How to tell if you have a crop sensor on your camera?

I own a nikon D90. I was watching some viedos and the people are talking about crop sensors and how it can change numbers because you have to times by something or rather. ARGH! Anyways i was wondering if anyone can explain to me, how can you tell if you have a ful frame sensor or a crop frame sensor, and which one is better and why would you want to go for a full or a crop.

Here's the list of specs for your D90 - yes it does have a crop sensor.
http://www.bhphotovideo.com/...amera.html

It really depends on the kind of shooting you're doing. If you're a pro you wouldn't be asking this question because you'd probably own a full frame sensor dslr.

As displayed on a computer screen the real difference between the crop in your camera and a full frame doesn't matter much. It really matters when being published in say a magazine or when making very large prints.

All cameras, save for a few in the $3, 000 range and up have crop sensors. The smaller the camera the smaller the sensor.

I wouldn't worry about it if I were you.

You have a crop sensor camera. That's something that is clearly written in the specification of the cameras. E. G. The very title line of the D90 on adorama reads, "Nikon D90 12.3 Megapixel Digital SLR Camera Body with DX Format CMOS Sensor"

A DX format sensor is a crop one.

You don't have to multiply any numbers in everyday handling of the camera, only if you wish to compare focal lengths to those of cameras with a different sensor size.

Full frame is generally considered to be better, mostly because a bigger sensor gathers more light. That results in more accurate sensor readings for each individual pixel. This means that it will perform better especially in low light situations, Full frame DSLRs are very expensive though, you won't get one for less than $2500 (body only) or so, as the sensors are expensive to make and less numbers of them are made, so the economies of scale don't come into play as much as with crop sensor cameras.

For very most intents and purposes crop sensor cameras are just fine though, the difference mostly comes to play in very special applications, such as shooting sports in low light situations where you need crazy high ISO.

Crop sensor cameras on the other hand have the benefit of relatively cheaper lenses, as dedicated lenses for crop sensor cameras need not be as big as those for full frame, and they get extra reach due to the crop factor. E. G. On 1.5x crop frame such as your D90 a 200mm lens will give you the same reach as 300mm on full frame, and that 200mm lens, all other things being equal, will be cheaper than a 300mm one.

The only time you need to know what the Focal length multiplier is, is when you are choosing lenses for your camera.

Actually if you consider that All Nikon dSLR's have cropped senors but for the Nikon D3, D3s, D700 and D3X you will be fine