The procedure is described in more detail in the section Focus and f -number from DOF limits. Some view cameras include DOF calculators that indicate focus and f -number without the need for any calculations by the photographer Tillmanns , 67—68; Ray , — The hyperfocal distance is the nearest focal distance at which the DOF extends to infinity; focusing the camera at the hyperfocal distance results in the largest possible depth of field for a given f -number Ray , Focusing beyond the hyperfocal distance does not increase the far DOF which already extends to infinity , but it does decrease the DOF in front of the subject, decreasing the total DOF.

Some photographers consider this wasting DOF; however, see Object field methods above for a rationale for doing so.

Focusing on the hyperfocal distance is a special case of zone focusing in which the far limit of DOF is at infinity. If the lens includes a DOF scale, the hyperfocal distance can be set by aligning the infinity mark on the distance scale with the mark on the DOF scale corresponding to the f -number to which the lens is set.

Some cameras have their hyperfocal distance marked on the focus dial. For example, on the Minox LX focusing dial there is a red dot between 2 m and infinity; when the lens is set at the red dot, that is, focused at the hyperfocal distance, the depth of field stretches from 2 m to infinity.

Depth of field can be anywhere from a fraction of a millimeter to virtually infinite. In some cases, such as landscapes, it may be desirable to have the entire image sharp, and a large DOF is appropriate.

In other cases, artistic considerations may dictate that only a part of the image be in focus, emphasizing the subject while de-emphasizing the background, perhaps giving only a suggestion of the environment Langford , For example, a common technique in melodramas and horror films is a closeup of a person's face, with someone just behind that person visible but out of focus.

A portrait or close-up still photograph might use a small DOF to isolate the subject from a distracting background. The use of limited DOF to emphasize one part of an image is known as selective focus , differential focus or shallow focus.

Although a small DOF implies that other parts of the image will be unsharp, it does not, by itself, determine how unsharp those parts will be.

The amount of background or foreground blur depends on the distance from the plane of focus, so if a background is close to the subject, it may be difficult to blur sufficiently even with a small DOF.

In practice, the lens f -number is usually adjusted until the background or foreground is acceptably blurred, often without direct concern for the DOF.

Sometimes, however, it is desirable to have the entire subject sharp while ensuring that the background is sufficiently unsharp.

When the distance between subject and background is fixed, as is the case with many scenes, the DOF and the amount of background blur are not independent.

Although it is not always possible to achieve both the desired subject sharpness and the desired background unsharpness, several techniques can be used to increase the separation of subject and background.

For a given scene and subject magnification, the background blur increases with lens focal length. If it is not important that background objects be unrecognizable, background de-emphasis can be increased by using a lens of longer focal length and increasing the subject distance to maintain the same magnification.

This technique requires that sufficient space in front of the subject be available; moreover, the perspective of the scene changes because of the different camera position, and this may or may not be acceptable.

The situation is not as simple if it is important that a background object, such as a sign, be unrecognizable. The magnification of background objects also increases with focal length, so with the technique just described, there is little change in the recognizability of background objects.

Although tilt and swing are normally used to maximize the part of the image that is within the DOF, they also can be used, in combination with a small f -number, to give selective focus to a plane that isn't perpendicular to the lens axis.

With this technique, it is possible to have objects at greatly different distances from the camera in sharp focus and yet have a very shallow DOF.

The effect can be interesting because it differs from what most viewers are accustomed to seeing. When the subject is at the hyperfocal distance or beyond, the far DOF is infinite, so the ratio is 1: For large apertures at typical portrait distances, the ratio is still close to 1: As a lens is stopped down, the defocus blur at the DOF limits decreases but diffraction blur increases.

The presence of these two opposing factors implies a point at which the combined blur spot is minimized Gibson , 64 ; at that point, the f -number is optimal for image sharpness.

If the final image is viewed under normal conditions e. But this may not be true if the final image is viewed under more demanding conditions, e.

Hansma also suggests that the final-image size may not be known when a photograph is taken, and obtaining the maximum practicable sharpness allows the decision to make a large final image to be made at a later time.

Hansma and Peterson have discussed determining the combined effects of defocus and diffraction using a root-square combination of the individual blur spots.

Hansma's approach determines the f -number that will give the maximum possible sharpness; Peterson's approach determines the minimum f -number that will give the desired sharpness in the final image, and yields a maximum focus spread for which the desired sharpness can be achieved.

Gibson , 64 gives a similar discussion, additionally considering blurring effects of camera lens aberrations, enlarging lens diffraction and aberrations, the negative emulsion, and the printing paper.

Hopkins , Stokseth , and Williams and Becklund have discussed the combined effects using the modulation transfer function. In semiconductor photolithography applications, depth of field is extremely important as integrated circuit layout features must be printed with high accuracy at extremely small size.

The difficulty is that the wafer surface is not perfectly flat, but may vary by several micrometres. Even this small variation causes some distortion in the projected image, and results in unwanted variations in the resulting pattern.

Thus photolithography engineers take extreme measures to maximize the optical depth of field of the photolithography equipment. To minimize this distortion further, semiconductor manufacturers may use chemical mechanical polishing to make the wafer surface even flatter before lithographic patterning.

A person may sometimes experience better vision in daylight than at night because of an increased depth of field due to constriction of the pupil i.

The basis of these formulas is given in the section Derivation of the DOF formulae ; [17] refer to the diagram in that section for illustration of the quantities discussed below.

Thus, for a given image format, depth of field is determined by three factors: For close-up work, the hyperfocal distance has little applicability, and it usually is more convenient to express DOF in terms of image magnification.

In other words, for the same subject magnification, at the same f -number, all focal lengths used on a given image format give approximately the same DOF.

The discussion thus far has assumed a symmetrical lens for which the entrance and exit pupils coincide with the front and rear nodal planes , and for which the pupil magnification the ratio of exit pupil diameter to that of the entrance pupil [18] is unity.

Although this assumption usually is reasonable for large-format lenses, it often is invalid for medium- and small-format lenses.

When the pupil magnification is unity, this equation reduces to that for a symmetrical lens. Except for close-up and macro photography, the effect of lens asymmetry is minimal.

At unity magnification, however, the errors from neglecting the pupil magnification can be significant. If only working f -number is directly available, the following formula can be used instead:.

When the subject distance is large in comparison with the lens focal length, the required f -number is. In practice, these settings usually are determined on the image side of the lens, using measurements on the bed or rail with a view camera, or using lens DOF scales on manual-focus lenses for small- and medium-format cameras.

In practical terms, focus is set to halfway between the near and far image distances. The required f -number is. The image distances are measured from the camera's image plane to the lens's image nodal plane, which is not always easy to locate.

Most lens DOF scales are based on the same concept. The focus spread is related to the depth of focus. Ray , 56 gives two definitions of the latter.

The first is the tolerance of the position of the image plane for which an object remains acceptably sharp; the second is that the limits of depth of focus are the image-side conjugates of the near and far limits of DOF.

With the first definition, focus spread and depth of focus are usually close in value though conceptually different. With the second definition, focus spread and depth of focus are the same.

If the detail is only slightly outside the DOF, the blur may be only barely perceptible. For a given subject magnification, f -number, and distance from the subject of the foreground or background detail, the degree of detail blur varies with the lens focal length.

For a background detail, the blur increases with focal length; for a foreground detail, the blur decreases with focal length.

For a given scene, the positions of the subject, foreground, and background usually are fixed, and the distance between subject and the foreground or background remains constant regardless of the camera position; however, to maintain constant magnification, the subject distance must vary if the focal length is changed.

For small distance between the foreground or background detail, the effect of focal length is small; for large distance, the effect can be significant.

For a reasonably distant background detail, the blur disk diameter is. The magnification of the detail also varies with focal length; for a given detail, the ratio of the blur disk diameter to imaged size of the detail is independent of focal length, depending only on the detail size and its distance from the subject.

This ratio can be useful when it is important that the background be recognizable as usually is the case in evidence or surveillance photography , or unrecognizable as might be the case for a pictorial photographer using selective focus to isolate the subject from a distracting background.

As a general rule, an object is recognizable if the blur disk diameter is one-tenth to one-fifth the size of the object or smaller Williams , , [19] and unrecognizable when the blur disk diameter is the object size or greater.

The effect of focal length on background blur is illustrated in van Walree's article on Depth of field. The distance scales on most medium- and small-format lenses indicate distance from the camera's image plane.

Moreover, for many zoom lenses and internal-focusing non-zoom lenses, the location of the front nodal plane, as well as focal length, changes with subject distance.

When the subject distance is large in comparison with the lens focal length, the exact location of the front nodal plane is not critical; the distance is essentially the same whether measured from the front of the lens, the image plane, or the actual nodal plane.

The same is not true for close-up photography; at unity magnification, a slight error in the location of the front nodal plane can result in a DOF error greater than the errors from any approximations in the DOF equations.

The asymmetrical lens formulas require knowledge of the pupil magnification, which usually is not specified for medium- and small-format lenses.

The pupil magnification can be estimated by looking into the front and rear of the lens and measuring the diameters of the apparent apertures, and computing the ratio of rear diameter to front diameter Shipman , However, for many zoom lenses and internal-focusing non-zoom lenses, the pupil magnification changes with subject distance, and several measurements may be required.

The lens designer cannot restrict analysis to Gaussian optics and cannot ignore lens aberrations. However, the requirements of practical photography are less demanding than those of lens design, and despite the simplifications employed in development of most DOF formulas, these formulas have proven useful in determining camera settings that result in acceptably sharp pictures.

It should be recognized that DOF limits are not hard boundaries between sharp and unsharp, and that there is little point in determining DOF limits to a precision of many significant figures.

A symmetrical lens is illustrated at right. Setting the subject distance to the hyperfocal distance and solving for the near limit of DOF gives.

Substituting the expression for hyperfocal distance into equations 7 and 8 for the near and far limits of DOF gives. Substituting the approximate expression for hyperfocal distance into the formulas for the near and far limits of DOF gives.

As subject distance is decreased, the subject magnification increases, and eventually becomes large in comparison with the hyperfocal magnification.

Thus the effect of focal length is greatest near the hyperfocal distance, and decreases as subject distance is decreased. Stated otherwise, for the same subject magnification and the same f -number, all focal lengths for a given image format give approximately the same DOF.

This statement is true only when the subject distance is small in comparison with the hyperfocal distance, however. Use formulas 9 and 10 instead. It usually is more convenient to express DOF in terms of magnification.

The distance is small in comparison with the hyperfocal distance, so the simplified formula. For a given magnification, DOF is independent of focal length.

When the subject is at the hyperfocal distance or beyond, the far DOF is infinite, and the near: At closer subject distances, it's often more convenient to express the DOF ratio in terms of the magnification.

When the subject distance is much less than hyperfocal, the total DOF is given to good approximation by.

Essentially the same approach is described in Stroebel , — The results of the comparison depend on what is assumed. One approach is to assume that essentially the same picture is taken with each format and enlarged to produce the same size final image, so the subject distance remains the same, the focal length is adjusted to maintain the same angle of view, and to a first approximation, magnification is in direct proportion to some characteristic dimension of each format.

If both pictures are enlarged to give the same size final images with the same sharpness criteria, the circle of confusion is also in direct proportion to the format size.

If the formats have approximately the same aspect ratios, the characteristic dimensions can be the format diagonals; if the aspect ratios differ considerably e.

If the DOF is to be the same for both formats the required f -number is in direct proportion to the format size:. Adjusting the f -number in proportion to format size is equivalent to using the same absolute aperture diameter for both formats, discussed in detail below in Use of absolute aperture diameter.

If the same lens focal length is used in both formats, magnifications can be maintained in the ratio of the format sizes by adjusting subject distances; the DOF ratio is the same as that given above, but the images differ because of the different perspectives and angles of view.

If the same DOF is required for each format, an analysis similar to that above shows that the required f -number is in direct proportion to the format size.

Another approach is to use the same focal length with both formats at the same subject distance, so the magnification is the same, and with the same f -number,.

The perspective is the same for both formats, but because of the different angles of view, the pictures are not the same. Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format; the cropped image requires greater enlargement and consequently has a smaller circle of confusion.

A cropped then enlarged image has less DOF than the uncropped image. The aperture diameter is normally given in terms of the f -number because all lenses set to the same f -number give approximately the same image illuminance Ray , , simplifying exposure settings.

When the diameters are the same, the two formats have the same DOF. Von Rohr made this same observation, saying "At this point it will be sufficient to note that all these formulae involve quantities relating exclusively to the entrance-pupil and its position with respect to the object-point, whereas the focal length of the transforming system does not enter into them.

Using the same absolute aperture diameter for both formats with the "same picture" criterion is equivalent to adjusting the f -number in proportion to the format sizes, discussed above under "Same picture" for both formats.

Most discussions of DOF concentrate on the object side of the lens, but the formulas are simpler and the measurements usually easier to make on the image side.

If the basic image-side equations. The harmonic mean is always less than the arithmentic mean, but when the difference between the near and far image distances is reasonably small, the two means are close to equal, and focus can be set with sufficient accuracy using.

View camera users often refer to this difference as the focus spread ; it usually is measured on the bed or focusing rail.

Focus is simply set to halfway between the near and far image distances. For close-up photography, the magnification cannot be ignored, and the f -number should be determined using the first approximate formula.

On manual-focus small- and medium-format lenses, the focus and f -number usually are determined using the lens DOF scales, which often are based on the approximate equations above.

The diameter of the background blur disk increases with the distance to the background. For a given scene, the distance between the subject and a foreground or background object is usually fixed; let that distance be represented by.

For a relatively distant background object,. With the plus sign, the derivative is everywhere positive, so that for a background object, the blur disk size increases with focal length.

With the minus sign, the derivative is everywhere negative, so that for a foreground object, the blur disk size decreases with focal length.

The magnification of the defocused object also varies with focal length; the magnification of the defocused object is. This discussion thus far has assumed a symmetrical lens for which the entrance and exit pupils coincide with the object and image nodal planes , and for which the pupil magnification is unity.

For an asymmetrical lens, the DOF ahead of the subject distance and the DOF beyond the subject distance are given by [20].

When the pupil magnification is unity, the equations for asymmetrical lenses reduce to those given earlier for symmetrical lenses.

A slight rearrangement of the last equation gives. Complete Digital Photography , Ben Long, Another important control for landscape photography is depth of field, the amount of sharpness in a scene, from close to the camera into the distance away from the camera.

It's sharpness in depth. Depth of Field Definition Hyperfocal, near, and far distances are calculated using these equations. Circles of confusion for digital cameras are listed here.

Depth of Field Calculator. Camera, film format, or circle of confusion. Use the actual focal length of the lens for depth of field calculations.

The calculator will automatically adjust for any "focal length multiplier" or "field of view crop" for the selected camera.

Focal lengths of digital camera lenses are listed here.

The use of limited DOF to emphasize one part of an image is known as selective focus , differential focus or shallow focus.

Although a small DOF implies that other parts of the image will be unsharp, it does not, by itself, determine how unsharp those parts will be.

The amount of background or foreground blur depends on the distance from the plane of focus, so if a background is close to the subject, it may be difficult to blur sufficiently even with a small DOF.

In practice, the lens f -number is usually adjusted until the background or foreground is acceptably blurred, often without direct concern for the DOF.

Sometimes, however, it is desirable to have the entire subject sharp while ensuring that the background is sufficiently unsharp.

When the distance between subject and background is fixed, as is the case with many scenes, the DOF and the amount of background blur are not independent.

Although it is not always possible to achieve both the desired subject sharpness and the desired background unsharpness, several techniques can be used to increase the separation of subject and background.

For a given scene and subject magnification, the background blur increases with lens focal length. If it is not important that background objects be unrecognizable, background de-emphasis can be increased by using a lens of longer focal length and increasing the subject distance to maintain the same magnification.

This technique requires that sufficient space in front of the subject be available; moreover, the perspective of the scene changes because of the different camera position, and this may or may not be acceptable.

The situation is not as simple if it is important that a background object, such as a sign, be unrecognizable. The magnification of background objects also increases with focal length, so with the technique just described, there is little change in the recognizability of background objects.

Although tilt and swing are normally used to maximize the part of the image that is within the DOF, they also can be used, in combination with a small f -number, to give selective focus to a plane that isn't perpendicular to the lens axis.

With this technique, it is possible to have objects at greatly different distances from the camera in sharp focus and yet have a very shallow DOF.

The effect can be interesting because it differs from what most viewers are accustomed to seeing. When the subject is at the hyperfocal distance or beyond, the far DOF is infinite, so the ratio is 1: For large apertures at typical portrait distances, the ratio is still close to 1: As a lens is stopped down, the defocus blur at the DOF limits decreases but diffraction blur increases.

The presence of these two opposing factors implies a point at which the combined blur spot is minimized Gibson , 64 ; at that point, the f -number is optimal for image sharpness.

If the final image is viewed under normal conditions e. But this may not be true if the final image is viewed under more demanding conditions, e.

Hansma also suggests that the final-image size may not be known when a photograph is taken, and obtaining the maximum practicable sharpness allows the decision to make a large final image to be made at a later time.

Hansma and Peterson have discussed determining the combined effects of defocus and diffraction using a root-square combination of the individual blur spots.

Hansma's approach determines the f -number that will give the maximum possible sharpness; Peterson's approach determines the minimum f -number that will give the desired sharpness in the final image, and yields a maximum focus spread for which the desired sharpness can be achieved.

Gibson , 64 gives a similar discussion, additionally considering blurring effects of camera lens aberrations, enlarging lens diffraction and aberrations, the negative emulsion, and the printing paper.

Hopkins , Stokseth , and Williams and Becklund have discussed the combined effects using the modulation transfer function. In semiconductor photolithography applications, depth of field is extremely important as integrated circuit layout features must be printed with high accuracy at extremely small size.

The difficulty is that the wafer surface is not perfectly flat, but may vary by several micrometres.

Even this small variation causes some distortion in the projected image, and results in unwanted variations in the resulting pattern.

Thus photolithography engineers take extreme measures to maximize the optical depth of field of the photolithography equipment. To minimize this distortion further, semiconductor manufacturers may use chemical mechanical polishing to make the wafer surface even flatter before lithographic patterning.

A person may sometimes experience better vision in daylight than at night because of an increased depth of field due to constriction of the pupil i.

The basis of these formulas is given in the section Derivation of the DOF formulae ; [17] refer to the diagram in that section for illustration of the quantities discussed below.

Thus, for a given image format, depth of field is determined by three factors: For close-up work, the hyperfocal distance has little applicability, and it usually is more convenient to express DOF in terms of image magnification.

In other words, for the same subject magnification, at the same f -number, all focal lengths used on a given image format give approximately the same DOF.

The discussion thus far has assumed a symmetrical lens for which the entrance and exit pupils coincide with the front and rear nodal planes , and for which the pupil magnification the ratio of exit pupil diameter to that of the entrance pupil [18] is unity.

Although this assumption usually is reasonable for large-format lenses, it often is invalid for medium- and small-format lenses.

When the pupil magnification is unity, this equation reduces to that for a symmetrical lens. Except for close-up and macro photography, the effect of lens asymmetry is minimal.

At unity magnification, however, the errors from neglecting the pupil magnification can be significant. If only working f -number is directly available, the following formula can be used instead:.

When the subject distance is large in comparison with the lens focal length, the required f -number is. In practice, these settings usually are determined on the image side of the lens, using measurements on the bed or rail with a view camera, or using lens DOF scales on manual-focus lenses for small- and medium-format cameras.

In practical terms, focus is set to halfway between the near and far image distances. The required f -number is.

The image distances are measured from the camera's image plane to the lens's image nodal plane, which is not always easy to locate.

Most lens DOF scales are based on the same concept. The focus spread is related to the depth of focus. Ray , 56 gives two definitions of the latter.

The first is the tolerance of the position of the image plane for which an object remains acceptably sharp; the second is that the limits of depth of focus are the image-side conjugates of the near and far limits of DOF.

With the first definition, focus spread and depth of focus are usually close in value though conceptually different. With the second definition, focus spread and depth of focus are the same.

If the detail is only slightly outside the DOF, the blur may be only barely perceptible. For a given subject magnification, f -number, and distance from the subject of the foreground or background detail, the degree of detail blur varies with the lens focal length.

For a background detail, the blur increases with focal length; for a foreground detail, the blur decreases with focal length.

For a given scene, the positions of the subject, foreground, and background usually are fixed, and the distance between subject and the foreground or background remains constant regardless of the camera position; however, to maintain constant magnification, the subject distance must vary if the focal length is changed.

For small distance between the foreground or background detail, the effect of focal length is small; for large distance, the effect can be significant.

For a reasonably distant background detail, the blur disk diameter is. The magnification of the detail also varies with focal length; for a given detail, the ratio of the blur disk diameter to imaged size of the detail is independent of focal length, depending only on the detail size and its distance from the subject.

This ratio can be useful when it is important that the background be recognizable as usually is the case in evidence or surveillance photography , or unrecognizable as might be the case for a pictorial photographer using selective focus to isolate the subject from a distracting background.

As a general rule, an object is recognizable if the blur disk diameter is one-tenth to one-fifth the size of the object or smaller Williams , , [19] and unrecognizable when the blur disk diameter is the object size or greater.

The effect of focal length on background blur is illustrated in van Walree's article on Depth of field. The distance scales on most medium- and small-format lenses indicate distance from the camera's image plane.

Moreover, for many zoom lenses and internal-focusing non-zoom lenses, the location of the front nodal plane, as well as focal length, changes with subject distance.

When the subject distance is large in comparison with the lens focal length, the exact location of the front nodal plane is not critical; the distance is essentially the same whether measured from the front of the lens, the image plane, or the actual nodal plane.

The same is not true for close-up photography; at unity magnification, a slight error in the location of the front nodal plane can result in a DOF error greater than the errors from any approximations in the DOF equations.

The asymmetrical lens formulas require knowledge of the pupil magnification, which usually is not specified for medium- and small-format lenses.

The pupil magnification can be estimated by looking into the front and rear of the lens and measuring the diameters of the apparent apertures, and computing the ratio of rear diameter to front diameter Shipman , However, for many zoom lenses and internal-focusing non-zoom lenses, the pupil magnification changes with subject distance, and several measurements may be required.

The lens designer cannot restrict analysis to Gaussian optics and cannot ignore lens aberrations. However, the requirements of practical photography are less demanding than those of lens design, and despite the simplifications employed in development of most DOF formulas, these formulas have proven useful in determining camera settings that result in acceptably sharp pictures.

It should be recognized that DOF limits are not hard boundaries between sharp and unsharp, and that there is little point in determining DOF limits to a precision of many significant figures.

A symmetrical lens is illustrated at right. Setting the subject distance to the hyperfocal distance and solving for the near limit of DOF gives.

Substituting the expression for hyperfocal distance into equations 7 and 8 for the near and far limits of DOF gives.

Substituting the approximate expression for hyperfocal distance into the formulas for the near and far limits of DOF gives.

As subject distance is decreased, the subject magnification increases, and eventually becomes large in comparison with the hyperfocal magnification.

Thus the effect of focal length is greatest near the hyperfocal distance, and decreases as subject distance is decreased.

Stated otherwise, for the same subject magnification and the same f -number, all focal lengths for a given image format give approximately the same DOF.

This statement is true only when the subject distance is small in comparison with the hyperfocal distance, however.

Use formulas 9 and 10 instead. It usually is more convenient to express DOF in terms of magnification.

The distance is small in comparison with the hyperfocal distance, so the simplified formula. For a given magnification, DOF is independent of focal length.

When the subject is at the hyperfocal distance or beyond, the far DOF is infinite, and the near: At closer subject distances, it's often more convenient to express the DOF ratio in terms of the magnification.

When the subject distance is much less than hyperfocal, the total DOF is given to good approximation by. Essentially the same approach is described in Stroebel , — The results of the comparison depend on what is assumed.

One approach is to assume that essentially the same picture is taken with each format and enlarged to produce the same size final image, so the subject distance remains the same, the focal length is adjusted to maintain the same angle of view, and to a first approximation, magnification is in direct proportion to some characteristic dimension of each format.

If both pictures are enlarged to give the same size final images with the same sharpness criteria, the circle of confusion is also in direct proportion to the format size.

If the formats have approximately the same aspect ratios, the characteristic dimensions can be the format diagonals; if the aspect ratios differ considerably e.

If the DOF is to be the same for both formats the required f -number is in direct proportion to the format size:.

Adjusting the f -number in proportion to format size is equivalent to using the same absolute aperture diameter for both formats, discussed in detail below in Use of absolute aperture diameter.

If the same lens focal length is used in both formats, magnifications can be maintained in the ratio of the format sizes by adjusting subject distances; the DOF ratio is the same as that given above, but the images differ because of the different perspectives and angles of view.

If the same DOF is required for each format, an analysis similar to that above shows that the required f -number is in direct proportion to the format size.

Another approach is to use the same focal length with both formats at the same subject distance, so the magnification is the same, and with the same f -number,.

The perspective is the same for both formats, but because of the different angles of view, the pictures are not the same.

Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format; the cropped image requires greater enlargement and consequently has a smaller circle of confusion.

A cropped then enlarged image has less DOF than the uncropped image. The aperture diameter is normally given in terms of the f -number because all lenses set to the same f -number give approximately the same image illuminance Ray , , simplifying exposure settings.

When the diameters are the same, the two formats have the same DOF. Von Rohr made this same observation, saying "At this point it will be sufficient to note that all these formulae involve quantities relating exclusively to the entrance-pupil and its position with respect to the object-point, whereas the focal length of the transforming system does not enter into them.

Using the same absolute aperture diameter for both formats with the "same picture" criterion is equivalent to adjusting the f -number in proportion to the format sizes, discussed above under "Same picture" for both formats.

Most discussions of DOF concentrate on the object side of the lens, but the formulas are simpler and the measurements usually easier to make on the image side.

If the basic image-side equations. The harmonic mean is always less than the arithmentic mean, but when the difference between the near and far image distances is reasonably small, the two means are close to equal, and focus can be set with sufficient accuracy using.

View camera users often refer to this difference as the focus spread ; it usually is measured on the bed or focusing rail. Focus is simply set to halfway between the near and far image distances.

For close-up photography, the magnification cannot be ignored, and the f -number should be determined using the first approximate formula. On manual-focus small- and medium-format lenses, the focus and f -number usually are determined using the lens DOF scales, which often are based on the approximate equations above.

The diameter of the background blur disk increases with the distance to the background. For a given scene, the distance between the subject and a foreground or background object is usually fixed; let that distance be represented by.

For a relatively distant background object,. With the plus sign, the derivative is everywhere positive, so that for a background object, the blur disk size increases with focal length.

With the minus sign, the derivative is everywhere negative, so that for a foreground object, the blur disk size decreases with focal length.

The magnification of the defocused object also varies with focal length; the magnification of the defocused object is.

This discussion thus far has assumed a symmetrical lens for which the entrance and exit pupils coincide with the object and image nodal planes , and for which the pupil magnification is unity.

For an asymmetrical lens, the DOF ahead of the subject distance and the DOF beyond the subject distance are given by [20].

When the pupil magnification is unity, the equations for asymmetrical lenses reduce to those given earlier for symmetrical lenses. A slight rearrangement of the last equation gives.

From Wikipedia, the free encyclopedia. For other uses, see Depth of field disambiguation. For the seismology term, see Depth of focus tectonics.

Simulation of the effect of changing a camera's aperture in half-stops at left and from zero to infinity at right. Depth of field for different values of aperture using 50 mm objective lens and full-frame DSLR camera.

Focus point is on the first blocks column. For most treatments of DOF, including this article, the assumption of a point is sufficient.

University of California Press. Retrieved 24 February Handbook of Machine Vision. Practical Use in Landscape Photography.

Most helicoid-focused lenses are marked with image plane—to—subject distances, so the focus determined from the lens distance scale is not exactly the harmonic mean of the marked near and far distances.

The feature has not been included on models introduced after April He concludes that with the subject and background distances fixed, no f -number will achieve both objectives, and that using a lens of different focal length will make no difference in the result.

We can achieve critical focus for only one plane in front of the camera, and all objects in this plane will be sharp.

In addition, there will be an area just in front of and behind this plane that will appear reasonably sharp according to the standards of sharpness required for the particular photograph and the degree of enlargement of the negative.

This total region of adequate focus represents the depth of field. If you set the camera's focus to the hyperfocal distance, your depth of field will extend from half of the hyperfocal distance to infinity—a much deeper depth of field.

Complete Digital Photography , Ben Long, Another important control for landscape photography is depth of field, the amount of sharpness in a scene, from close to the camera into the distance away from the camera.

It's sharpness in depth. Depth of Field Definition Hyperfocal, near, and far distances are calculated using these equations.

Circles of confusion for digital cameras are listed here. Depth of Field Calculator.

Im Gegensatz zu ersterem Verfahren erzeugt es glaubhaftere und realistischere Ergebnisse Bokehetc. Die Kamera zeichnet die zentrale Figur scharf, eventuell nur das Auge einer Person, [2] während alles vor und hinter ihr unscharf erscheint. Um eine neue Diskussion zu starten, müssen Sie angemeldet sein. Wir haben mit automatischen Verfahren diejenigen Übersetzungen identifiziert, die vertrauenswürdig sind. Dazu schränkt der Fotograf die Schärfentiefe so eng Beste Spielothek in Klein Heidorn finden möglich um king of luck app Ebene ein, auf der sich das Hauptmotiv befindet.
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