Part 1 - Introduction
Part 2 - High ISO Noise
Part 3 - Dynamic Range

In practical terms, the dynamic range (DR) of a camera refers to it's ability to capture image detail in both very dark and very well lit areas of a single exposure. Using conventional sensor technology, this capability tends to correlate with sensor pixel (sensel) size. Working with RAW files generally allow one to access a greater portion of the DR captured in an exposure, and combining multiple exposures is a commonly-used method for capturing the dynamic range of a scene. For more on DR and the explanation of why pixel size matters, this DPReview article is a good place to start.

With the S3 and S5 DSLRs, Fujifilm implemented a novel sensor technology which incorporates two types of pixels of different sizes. The larger pixels are of the conventional DSLR type, whereas the smaller pixels capture additional "bright area" information. The simultaneous capture using these two different pixel types essentially allows the camera to obtain two different apparent exposures in a single image, and the result is class-leading DR based on additional highlight detail.

To date, no other manufacturer has introduced a production camera with such an effective system for improving the DR capability of a sensor. Instead, the approach taken by others has largely been to underexpose and then selectively map tones to incorporate greater highlight detail without actually increasing the DR. Highlight Tone Priority (HTP), featured on the latest Canon DSLRs, is an example of such an approach. The way HTP works is that the camera underexposes the shot to preserve highlights and then applies a proprietary contrast adjustment to "push up" low and midrange tones. For example, a Canon DSLR set to ISO 200 with HTP engaged will use aperture and shutter speed settings corresponding to those necessary for a proper apparent exposure at ISO 200. Meanwhile, the analog gain applied to the sensor is that of ISO 100 rather than ISO 200. Thus, the actual apparent exposure will be one stop underexposed. However, the in-camera JPEG processing is such that everything but the highlights is brightened as needed to simulate a proper apparent exposure in those areas. The result is that the highlights are properly exposed, and the expense is that the low and midtones are noisier because they represent ISO 100 (analog gain) "pushed" to ISO 200 (equivalent) using digital gain. This application of digital gain results in increased noise as explained in this rather technical thread and demonstrated in these examples from Joe Mama.

It is worth noting that the actual DR captured in a RAW file taken at ISO 200 with HTP enabled is no different than that of a corresponding RAW file taken at ISO 100 set for 1 stop of negative exposure compensation with HTP disabled. Nevertheless, this feature provides great value to the JPEG shooter for scenes prone to highlight clipping and may also benefit the RAW shooter who does not want to invest the time and energy in adjusting levels/curves after the fact (Canon's RAW conversion software will do the manipulation for you on RAW files obtained with HTP enabled). Click here to see Ron Purdy's excellent example of the benefit of HTP. Nikon's approach, termed Active D-Lighting, is also based on underexposure, though the implementation is different.

Fujifilm's press release for the F100fd states the following:

NEW Wide Dynamic Range

Dynamic Range, or the gradations of light that exist between bright and dark in any scene, can be easily detected by the human eye, but not by most cameras. Fujifilm first expanded dynamic range capture functionality on the professional imaging side with its FinePix S3 Pro digital camera. The technology, now perfected in the EISA Award-winning FinePix S5 Pro, has been brought to the consumer in the FinePix F100fd.

Through a combination of advances in Fujifilm’s new Super CCD HR VIII sensor and RP (Real Photo) Processor III, this wide dynamic range dramatically broadens tonal capability and guarantees exceptional rendition of photos with both bright highlights and dark shadows. This expansion of sensitivity captures greater detail, and subtle nuances of brightness and tonality that bring the photo closer to what the human eye actually sees helping to avoid the ‘white sky’ effect caused by the loss of fine highlight detail.

What isn't clear from this press release is exactly how the F100fd achieves "wide dynamic range" despite having tiny pixels (sensels). Does it truly, as they imply, feature a similar technology to that seen in the S3 and S5 DSLRs? Seems doubtful given that Fuji hasn't mentioned anything about different pixel types in the sensor. On the other hand, if it employing the same underexpose/tonemap approach being used by Canon and others, it would seem somewhat disingenuous to bill it as "wide dynamic range." Perhaps they are implementing an entirely novel way to boost actual DR. All they really say is that the wide DR is made possible by advances in the new sensor and onboard image processor. My guess is that the new sensor has implemented slightly lower read noise and that the rest of what we're getting here is similar to Canon's HTP.

Consider the following excerpt from the F100fd manual:


The relevant portions are as follows:
"When dynamic range is set to 200 % or 400 %, some [ ISO] settings cannot be selected. Also, some [ DYNAMIC RANGE] settings may not be selectable depending on the [ ISO] setting."
"Although wider dynamic range settings will allow you to take pictures with good levels of contrast, they will also increase the amount of speckling in your images. Choose the dynamic range setting that best suits the conditions."

So, basically, the use of "wide dynamic range" settings requires setting the camera to higher ISO values (probably ISO 200 minimum for 200% DR and ISO 400 minimum for 400% DR) and increases noise. To me, this strongly suggests that the wide DR function uses a similar approach to Canon's HTP, namely underexpose the whole image and then selectively "push up" everything but the highlights. Note that this approach to tone mapping does not preclude the possibility of other true contributions to improved DR such as measures to decrease read noise.

Let's look at an actual example. The following crops were taken from images provided at http://f100fd.seesaa.net/. Each image in the comparison was taken at a nominal ISO 400, f3.3, 1/100s, and these are 100% crops from the 6MP output mode of the F100fd. Click the image below to view at the intended size.


Don't know about you, but I am impressed. If Fuji is accomplishing this the way I think they are, then the noise we're seeing in the shadows and midtones of the DR 400% crop actually represents ISO 100 noise pushed two full stops. Yet to my eye, it's only barely more prominent than the noise in the native ISO 400 (DR 100%) crop. In fact, the most disturbing noise to me is the subtle pink and green blotching in the flat gray regions, and this is no different between the two crops. The highlight detail has been effectively reclaimed, and the rest of the image is virtually undisturbed with "good contrast levels" just as the manual claimed.

The Fuji F100fd has several strikes against it from the standpoint of a "serious" user, some or all of which may or may not matter to any given photographer. It lacks manual controls for aperture and shutter speed, RAW capability, and a viewfinder. The lens, in exchange for covering a long range, is relatively slow. The high ISO noise reduction cannot be disabled. However, as I mentioned in Part 1 of this series, there are now a number of full-resolution samples online to demonstrate that the F100fd output is of high quality, up to the standards for "serious" use. Add to that the fact that the high ISO output is unusually low in noise without what I'd consider an obnoxious level of smearing (though this is highly subjective) and that the highlight preservation is rather effective (albeit limited to use at high ISO settings), and I'd imagine that the Fuji F100fd will be the compact of choice for many of the photographers who don't enjoy postprocessing. We'll soon find out. I look forward to learning more with you when the F100fd hits the streets.