What do SLR cameras and stand-alone cameras mean?

Your question is a bit big, so you should answer it separately.

A camera is a kind of equipment that uses the principle of optical imaging to form an image and records the image with a negative. According to the different internal structure, it can be divided into SLR, double reaction, paraxial, single electricity and so on.

SLR, there is a reflector behind the camera lens, which reflects the light entering the lens up to 90 degrees and forms an image on the ground glass. Then, through a series of optical elements such as Fresnel lens and pentaprism (also pentaprism), our eyes can see the image on the ground glass. The benefits are self-evident. The eye can directly see the light emitted by the lens without any photoelectric conversion, so it can still be seen in the dark without delay.

The lens of a SLR is detachable, so a SLR camera without a lens is called a stand-alone camera.

Paraxial and double reflection, the eyes observe through another light path parallel to the lens. Because it is not the same optical path as the lens, there will be differences between what you see and what you shoot. The closer the distance, the greater the difference.

Single electricity only appeared in recent years. Because film is not used, it is imaged on CMOS, then put on the screen, take pictures, and view the light path like a SLR, so what you see is what you get. However, due to the photoelectric conversion, there is a delay and the light is too dim to take a photo.

The difference between an entry-level SLR and a professional SLR is usually in several aspects: the entry-level SLR has no shoulder screen, the focusing system is slightly behind (slow), the resolution is slightly lower, the continuous shooting speed is slightly slower, and some external accessories (handles, cables, etc.). ) are simplified, and the shutter system is slightly lower (fewer times and more noise).

Although it seems that the entry-level SLR is not as professional as everything, it is really enough for home use, except for enthusiasts. Which means you can buy it.

Finally, what brand is good now? Canon (the eldest), Nikon (the second), Pentax, Sony and Olympus all have SLR. I recommend the first three. Panasonic, Sony, Olympus and Samsung all have single batteries, and the first three are also recommended.

Specific models: Canon 50D, 60D, Nikon D3 100, D5 100, Pentax K-r, K-30, K0 1 (single electricity) Panasonic GF series (single electricity) Sony NEX series (single electricity) are all good. Be specific and compare prices, hehe.