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*Editor's Note: We're introducing a new feature called On Assignment. For each camera we select for this feature, we'll take a look at a particular feature or strength of the system and give it a real-world test. We'll report our findings in a concise, more narrative-like article with plenty of photos from the shooting experience.

About a month after Nikon's D3S hit the market with an ISO sensitivity range that topped out at an amazing 102400, Canon fired back with the EOS 1D Mark IV that also reached that atmospheric number. Canon provided a Mark IV body and two of their premium "L" series lenses (the new hybrid stabilization system EF 100mm macro that is already the subject of a lens review on this site as well as the EF 24-105mm zoom) for a review period that included a trip to the Whistler Olympic Village for a week at the games. With an ISO peak going where only one camera has gone before, the Mark IV drew the assignment to explore the low light envelope and see just how useful 102400 might be.

The EOS 1D Mark IV is the latest generation of Canon's fast-shooting professional DSLR and has received a 60% bump in resolution (to 16 megapixels) over the Mark III. The IV retains the 10 frame per second shooting rate enjoyed by the III and adds 1080p HD video, an improved 3.0 inch LCD monitor, dual Digic 4 processors and Canon's "most advanced" autofocus system to date.

We'll have a complete review of the Mark IV in the near future, but for this feature we wandered the Olympic Village in the evening to see just what the Mark IV had in store when things got dim.

IN THE FIELD
As you might imagine, the Olympic Village here at Whistler becomes a pretty lively place after dark. Site of the Nordic and Alpine events at the games, most competitions here wrap up by, or shortly after dark. In addition to the Olympic competitions most of the ski runs at the resort remain open to the public, so there's a large contingent in town enjoying the slopes as well as the games, particularly over the weekend.

As light levels drop, if we're content to tolerate longer and longer shutter speeds and camera support to eliminate shake, we can sit happily at any camera's base ISO and get nice images of stationary objects. Moving subjects are a different matter, and mixed scenes with fixed and moving subjects give rise to "ghosts" as the movers change position during the lengthy shutter open times.

Obviously, the wide range of high end ISO sensitivities available in the Mark IV, combined with a fast stabilized lens gives rise to hand held possibilities in situations that formerly would require a tripod, monopod or some other form of camera support to pull off. But there's no such thing as a free lunch - in exchange for the ability to shoot hand held in some pretty dim environments, the high ISOs extract a penalty in image quality degraded by noise. The question becomes twofold: how high an ISO do you need to shoot in the conditions you'll encounter, and is the image quality at that level of sensitivity acceptable?

I shot a series of images at each full stop of ISO sensitivity from 100 to 102400 to see what the results would be.

ISO 100	ISO 200
ISO 400	ISO 800
ISO 1600	ISO 3200
ISO 6400	ISO 12800
ISO 25600	ISO 51200
ISO 102400

The Mark IV was set in aperture priority at f/5.6 and with center-weighted exposure metering. In addition, the camera's "long exposure noise reduction" setting was fixed at "auto" (default is off) and the "high ISO speed noise reduction" was at the default value of "standard."

Next, I shot full stop ISO sensitivities from 3200 to 102400 with the same camera settings except for high ISO speed noise reduction switched to "strong."

ISO 3200, strong noise reduction	ISO 6400, strong noise reduction
ISO 12800, strong noise reduction	ISO 25600, strong noise reduction
ISO 51200, strong noise reduction	ISO 102400, strong noise reduction

The "strong" setting for high ISO noise reduction makes for somewhat smoother images at the expense of some detail, so the decision to enable it depends on personal preference. I left "strong" enabled for the balance of the shoot. No matter what level of noise reduction was set in the camera, review of the ISO shots made it pretty clear we really wanted nothing to do with 51600 and 102400 from a noise standpoint, with 25800 looking like an option if all else failed.

Since I was shooting the stabilized EF 24-105mm lens on the Mark IV (whose 1.3x crop factor gave me a working focal range of about 31 to 136mm), I looked for an ISO setting that would give me shutter times of about 1/15th of a second at wide angle and 1/30th at telephoto. Taking meter readings of several dimly lit areas about the village, I settled in on 6400 ISO as the setting that seemed to produce the numbers I was looking for. Assuming the lens gave me a couple of stops of correction for camera shake, 6400 seemed the best combination of noise and shutter speed to insure sharp photos. I left exposure metering at center-weighted since I was most concerned that the main subject exposure be accurate, with outlying areas of the image getting less priority.

The shots that follow are all hand held. Not having to rely on a tripod and long shutter speeds frees you up to wander and capture images spontaneously, quickly switching position if need be to get a different angle (or a clearer shot with people milling about). Here are 3 shots of the small memorial erected in the village to honor the Georgian luge competitor who was killed in a practice crash at the sliding center.

I had just captured this flag shot when I noticed one of the revelers taking a moment to check his e-mails...

While the shot of the bears that follow looks well lit, this side of statue was in fact very dimly lit by light from a parking lot about 100 feet away. This proved to be the toughest autofocus situation of the night - as well as too dark to manually focus. With the camera in one-shot AF mode I moved the focus point around the statue until I got a lock on some point that would give me the focus I was looking for, then recomposed the shot and completed the full push to make the capture. With the center-weighted metering the camera read the very dark bears and exposed accordingly - shutter speed was down to 1/6th of a second.

A similar situation existed for the Norwegian flag hanging on a nearby building - despite being partly backlit by light coming through the window, it too was in very dim light. Shutter speed was 1/6th of a second on this shot also. And finally, same situation for the kid on the rock - very dark area despite the building in the background - another 1/6th second shot.

While the dark shots above proved difficult for focus purposes, here's another focus exercise: I wanted to capture this scene with focus based on the flame area of the image, so I zoomed in to 105mm and did the half push for focus (the Mark IV also establishes exposure at that point if you happen to be using evaluative metering), then held the half push (and focus) while I zoomed out to get the framing I wanted.

Finally, just a couple of walking around shots that caught my eye.

While all the previous shots were made at f/5.6, I also took shots with the lens wide open at f/4 and experimented a bit with exposure compensation. Shooting at f/4 gains a full stop over f/5.6, which allows a lower ISO sensitivity while producing similar shutter speed, all else being equal.

Dialing in underexposure as compensation has the effect on the camera of shortening shutter speeds, which is a plus for helping battle camera shake. The shots that follow were made at various ISO sensitivities - the medal ceremony for men's Super G (sample 1) came off at 1/125th with no compensation.

Sample 1

Sample 2 and sample 3 below each had -1 stop of compensation and shot at 1/6th and 1/8th of a second respectively.

Sample 2

Sample 3

Finally, the last sample image below was a relatively fast 1/40th of a second with -3 stops of exposure.

CONCLUSIONS
As technology marches on, digital cameras continue to push resolution and particularly ISO sensitivities to new levels. Nowhere is the latter more apparent than at the top end of the DSLR food chain with both the D3S and the 1D Mark IV setting their ceilings at 102400. Is that sensitivity usable? It is, but with reservations. Here's the same shot at 3200 and 102400 ISO with identical camera settings (and ¼ and 1/125th second shutter speeds respectively) - which would you prefer?

ISO 3200

ISO 102400

The ability to shoot at high ISO is a plus, and if going to 102400 is the only way to get that shot of the Martian flying saucer landing at a remote desert location, fire away. For just about anything else the highest sensitivities will remain largely unused. The Mark IV turned in a good performance shooting hand held in dim light - autofocus was generally fairly quick in any but really dim conditions, and even in those a bit of work moving the active focus point around the subject usually got results. Manual focus is always available in dim light if the camera won't acquire focus on its own, assuming there's enough light to let you be accurate with your eye.

One benefit I see from the expanded high end ISO settings is noise performance seems improved at the mid range ISO sensitivities that make hand holding a possibility. For internet, photojournalist and small print work the mid range settings offer the freedom to hand hold and still produce acceptable results - but if your goal is to print large and clean don't get rid of that tripod just yet.

Related Articles:

• Canon EF 100mm f/2.8L Macro IS USM Lens Review
• Under the Big Top with the Nikon D3S
• Nikon D3S announced with HD video, new FX sensor