SPEEDLITE 320EX

The 320EX is a new flash designed to serve two purposes simultaneously. It’s a traditional flash for still photography, but it also contains a white LED to provide continuous light for shooting video with the new video DSLR’s.
Unfortunately, I found the 320EX to be the worst of both worlds. It was mediocre both as a still flash as as a video light.
As a traditional flash, it lacks the focus-assist beam, the manual power mode, and the automatic zoom head found on the larger flashes (you can zoom it manually—if you remember to.)
As a video light, its LED is only useful in fairly dark situations. It can’t provide enough fill light to overcome even moderate backlight, and for shooting professional-looking video it’s not an option. (However, it could be a lifesaver in a truly dark setting where you suddenly needed to shoot some video.)
I find that when I’m shooting video, I need stronger lights, and when I’m shooting stills, I need a more capable flash.
So I sold my 320EX on eBay and used the money toward another 430EX II.

SPEEDLITE 270EX II

Starting with the least expensive flash, the 270EX II is a “mini” Speedlite that lacks some of the key functions found in the larger flashes.
It has no infrared focus-assist beam to help you focus in the dark (instead it does that annoying strobe thing), and while it can tilt to bounce from a ceiling, it cannot swivel from side to side.
It lacks a manual power mode, so even though it can serve as a remote TTL slave using the Canon wireless (light-based) signaling system, it cannot be used with third-party radio triggers.
Given these limitations, I see only three situations where the 270EX II makes sense:
1. You need some quick fill flash on one of the professional cameras (5D, 1D, etc.) that lack a built-in pop-up flash. The 270 makes a great replacement for that missing flash.
2. You have one of the small G-series Canon cameras that has a flash hot-shoe, but which would be overwhelmed by the size of a full Speedlite.
3. You need a very lightweight or very inconspicuous flash for some reason.
Otherwise, I suggest moving up to one of the full-size flashes.

Read more: http://digital-photography-school.com/choosing-the-best-canon-speedlite-flash-for-your-needs#ixzz1yBRTg5ye

Minimizing the need for sensor cleaning
The best way to clean the sensor is, of course, not to get it dirty in the first place! While it’s not really possible to totally eliminate sensor dust, there are some things you can do to minimize it.
Dust gets into the camera when you change lenses, so it’s wise to be cautious when changing lenses, especially in dusty conditions. You can change lenses quickly, with the camera pointing downwards for example. If you must change lenses in very dusty conditions, you can do so in a protected environment, such as inside your car rather than outside, or even inside a protective plastic bag. Another alternative if you know the conditions are going to be bad is to choose a wide to telephoto zoom, which may minimize the number of lens changes that you need.

The software solution
Quite a few cameras have a software based “dust deletion” feature. These generally work by first taking a blank frame which the camera uses to record the position of any dust particles on the sensor. This information can then be used (normally during RAW processing) to automatically clone out dust spots on the image. If you’re stuck in the field without the chance to do a sensor cleaning and you know you have a problem, then using this software solution can save you a lot of work later manually cloning out each dust spot on each image.