Question about my lens

[Carissa]

I don't know a whole lot about cameras and lenses and such so I'll throw this out there. Last year I bought a Canon 10D and I took the stock lens off of my Canon Rebel 2000 (film) to use on it. I quickly figured out that something is different on digital cameras as opposed to film cameras (distance from the lens to the sensor, maybe?), so my 28-80mm lens was giving me great close ups but no wide angle. So I bought this adapter off of ebay and it says "digital super wide 0.42x AF lens". It works great for wide angling stuff in conjunction with my other lens. But screwed into the back of this adapter is a lens that says "macro" on it. I thought macro meant close up, but this thing is giving me wide angle. What's the deal with that extra thing, is there some other use for it other than needing to be screwed into the back of this wide angle adapter for it to work right? I've tried putting it on my lens by itself and everything is blurry.

[gregr]

The first part of your question- about the 28-80 not being the same on the 10D as it is on your film camera--- that's due to the size of the sensor on the 10D as compared to the size of a piece of film. The sensor on the 10D is smaller. The explanation and the math behind the explanation get a little complicated but the bottom line is for all of your lenses you need to multiply the focal length by 1.6x to get the correct focal length for the lens on the 10D. The 1.6x is known as a 'lens multiplier' or 'crop factor'. So that 28-80 works like a 44.8-128mm lens. A 100-400 works like a 160-640. It's great for close-up, wildlife and sports photographers, who always need to be a little bit closer to the subject, but you can see how it is not so good for wide angle photography because you lose so much on the wide end.
When dslrs started to become popular ten or so years ago lens manufacturers started designing wide angle zooms to help us out. Now you can find lenses like 12-24mm that help make up for the crop factor.
Regarding the adapter you bought-- not sure about that- it probably a diopter/close-up filter-- that just means it helps the lens focus on something closer to you. Without it you would need to be further away from the subject. What is the name/brand/model of the adapter- we can check out the specs to know for sure.