Wednesday, 25 August 2010

Canon 7D: It's Not Me, It's You

If you’re a Canon shooter, you may have heard of users having problems with the 7D’s autofocus. Hell, even those-who-must-not-be-named have heard of issues with this camera (they seem to like to laugh about it and try to tempt me over to the dark side.) Anyway, after ploughing my way through a few 7D copies, I finally hit my Eureka moment when I landed one that actually works.

The history (the boring bit – skip this is you’d rather read my findings on the 7D’s workings and quirks!):

7D 1: Returned to the shop for a replacement within an hour of purchase. Why? I noticed the viewfinder was scratched right out of the box. I’m not sure if I should really label this 7D number 1 since I have no idea if it had any focus problems or not – I didn’t even get as far as charging the battery.

7D 2: The problem? Total inconsistency with focussing, even in its most basic, simplest AF mode, on still objects, on a tripod etc. I shot wide-open, all in one-shot, single-point with the centre-point manually selected. One shot would be fine, the next would be front focused, the next would be completely OOF, and the next would be back focused. Micro adjustment was useless since I was getting crazy results that showed -2 and -9 to be perfect, but every value in between was OOF. I tested it on tripod, centre-point, mirror lock-up, the works, but still no joy or consistency with my test results. I returned the camera for a refund and decided to try a different retailer.

7D 3: Well this time, it was consistent all right – the problem was that when I increased the camera-to-subject distance, it would front-focus massively... every single time. Basically, for headshots when I was up close and personal, it would nail focus, but for full body shots, focus would go AWOL. If I only had one lens I might’ve said the lens was at fault and needed micro adjusting at different values through its focal lengths… but for this problem to occur with all 5 of my lenses?! Nope, this was yet another pesky camera problem. This time, I sent it to Canon under warranty, along with my Canon 50mm f1.8.

Canon recalibrated 7D 3 and sent it back. Did they fix the problem? Yes! Except… Oh no, except that it came back with a whole new problem. Now I could get a focused full body shot, hooray – but unfortunately it came back with total inconsistency – the same sort I’d experienced with 7D 2. Canon also kindly replaced the AF in my nifty fifty (Canon 50mm 1.8 lens).

Canon 7D 3 was sent back to Canon under warranty for a second time. For a start, they realised that in replacing the AF mechanism in my nifty-fifty lens, they’d actually busted it. Ho hum. Canon then tested the camera and called me to say they would like to send me brand new replacements for my 7D and my lens.

7D 4 arrived, along with my new lens. All seemed fine. While waiting for the replacement to come through, I sold all my Sigma lenses. I wanted optimum focus performance so thought I’d better go with Canon. The Canon 17-55mm arrived and there were a few issues, but I solved them (with the help of my fellow Flickrites) by micro adjusting (this time all the results were consistent – I knew this was a great sign) and also by avoiding Spot AF (I’ll explain more later). My thoughts on this copy of the 7D? This camera rocks!

If you’ve read this far and you’re still awake, well done!

Now I've actually had a chance to use this camera for a while, I thought I'd write up some of my findings, plus some notes I made from Rudy Winston’s must-see video.


Rudy Winston says that Spot AF roughly covers just the focus point's box, but single-point will extend beyond the box. I'm not going to quibble about whether Spot AF does in fact extend a tiny bit beyond the box or not - 'in the box', 'out of the box' is the simplest and most visual way to compare the two modes here.

I experienced a few problems with Spot AF when shooting wide-angle shots. I would select it to focus on something I thought had enough contrast e.g. an eye - something dark against pale skin - and it would struggle to lock focus; possibly because the eye was too small in the frame/box. Then it would exhibit some strange behaviour (see below) that would mean my focus was way off.

I don’t know if all 7Ds are the same, or whether it’s a quirk of my 7D, but my camera seems to do this: if it’s trying to spot focus on a face, when the box nearly covers the whole face (because you’re further away), and it can’t focus because it’s hitting on plain, non-contrasty skin, it then attempts to lock focus on the nearest thing to the camera instead of focusing on the nearest thing outside the focus point box (as would seem to be the more common sense thing to do!). This means I might focus on the face and end up with something a few inches away from the camera in focus. (This behaviour is designed to happen in 19 point AF – and I can see the benefit of it there - but I wasn’t expecting it to happen when it struggles with the other modes too - especially when the focus point has lit up red and beeped to confirm it has locked focus... I didn't realise it was just to confirm it had locked focus wherever it felt like!).

Oh and you may have wondered now if this was what was causing the problems with 7D3 front focussing when the camera-to-subject distance was wider. Sadly not - this only happens to me in Spot AF, and all my 7D3 tests were done in single-point, shooting very constrasty subjects e.g. a double-spread black & white newspaper, where there's no way it should've struggled to lock focus.

Spot AF is fine for precision focussing on the eye in headshots, where the focus point isn’t going to overlap with anything outside the eye socket. It's also good for macro, and for separating detail e.g. focussing on a bird when it’s surrounded by branches, or focussing on something behind bars (mass murderers and such like… ahem). However, for anything but the latter, I have much more luck using single-point under most circumstances.

For wider angle shots, where, as I mentioned before, the focus point will cover a larger section of the face (or indeed will cover the whole face) you don’t need to be so obsessive about putting the focus point on the eye – if you do, it might overlap the side of the head and catch some of the background, throwing the camera into confusion. Just focus on the face in general – if you’re far enough away, your DOF is wider anyway. I use ordinary single-point for this quite successfully.

The following is particularly important with shooting children, and especially regards headshots: children’s skin is smooth, without texture. If you try to focus on the skin on its own, e.g. (a common one) the bridge of the nose, between the eyes, then the camera hasn’t got enough detail to focus on. (Older people are more likely to have some sort of texture on their skin e.g. wrinkles, scars etc so the camera MAY be able to lock focus on the bridge of the nose). Depending on the extent to which your subject fills the frame, spot AF may increase the chances of pin-point focus hitting the non-contrasty skin instead of a detailed area, and missing focus.

Remember, there’s less contrast if the subject is backlit so it may be harder to lock focus. If you don't use a hood, try shielding the end of your lens from the sun with your hand, locking focus, removing your hand and then fully pressing the shutter button.

AI Servo – don’t hit the shutter immediately if you're using this mode – let the camera’s AF track the subject for a couple of seconds before you start shooting and you will get more keepers.

My 7D still produces soft photos. In a burst of, say, 3 shots, the middle one will usually be soft but I’m still happy with my results. (By the way, this happens using IS lenses at 1/1000 shutter speeds so it's not down to camera shake - still, I can live with it, and I can't complain anyway because Canon says it's normal.)

Expanded AF mode: I sort of like it, as long as you’re shooting something where the background/foreground is very plain i.e. birds in flight, where it will obviously lock on the contrasty bird rather than the plain sky behind it. For most other things I find it a bit hit and miss – it often finds the background or foreground far more interesting, and with those expanded points you can’t see how far they actually expand outside of their focus point boxes.

Zone AF: I really like this mode. I use it a lot for action shots. It's supposed to focus on the thing closest to the camera within that zone. This means it’s less likely to lock onto the background. It will only hunt for focus INSIDE your zone, so you can include/exclude whatever you want. For people, you can cover just their upper torso with the zone and it will lock onto the closest thing in the frame – therefore not including the feet in the zone, and so avoiding the dreaded ‘feet are most in focus’ scenario people have complained about when using 19 point AF.

I shot a wedding reception recently and by the time the bride and groom got up for their first dance, it was seriously dark. The camera couldn’t lock focus AT ALL. I ended up trying to manually focus in the pitch black, fiddling with the flash, all sorts – then in a last ditch attempt, I switched from single-point to zone AF and all of a sudden the camera nailed it! So if it’s dark and you can’t lock focus, try going with zone AF; it gives the camera more to work with. If I’d gone for expanded mode instead, it might have locked focus anywhere it felt like – the background, foreground, wherever – but with zone, it hunted through all of the focus points inside the zone and tried to lock focus there, again giving priority to whatever was closest to the camera.

The focus modes I use most often are are: single-point (manually selecting my focus point - I never focus and recompose), and zone AF. I sometimes use Spot AF, depending on the circumstances, but I rarely use expanded and never use 19 point AF.

Noise: I haven’t had any of the issues with noise that have been reported by other users, thankfully. One thing I will say is that I took some wide-angle shots at ISO 4000 yesterday and was zooming in as far as I could on the LCD screen and was becoming distressed at how grainy they were. Guess what? When I uploaded them to my computer, the noise was very fine and not a problem at all (I should mention I like grain though). At 50% size, I had zero problem with the noise issue, even with full body shots where they have fewer pixels dedicated to the face (and thus tend to lack as much detail as headshots anyway.)

Stop viewing your files at 100%! Seriously, there is no sense in this at all – all it does is make people paranoid about soft shots vs shots from their old camera. Do you know how big your print would be if you printed your 18 megapixel file at 100% full size? About 3 metres x 1metre! And if you made a print that size, would you be standing looking at it nose-to-nose so you could view every minor flaw? No, you’d be about four feet away so you could actually see the whole thing! So save yourself a few sleepless nights and look at your files at the biggest size you’ll print them at – about 50% max.

(P.S. Don't compare 100% shots from the 7D with 100% shots from your old camera that had fewer pixels. All those extra pixels make the image size huge, much bigger than the ones from smaller megapixel cameras. In a basic way, this means you're comparing  a massive file against a smaller one, where the resolution and sharpness will look better on the smaller- kind of like viewing a 100% 7D image vs a 50% 7D image.)

Lenses: I sold all my 3rd party lenses. I didn’t get as far as testing them on my only working 7D, but the chances are you will always have more consistency with Canon-branded lenses. The not-remotely-biased (!) Canon technician suggested as much – and also hinted that some older Canon lenses like the nifty-fifty may struggle to keep up with the 7D’s innovative new AF system. The thing about 3rd party lenses is this: Canon don’t sell their engineering secrets, so Sigma and Tamron have to backwards engineer their lenses so that they work on the cameras currently on the market. The 7D was very different to the cameras that have gone before (excluding the 1D series) – again, I don’t know for sure, because I only used my lovely Sigmas (and I truly do love Sigma) on dud 7Ds, but I do wonder if the 7D’s AF may be a step too far for some of the older 3rd party lenses. That said, the next lens on my list will be the magnificent Sigma 30mm f1.4.

There are undoubtedly 7D lemons out there – the fact my very first one was scratched out of the box was a bad omen in regards Canon’s quality control… and there are undoubtedly inexperienced users out there too. I didn't change my technique whatsoever across the ownership of my various 7Ds, so nothing changed for me in that regard - everything was tested in single-point one-shot mode, on tripods with mirror lock-up and using timers etc. I knew I had a good one when my micro adjustment results were consistent on my current 7D - all the previous ones had been all over the place. In the end, you have to trust your gut instinct and if you’re still not happy, send it in to Canon or go for a refund. Overall, after all the drama, it was worth it – I love this camera!


mtpphotography said...

Thank you! Thank you! I really appreciate you taking the time to share your knowledge of the 7D. I, like you, have had a rough start with this camera but after getting it back from Canon for the 2nd time (fingers crossed) it seems to be more consistent. Originally, it was super soft and grainy at at very low ISOs and when I got it back, that was fixed, but I couldn't achieve focus at all... AT ALL! I was about to pull my hair out! So back it went, with my Canon lens's. I have had a hard time with spot AF as well and appreciate your advice regarding the different Af points. I can't wait to get out and shoot in zone tomorrow! Thanks for your time and tips!!

Anonymous said...

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Anonymous said...

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