Buying photography gear?

I have a Canon EOS 500D and I'm thinking to buy a micro lens. I know it is better to buy a Canon micro lens for Canon camera but I might upgrade my camera and switch to Nikon. Is there any other brand of micro lens which compatible with Canon 500D and Nikon? Also does it mean that I have to buy all the gear again if I upgrade my camera? For example the polarized lens, neutral density?

Lenses between different brands of cameras are not interchangable. Means you can't fit a canon lens on a nikon or vice versa.

If you do not want to buy an original canon lens, check out lenses made by SIGMA, TAMRON. They have canon compatible lenses.

Hope that helps

If you are calling a filter a lens, then know that any filter can be used on any brand lens as long as the filter thread size is correct (or you buy a filter thread adapter ring).

But a Nikon lens belongs on a Nikon camera, and a Canon lens belongs on a Canon camera.

And third party lenses are made for either Nikon or Canon, and are not interchangeable.

1- "I'm thinking to buy a micro lens."

What's a micro lens? Did you mean MACRO?

2- "I know it is better to buy a Canon micro lens for Canon camera but I might upgrade my camera and switch to Nikon."

Switching brands is a waste of money. Choose a brand (whatever brand that happens to be: Nikon, Canon, Olympus, Sony… ) and stick to it.

3- "Is there any other brand of micro lens which compatible with Canon 500D and Nikon?"

You mean you would like a lens that you can switch between the two cameras? No. The mounting system on the camera is different for both brands. There are some adapters you can get but you lose through the lens metering and auto-focus.

4- "Also does it mean that I have to buy all the gear again if I upgrade my camera?"

It depends one a few things:

A- If you are "upgrading" from a Canon 500D (Rebel T1i) to another Canon cropped sensor body like the 60D or 7D? Then no. You can use the same lenses.

B- If you are "upgrading" from a Canon 500D (Rebel T1i) to a Canon FULL FRAME sensor body like a 5DMkII or up then it depends on the lenses. If the lenses are EF-S lenses then yes, you need to get rid of those as they don;t mount on full frame Canon bodies. Only EF lenses mount on the 5D and 1D series.

C- If you are "upgrading" from a Canon 500D (Rebel T1i) to ANOTHER BRAND then yes. You have to change EVERYTHING! Lenses, shoe mount flashes, extra batteries, infra red remotes… Pretty much everything has to go except your tripod and lens filters and that's why it. A bad idea to switch brands.

You spent let's say 1800$ (taxes included) on a 24-70 f2.8 L lens from Canon, you switch to Nikon you sell the lens for let's say 2/3 the price (1066$) you then buy the Nikon version for 2185$ (taxes included) and, when we factor in the loss of value on the original lens, the new Nikon lens suddenly cost you 2919 instead of 2185… You are throwing out 800$ out the window.

(1800 + 2185) - 1066 = 2919$
2919 - 2185 = 734$ wasted

And my 2/3 value on resale was generous.

Now let's say you have 3 lenses and 2 flashes… You are literally throwing out THOUSANDS of dollars out the window.