Photography Techniques

Aperture Optical Aberrations – Minimize them to enhance quality in photography

Aperture Optical Aberrations – Minimize them to enhance quality in photography
Written by Dave Peterson

Aperture Optical Aberrations – Minimize them to enhance quality in photography

Aperture Optical Aberrations – Minimize them to enhance quality in photography.  Aberrations are deviations from the perfect performance of an optical system. Aberration results into blurring of the image as formed by the optical system. Technically it is the situation where light from a single point does not converge to a single point after the transmission through the optical system. Proper correction in optical system is to be done to compensate the aberration in the system.

In an ideal situation a parallel beam of light incident on a lens will converge into a point called focal point. The size for the focal point has to be extremely small but due to diffraction and aberrations the focal point of a lens is of finite size. The focal spot’s size is actually the magnitude of diffraction and aberrations in lens of the camera. The object not on axis when focused by the lens results into astigmatism due to natural asymmetry. In such a case there are two focal lengths.

The extent of astigmatism depends on the shape of the lens in case aperture is not in contact with the lens. In photography the amount of light that reaches the film or sensor can be controlled with adjustments in lens of the camera. When combined with change in shutter speed, the extent to which the film or sensor is exposed can be regulated with aperture size. Faster speed of shutter will require larger aperture to have sufficient exposure of light while the slower shutter speed will need smaller aperture is keep a check on excessive exposure.

Aperture Optical Aberrations – Minimize them to enhance quality in photography

Diaphragm is used as aperture stop which keep a check on aperture. It controls the effective opening of the diameter of the lens. The depth of field will increase on reduction of aperture size. Depth of field is the extent to which the subject remains closer or farther from the actual focal plane. Aperture and the distance of the subject from the focal plane are inversely proportional.

The lens aperture is expressed in terms of f-number which is numerically equal to the ratio of focal length and the effective aperture diameter. The value of f-number can be set to definite values. The low value of f-number means higher aperture opening. Each lens has a minimum and maximum value of apertures. The photojournalists use lenses with fixed focal length and low f-number. The range of maximum aperture for zoom lenses is f/2.8 to f/6.3.

Aperture Optical Aberrations – Minimize them to enhance quality in photography

Since it is very hard to maintain effective aperture and focal length proportional for long focal lengths, the usual consumer zoom lenses are having variable relative aperture. For consumer zoom lens the aperture range is from f/3.5 to f/5.6. Aperture of the lenses in camera is used to set sharpness of the image to be taken. The diffraction in lens makes the optimal sharpness of the lens to occur few stops lower than minimum aperture of the lens. Though you don’t need to use optimum aperture and working distance you should know about them to improve your photography.

With this the important points regarding lenses in camera have been covered. Hope you enjoyed this master class in Digital Photography brought to you by Australia Unwrapped, would love to hear your opinion and how it helped you in the comments box.

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About the author

Dave Peterson

Dave Peterson
Passion for adventure and sharing his life long journey with as many others as possible.

"What lies behind us and what lies before us are tiny matters compared to what lies within us." HENRY S. HASKINS

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