Canon 1D MKIV AF Review | May 2010
I purchased the MK4 in January 2010 with great anticipation of what changes had been made to both the AF and the sensor from the much maligned 1D MK3. The objective in writing this review is to offer my opinion on the MK4, what I like, what I dislike and some thoughts as to how the camera should be set up.
What I Like
The body looks just about identical to the MK3 with many of the buttons in the same place and all the menu items set just as the MK3 with the addition of some extra settings. The biggest improvement is the ISO performance. I rarely bothered shooting above ISO 800 on the MK3 but have no hesitation in increasing to 1200 knowing I will get a very good quality image. Of course when shooting at high ISO's exposing to the right ensures the sensor captures maximum data. Even at 2000 ISO the images are good and with some careful application of noise reduction software can yield strong results and much better than anything from a 7D.
The AF has clearly been upgraded. The new AI Servo does a superb job of tracking an image aided by an extra area focus option to sit alongside those on the MK3. The introduction of Spot AF, as on the 7D, is an excellent addition. The new 45 Point Area Focus is an incredibly powerful addition (more later). The rear screen is a big improvement of the MK3 of both the 1D and 1Ds. You can actually make better judgements on the sharpness of an image when compared to the MK3.
What I Dislike Updated May 2010.
When I first got the MK4 I saw the addition of a built in video as a potentially useful tool for press photographers wanting to capture a vital moment. Having now tried it I have been amazed at the quality it offers and while I still find it difficult to control, and indeed set up, it does offer a highly viable alternative to the more standard HD videos Canon offer.
I do not understand why Canon would introduce a superb function for accessing the AF on the 7D and not have it on the MK4. On the 7D there is a Mfn button which when used with the AF point selector button gives instant access to switching from say single point AF point, spot AF, AF expansion, Zone AF and 19 point AF. On the MK4 this has to be changed in the custom functions - CFn 111 - 8, AF expansion w/selected pt.
While Spot AF can be accessed on the AF Stop buttons on large telephotos, such as the 500 f4, I do not understand why this cannot be accessed via say the Set button. As mentioned above it can be accessed via the Mfn button on the 7D.
The MK4 offers 39 high precision cross type AF (horizontal and vertical) points when a lens with a max aperture of f2.8 or more is used or when combined with an extender. The cross type sensors vertical line sensitivity is approx two times more than the horizontal line sensitivity. When using an f4 lens, say the 600 f4, then only the centre AF point is usable as a cross type with the other 44 horizontal sensitive only. At f5.6 all the AF points are horizontal sensitive and at f8 only the centre AF can be used with horizontal sensitivity.
Contrast the above with the 7D where at f5.6 or brighter all AF points are cross type AF sensitive. Interestingly, in the 7D manual (page 91) it refers to lenses with max aperture of f2.8 or brighter that the centre AF point has high precision cross type AF sensitive with the centre AF point's sensitivity to vertical and horizontal lines is about twice as sensitive as the other AF points. I can understand that there is probably a difference in the AF points on the 7D compared to the MK4 given Canon use the word high precision on the MK4 for 39 AF points but only use it once for the centre AF point. However, why would the 7D have a high precision cross type AF for f5.6 and the MK4 has only horizontal sensitivity? Why aren't all the AF points cross type to f4, even if they weren't high precision? It seems odd that there is such a difference.
Setting the MK4
This section will consider setting the camera up for a moving subject using AI Servo.
Selecting the correct AF point(s).
This requires very careful consideration of the subject matter and its surroundings, failure to set this correctly will cause the camera to jump focus.
One Selected point - When a background is busy this setting is ideal as the camera only has the centre point to worry about when compared to say All 45 point area. This is Cfn111 - 8, 0.
One Selected Point + Left and Right - An extension of just one point, focus must first be achieved with the manually selected AF point but it can then be handed off if it loses focus.
Cfn111 -8, 1. Surrounding AF Points - This is a halfway house between all 45 and just one AF point. The surrounding AF points are activated thereby increasing the size of the AF area. Care should be exercised here as a busy background or foreground, such as reeds in front of a hunting Marsh Harrier can force the AF to jump off the subject.
- Cfn111 - 8, 2. 45 Point Area Focus
This is a new and excellent feature of the MK4. As the other modes initial focus has to be with the manually selected AF point. The similar to the left &right and surrounding options focus can be handed off to another point which in this mode is a cluster of 17 focus points, so 18 are in use. What is very clever is that if focus is handed off then immediately another 17 become active and so on. Ultimately, all 45 points are in play with 18 active at any given point. This option is excellent for birds or aircraft in flight.
- Cfn111 - 8, 3
The key in selecting the right option is to assess the environment and if the background is busy the AF system could become fooled and pass focus where it isn't wanted. I have had great success with Area AF for my low level military aircraft pictures and for birds in flight. Conversely, Barn Owls hunting low over grassy banks are best tackled with a single AF point with perhaps left & right engaged.
The Subtleties of the Custom Functions Set 111
I have played about with all of the functions below and can only conclude that an understanding of them will allow their correct application at the appropriate time. Several are inter related and changing one may affect another, which I will endeavour to identify.
CF111 - 2 Tracking Sensitivity
This function sets the speed/time for the AF to switch focus, set it Fast and it will change comparatively quickly, set it slow and it will change comparatively slowly. While it is instinctive to set this to slow as the camera will not shift focus quickly if the photographer moves off the subject, if he/she does move off and focus reacquired on say the background it will take comparatively longer for the AF to snap back. Getting the balance right is important and I normally settle on the default 0 setting or one notch below.
CF111 - 3 AI Servo 1st/2nd Image Priority
4 options here but in my view only one choice, leave it set at 0, AF priority/tracking priority. The other settings may be suitable for press photographers where the objective is getting the shot and keeping the frame rate up. However, as I want the shot in focus and it tracked setting this on anything other than 0 is, for me anyway, incorrect.
CF111 - 4 AI Servo Tracking Method
2 options here dealing with how the camera tracks focus. At the default setting, 0, it places priority on whatever is below the active AF point. At 1 tracking is given priority. I have this set to 1, but will switch to 0 if I know I will have clear line of sight to my subject and nothing will come inbetween.
CF111 - 5 Lens Drive when AF impossible
Set to 0
CF111 - 6 Lens AF Stop Button
As mentioned earlier this is where Spot AF is accessed, so I have this set to option 7. On my MK3 I had the IS Start activated. I do hope Canon allow the Spot AF to be accessed from the SET button so it releases options for this CF.
CF111 - 7 Microadjustment
There is all sorts of weird and wonderful ways this CFn is used on the Internet forums. I have never altered this (it is on the MK3) and if I felt there was a need I'd send the camera and lens to Canon to be properly calibrated. Adjust at your peril!!!
The relationship between CF Set111 2 - Tracking Sensitivity, 4 Tracking Method and 8 AF expansion.
The settings on these CF's influence each other. If for example the AF point expansion is turned off (CF111 - 8, 0) then the AI Servo tracking method (CF111 - 4) will not function regardless of which setting is used. Regardless of which Tracking method is selected (CF111 - 4, 0 or 1) AI Servo Tracking sensitivity takes priority (CF - 111, 2). However, if the tracking method is set to 0 (main focus priority) and another subject blocks the targeted subject the camera will refocus on the new subject regardless of what level of tracking sensitivity has been set.