The Magnification of Microscopy in the digital microscopes
Magnification is a key term in selecting the best optical lenses and system for your applications.
The following information can help you better understand it.
- Definition of Magnification: a measure of the apparent enlargement in size between the object and the image
Magnification is obtained in two ways—different lenses create different magnifications at the camera, and camera/monitor combination develop magnification between themselves.
Magnification on the sensor of the camera: the camera only “look at” the portion of the subject equal to the sensor size. What the camera”sees” is called the field of view. The optic magnification affects it. The lower the magnification, the larger the field of view.
Usually we call it optical magnification, in a zoom lenses it is calculated as zoom body magnification X CCD adaptor magnification X auxiliary objective magnification. Such as if you choose MZDH0850(0.75X~5.0X zoom body) with 0.5X CCD adaptor and 0.75X auxiliary objective, then the optical magnification range is 0.58X~1.875X.
Magnification at the monitor: the diagonal of the camera sensor is expanded to the diagonal of the monitor. We name it as digital magnification.
For example, when a 1/2” camera works with a 24” monitor. The 8mm diagonal of the sensor will increase to 24”(606.9mm) for a magnification of 75.9X.
Sensor size (mm) | Width*length(mm) | Diagonal (mm) |
1/3” | 3.6*4.8 | 6 |
1/2” | 4.8*6.4 | 8 |
2/3” | 6.6*8.8 | 11 |
1” | 9.6*12.8 | 16 |
Sensor size in Camera | Monitor Size(diagonal) | ||||
9”(228.6mm) | 12”(304.8mm) | 13”(337.8mm) | 24”(606.9mm) | 27”(685.8mm) | |
1/3” | 38.1X | 50.7X | 55.0X | 101.2X | 114.1X |
1/2” | 28.6X | 38.1X | 41.3X | 75.9X | 85.7X |
2/3” | 20.8X | 27.7X | 30.0X | 55.2X | 62.3X |
1” | 14.3X | 22.2X | 23.8X | 37.9X | 42.9X |
The total magnification is the result of optical magnification multiplied by digital magnification.
Such as if MZDH0850(with 0.5X CCD adaptor and 0.75X auxiliary objective) equipped with a 1/2” camera works and a 24” monitor, the total magnification becomes 21.3X~142.3X (optical magnification 0.28X~1.875X multiplied by 75.9X).
- A few factors related to optical magnification:
Numerical Aperture, a measure for its angular acceptance for incoming light in a lens system.
As numerical aperture increases, depth of field (the distance allowing clear image definition to be maintained without refocusing) decrease and resolution increases.
Field of view, the visible area displayed by a lenses.
As magnification increases, field of view decreases.
How to calculate field of view?
Sensor size divided by optical magnification. In the optical specification metrics, we valued the field of view by 1/3 sensor camera. Such as MZDH0850(with 0.5X CCD adaptor and 0.75X auxiliary objective), the optical magnification is 0.28X~1.875X, then the field of view is 12.9*17.1~1.92*2.56(the width and length of 1/3 sensor is 3.6*4.8; 3.6/0.28=12.9,4.8/1.875=17.1; 3.6/1.875=1.92, 4.8/1.875=2.56).
Illumination, more light may be needed when magnification increases, especially in coaxial lenses.
Resolution is the ability to see fine details in an image. The useful range of visual magnification importantly depends on the maximum resolving power of the optic microscopy system. When the magnification is beyond the useful range, then no more fine details on the sample can be got. We call it useless magnification.
High-magnification without enough resolution lead to useless magnification, no practical meaning.