Camera Sensor Crop Factor
As the sensor size gets smaller you have what is called a crop factor which is a dimensionless reference number, associated with image sensors. It compares the diagonal distance across each specific camera sensor compared to the diagonal distance across the full frame camera sensor. It is called this because when using a 35 mm lens, such a sensor effectively crops out this much of the image at its exterior (due to its limited size).
Understanding camera sensor size and why it actually matters is one of the most important aspects of learning photography.
I have used what is called a full frame camera for almost all of my images on this site. The camera sensor size is the most important factor in determining overall camera performance & image quality, given the optimal focus, f-stop, ISO, and shutter speed settings have already been obtained.
What is a Camera Sensor?
The camera sensor, also known as an image sensor, is an electronic device that collects light information, consisting of colour & intensity after it passes through the lens opening, known as the aperture. It is what replaced film in old film cameras.
Physical sensor sizes are shown in terms of width and height, usually in millimetres. A full frame standard sensor size is 36mm × 24 mm and is known as a full frame 35mm format camera.
The typical smartphone sensor is a 1/2.6″ to 1/2.5″ sensor, so about a 6x crop factor.
Let us assume you have an iPhone with a 4mm lens, and so, even at f/1.8, everything that’s basically not touching the front lens is in focus. Well, close. You will get a very deep depth field so it is hard to create BOKEH.
The following graphic shows a camera sensor size comparison for varying popular sensor formats.
As the sensor size gets smaller you have what is called a crop factor which is a dimensionless reference number, associated with image sensors. It compares the diagonal distance across each specific camera sensor compared to the diagonal distance across the full frame camera sensor. It is called this because when using a 35 mm lens, such a sensor effectively crops out this much of the image at its exterior (due to its limited size).
Understanding camera sensor size and why it actually matters is one of the most important aspects of learning photography.
I have used what is called a full frame camera for almost all of my images on this site. The camera sensor size is the most important factor in determining overall camera performance & image quality, given the optimal focus, f-stop, ISO, and shutter speed settings have already been obtained.
What is a Camera Sensor?
The camera sensor, also known as an image sensor, is an electronic device that collects light information, consisting of colour & intensity after it passes through the lens opening, known as the aperture. It is what replaced film in old film cameras.
Physical sensor sizes are shown in terms of width and height, usually in millimetres. A full frame standard sensor size is 36mm × 24 mm and is known as a full frame 35mm format camera.
The typical smartphone sensor is a 1/2.6″ to 1/2.5″ sensor, so about a 6x crop factor.
Let us assume you have an iPhone with a 4mm lens, and so, even at f/1.8, everything that’s basically not touching the front lens is in focus. Well, close. You will get a very deep depth field so it is hard to create BOKEH.
The following graphic shows a camera sensor size comparison for varying popular sensor formats.
Larger sensor sizer give a larger sensor surface areas providing more area for the capture of light information over a standard interval, known as the exposure time. Imagine that you are on a sailboat. The larger the sail, the greater the surface area, the more wind it will catch.
As the sensor size gets smaller you have what is called a crop factor which is a dimensionless reference number, associated with image sensors. It compares the diagonal distance across each specific camera sensor compared to the diagonal distance across the full frame camera sensor. It is called this because when using a 35 mm lens, such a sensor effectively crops out this much of the image at its exterior (due to its limited size).
Smaller sensor sizes do have some advantages. Nearly all the lenses produced are sharpest at their centres, while quality degrades progressively toward to the edges. This means that a cropped sensor effectively discards the lowest quality portions of the image, which is quite useful when using low quality lenses (as these typically have the worst edge quality) and allows for cheaper lenses to be made for the camera. You will also get an in-focus image every time due to the DEPTH OF FIELD and there is no need therefore to focus. Of course one does lose the creative effects of these outer edge distortions, out of focus areas and the optical performance of wide angle lenses is rarely as good as longer focal length lenses.
Since a cropped sensor is forced to use a wider angle lens to produce the same angle of view as a larger sensor, this can degrade quality. Smaller sensors also enlarge the centre region of the lens more.
Similarly, the focal length multiplier relates the focal length of a lens used on a smaller format to a 35 mm lens producing an equivalent angle of view, and is equal to the crop factor. This means that a 50 mm lens used on a sensor with a 1.6X crop factor would produce the same field of view as a 1.6 x 50 = 80 mm lens on a 35 mm full frame sensor
Summary
Larger sensors generally provide more control and greater artistic flexibility, but at the cost of requiring larger lenses and more expensive equipment. This flexibility allows one to create a shallower depth of field than possible with a smaller sensor and achieve better BOKEH, but yet still achieve a comparable depth of field to a smaller sensor by using a higher ISO speed and smaller aperture (or when using a tripod).