http://www.cambridgeincolour.com/cambridge-gallery.htm http://www.pixelandpoly.com/nyc_in_hdr.htm This site is composed of detailed information and a large impressive gallery by Sean T. McHugh. PhD.. Go there and come back here and read the rest.
In real life situations, when one stands inside a room observing the interior, the interior appears to be illuminated sufficient or adequate to see detail. If one looks outside the interior through an open window or doorway into a well lit outside location, the detail of the view is clearly visible as well. The reason for this is that the eye makes the adjustment between the two light levels instantly. The camera however does not have that capability therefore producing an image correctly exposed for the interior and over exposed for the outside light levels or, correctly exposed for the outside illumination and under exposed for the inside. High dynamic range imaging was originally developed in the 1930s and 1940s by Charles Wyckoff who did extensive experimentation with bracketed exposure techniques and "sandwiching" the correct-under-over exposed images into one image. Under exposed images have better detail in the brighter part of the image where over exposed images have better detail in the shadow parts of the image and the correct exposed image has better detail in the mid range and lost detail in both upper and lower part of the exposure range. Sandwiching the three or more different exposed images together combines the best of all into one image therefore showing a wider dynamic visual range of the scenery photographed. The process of tone mapping together with bracketed exposures of normal images, giving the end result a high, sometimes exaggerated dynamic range, was first reported in 1988. In 1995 a paper was published by Steve Mann and Rosalind Picard discussing a mathematical theory regarding differently exposed pictures of the same subject matter and combining them into one high resolution image. In 1997 this technique of combining several differently exposed images to produce a single (HDR) image was presented to the computer graphics community by Paul Debevec and the method to produce a high dynamic range image from a set of photographs taken with a range, usually of three or more exposures, was officially coined High Dynamic Range Imaging. With the rising popularity and capabilities of digital cameras and consequent computer software, the term HDR is now universally used to refer to this process.
In the event of outside night photography, a sensitive light meter is needed to calculate the bracketing or stop spread from the nominal. A small flashlight and an assistant to help and hold things is a nice addition.
The above images were made with a Canon 50D and auto-bracketed one stop plus and minus of the auto/nominal exposure. Note the HDR outside and inside detail. The HDR processing was done with Photomatix software. This technique applied to interior decorating and architectural photography provides for an outstanding quality product. High dynamic interior scenes with lots of glass and a sunny day may need as many as six 1.5 to 2.0 stops apart or nine exposures 1 stop apart. If bracketing exceeds more than three, shooting manually would probably the thing to do.
HD images taken with people in the frame requires these subjects to be motionless for the duration of the triple exposures needed. Anything that moves, looses its crispness but sometimes can accentuate something in the image to make it outstanding. Landscape photography requires a wind still moment. No movement can be tolerated otherwise greenery of any kind becomes a blurry scene during the lapse of time it takes to take the three exposures destroying the objectivity of the shot. As a point of interest, if the wind rocks the lens 1 minute (1/60 degree) left and right, (two minutes total) an object at 100 feet (120 inches) moves about an imaginary* 0.070 inch total. That is enough to remove tag sharp quality from an image. * It is not the scenery that moves but the lens and camera on the tripod. Some HDR processing software like Photomatix, provide for "Source Subject Realignment" and "Ghosting Artifact Reduction" allowing for a certain amount of subject movement realignment. This usually goes at the cost of some loss of image sharpness. What's left one would say? Still's, early morning and/or night scenes, buildings, churches, architectural, indoor/outdoor decorating all make excellent subjects especially if you pay attention to the available light. Momentary light sources such as fill flash can not be used although fore ground fill lightning in the form of soft box light or even a simple hand light (stationary positioned) can do wonders. Camera settings
Night or twilight photography may require a light meter if the exposure levels go beyond the slowest camera exposure settings and into the "bulb" method of setting . Also, paper and pencil may help you calculate the "bulb" bracketing settings. Shooting HDR
Image in-process evaluation and criteria.
Input files accepted,
Output file capability,
A product manual is available on the Photomatix download site. I suggest highly to try the Photomatix and get the manual for orientation.
Three images bracketed two stop apart can make for an outstanding picture. Six images 1.5 stops apart make an even better one and for some bright lit inside/outside scenes Photomatix recommend nine images one stop apart. I have not had the opportunity to do the latter however, I have however experimented adequately with two-stop bracketed HDR images because my Canon 50D has simple camera setting capabilities to make "triple image two-stop bracketed" picture taking rather simple. I am impressed with the results of the two-stop bracketed HDR pictures but I am very impressed with the pseudo HDR images obtained from a single RAW image! Below is an example of a triple image Photomatix processed HDR Image.
When it comes to a single processed image, there is no question about it! A single RAW Images processed with Photomatix compared to images processed manually with Photoshop, Dxo, Therapy or Canon EOS professional, have more luminance, proper contrast, better highlights and as a whole look better. In addition, Photomatix gives one an opportunity to enhance and change the character of the image. See the example below.
How did Photomatix do this? Probably by creating two additional images in memory, two exposure levels apart using the EXIF data from the original RAW input image and reassembling the original and the two pseudo images into a tone mapped end result. Clever and rewarding! One can also take a RAW image, use any RAW editor like Photoshop to make two copies each two exposure values plus and minus and use the Photomatix multiple image input HDR processor to generate a similar or better quality HDR picture. Better yet, take one deserving JPEG image, use an editor to make two copies, one plus two exposure values and the other minus two exposure values then use the Photomatix multiple image input HDR processor to generate a noticeable improved HDR picture! This technique and the software are opening up a whole new way of generating high quality selective imaging making adaptable to landscape, stills, architectural and many other non-activity photography. Now we need a new camera with three processors making three images at once, each two stops apart to create high dynamic range action photography. What else do we crave? Note, A number of HDR images can be found on the following pages of this web site. For Canon 20D and up users As a matter of convenience for myself, I wrote a the working sequence as related to shooting HDR images on 4 x6 inch standard size glossy print stock to refer to in the event of senior citizen moment. For those readers who own Canon digital SLR's the instructions are below. Copy them if you can make use of them!
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