoshop or Elements. You’ll need to fine-tune your image in Photoshop or Elements in this step. There may be a color cast that may need to be corrected. Additionally, you may want to make adjustments to Levels and/or Curves to improve contrast to your liking.
That Unreal Look
HDR images, or actually, the photographers preferred output of HDR images can be what is considered “hyper-real”, or surrealistic images. Cruise the net for HDR images, and you’ll see a lot of portfolios out there where the photographer displays very hyped up versions of their images. It seems to be a trend that goes hand in hand with HDR imaging. Actually, its one that I add to my “arsenal”, and one that you should investigate as well.
I’ve heard some so called “experts” in the field call these images “cartoons”, or not true photographs. Au Contrair Pierre! I beg to differ. I’ve seen absolutely stunning work from photographers using HDR techniques. Folks its here to stay. I actually prefer that surrealistic appearance for some of my work, particularly my portfolio work on abandoned structures and urban decay.
In the least, whatever your personal taste is as an artist, you can have it both ways, straight or unreal.
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