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The image resolution for the respective megapixels remains the same whether the camera is of medium format or full frame or APS-C or even mobile phones. However the sensor sizes differ in these aspects.
For example, the maximum output image resolution remains the same for a 20 megapixel full frame or APS-C sensors.
How is the image impacted here?
How is the image impacted here?
Two sensors with different sizes having same pixel resolution are capable of giving roughly same images (not discussing noise, dynamic range and colour reproduction now). However, this is only possible in theory.
If an objective is used to photograph a black to white transition (say the brightness ratio be 1:1000, rough example) it won't create a sharp transition with same brightness ratio. An objective will create the mentioned contrast only between point distant by several pixels, like this. Ideal camera will create this brightness transition in adjacent pixels (or separated by one pixel) but no real camera would do that. If you photograph fine details with objective which is not capable of reproducing this contrast you will get gray grid of varying paleness, like this, or just even gray area if objective is not good enough.
Here is a real example, this is a comparison between sensors with roughly same resolution but one left camera features 12x9mm sensor and right camera features 36x24mm sensor.
The right camera gives much more readable text. This means that objective used with right camera can create smaller brightness transitions in relation to image height.
It happens so that optics still are dependent on sensor size: given a larger sensor one may achieve better visible resolution than with objective made specially for smaller sensor. So, using smaller sensor results in inferior resolution because of currently manufactured optics.
how the resolution of images shot with particular mega pixel sensor is being maintained? Like a 20 megapixel full frame or APS-C have the same resolution of output image, although sensor size differs.
Different sensors have different sized pixels. If you have an APS-C sensor and a full frame sensor that have the same pixel count, say 20 megapixels or whatever, you can infer that the full frame sensor simply has larger pixels.
Resolution can be a misleading word. It relates to the resolving power of a sensor, i.e. the ability to image fine detail such as very small parallel lines. But it also relates to the overall pixel dimensions of an image, sensor, or display. So, a 20Mpx full frame sensor and a 20Mpx APS-C sensor have the same "resolution" in terms of overall pixel dimensions, but the smaller sensor packs more pixels into a given unit of area and would therefore be able to resolve finer details than the full frame sensor (provided that the lens projects a sharp enough image).
How is the image impacted here?
A larger sensor will see more of the image circle projected by the lens, and so will have a wider field of view than a smaller sensor would. This is exactly the reason for the "crop factor" adjustment that makes a 50mm lens on a crop sensor work like an 85mm lens on a full frame sensor. The smaller sensor sees only the middle of the image, and therefore has a narrower field of view.
