I note toggerman's comment about zone AF but last weekend I found exactly the opposite….
Here is my scenario and
looking for feedback/suggestions:
I have done quite a few airshows before, but last weekend was my first with the 7D Mark 2 and 100-400 Mk2. Had prepped with birds at the local lake to get used to the new body & lens, sorting out AF cases and refreshing my panning technique.
Taking out those shots with motion blur or heat haze distortion; what was in focus was rivet-counting sharp, but a lot were just a bit mushy, even at shutter speeds that where blur should rarely be an issue. 1st/2nd image all set to focus priority. I usually use single-AF with expansion. I tried different settings during the day including: AF points, bump focus, even reducing fps. Did not play around much with AF cases though.
What really surprised me was Zone-AF with iTR (since its not just for faces and brings in data from the RGB metering sensor). My hit rate of tack sharp shots went up to ~75%, even during the same display.
Still lots to assess why the other AF modes didn't work very well but now I know just how sharp the images from this camera
can be.
Technique can always be improved but am not an airshow newbie. Here are a couple of examples where I can explain each one individually but not work out the overall pattern.
Helicopter in hover so not a huge risk for motion blur.
View attachment 39207
Focus point is on the cabin but the DOF (it was an unplanned grab shot) shows area ion focus is clearly towards the tail rotor. This suggests lens is back focussing massively. Based upon Reikan Focal, the lens is MFA'd to -2 at Wide angle. A few test shots early in the day did not indicate a 'local' change was needed.
50% crop unprocessed
Shutter: 1/125
Aperture: f8
Focal length: 100mm
Focus point: Single with expansion
Mode: AI Servo. Lens IS mode 2
I was wondering if rotational axis/parallax may be an issue but it was turning so slowly I ruled that out; besides the rotational axis would be further forward than the area of focus.
Next shot - all in focus - still 100mm
View attachment 39208
50% crop unprocessed
Shutter: 1/160
Aperture: f8
Focal length: 100mm
Focus point: Single with expansion
Mode: AI Servo. Lens IS mode 2
So… not back focussing after all.
Air shot: tack sharp. All of it. - can even see the vortex off the right wing
View attachment 39210
50% crop unprocessed
Shutter: 1/2000
Aperture: f8
Focal length: 400mm
Focus point: Single with expansion
Mode: AI Servo. Lens IS mode 2
Air shot: mushy. This is the following shot in the continuous burst sequence.
View attachment 39211
50% crop unprocessed
Shutter: 1/2000
Aperture: f10
Focal length: 400mm
Focus point: Single with expansion
Mode: AI Servo. Lens IS mode 2
and now for Zone AF with iTR:
View attachment 39213
50% crop unprocessed
Shutter: 1/800
Aperture: f5.6
Focal length: 400mm
Focus point: Zone AF with iTR
Mode: AI Servo. Lens IS mode 2
Firmware 1.0.4. Yes I did do the battery out thing after the firmware update.
Here are the things I am trying to work out:
- Why the huge back focus on the helicopter?
- Some tack sharp shots at 1/250 f/7.1 and 400mm
- lots of mushy ones at 1/1000+ or 1/2000+ f8 and 400mm
- Reikan Focal gave consistent MFA results and a few local test shots at the start of the day seemed to confirm MFA settings.
- Technique is always a factor but just seems too much inconsistency.
So far am loving Zone AF with iTR but at a loss with the poor performance of the staple that is Single point with expansion.
Keen for suggestions/advice.
John.