Grundig CCTV Cameras: Guide to Megapixel Counts and Focal Lengths

Grundig CCTV Cameras: Guide to Megapixel Counts and Focal Lengths

28 Apr 2021 | 5 min read

Quick Summary

Our guide to megapixel counts and focal lengths when choosing an IP security camera.

Megapixel Counts

Grundig cameras are available in a wide range of Megapixel resolutions, from 1 to 12MP. This comprehensive range means the most cost-effective camera is always available. Applications that require image rescaling after capture may want higher megapixel counts, since they can result in higher detail being captured. If you’re likely to need to identify license plates, text or other finer details with accuracy, a higher megapixel count will often be preferable, along with a greater optical zoom.

However, contrary to what smartphone marketers would have you believe, more isn’t always better when it comes to megapixel sensors. Here’s an example:

A smartphone with a 12MP sensor and a digital camera with a 12MP sensor will produce images of very different quality. This is because the megapixel sensor on the smartphone will be much smaller in size than that on the full-frame camera.

Both sensors digitise a captured image using the same number of pixels, but those physical pixels are of very different size since a smaller sensor has to cram those same 12 million pixels into a smaller physical space. Smaller individual pixels allow in much less light and, therefore, can capture less detail, resulting in more grain and a lower quality final image.

That’s why, all else being equal, a lower megapixel camera can actually perform better in low light conditions than a higher megapixel camera; fewer pixels in the same physical space means larger individual pixels which allow in more light despite the dark conditions.

Having said this, a higher number of megapixels will be preferable when light is abundant since more data is captured per pixel, allowing for more detail in the final image. There is therefore a natural point of no return at which a lower number of megapixels will be preferable.

Indeed, cameras and picture quality often comes down to light and how much of it can get into the camera’s lens. Larger lenses (all else being equal) produce better images, which brings us onto lens focal lengths.

Focal Lengths

The focal length of any camera lens refers not to the diameter of the lens, but to the length in mm from the the lens’ optical centre to the camera’s sensor. As focal length increases, field of view narrows and the lens’ magnification strengthens. For the widest field of view possible, you’ll want to choose a camera with a shorter focal length.

Where lens diameter does come into play is with a property known as the lens’ F-stop. The F-stop of a lens is a function of its focal length and diameter and a measure of its brightness at maximum aperture (i.e. fully zoomed out, if the lens zooms. Non-zoom lenses will always be at maximum aperture). Two lenses with the same focal length but differing in diameter will differ in brightness. The larger diameter lens will be brighter and will have a lower F-stop, since F-stop is calculated by dividing the focal length by the lens diameter, a larger denominator results in a lower F-stop value. In general, lower F-stop lenses have less grain and capture more image detail, especially in darker shooting environments.

Vari-focal lenses have a variable focal length (hence the name), which gives the lens an optical zoom. Grundig cameras are available with focal lengths of between 2mm and 12mm, with both motorised and non-motorised vari-focal lens cameras available, including PTZ dome cameras with optical zoom of up to 36x. For a more magnified final image, go with a longer focal length or a camera with variable focal length or zoom capabilities. Grundig cameras are equipped with excellent integrated LED IR Illuminators, which get around many of the low-light issues discussed here, offering excellent image quality even at night and in the dark.

Optical Zoom vs Digital Zoom

A camera’s optical zoom is a by-product of its lens’ ability to change in focal length. Naturally, only vari-focal lenses are able to zoom optically. An optical zoom will retain image sharpness and image quality throughout the full range of the zoom, provided lighting conditions are optimal.

When there is little light, an image that has been greatly zoomed in is likely to suffer in quality. This is because optical zoom achieves magnification by increasing the focal length. The camera’s aperture necessarily narrows as focal length increases, resulting in less light getting to the sensor, which in turn results in less data being captured. There will therefore be instances (primarily when lighting conditions are poor) when it’s preferable to preserve the amount of light getting into the lens and to use digital zoom rather than optical zoom.

Digital zoom is achieved by cropping the image digitally and rescaling it to redisplay the same image data over a larger physical area. This necessarily results in a reduction in image quality. Digital zoom still has its place, though, especially where it’s possible to shoot video in 4K or 1080p and rescale to 1080p and 720p respectively after cropping, resulting in a final image of reasonably high quality.

Digital zoom is used in smartphone cameras, so try zooming in on a subject with your smartphone camera to experience the reduction in image quality. Modern smartphones use software to varying degrees of success in an attempt to preserve as much detail as possible, though it is impossible to preserve completely. Smartphones have increasingly come to use multi-camera setups in order to get around the physics-problem of maintaining slim-phone design while offering the ability to capture images with the subject at varying distances from the camera (three-camera setups are most common, with telephoto, ultra-wide and primary lenses).

All of the various factors discussed here stress the importance of allowing as much light into the lens as possible when capturing video footage. Grundig IP security cameras get around many of these issues with their excellent night-vision IR sensors, essentially allowing these cameras to see in the dark, allowing you to monitor and secure your sites of interest effortlessly, no matter the environmental conditions.

Grundig CCTV Cameras: Guide to Megapixel Counts and Focal Lengths