aslack78 wrote in post #18584013
Well, I made my choice. Found a 7D local to me with less than 10k clicks for $340. Bought it and a 18-55 STM kit lens to get started. Time to start relearning. Thanks everyone.
That's a really good deal on a very low "mileage" camera. The lens will be fine to start. STM lenses are great for video, too, if you plan to shoot any of that.
7D is an excellent sports/action stills camera... It has a very high performance, all cross-type 19-point AF system that's supported by its own separate chip (like Canon 1D-series models... most others share the AF with the image processing, through a single processor). 7D also has dual processors to support high frame rates (up to 8 frames per second, though you'll find it slows a bit at times to allow time for focusing and metering). To take full advantage of 7D's high performance AF syste you will want USM lenses.
You may or may not be aware, Canon makes autofocus lenses using four different types of autofocus systems:
1. "Micro motor" are the cheapest and most entry level. They are not marked "STM" or "USM". Micro motor are the slowest, noisiest and least accurate.
2. "STM" or "stepper motor" are a bit faster and much quieter, smoother. They are desirable for video, in particular. Okay for sports/action, but not as good as USM.
3. "USM" or "ultrasonic motor" are the fastest acquiring focus and best tracking movement, making them the most ideal for fast action subjects. They are relatively quiet and smooth, but the STM lenses are more-so... the USM lenses are not as good for video, but are best for most other purposes. USM focus drive is used on mid-grade to premium-grade Canon lenses.
4. "Nano USM" is the latest and greatest, but so far is only found in three newer lenses. It's the best of both worlds.... fast and great tracking like USM, but also quiet and smooth for use with video. It's only found on the newer EF-S 18-135mm IS USM, EF 24-105mm f/4L IS USM "II" and the EF 70-300mm IS USM "II".
One difference in use is that the micro motor lenses do not support "full time manual override" (FTM, Canon calls it) of AF. With them it's necessary to first turn off AF at the switch, before focusing the lens manually. The other three types allow FTM, which can be very useful to quickly de-focus the lens to force the camera & lens to re-focus. It also allows slight manual adjustments and can be useful if doing focus and recompose or other advanced focusing techniques.
STM lenses are "fly by wire", meaning that they have to be getting power from the camera to focus automatically or manually. When the camera is powered off or the AF is in "sleep mode", the focus ring of the lens will turn, but not do anything. When you have the lens perform AF (by half press of the shutter release or back button focus), the system remains active for some 10 or 15 seconds... after which it "powers down" to save battery charge. During that time you can manually override the STM lenses. In contrast, USM lenses are electro-mechanical, so you can focus them manually even when the camera is powered off.
Sigma "HSM" and Tamron "USD" lens focus drives both are similar to Canon USM. Tamron also has a "PZD" drive on a few lenses, which seems similar to Canon STM. Sigma and Tamron lenses without these markings, I would think are using a system similar to Canon micro motor. AFAIK, most Tokina lenses use a micro motor type focus drive. I know they made a 70-200mm with ultrasonic type at one time, but it was only ever offered to fit Nikon. Tokina has just announced at least one new premium quality "Opera" lens that will be using ultrasonic and will be available in more mounts.
Have fun with your new camera!