EOS 7D AF performance for BIF

EOS 7D Field test

A. Hazeghi, October 2009

I. Introduction

Since posting my initial impressions about the AF performance of the new EOS 7D I have been asked by a few BPN friends as well as a few local fellow birders to update my findings about this new camera and its AF performance with respect to birds in flight. Although initially reluctant I decided to write a short summary as my final and honest verdict, hopefully it will answer some of the questions. Please keep in mind that these are solely my opinions and are based on field results from photographing birds in flight, they do not necessarily apply to other subjects or conditions. If you are a causal shooter the issues mentioned here most likely don’t apply to you.

First a little bit of background, I have been photographing birds for about 5 years now, mainly in San Francisco Bay Area, I am putting together a small collection of Northern California raptors for publication, these species include Red-tailed and Red-shouldered hawk, American Kestrel, White-tailed Kite, Northern Harrier, Barn Owl and Short-eared owl. From time to time I also photograph shorebirds such as Avocets, Godwits, Curlews, yellowlegs and related species but my current focus is raptors, you can view some of my raptor shots here. I use Canon gear for bird photography.

I tested two EOS 7D cameras extensively in the field and made about 3500 photos with each, the two 7Ds were purchased brand new, separately at different times from a reputable dealer and had different serial numbers. The lenses used were EF 400 f/5.6L USM and EF 400 f/4.0L DO USM IS. Both of the lenses passed static AF calibration, first body did not require any AF fine adjustment while an adjustment of +2 was dialed for 400 f/5.6L in the second body for the best static results. The first body had firmware 1.0.7 and the second one has firmware 1.0.9 loaded. Other cameras that I have used in the field in similar conditions include EOS 40D, 50D, 5DMKII and 1DSMKIII as well as a Nikon D700.

Based on recommendation from CPS as well as the white paper published by Canon USA, the following settings were applied to AF custom functions, these settings were also proved more effective in the field compared to factory defaults.

C.Fn-III-1 Servo Tracking sensitivity : slow

C.Fn-III-2 AI Servo 1st/2nd image priority : 0-AF priority/Tracking Priority

C.Fn III-3 AI servo AF Tracking method : 1-Continous AF Track priority

C.Fn III-4 Lens Drive when AF impossible : 1-OFF (to prevent focus hunt)

For perched birds Spot AF was used most of the time and for flight shots manual single AF point, 4-Point AF expansion with center point were used. It was previously found that All-point AF and zone AF may behave erratically when there are multiple subjects of high contrast in the frame and it is not logical to expect the camera to identify and pick the intended subject for the photographer among all the distractions, so these modes were not used.

After posting my initial impressions I got a number of emails and notes in particular referencing to samples posted in online forums which showed good servo tracking performance results. It is worth noting that not much can be concluded from a small 1024 pixel web image in terms of sharpness and AF accuracy especially when shooting conditions and the ratio of in-focus (IF) shots versus out of focus (OOF) shots is unknown. Therefore a direct comparison is not possible. Nevertheless I decided to shoot some more common species such as ducks and seagulls against water and sky backgrounds for comparison.

Also note that the conclusions here are based on the shots where the selected red Autofocus frame covered a good portion of the main subject and shutter speed was fast enough for action, in expansion mode the subject was covered by either the center point or any of the four surrounding points in diamond pattern. When evaluating the OOF shots, those with unfavorable composition or pose were deleted and not counted towards the “missed shots”. The shots where no AF point was near the subject were deleted as “operator error”.

Canon EOS 7D with EF 400 f/5.6L USM and lens coat.

II. Static AF performance:

Static AF performance of 7D is generally very good, especially against sky or water background and when the bird has different color (ex. Seagull against water or sky, heron against water or raptor against sky). For raptors with natural camouflage, however static AF in AI servo showed some small instability, mainly locking on the BG even when the AF point seemed to be perfectly on the bird, good news is spot AF feature solves this problem most of the time. Using spot AF it was also possible to focus on tiny features such as the eye. In the example bellow, by carefully placing the spot AF point on the eye in a very “busy” surrounding I was able to nail the AF on the harrier, the drawback of this method is that you have to be prepared to quickly change to a non-spot AF mode when action starts.

7D + EF 400 f/5.6L f/7.1 1/1600 sec ISO 400. Spot AF in AI-servo mode. RAW converted with DPP 3.7

Red-shouldered Hawk. 7D +EF 400 f/5.6L Spot AF in AI-Servo mode. 1/1250sec f/9 ISO 800. medium crop

Short-billed Dowitcher. 7D + EF 400 f/5.6L single AF point in AI-servo mode. 1/1600sec f/7.1 ISO 400. Almost full frame

American Kestrel (can you find the prey?) 7D + EF400 DO IS spot AF in AI-servo mode.1/2500 f/8 sec ISO800 +2/3EV, tight crop.

Overall static AF performance of 7D is good and addition of spot AF, if used effectively can open new possibilities when compared to previous XXD or even 1D series cameras. There are occasional miss focused shot, but they are relatively low in occurrence and with the advantage of 8fps, you can ensure you will get a sharp shot.

III. AI-servo AF– large birds against sky or water background

7D delivered good results when tracking large and slow birds against either sky or water background. Seagulls, terns, pelicans, ducks and egrets proved no real challenge for the camera as long as the AF point(s) were kept on the bird. However, any modern SLR with good technique can nail AF in most of these conditions, in fact I have a number of nice Forester's tern action shots with the 40D and I can’t remember missing a good tern shot with that camera, so the fact that 7D can focus on a flying tern or gull is not an indication of its capabilities in my opinion.

To give 7D a bit more challenge I photographed my favorite subject, the northern harrier against a plain sky background, harriers are more challenging because they bank and “wobble” erratically as opposed to flying in a straight line like a duck. Again 7D delivered good performance tracking the harrier against sky. Keep in mind that slight miss-focus in 7D images is compensated by the generous number of pixels so these imperfections will not be visible when the photo is resized for web posting and may only be visible in very large size prints.

Northern Harrier (female) 7D + 400 f/5.6L 1/2000 sec f/9 ISO 400 manual AF point AI-servo.

The second part of the test was tracking speedy shore birds such as willets and yellowlegs against water background, these birds also fly in somewhat random patterns and are more challenging for the AF system. As expected, the number of OOF shots increased, but still the camera was able to deliver good results from “peak of the action moment”. There were some situations were the camera lost focus during tracking for no apparent reason, I have provided some examples blow.

Short-billed Dowitcher 7D + 400 f/5.6L 1/1250sec f/8 ISO 400 manual AF point AI-servo.

Landing Willet, 7D + 400 f/5.6L f/6.3 1/1250sec ISO 400, 4-point expansion AF AI-servo.

Shot A was immediately after shot B (8fps), while camera has initially acquired sharp focus it loses focus momentarily between shots despite the fact that AF point is on the bird, in this case A has a slightly better wing position but B still works. AI-servo mode with manual focus point.

This is another example where focus has been lost between two shots. Ai-servo with expansion AF, again the focus points in this case remained on the bird.

Overall in tracking of fast shorebirds against water background, 7D delivered good to acceptable results if not perfect. There are a few “peak action” shots missed due to AF, but there are many keepers as well. With respect to XXD series, it is fair to say autofocus performance was similar but with the benefit of 8fps, more pixels and lower noise compared to 50D, the probability of capturing the peak moment has increased. I would still give an edge to the 1DSMKIII for AF performance alone in the fast shore bird category.

IV. AI-servo AF: Raptors against foliage

This is section is what I investigated more thoroughly, the first 7D was used extensively in a 2-day raptor shoot in Half Moon Bay, CA by myself and O. Klink who is a distinguished professional wildlife photographer. The second 7D was used in three days of shooting in two locations, Palo Alto Baylands nature preserve and Half Moon Bay. Raptor activity is high during this time of the year and there is enough shooting opportunities to get a real feel for the camera. The conclusion from both of us was that the camera, while occasionally producing acceptable results, struggles to keep AF when tracking raptors against the golden colors of California. Mother nature has armed the raptors with natural camouflage to give them predatory advantage, and this unfortunately fools the 7D AF system as much as it fools the voles and gophers. Acquiring initial autofocus on a flying raptor proved to be very difficult, no amount of pumping the AF-ON button or trying to grab the tail or wing tips as opposed to plain belly proved helpful in this case. More than 4,000 frames of raptors in flight delivered only a handful of keepers, all of the keepers where in conditions where raptor was exceptionally close and flying in a straight line right after take off as opposed to banking. Even in these conditions the focus is not as crisp as the examples above and we were at the mercy of filling the entire 18 mpixel frame with the bird and then down sampling to web size for posting.

Red-tailed hawk, 7D + 400 f/5.6L f/7.1 1/2000sec ISO 800.

100% crop from RAW converted with DPP sharpening 3. As you can see the detail is not very crisp and we are at the mercy of the large image size, however I still consider this a keeper for web and up to 8X10 prints.

This is the frame right after the above shot, as you can see focus is missed and softness is very evident even after down-sampling.

Harrier proved even more challenging than hawks, I wasn’t really able to capture the “peak of action” where I had good success with other gear in the same conditions. These include an EOS 1DSMKIII and a Nikon D700 which delivered a high percentage of in focus shots during tracking of the harrier in the same conditions.

Here is an example of famous banking position that was missed. 7D + 400 f/5.6L 1/1600sec f/5.6 ISO 400. Manual AF point in AI-servo, focus seems to be locked on the BG.

Here is a sequence of 8 shots tracking a harrier against variable BG. Each shot was down-sampled to about 2000 pixels from original 5184 so the harrier in the original was large enough to completely cover the AF point. It seems that as soon as camera sees a darker or brighter region in the BG, it shifts and locks the focus to BG.

I managed to grab the focus on the bird on a few occasions using the manual focus ring but it proved inadequate for critical sharpness.

Northern Harrier, 7D + 400 f/5.6 1/1600sec ISO 400. manual AF point in AI-servo, pumping the shutter button plus manual focus.

Northern Harrier with vole, 7D + 400 f/5.6L, 1/1600sec f/5.6 ISO 400. Manual AF point in AI-servo mode.

For comparison below is a shot taken in same conditions with a Nikon D700 and a 200-400 VR F/4 + 1.4X TC, naturally a full frame camera has a smaller AF coverage and a zoom lens plus a TC is not an ideal combo for AF performance either, however the mentioned combo as well as an EOS 1DSMKIII had no particular problem tracking the harrier and hawk in the given conditions, resulting in sharp photos capturing “peak of action” moments. This leads me to believe that user error is the unlikely reason for difficulties experienced above.

Update: I have uploaded short youtube video that shows the harriers in flight, it was shot while hand holding EF 400 f/4 DO so the quality isn’t great but it shows the flight pattern and backgrounds: clip1, clip2.

Nikon D700 + 200-400 f/4 AF-S VR + 1.4X TCII. 1/1000 sec, f/8 ISO 1600 hand hold and panning. 9-point Dynamic AF.

V. Conclusion

The long-awaited EOS 7D is on paper a birder’s dream camera with high pixel density and telephoto reach it can deliver good quality photos up to ISO 800 in good light and with correct exposure and allows lots of headroom for cropping and post processing. However AF performance is also a vital feature in bird photography. I personally judge a camera based on whether it produced a keeper from a “peak of action” moment in conditions where operator is not at fault. My conclusion is that EOS 7D AF is very good for some conditions but it may fail in certain other conditions, it clearly does not deliver the same level of performance seen from 1D(S)MKIII cameras or Nikon D700/D3 AF system. That is not to say 7D is a bad camera, it has many features and as noted in the beginning, if you are an armature or casual photographer it will most likely exceed your skills. If you just started bird photography it’s a great tool to help build up your skills and you will enjoy the experience. However if you are a professional wildlife photographer or an advanced birding enthusiast and feel you need something substantially better than the XXD cameras the 7D may not be your primary option and only you can tell whether its AF is adequate for your needs or not, so the best approach is to rent/barrow the body for a few days and try it with your favorite lenses. Canon has just announced EOS 1DMKIV which has yet a completely different AF system based on the foundations of 1D(S)MKIII, most likely Canon intended to put some clear distance between the $5,000 body and its $1700 sibling.

Disclaimer and notes:

All of the information above is solely my opinion. All material above is copyright 2009 Arash Hazeghi and is provided for personal inspection only. No reproduction or redistribution of any kind is allowed without written consent.