Now 6 years and 3 generations later the EOS 40D is clearly long in the tooth. In fact, it’s so long in the tooth there’s little point in reviewing its technical capabilities, as they’re hardly relevant anymore. However, while the hardware is nothing worth writing about, the user interface in the 40D marks what’s arguably the turning point in Canon’s DSLR UI design. Personally, I consider the UI from the 40D and its direct successors to be one of, if not the best, camera UIs I’ve ever seen or used.

When it was released in the fall of 2007, the Canon EOS 40D was the first major update to Canon’s line of prosumer APS-C format cameras since really the middle of 2004. It brought with it a new 10-megapixel sensor with the same self-cleaning capabilities introduced in the Rebel XTi (EOS 400D). In addition to the 2-megapixel increase in resolution and 2-bit increase in sensor bit-depth (14 bits instead of 12) the new Digic III processor allowed for frame rates to climb from 5 to 6.5 frames per second.

The EOS 40D improved upon the auto focus system in its predecessor with the inclusion of 9 cross type sensors. In addition all AF points are sensitive with lenses that have a maximum aperture of f/5.6 or faster. Autofocus performance is also quite good, making short work of tracking birds in flight athletes playing sports.

To this day, image quality is still quite good. Stills are usable up to ISO 800, and some would argue higher. I’ve long since relegated my 40D to backup camera status, and then to time-lapse body. When using the 40D for time lapses, the down sampling required for 2K resolutions makes the entire ISO range quite usable, and the sensor has sufficient resolution to support up to QHD resolutions (3840×2160), but not full 4K resolutions without resampling.

That said, the hardware is largely uninteresting now; nor are there any compelling reason to seek out the 40D at this point. However, what make the 40D interesting to me, aside from it being the first serious DSLR I owned, is the UI it brought to Canon’s products, and how that UI has stuck in the subsequent years.

Canon has never been shy about revising the UIs on their cameras, perhaps to the determent of some users who keep old bodies as backups. However, the overall progress has been tangible, as the UI has continued to evolve towards more and more efficient designs.

Comparatively, Nikon has been very slow to make any significant changes to their DSLR UI. Further, it doesn’t help that their DSLR UI largely appears to have stemmed from simply taking a film UI and placing digital specific controls where they wouldn’t interfere with existing ones. For example, while Canon has moved the ISO control to be more and more readily accessible, Nikon’s has remained in a position on the rear left of the camera back that makes it difficult to change one handed—though admittedly this is a situation they’ve been slowly rectifying via programmable buttons.

The development of Canon’s DSLR UI started out somewhat formatively. The first major shift in Canon UI design came with the EOS 10D. Prior to the 10D the EOS DSLRs UI oozed of not knowing where to put all these new controls, or what would be necessary for a digital user. Many controls were added as they were no necessary (like white balance) that simply didn’t exist on film bodies, others like ISO were buried in menus.

The EOS 10D was the first Canon dSLR to really start to address this. It did this by moving the drive, white balance, AF mode, metering mode, and flash exposure compensation buttons to the now familiar position across the front of the top LCD. In addition, the 10D brought the ISO speed selection out of the menus and made it a physical button.

What the 10D’s design didn’t do is recognize that ISO is a primary control for the digital photographer- placing it on the middle button and as the rear dial controlled/secondary function. This UI deficiency was kept for four and a half years, though the 20D and 30D until it was finally rectified in the 40D.

In practice, it’s very easy for a 40D (and its successors) to make very quick adjustments on the fly to settings like ISO and flash exposure compensation. A feature I’ve made use of extensively while shooting. On top of the ability to make adjustments while shooting, both flash exposure compensation and ISO are visible in the viewfinder, meaning you can make adjustments while not taking your eye away from the camera.

If there’s one problem with Canon’s mid-tier 2-button UI (and the Pro UI as well) it’s that it highly biased to the normal grip over the addon vertical grips. Canon made this one level more frustrating by failing to include both a multi-controller (finally rectified in the battery grip for the 5D mark 3) and an AF-On button to fully mirror the AF point select, exposure lock, AF-On button trio on the back of the hand grip.

The issues were most noticeable to someone coming from the 400D/Rebel XTI or earlier and also having used a battery grip on those bodies—modern Rebel UIs have relocated the ISO button to the top shoulder making them similarly biased though perhaps to a lesser extent.

In the end, the EOS 40D was highly competitive for its time. Only the Nikon D300, which was arguably a tier higher in terms of target market, was comparable to it. Further, the performance of the sensor held up quite well against the 50D’s 15MP replacement making the 40D sought after for quite some time in the used market. What I find most interesting though, is that even now 6 years later, the UI refinements shown in the 40D remain largely unchanged by subsequent cameras. It was only until the splitting of the 60D and 7D that Canon introduced a simplified (though arguably less elegant) UI for the high-end consumer cameras.