Now I'm using Canon 50mm prime lens with my Canon 700d.I need to capture a group of 100 people indoor and in low light.There is not enough space that I can move backward to cover everyone within the frame, So I'm thinking to buy Neewer Wide-Angle and Macro mount. I chose canon 50mm prime lens for it's wide aperture f/1.8.(Great for low light). I don't have budget to go for a real wide angle lens for now. So some of my peers told me that adding a additional lens can add Chromatic aberration to the picture, I haven't tried that yet. Does anyone have idea on that, Should I go for it? If I can go for it please suggest me the best mount. If so please advise.
Chromatic aberration isn't your only worry with these add-on wide angle converter screw-on "filters". Image quality will suffer quite a bit, especially away from the center of the image.
Additionally, to help clear up some of the loss of clarity, you will probably need to stop down your lens to at least ƒ/4, perhaps even ƒ/5.6 or ƒ/8. Of course, that works counter to your desire for a wide aperture because you're shooting in low light.
However, you'd probably not want to shoot at ƒ/1.8 anyways, if you're trying to capture the entire group of people. People will be stacked up several deep. With a wide aperture, if you focus on the eyes of the people in front, the people in the back will not be in sharp focus.
If this is an important shot (such as for a wedding, or corporate event, etc.), and you can't afford to miss it but just don't have the budget for anything else, I suggest you take several shots laterally and stitch them together panoramically.
To do this, I suggest mounting the camera on a tripod, and rotate the camera a small amount, taking at least 5 pictures to cover the total group. There will be lots of overlap between the shots, which is important, because it gives you lots of room to pick and choose which parts of the original images go into the composite shot.
Doing this with your 50mm, I suggest stopping it down to its sharpest aperture, around ƒ/4 or ƒ/5.6. Just ask everybody to stand as still as possible, and quickly take the necessary shots.