Sphericalaberration

Light meters can be invaluable when taking portraits. When using an incident light meter, hold it towards the subject right near the light source. You have a little more freedom with portrait photography because if you wanted to produce a lighter image, you could simply adjust your meter higher than what the reading suggested. Reflected meters require three spots again (still the darkest, brightest, and middle tone). Again, don’t be afraid of creativity. If you want your image to be a little darker, adjust your settings to mimic the darkest measurement.

Types ofaberrationinoptics

This page titled 4: Optical Aberrations is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Jeremy Tatum via source content that was edited to the style and standards of the LibreTexts platform.

Chromaticaberration

There is so much more to photography than just picking up a camera and snapping a photo. Photographers must consider lighting, spacing, and object placement before they can even think about taking a picture. Photographers must also have the right equipment to capture the perfect image. This includes a light measuring device known as a light meter. Light meters are necessary to photography; anyone involved in photography should know what they are and their importance in the field.

Astigmatismaberration

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Light meters are extremely useful tools in photography. Essentially, light meters help photographers capture the perfect image tone. These light measuring devices help photographers know if part of an image is overexposed or underexposed. There are specific types of photography where light meters can be particularly useful, including landscape and portrait photography.

Photographers must know what tools they need to capture the perfect image. It is a photographer’s responsibility to understand how the equipment is used and its role in taking the perfect picture. Luckily, Gamma Scientific is here to help. Our team has many experts in the photonics industry and sells high precision light measurement equipment to ensure both light meters and sensitive image sensors on cameras are calibrated to the highest standards. So, whether you’re an experienced photographer or just starting out, don’t be afraid to explore our page and let us help you in any way we can.

Incident light meters are extremely helpful in landscape photography. As long as the light is even-keeled throughout the scene, you only need to take one measurement—meaning you don’t need to travel around an area to get several measurements. Simply hold the light meter out in front of you and record the calculations. Things change a bit when discussing reflective light meters. When trying to get a read of the reflected light in a landscape photo, measure three points of the shot (darkest, brightest, and middle tone) and take their average recording.

Simply put, a light meter is a device that measures light. There are two different kinds of light meters—incident and reflective. An incident light meter measures all the light falling onto a subject. Incident light meters help a camera focus on a subject regardless of how light or dark the surrounding background is. Reflective light meters do the opposite—they measure the light reflected by or bouncing off a subject.

4.1: Introduction to Optical AberrationsWe have hitherto made the assumption that a lens or a curved mirror is able to form a point image of a point object. This may be approximately true if the depth of the mirror or the thickness of the lens is small compared with other distances, and if the angle that all rays make with axis of the mirror or lens is small, and if we are using monochromatic light. Usually none of these conditions is satisfied exactly, and consequently the image suffers from several aberrations.4.2: Spherical AberrationSpherical aberration is found in optical systems that use elements with spherical surfaces.4.3: AstigmatismIn Greek, stigma means a mark - in particular the mark made by the prick of a pointed instrument. An ideal optical instrument produces an image of a point source, which is also a point. If the image is not a point, then it is astigmatic. However, the use of the word astigmatic to describe an image of a point source that is not also a point is restricted to the kind of optical aberration described in this section.4.4: ComaComa, like astigmatism, is another aberration that appears off axis, near the edge of an image field.4.5: Curvature of FieldIn designing a lens or lens system, the problems of astigmatism and curvature of field are often closely related. For example a meniscus lens tends to suffer from astigmatism, and there is a focal surface for the tangential image, and a focal surface for the sagittal image, and the tangential and sagittal surfaces curve in opposite senses.4.6: DistortionThe magnification of an image is image distance divided by object distance, and image distance is different off-axis than on-axis, so the image magnification varies with distance from the axis. If this distortion is quite small, it may not be noticed in ordinary pictorial photography, but if one is using a photograph for precise positional measurements (for example, in astrometry) it is necessary to correct for the distortion.