I owned a Canon EOS 1D Mark III for over two years before I upgraded to its successor, the Canon EOS 1D Mark IV. I had great success and lots of fun using the 1D Mark III as my main camera for nature photography.

There is a thriving second-hand market for the 1D Mark III and I still get asked questions about tuning the now infamous auto-focus system and the best way to set up this highly customisable camera for nature photography. This page is a collection of my notes and personal observations on how to get the best performance from this camera.

Optimal Custom Function Settings

My preferred custom function settings for the Canon EOS 1D Mark III are given below, in shorthand form. These were worked out over years of trial and error, using live, wild subjects in the field and captive raptors flying at high speed.

My listing only includes changes to the default settings and many of these are personal preference functions (e.g. C. Fn I-9), that won’t materially affect the performance of the camera.

These settings worked well for me but they may not work as well for you, so don’t be afraid to experiment until you find the optimal combination of settings for your own shooting style. Many of my friends settled for subtle variations of this group of settings but we all more or less agreed on them in the end.

Problematic Custom Functions

Despite my general advice that you should not be afraid to experiment with the Canon EOS 1D Mark III’s custom function settings, I strongly advise against changing C. Fn III-4 from the default setting unless you have lots of objects coming between you and your subject as you track it.

Custom function C. Fn III-5 comes with an even stronger health warning: always leave it at the default setting or you will find that when you do lose focus on your subject, the auto-focus may, seemingly inexplicably, fail altogether. If you want a more detailed explanation of what this custom function does and why this behaviour occurs, check out my guide to the Canon EOS 1D Mark IV.

Tuning the Autofocus System

The Canon EOS 1D Mark III has an incredibly sensitive auto-focus system, which has both pro’s and con’s: tracking fast-moving subjects is easier than it was with predecessor cameras but sometimes the 1D Mark III will unintentionally refocus on the background of the scene, especially if you don’t position the active auto-focus point accurately prior to activating the auto-focus system.

The consequences of this could have been dampened if Canon had chosen to broaden the range of control the user has by modifying the functionality of C. Fn III-2 to allow slower settings to be chosen. But Canon never got around to doing that and so you should experiment a lot with this custom function’s settings to find the value that suits you best.

Like most cameras, the Canon EOS 1D Mark III often struggles to acquire focus on fast-moving, low contrast subjects, particularly if the light is poor or the scene’s background is distracting. When this camera was quite new, lots of people put this down to a defect in the camera’s auto-focus system. On reflection, it’s clear to me that many commentators at that time lost sight of what they should reasonably expect a camera to be able to do for them: this is one area where people’s expectations were too high.

That said, the 1D Mark IV has much better performance in this area, so Canon have clearly worked hard on improving this aspect of 1 series performance.

Focus Micro-adjustment

Custom function C. Fn III-7 allows the user to incrementally adjust the plane of focus for each lens they use, by tiny amounts. Use this setting very cautiously: the popular photography forums are littered with tales of people claiming that their lenses don’t focus accurately and their findings are often based entirely on their experimentation with this custom function. If you are not experiencing appreciable problems with front or back focusing with any of your lenses, I recommend that you do not use this custom function.

Which Canon EOS 1D Mark III Firmware Works Best?

There’s no doubt in my mind that Canon EOS 1D Mark III firmware v1.2.3 is vastly superior to v1.2.5 for nature photographers, especially for bird-in-flight specialists. For the record, I did not try any of the subsequent firmware releases, so I cannot offer an opinion on them.

I used firmware v1.2.5 extensively and quickly realised that it was terrible, inexplicably dropping frames at the start, middle or end of a shooting sequence, failing to acquire focus at all when the scene’s contrast was low (but not unreasonably so) and, worst of all for me, in bright sunlight, giving the impression of achieving focus lock only for me to discover later, when examining the results on my computer, that it had not. The camera became unpredictable and unreliable and let me down very badly during a trip to Spain to photograph Griffon Vultures, a subject I would normally find quite easy to track and photograph accurately.

When I reverted to firmware v1.2.3 (to do this, I followed the upgrade process described in the user manual but used the older version of the firmware for the ‘upgrade’), I was instantly happier with the improved consistency in the behaviour of the camera’s auto-focus system. The results were significantly better than those I achieved with firmware v1.2.5.

If you are having problem with a Canon EOS 1D Mark III’s auto-focus and your camera has a later release of the firmware installed, you may want to try the firmware ‘downgrade’ to see if it improves matters. In my experience, the same camera, custom function and micro-adjustment settings will be preserved and will work just as before. But you may want to write them all down first, just in case you find they are subsequently different. If you do take the plunge, follow the instructions and guidance provided by Canon carefully and don’t blame me if your camera is turned into a door-stop!