This is a Step converter adapter for any camera, or camcorder with a 37mm thread to fit some Vivitar telephoto lens.It bridges the gap between smaller threads to larger thread sized lens attachmentsThis attachment is meant for certain Cannon digital cameras.Usually the lens size is marked with a O with a line through it. Alternatively you can get a millimeter ruler with slider bars to count all the lines.But I actually had to ask the manufacturers lol.What you see is an the side screen. When zoomed out or 1x at the lowest end, that fish eye crop shows up.If I zoom in a bit more, that interior view goes away.The camcorder has no optical zoom so this as the diameter size of the lens attachment was marked on the cap cover.But not marked on the Camcorder. Usually a circle with a line through it indicates the thread size.I will later order a manual zoom dial thing but the Vivitar gives you 2x zoom.It’s a fixed or prime lens. Also among the cheapest. But when you increase the focal ranges, the image that is captured gets smaller.You loose the background sharpness but you zoom in on a subject or object.Basically the field of view narrows but gives you what is important. 50 is mid range. But get below that, you get a wider field of view.And when to use attachments is for things out of its range. This particular camcorder is a Camworld AC13. With f/3.6mm to f=7.63mm .Those lower ranges is actually good for wide angle shots to give you both sharp background and good visuals of faces.And guessing that 40 feet ? with no optical zoom is where most camcorders get fuzzy, when you zoom out too far.But it’s more about the type of scenery you intend to get. So a sports stadium lol is not going to be clear. You would need a higher focal lens.And you shouldn’t expect a camcorder to pull in the faces of a sports player.You need the bigger things that film makers use, that are easily $3,500 vs $80-$350s for camcorders. Camcorders aren’t meant for professional grade filming.Now for Aperture that is on the lower end gives you good low light and not an over exposed picture.It might be labeled as 1:2:3. 1-5 which is basically the shutter, to regulate how much light comes in.What it all boils down to, when it comes to lens attachments: The lens attachment, needed depends on what your filming or taking shots of; and is more important than the device itself.This Camcorder has 4K resolution, 42MP camera and an full HD 3 inch display. The AC13. Made by Camworld.And, it’s actually impressive for the price. It comes with an external mic, lens hood, stabilizer bar, two batteries, SD card, battery bay charger, a remote, and a USB C cable. Soon I will post my review on that. It’s all USB C charging/powered.The AC13 connects via USB C to charge, or data (to any PC).The other mode is webcam. You can then use it to live stream, via a laptop with Internet access. For things like YouTube, Skype, Facebook and such.The mic is rechargeable. Standard 1/4in thread for tripod mount and it’s got “hot shoe” connector. It’s a port that slides in and tighten or loosen.To pull footage off-You either pop the memory card out or connect it via USB C to pull the footage.The mic of course should only be used for audio further away and not 3 feet away. As it will record and be barring.Though you can always lower the master volume.