Tuesday, March 23, 2010

1D Mark IV Low Light Image Quality and Autofocus

First, if you haven't already done so, go out and get the new Lightroom 3.0 Beta 2, its awesome. I fully admit that I'm biased, but I'm also very proud of what the Lightroom and Camera RAW teams have put together here. Even if I didn't work here, I can guarantee you that I'd be there credit card in hand to upgrade to Lightroom 3.

I have been using Lightroom 3 exclusive for my RAW processing for a while now so all of my comments and observations are with LR3. The above image was taken at ISO 4000, hand held at 1/25s @ f/2.8 in terrible lighting (~3.5 EV). For an ISO 4000 image, I am very pleased with the image quality. This was processed with the default color NR and just a little bit of luminance NR. Here is a 100% crop:

Here is another test image at ISO 6400 in very bad fluorescent lighting (1/100s, f/2.8 ~= 3 2/3 EV).

Once again, the noise levels are controlled and the detail is good. In particular I am pleased with the low levels of shadow noise:

Finally, here is am image taken at ISO 12,800:

This was taken at 1/100s, f/2.8 (~2 2/3 EV). Once again, here' s a crop (higher color NR and some luminance NR):

With the amount of reach the 1D Mark IV offers for bird photographers (due to its high sensel density) I find very little to complain about when it comes to image quality.

There have been a few people who have made comments about the 1D Mark IV's "low light" auto-focus performance (some being critical of it, others refuting the criticism). Any statements made about such performance without a clear quantitative description of the light levels (either by EV level or combination of ISO, aperture & shutter speed) are useless.

I have noticed some quirks in low light auto focus. Most notably, it seems that the 1D4 walks off a cliff at certain light levels (right around 2 EV to 3 EV by my observations). In the images of the plastic tub above, the light level was around 2 2/3 EV and the camera had no problem locking on (with an f/2 lens). However in the image below, the camera refused to acquire focus on any part of the net.

I eventually had to use live view to get focus (which worked without issue). The image was taken at ISO 2500, f/1.4 & 1/25s (~ 1 EV). What I find curious is that I was using an f/1.4 lens which should allow a lot of light to the auto-focus sensors.

In contrast, the Nikon D3s is able to lock on quickly and accurately on the same subject in the same light level with an f/2.8 lens (i.e with 2x less light reaching the AF sensors), taken at ISO 51200, 1/60s:

Not only is the D3s able to lock onto a static subject, its able to track a moving subject with reasonable accuracy. Here is the first frame where the D3s locked on instantaneously:

and then I've created an animated GIF sequence cropped down to show how the D3s maintains focus and continues to track the plane even at these ridiculously low light levels (same as above):

I did a similar test with the 1D Mark IV and the results were so embarrassingly bad (the camera couldn't lock on at all) that I immediately deleted the images.

Here is another example of the D3s' low light prowess (ISO 16000, f/2.8, 1/60s ~= 1 2/3 EV), focus was on the "For Assistance" sign and the lock was lightning fast:
and a 100% crop:

One last example of the D3s locking onto something in light and contrast so low that I could barely even see the object.
I had to reset the focus and do this a couple of times just to believe that it was a fluke and that the D3s was actually consistently locking onto the garbage can. Here is a 100% crop:

Very impressive indeed. I know I've praised the performance of the D3s a lot in a post that is supposed to be about the 1D Mark IV's low light performance. Its difficult to not compare these two cameras since both were released around a similar time at almost the same price point. The 1D Mark IV's auto focus performance isn't bad and I'm certain that in light conditions that most wildlife and sports photographers work in they are unlikely to encounter its deficiencies. Its just the D3s is so very good.

Finally, I see these two bodies as complementing each other rather than competing. There is no doubt in my mind that for bird photography the 1D Mark IV is the better tool. Its auto focus is very competent and ISO performance up to 6400 is good enough to deliver richly detailed files with controllable noise. All this with a pixel pitch that puts an impressive number of pixels on your subject. For extreme low light conditions (less than 4 EV), the larger sensels of the D3s and its auto focus system make it the better tool.
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