"This phone's camera is good because it has a 21 MP f/2.0 sensor and 1.5 micrometer pixels." If you get stumped by statements like these, read this article and I can ensure you that you can weigh in on conversations with your shutter bug friends!
Aperture is measured using the "f-number", sometimes called the "f-stop", which describes the diameter of the aperture/lens. A lower f-number relates to a wider aperture (one that lets in more light), while a higher f-number means a narrower aperture (less light). Generally good phone cameras have f/2.2 or smaller. f/2.4 lenses are very common in phones nowadays, just to give you an idea. A wide aperture produces a narrow depth of field, so if you make it too wide you may have trouble keeping everything in focus. On the other hand, a narrow depth of field can help to isolate the subject, and is often something that you want; if so, you need to avoid using a narrow aperture.
Pixels are the building blocks of displays and images. "Mega" is a prefix for 10^6 and correspondingly, a "Megapixel" means a million pixels. So, why do the camera's megapixels matter? Megapixels or pixels are the standard to measure the resolution of an image which means, more the megapixels, the clearer is the image. If the image is clearer, you can zoom in more without the image pixelating. More megapixels don't always mean a better picture, it means that the image will be bigger in size and will take up more of your storage.
The size of a single pixel matters because it determines the amount of light you let in. A bigger pixel means more light and better pictures in low lighting conditions. The downside to bigger pixels is that the resolution of the image has to be compensated. Standard phone cameras have pixels of about 1-1.2 micrometers. iPhones have 1.5 micrometer pixels and the "UltraPixels" in the HTC One are 2 micrometers big.
ISO is a setting you can find in many camera applications and you will notice that by changing the ISO, the image colors or brightness changes. What ISO means is basically the sensitivity of the sensor towards light. More ISO means more light in the image. You will hear photographers increasing or decreasing in "stops". Increasing one stop means doubling the amount of light in the image and decreasing one stop means halving the amount of light in the image. The more you increase your camera's ISO, the more digital noise your photos will exhibit. This can make your image look grainy and reduce its sharpness.
Exposure is the amount of light per unit area. It is measured in lux seconds. In simple language, increasing exposure will increase the brightness in your image and decreasing it will darken your image. In dark situations, high exposure level can be helpful.
HDR: High Dynamic Range
HDR is used to generate a greater dynamic range of luminosity than possible using standard digital imaging. This is achieved by merging Low Dynamic Range and Standard Dynamic Range pictures. That's why taking a picture in HDR takes longer than it does when HDR isn't used.
OIS: Optical Image StabilizationImage stabilization (IS) is a family of techniques used to reduce blurring associated with the motion of a camera or other imaging device during exposure. OIS is a mechanism used in a still camera or video camera that stabilizes the recorded image by varying the optical path to the sensor. This technology is implemented in the lens itself, or by moving the sensor as the final element in the optical path. The key element of all optical stabilization systems is that they stabilize the image projected on the sensor before the sensor converts the image into digital information.
A video is basically a series of pictures taken and sewn together. More the number of images, the video seems smoother. If you want to take a video in slow motion, you need more FPS but since we don't have unlimited storage, FPS has to be under control.
Video resolutions: 240p, 360p, 1080i, 1080p, 4K etc.
Resolution are the Megapixel equivalent of images for videos. Larger the resolution, more the detail and video size. The number indicates resolution and the following "p" or "i" tells us whether the video is interlaced or progressive.
The Triangle of Exposure
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