I have been distracted this week by focus, several things sent me in to a voyage of discovery and I thought I would share my findings and the circumstances that sent me to find them.
Firstly over the last month or two most of the pictures I have submitted to my better photo courses have carried the comment that they are not quite tack sharp, I have to be honest this has driven me round the bend, Kerry Drager is the worst (and the best) at telling me this, that’s not a dig at Kerry but rather the reason I love his classes so much, he tells me straight and has an eye for these things, often I have read the comment and thought he was seeing things but on every inspection he was bang on the money. The first discovery I made happened about two to three months ago when I was trying to figure out how an autofocus system doesn’t!
I came across lots of reviews and forum comments that suggested my old Canon EF Ultrasonic 28 to 200 was a badly built lens that suffered from poor quality:
Like this for instance: Canon EF 28-200mm f/3.5-5.6 USM Lens Review
I took it to the local camera shop who looked at it and found it also had a tightening in the middle of its zoom range that didn’t help. Thy offered to get it serviced for me but since I had just invested in a new Canon 7D I thought it deserved a new main telephoto lens, I went to the local camera shop who sold me after much uming and ering a Tamron 18 to 270 f3.5-6.3 Di II V PZD. This lens was supposed to be a great quality lens but cheaper than the canon equivalent.
My problems were over or so I thought, my photos continued to get not quite sharp comments from Kerry, REALLY? maybe his eyes are not what they were, no such luck as usual Kerry was spot on the money, so what could be wrong, I did the one thing I don’t think anyone who spent a lot of money on a camera body should ever do! I googgled “Canon EOS 7D Focus problems”, OH MY GOD! The forums are alive with chatter on this; mostly hear say and lots of ignorance I discovered.
So do I have the one flawed body that Canon Make???? Well if you own a canon EOS 7D calm down you don’t!
It’s perfectly capable of producing Tack Sharp images to equal any Nikon body, this is where it gets hard and where the skill arrives, there are so many factors that effect this problem and many of them relate to workflow.
First of all I was using the standard ONE SHOT AF setting with the 19 point auto AF selection enabled that should work for all situations right? Wrong! It will focus on an object or series of objects that are closest to the camera not necessarily the object that is your main subject.
Lesson 1 Take control you decide where to place the focus after deciding to take Charlotte Lowrie’s Better photo Class on the 7D (Highly recommended by the way) the first week’s lesson got me looking at the Auto Focus System and adjusting it for the shot I am taking to ensure that the focus sensor is the one over the subject (I won’t try to teach the how of that go take Charlottes class if you need to know). So now I am actually focussing on the right thing that’s good
I took a photo of a tractor wheel, it was one of the picture that set me on this quest, I thought that Lesson 1 would fix that problem, oh no! When I looked at it there was not a single place on the picture that was sharp it was all fuzzy. Now how can a camera with one of the most complex auto focus systems on the market fail to focus on any point in the frame maybe the EOS 7D really does have a focus problem WRONG!!!, looking at the data I took the shot hand held with a shutter speed of 1/40sec at f6.3 ISO 100 and a focal; length of 219 mm, anyone spot the problem? Shutter speed, you ant hand hold 1/40 of a second at 216mm without the shacking of your hands sending the image fuzzy, so the old age rule has always been shutter speed should be the reciprocal of the length of the lens to hand hold that 1/216 sec or in this case 1/270 sec minimum as I am reliably told by Kerry that the rule is for telephotos to use the longest focal length for all shots with a zoom lens to compensate for the weight of the thing.
Lesson 2 USE a tripod and if you can’t get the shutter speed up to allow for a hand held response, don’t forget you can raise the ISO if you can’t get the shutter speed you need but watch out that you balance this with the digital noise you get from higher iso numbers.
Lesson 3 Set up your camera and test it. I found that you can adjust the micro focus of your lens on the EOS 7D and I found a great sight that tells you how PUT IT HERE I did this and found my Tamron lens was slightly out so worth doing.
Next I was given a link to a forum where there was a raging discussion about getting a sharp focus on a product shoot at f22, now I use f22 quite a lot in the belief that I will get great depth of field like this, and there was some comment that at f22 most lenses go a little soft, not sure if that is even slightly true but some physics was quoted which in an internet forum almost always means its rubbish, however I did find this site which may help to offset this conundrum you can decide for yourself I have included a range of test shots with all parameters fixed except aperture to show my 7D with mu Tamron Zoom set to a focal length of 39 mm focused using the Manual Single point AF with the centre sensor active in ONE SHOT AF with the sensor over the centreline of the chart you can see the results for yourself and decide if there is a focus problem or not.
39mm Focal Length at f/4.5
39mm Focal Length at f/8
39mm Focal Length at f/11
39mm Focal Length at f/22
39mm Focal Length at f/29
Links you may Find Helpful:
A blog on the Nikon D70 the chart above came from here
Ugly Hedgehog.com: The forum discussion on focusing at f22 thanks to Jan