Close-up lens

Last updated August 18, 2024

Optical scheme of close-up photography.
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1 - Close-up lens.
2 - Camera objective lens (set to infinity).
3 - Camera.
4 - Film or CCD plane.
y - Object
y" - Image Close-up.png — **Optical scheme of close-up photography.**
1 - Close-up lens.
2 - Camera objective lens (set to infinity).
3 - Camera.
4 - Film or CCD plane.
y - Object
y" - Image

In photography, a close-up lens (sometimes referred to as close-up filter or a macro filter) is a simple secondary lens used to enable macro photography without requiring a specialised primary lens. They work like reading glasses, allowing a primary lens to focus more closely.^[1] Bringing the focus closer allows the photographer more possibilities.^[2]

Close-up lenses typically mount on the filter thread of the primary lens,^[3] and are often manufactured and sold by suppliers of photographic filters. Nonetheless, they are lenses and not filters. Some manufacturers refer to their close-up lenses as diopters, after the unit of measurement of their optical power.

Close-up lenses do not affect exposure, unlike extension tubes, which also can be used for macro photography with a non-macro lens.^[4]

Optical power

Close-up lenses are often specified by their optical power in diopters, the reciprocal of the focal length in meters. For a close-up lens, the diopter value is positive: the bigger the number, the greater the effective magnification.

Higher quality achromatic lenses commonly lack a strength specification in diopters. It can be inferred as the reciprocal of the maximum specified working distance in meters (i.e., a lens with a maximum working distance of 25 cm has a strength of +4 diopters).

Several close-up lenses may be used in combination; the optical power of the combination is the sum of the optical powers of the component lenses.^[5] For example, a set of lenses of +1, +2, and +4 diopters can be combined to provide a range from +1 to +7 in steps of 1.

Working distances and magnifications

Close-up lenses change both the maximum and minimum focus distances of a lens. The range can be rather small.

Working at maximum distance

Adding a close-up lens to a lens focused to infinity changes the focus point to the focal length of the close-up lens, that is, the inverse of its optical power. This is the combination's maximal working distance:

$X_{\text{max}}={\frac {1}{D}}$

That distance is sometimes given on the filter in millimeters. A +3 close-up lens has a maximal working distance of 0.333 m or 333 mm.

The magnification is the focal distance of the objective lens ( $f$ ) divided by the focal distance of the close-up lens; i.e., the focal distance of the objective lens (in meters) multiplied by the diopter value ( $D$ ) of the close-up lens:

$M_{X{\text{max}}}=fD$

In the example above, if the lens has a 300 mm focal distance, the magnification is 0.3 × 3 = 0.9.

Given the small size of most sensors (about 25 mm for APS-C sensors) a 20 mm insect will almost fill the frame at this magnification. Using a zoom lens makes it easy to frame the subject as desired.

Working at minimal distance

When you add a close-up lens to a camera which is focusing at the shortest distance at which the objective lens can focus, the focus will move to a distance which is given by following formula:

$X_{\text{min}}={\frac {X}{DX+1}}$

$X$ being the shortest distance at which the objective lens can focus (in meters), and $D$ being the diopter value of the close-up lens. This is the minimal working distance at which you will be able to take a picture with the close-up lens.

For example, a lens that can focus at 1.5 m combined with a +3 diopter close-up lens will give a closest working distance of 1.5 / (3 × 1.5 + 1) = 0.273 m.

The magnification reached in those conditions is given by following formula:

$M_{X{\text{min}}}=M_{X}(DX+1)$

$M X$ being the magnification at distance $X$ without the close-up lens.

In the example above, the gain of magnification at $X min$ will be (3 × 1.5 + 1) = 5.5.

While it would seem obvious that at this $X min$ distance you will get the highest magnification, focus breathing can cause more of a difference in actual magnification than the small overall in-focus working distance range particularly for higher strength diopters.

Macro photography with a close-up lens

Close-up lenses can make a telephoto lens function as a macro lens with a large working distance. This is useful, for example, to prevent scaring small animals or isolating the subject from messy surroundings. To use the filters for animals the size of the animal will determine the working distance (small snakes 1 m to 50 cm, lizards 50–25 cm, small butterflies, beetles 25–10 cm), so it is essential to know what will be the favorite subject before screwing on a close-up lens. The close-up lenses are most effective with long focal length objectives and using a zoom lens is very practical to have some flexibility in the magnification. A good technique for sharp focussing is to take a picture at a long focal length first to have optimal sharpness at the essential details and then zooming out to have the desired size in the frame.

Optical issues

Some single-element close-up lenses produce images with severe aberrations but there are also high-quality close-up lenses composed as achromatic doublets which are capable of producing excellent images, with fairly low loss of sharpness.

Related Research Articles

In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration. Aberration can be defined as a departure of the performance of an optical system from the predictions of paraxial optics. In an imaging system, it occurs when light from one point of an object does not converge into a single point after transmission through the system. Aberrations occur because the simple paraxial theory is not a completely accurate model of the effect of an optical system on light, rather than due to flaws in the optical elements.

<span class="mw-page-title-main">Depth of field</span> Distance between the nearest and the furthest objects that are in focus in an image

The depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera. See also the closely related depth of focus.

In optics, chromatic aberration (CA), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing wavelength. Since the focal length of a lens depends on the refractive index, this variation in refractive index affects focusing. Since the focal length of the lens varies with the color of the light different colors of light are brought to focus at different distances from the lens or with different levels of magnification. Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image.

The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light. A system with a shorter focal length bends the rays more sharply, bringing them to a focus in a shorter distance or diverging them more quickly. For the special case of a thin lens in air, a positive focal length is the distance over which initially collimated (parallel) rays are brought to a focus, or alternatively a negative focal length indicates how far in front of the lens a point source must be located to form a collimated beam. For more general optical systems, the focal length has no intuitive meaning; it is simply the inverse of the system's optical power.

An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil. The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f/N, where N is the f-number.

In photography, angle of view (AOV) describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.

An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.

<span class="mw-page-title-main">Objective (optics)</span> Lens or mirror in optical instruments

In optical engineering, an objective is an optical element that gathers light from an object being observed and focuses the light rays from it to produce a real image of the object. Objectives can be a single lens or mirror, or combinations of several optical elements. They are used in microscopes, binoculars, telescopes, cameras, slide projectors, CD players and many other optical instruments. Objectives are also called object lenses, object glasses, or objective glasses.

In photography and cinematography, perspective distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features. Perspective distortion is determined by the relative distances at which the image is captured and viewed, and is due to the angle of view of the image being either wider or narrower than the angle of view at which the image is viewed, hence the apparent relative distances differing from what is expected. Related to this concept is axial magnification – the perceived depth of objects at a given magnification.

Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a size ratio called optical magnification. When this number is less than one, it refers to a reduction in size, sometimes called de-magnification.

An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is named because it is usually the lens that is closest to the eye when someone looks through an optical device to observe an object or sample. The objective lens or mirror collects light from an object or sample and brings it to focus creating an image of the object. The eyepiece is placed near the focal point of the objective to magnify this image to the eyes. The amount of magnification depends on the focal length of the eyepiece.

Macro photography is extreme close-up photography, usually of very small subjects and living organisms like insects, in which the size of the subject in the photograph is greater than life-size . By the original definition, a macro photograph is one in which the size of the subject on the negative or image sensor is life-size or greater. In some senses, however, it refers to a finished photograph of a subject that is greater than life-size.

Depth of focus is a lens optics concept that measures the tolerance of placement of the image plane in relation to the lens. In a camera, depth of focus indicates the tolerance of the film's displacement within the camera and is therefore sometimes referred to as "lens-to-film tolerance".

Panasonic Lumix DMC-FZ30 is a bridge digital camera by Panasonic. It is the successor of the Panasonic Lumix DMC-FZ20. The highest-resolution pictures it records is 8 megapixels.

<span class="mw-page-title-main">Extension tube</span> Tool for macro photography

An extension tube, sometimes also called a closeup tube or an extension ring, is used with interchangeable lenses to increase magnification. This is most often used in macro photography.

Panasonic Lumix DMC-FZ50 is a superzoom bridge digital camera by Panasonic.

In optics, an afocal system (a system without focus) is an optical system that produces no net convergence or divergence of the beam, i.e., has an infinite effective focal length. This type of system can be created with a pair of optical elements where the physical distance d between the elements is equal to the sum of each element's focal length f_i (d = f₁+f₂). A simple example of an afocal optical system is an optical telescope imaging a star, the light entering the system is from the star at infinity (to the left) and the image it forms is at infinity (to the right), i.e., the collimated light is collimated by the afocal system. Although the system does not alter the divergence of a collimated beam, it does alter the width of the beam, increasing magnification. The magnification of such a telescope is given by

The Sigma 8–16mm lens is an enthusiast-level, ultra wide-angle rectilinear zoom lens made by Sigma Corporation specifically for use with APS-C small format digital SLRs. It is the first ultrawide rectilinear zoom lens with a minimum focal length of 8 mm, designed specifically for APS-C size image sensors. The lens was introduced at the February 2010 Photo Marketing Association International Convention and Trade Show. At its release it was the widest viewing angle focal length available commercially for APS-C cameras. It is part of Sigma's DC line of lenses, meaning it was designed to have an image circle tailored to work with APS-C format cameras. The lens has a constant length regardless of optical zoom and focus with inner lens tube elements responding to these parameters. The lens has hypersonic zoom autofocus.

<span class="mw-page-title-main">History of photographic lens design</span>

The invention of the camera in the early 19th century led to an array of lens designs intended for photography. The problems of photographic lens design, creating a lens for a task that would cover a large, flat image plane, were well known even before the invention of photography due to the development of lenses to work with the focal plane of the camera obscura.

References

↑ Meehan, Joseph (2006). The Magic of Digital Close-Up Photography. New York: Lark Books. p. 59. ISBN 978-1-57990-652-8. For real close-up work, some cameras need help—their own version of reading glasses.
↑ Timacheff, Serge (2008). Canon EOS Digital Photography: Photo Workshop. Wiley. p. 8. ISBN 978-0-470-11434-6. ...a variety of accessories increase your creative options. Additional components include Canon Softmat filters and close-up lenses,...
↑ Busch, David D. (2009). Digital SLR Cameras & Photography for Dummies (3rd ed.). Wiley. p. 84. ISBN 9780470466063. A lot of available add-ons can help you focus close, including filter-like close-up attachments that screw onto the front of the lens,...
↑ Busch, David D. (2009). Digital SLR Cameras & Photography for Dummies (3rd ed.). Wiley. p. 139. ISBN 9780470466063.
↑ Grimm, Tom; Grimm, Michele (1997). The Basic Book of Photography (4th ed.). Plume. p. 137. ISBN 0-452-27825-2. They can be used alone, or two can be combined.

External links

Close focus Archived 2020-10-31 at the Wayback Machine Close-up lenses technique

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[1] Meehan, Joseph (2006). The Magic of Digital Close-Up Photography. New York: Lark Books. p. 59. ISBN 978-1-57990-652-8. For real close-up work, some cameras need help—their own version of reading glasses.

[2] Timacheff, Serge (2008). Canon EOS Digital Photography: Photo Workshop. Wiley. p. 8. ISBN 978-0-470-11434-6. ...a variety of accessories increase your creative options. Additional components include Canon Softmat filters and close-up lenses,...

[3] Busch, David D. (2009). Digital SLR Cameras & Photography for Dummies (3rd ed.). Wiley. p. 84. ISBN 9780470466063. A lot of available add-ons can help you focus close, including filter-like close-up attachments that screw onto the front of the lens,...

[4] Busch, David D. (2009). Digital SLR Cameras & Photography for Dummies (3rd ed.). Wiley. p. 139. ISBN 9780470466063.

[5] Grimm, Tom; Grimm, Michele (1997). The Basic Book of Photography (4th ed.). Plume. p. 137. ISBN 0-452-27825-2. They can be used alone, or two can be combined.

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