If you use a crop sensor lens with a full-frame camera, your photographs will have black margins around them. Full frame lenses function perfectly with crop sensor cameras since their picture coverage is 35mm, which is more than enough to cover the crop camera's roughly 24mm sensor. However, since sensors are smaller in diameter for crop cameras, the focal length of the lens needs to be adjusted proportionally.
When you attach a full-frame lens to a crop camera, the resulting image will be slightly wider than it would be if you were using a full-frame lens and a crop camera body. In order to keep the same perspective as if you were using a full-frame lens, you need to adjust your shooting location or subject position. The closer an object is to you, the larger it looks on screen; thus, if you want to maintain the same perspective, you'll need to move further away from your subject.
For example, if you were to shoot someone standing next to a window with a 24-70mm f/2.8 lens attached, the person would appear much taller in the photograph than they would if you were using a 70-200mm f/2.8 lens.
This is because windows are relatively close-up subjects; therefore, if you want to include both, you'll need to move farther away from your subject.
When utilizing full-frame lenses on a crop sensor camera, you simply do not receive a crop. Regardless of whether a lens is built for a full frame camera or a crop sensor camera, the focal length of any lens will generate the same image on your crop sensor camera. Because the size of the photo sensor is smaller, it can only capture a section of the scene in front of it. The remaining portion of the scene will be captured by the lens even though part of it isn't visible to the photographer.
There are two ways to correct this problem: switch to a shorter lens or use an accessory lens kit. Using a short lens allows you to keep all of your existing lenses and still obtain the desired effect. Accessory lens kits consist of several lenses that fit together to create a longer focal length. These add some extra width to your camera body which allows you to use larger sensors without having to buy new lenses.
Full-frame lenses may be used on APS-C cameras but must be cropped or multiplied. When you use an APS-C lens on a full-frame camera, it either doesn't function or just uses a very small fraction of the sensor. Lenses for both systems will say on their packaging whether they'll work on the other system.
With today's high-quality crop sensors, it's possible to get excellent results using only a few hundred pixels across. For example, an 80-200mm lens on a 200mm focal length could be cropped in half to serve as a 160mm lens on a 400mm focal length camera. Such lenses are called "crop lenses." They share many characteristics with standard full-frame lenses, including maximum aperture and price. However, they cover a much smaller area of the overall image plane, so they yield a more compact package and reduce weight compared to full-frame lenses of equal power.
There are two types of crop sensors: those that measure exactly 1/1.7" across (often called "170" or "180" film format) and those that vary in size from 1/3" to 1/5". Lenses for the first type are hard to find, while those for the second type can be expensive.
In general, the wider the angle of view, the more difficult it is to obtain good performance with a crop lens.
Generally, a full-frame sensor can provide a broader dynamic range and better low-light and high ISO performance, yielding a higher quality image than a crop sensor. Shooting full-frame, you get the benefit of a shallower depth of field. With most lenses, full-frame allows for less obstruction between subject and camera.
Crop sensors limit how much of the scene can be recorded at once, so they require more careful alignment to avoid cutting out parts of the image. They also cannot record as wide of a view as full-frame, so if you want to include a lot in your photo, it's best done with multiple frames or layers.
Full-frame cameras are generally larger and more expensive than crop-sensor cameras, but they offer better performance when it comes to taking pictures. If you plan to take lots of photos over time, consider buying a full-frame camera instead of a crop-sensor model; this will give you the best quality overall.
Full Frame Advantages: In general, a full frame sensor may give a wider dynamic range and better low-light and high ISO performance than a crop sensor, resulting in a higher quality image. A full frame sensor also allows for more shallow depth of field, which can be useful for getting away from the background. Finally, due to its size, a full frame sensor does not have to be as expensive as you might think.
Full Frame Disadvantages: They are much harder to use with fast lenses (because there's less space between the lens and the sensor), and they take up more room on a camera body. This can be an issue if you want to keep your camera small or travel with it a lot.
Crop Sensor Advantages: Because they aren't as big, crop sensors don't take up as much room on a camera body and may even be smaller than full frame. This makes them ideal for small cameras or those who want to travel with their gear a lot. They also tend to cost less because you don't need as many of them to make one camera body. However, crop sensors don't have the same dynamic range or low light performance as full frame sensors so they tend to degrade information toward the darker parts of the picture.