C family is Canon, C is its initial letter, the same applies below;

N family is Nikon;

P family is Pentax;

The S family is Sony;

There is also the O family, Olympus.

Princess and Biscuits: Actually commonly known as Three Princesses and Three Biscuits, they are one of six limited edition fixed focus lenses from Pentax. It is characterized by its small size (Pentax's philosophy is that small is beautiful), exquisite workmanship (all-metal lens body and rigorous embedded mounting), good color, and guaranteed image quality.

The three princesses are: the eldest princess FA43mm f/1.9; the second princess FA77mm f/1.8; and the third princess FA31mm f/1.8. Three lenses are used on full-frame (or film) bodies for full-body portraits, close-up portraits, and landscape portraits.

The three cookies are: DA40mm f/2.8; DA70mm f/2.4; DA21mm f/3.2. These three biscuit lenses can actually correspond to the three focal lengths of the Three Princesses respectively. However, the three biscuits are exclusive to digital bodies, so the lens group structure has also been specially optimized, and its anti-glare and purple fringing capabilities have been improved. In terms of volume, it truly reaches the standard of a biscuit mirror. Special mention is made of the DA40, which is one of the smallest biscuit mirrors in the world.

As for photographing children, the light source is very important. But flash will cause their eyes to age prematurely, so if natural light is not used, a large aperture lens must be used to compensate. Although the three princesses and three biscuits are Pentax's special features, the aperture is not very wide, so it is not suitable for photographing children in this aspect. It is recommended to use a large aperture lens, such as the Canon 50mm F/1.8 standard lens, which will meet your requirements. It is very cost-effective and not expensive (about ￥800). It is a must-have for users with a small budget. If you can spend 3000, you can buy 50/1.4, which has a larger aperture and better image quality.

But in fact, when it comes to lenses and optical products, there is generally no price/performance ratio. You get what you pay for. The more expensive the lens, the better the image quality, and the cheaper lens can never replace it. So if you want good results, you have to spend more money.