@Bankesmom1 wrote:
...I'm still baffled why it has worked for years, and all of a sudden does not. I'm thinking that it is getting to be time to upgrade.
Most likely it is something you changed that has caused the problems you are seeing... not anything wrong with the camera or lens.
I agree with a previous response to get out of the highly automated "Sports" mode. Sure, use one of the auto exposure modes (Av, Tv or P)... that way you still get some automation. But you are now free to set up the AF system to better suit your needs.
Why is this important? Well, your camera has nine AF points. But they are not all the same. The point in the center is more sensitive and higher performance than the eight points surrounding it. If you switch your camera to Single Point AF and use only that center point, you will have MUCH better results than if you leave it to the camera to decide which point to use (as it is probably doing when in Sports mode).
You also want to set the autofocus to "AI Servo" mode. This is necessary with moving subjects. it focuses continuously when the shutter release button is half pressed. (Note, a technique many sports photographers use is called Back Button Focus... it is possible to set this up, using a button under your thumb to start and stop AF instead of the shutter release... but for now just stick with what you know.)
Now it is on you to keep that center AF point right on the subject, right where you want the camera and lens to focus. In the future most "missed focus" issues will be your fault, not the camera's or lens'.
I don't have that Tamron lens and would never buy a lens of that type (I have never found ultra wide ranging zooms to be very good). I don't know if it is very fast focusing or not. Canon's fastest focusing lenses have "USM" or "ultrasonic" focusing motor. Their "STM" or "stepper motor" is also reasonably quick, but not as fast as USM. Worst is "micro motor" (Canon lenses not labelled USM or STM).
Tamron calls that a "PZD" lens. According to one website that stands for "piezo ultrasonic focus drive". I have no idea if this is same as Canon USM or not. Even if it were, with f/6.3 aperture at the telephoto end of that lens, it simply is not sending a lot of light through the lens for the AF sensors to work with. For example, a lens with f/2.8 aperture passes twice as much light as one with an f/4 aperture. And an f/4 aperture passes twice as much as an f/5.6. In other words, an f/2.8 lens passes 4X as much light as an f/5.6 lens... and your lens is 1/3 stop dimmer than f/5.6 so doesn't even pass that much. Here's a breakdown of how much light is passed by full f-stops:
- f/1.0... 100%
- f/1.4... 50%
- f/2.0... 25%
- f/2.8... 12.5%
- f/4.0... 6.25%
- f/5.6... 3.125%
- f/8.0... 1.5625%
So your lens is only passing about 3% of the light in front of it! In addition, DSLRs use mirrors to redirect light... part to the viewfinder (70%) and part to the AF sensors (30%). So in truth your camera's AF sensors are working with only about 1% of the light in any scene you're photographing! (FYI: Modern mirrorless cameras have AF sensors embedded directly in their imaging sensors... no mirrors redirecting some of the light. Therefore they're able to autofocus effectively in much dimmer light and with lenses that have smaller apertures.)
Another possibility... You mentioned losing focus when "zooming". I would bet that your Tamron zoom is a "varifocal" design. This means the lens doesn't maintain focus when the focal length is changed. If your camera is in One Shot mode when that happens, you have to consciously re-focus after any "zooming" by lifting off the shutter button and re-applying half-press. Otherwise focus will probably be off, even with stationary subjects. However, if your camera is in AI Servo focus mode, it will automatically and quickly correct for any loss of focus caused by zooming. This is yet another reason to get out of the highly automated "scene" modes like Sports and take control of the AF system yourself. Once you set it to AI Servo it will stay there until you change it (and if you learn to use Back Button Focusing, you may never need to change it).
There is a third AF mode on your camera: AI Focus. NEVER USE IT. This is more automation. It is not an actual 3rd AF mode. Instead the camera is supposed to detect whether your subject is moving or not, then depending upon what it thinks is happening, switch to using either AI Servo (moving subjects) or One Shot (stationary subjects). I experimented with it ages ago and found it caused a delay, sometimes chose the wrong mode, or failed to switch if a subject started or stopped moving while I was focusing upon them. I stopped using it and immediately increased my in-focus keepers by a large margin. P.S. It might tell us something that Canon's most pro-oriented cameras don't even have AI Focus mode... they only have One Shot and AI Servo.
I wouldn't be too quick to upgrade. But if you do, you might want to look into lenses before you worry about the camera they are used upon. If you do the above, take control of AF yourself, you will see improvement even with your current lenses. It will be even better if you get a good, fast lenses like an EF 70-200mm f/2.8 or f/4, 300mm f/4, etc. with larger apertures and faster USM focus drive.
It is possible something is wrong with the lens... maybe even the camera. But it's more likely something the photographer has done wrong! Hopefully the above will help you get to the bottom of it.
NOTE: I saw another response told you to use One Shot mode. That's 100% incorrect with sports photography where the subjects are often moving. You MUST use AI Servo if you hope to have them in focus. But you also still need to take control of the AF system... not leave it to the camera with a "point and pray" technique!
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5, some other cameras, various lenses & accessories
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