First you need to decide what you want to take pictures of! I only have experience with canon and Leica. Any canon body will take good pictures. That said your budget will dictate what you buy unless you decide to wait and spend more money later. I wouldn't think your going to touch a macro lens and body for $500 but you can get a good body and kit lens that will be a good start. There are many folks that take great tank photos with the Canon 18-55 kit lens.
Macro lenses give you 1:1 magnification and on the other hand are very sharp fixed length lenses that can be used for everyday photos also. So yes you do need to think about mm or focal length when looking for a macro. How close can you get to your favorite subject. 60mm would not be all that great for bugs but for flowers and shallow tanks its fine. 100mm will get you a little further away and 180 even further. Those are the three most popular Canon lens lengths. Now with a $500 budget you will end up with a crop body. This means that the 100mm will be the equivalent of 160mm which is why its almost the perfect lens and the most popular macro for Canons. I have the 180mm and a full frame camera which is perfect for pretty much any macro photography, but its actually 180mm on my camera. On a crop body it would be 288mm which is quite abit to long IMO.
As far as non macro goes the average person back in the film days would have shot the majority of their shots in the 24-70mm range. This is why most cameras come with a 18-55mm kit lens. It gives you on average what you will need with a small amount of post process crop room. If your looking around the internet seeing all these razor sharp images and want to get those yourself, a dslr is the way to go. You wont get those with the little ccd point and shoot cameras, the only point and shoot that comes close is the Leica X1 and is out of your budget. You can make the most of your point and shoot. First never use the zoom, zoom with your feet. Frame your images dont crop. If its an option shoot in RAW format. I have a little Lumix lx5 point and shoot and it offers RAW I dont know about others.
Dslr's are all about glass (lenses). The better the glass the better the pictures. A word of warning, don't get caught up in the "L" lens crowd. Yes they are fantastic but are more than most will ever need, most dont even print their images. Crop cameras only use a small portion of the lens, granted its the best part of the lens but still only a small portion. The only reason I can see to buy L glass is with a full frame or you print large prints. If I was just starting out I'd get the best canon camera with the 18-55 EFS IS kit lens that was in my budget. Then I'd add the 100mm macro not the L for taking tank photos. The 100mm macro will give a beautiful portrait lens and a macro in one lens.
Confused yet?
Don
all of the recent pics in my tank thread i posted earlier are taken with the little camera. sucker focuses at about 2cm. it's hd, 16 mp, and shoots 3D panoramic and standard if you're into that sort of thing. its a fun little camera and well worth the $$.
