Managing High Dynamic Range Scenes
The first question that needs to be answered is “what is a high dynamic range” scene. The answer is quite simple, as it is a scene that exceeds your camera’s sensor’s ability to record the entire scene without blocking up shadow details or clipping highlight details at a given ISO setting. If you look at your histogram and see a scene where there is a spike at both the extreme left hand side and the extreme right hand side, as shown in this example. The camera’s sensor cannot capture the dynamic range of an image like this one without resorting to a special technique using multiple bracketed shots that are blended together using software.
In this example, the Adobe Camera Raw histogram shows a little triangle at both the left and right side indicating that this is an image where I have exceeded the camera’s ability to capture the scene. This is referred to as the camera’s dynamic range and can range from around 10 eV (stops) for older consumer level camera to close to 15 eV for some modern high end camera. Dynamic range is highest at base ISO and can drop rapidly as higher ISO values are used. A good source of information on a specific camera model can be found at DxO Lab’s DxOMark website: https://www.dxomark.com/
This screen capture of the currently top-rated Nikon D810, taken from the DxO Mark website, shows the how ISO settings affect dynamic range. Shooting at higher ISO settings increase the likelihood of needing to use a technique like the ones in this document.
All the techniques for dealing with this situation require taking multiple bracketed exposures and then blending them in software. These techniques generally only work well if there is NO motion, so are applicable to static subjects like landscapes. It is best to shoot with a tripod, but modern software can cope with handheld shots too, so long as there is relatively little movement between frames. Many cameras feature an auto-bracket function that lets the photographer fire off a sequence of three or more shots that vary by at least 1 eV. When bracketing, make sure to turn off auto focus, auto ISO either shoot on manual or aperture priority to ensure that the depth of field on each of the shots is the same. If using a zoom lens, it is critical that there is no change in focal length between any of the shots, otherwise the technique will not work
This is what a series of five bracketed shots looks like. Here I shot a range of exposures of -2. -1, 0, +1 and +2.
So far as I understand it, there are three main techniques for blending theses shots to create a well exposed image:
1 – HDRI (High Dynamic Range Image) – which uses a specialized software and tone-mapping techniques where colours are replaced with appropriate colours. Photoshop, Adobe Camera Raw and Lightroom all have this functionality. There is also commercial software (PhotoMatix is probably the best known) and there is also free software, like Google’s Nik Collection Hdr Efex Pro 2 which are specifically designed to create HDR images.
All have strengths and weaknesses. Some of these packages can produce very funky colours, much loved by amateurs but generally frowned upon by many serious photographers. If pushed too hard, unattractive halos will be created in the final image.
Generally, HDR images are low contrast and need addition post-processing work to tweak the image. A common mistake is to use HDR images without tweaking them in post.
2 – Image fusion – the donation-ware software like command line Enfuse or LR/Enfuse blends properly exposed areas of the various images to create the final image. This approach tends to have a more natural look with more realistic colours than the HDRI process. Just like the HDRI process, the overall contrast is low and some additional post-processing work will be required on the image.
3- Manual blending – This requires a good working knowledge of layers and layer masks in Photoshop. The technique is somewhat similar to how Enfuse works, except that the photographer, rather than an algorithm determines how to blend the image. While this is the most time-consuming of the three processes, I find that the results are superior.
And here is the final image after manually blending 5 different exposure images.
Post by: Manfred Mueller
Manfred got his first camera as a child and by the time he was in his late teens, he was being mentored by a commercial photographer, so he was quite familiar with handling cameras as well as developing and printing in both B&W and colour in the wet darkroom. He also have quite a few professional level college courses on photography and videography under his belt.
With all that training and experience, one might think he was a career photographer, but he’s not. He’s strictly an amateur. From a career standpoint, he’s an engineer, so as one might imagine, he is extremely analytical and interested in the technical as well as the aesthetic sides of photography. He retired almost two years ago and have spent much of that time pursuing another one of his favourite activities, traveling around the world with his wife, photographing the people and places he sees along the way. He has been to well over 50 countries and have visited well known and sophisticated cities and some rather remote and primitive places on every continent except Antarctica.
When it comes to photography, he is interested in photographing most things, from formal studio work to shooting wildlife in some rather out of the way places. He is quite knowledgeable in the digital darkroom (He has been using Photoshop since 2003) and he is someone who still feels that the print is the ultimate output of an image, so he is an experienced digital printer as well.
And as you might have guessed, he is not Indian. He was born in Germany, but he lives in Ottawa, which is the capital city of Canada. In his own words, “It has the honour of being the second coldest capital city in the world (Ulan Bator in Mongolia is the coldest) and it is also one of the snowiest cities in Canada, receiving around 2.25 meters of snow every winter. I think you can guess at why I like traveling…”