The nitty-gritty details of macrophotography

M.Zuiko macro objectives and OM-1 camera

macro photography
Author

Pedro J. Aphalo

Published

2024-02-11

Modified

2024-02-13

Abstract

With modern macro objectives and modern cameras some of the traditional rules-of-thumb for macro photography need to be reassessed. In this page, I summarize what I have learnt through experience and from various sources. The account is based on the micro-four-thirds and adapted lenses and micro-four-thirds cameras that I use. This notes will continue envolving as I learn new things.

Keywords

OM-1 digital, BSI sensor

Introduction

Modern macro objectives and modern cameras are complex, and, thus, the traditional rules-of-thumb for macro photography need to be in part revised. Modern macro objectives rely on internal focusing mechanisms for close focusing instead of on the displacement of the optics as a whole away from the sensor or film. Given that for digital sensors, in contrast to film, an angle of incidence of light deviating from the normal can degrade image quality, most lenses designed for mirrorless cameras tend to be telecentric towards their rear end (telecentric means that the light beam does not expand, or expands less, than in the case of a simple lens as the distance increases. Some modern macro objectives are also telecentric at their front, to increase the working distance between the front of the objective and the subject relative to that of a simple lens of the same focal length. These developments alter how changes in magnification affect the effective f-value making the simple optical formulae even less useful than in the past. The result is that the nominal f-number of an objective, describing its aperture when focused at infinity, does not inform reliably about the lens aperture at macro magnifications.

Modern cameras like the OM-D OM-1 have features that affect their use for macro photography. Some, add new capabilities, such as image stabilization and fast auto-focus, that facilitate work and just expand possibilities by shifting the situations under which hand-holding the camera is feasible. The situation is less straightforward in relation to focus-bracketing (including for focus-stacking), because the way it is controlled in-camera is different from focusing rails. In the case of focusing rails, manual and motorized, the change in focus-point is achieved by moving the whole camera to change the camera to subject distance, which is doable at short focusing distances. At high magnification, manual focusing rails or manually adjusting the focus at the objective are difficult to use without disturbing the position of the camera. Motorised rails are bulky and expensive. Modern Olympus/OM-System cameras have supported for several years automated focus bracketing using the autofocus mechanism of objectives. Optically, when focus stacking is the intended use of the focus bracketed photographs, it is also preferable to adjust focus distance at the objective than by displacing the camera as it keeps the viewpoint unchanged. Camera based focus bracketing in the OM-1 camera is extremely fast, which is a huge benefit with live subjects in the field. However, when using a focusing rail displacement distances are given in constant units, such as millimetres, while in Olympus/OM-System cameras the focus step depends on the distance, f-number and lens focal-length. This helps by keeping the scale in use to 10 discrete steps 1 to 10, in the OM-1, but makes it more difficult for the user to guess what is a good setting for each individual situation.

A disadvantage of modern macro objectives is that the use of macro extension tubes to increase magnification can lead to a very significant degradation in optical performance. This explains why Olympus never offered macro extension tubes for the MFT mount. In contrast, as the FT D.Zuiko 50 mm f:2.0 macro objective did not have an internal focusing mechanism, and it could be used with an extension tube, supplied by Olympus for the FT mount.

Below I summarize my own exploration of this subject, and what I have learnt both from various sources and through experimentation. This page is work in progress and I intend to still to revise and expand it.

Why are modern objectives so complex?

Modern “pro” objectives are corrected over a broader range of focusing distances than older designs, like those from the OM system of film cameras from the 1970’s to 1990’s, or cheaper modern designs, like some of the Venus Laowa or other modern even cheaper Chinese optics.

To achieve fast autofocus, the mass of the moving optics has to be lowered, thus modern autofocus objectives use internal focusing mechanisms, and sometimes also internal zoom mechanisms. Optical image stabilization adds the need for additional optical groups that move separately from those implementing focusing.

The resolution of digital camera sensors is much higher than that of film, and to be exploited requires higher image resolution from objectives. Modern Pro objectives from Olympus/OM-System are designed to resolve 100 MPix or more on a MFT sensor, which makes sense given that the sensor-shift high-resolution mode of OM-D cameras can already produce photographs at an 80 Mpix resolution.

An objective like the M.Zuiko 90mm f:3.5 able to produce very high quality images from infinity to a very high magnification was unheard of in the past. In the Olympus OM film system from the 1980’s, several different objectives were needed to cover this range of magnifications, with individual objectives optimized for different limited ranges of magnification.

Before the availability of highly effective anti reflection coatings, air-glass interfaces had to be few, as reflections at each interface significantly decreased image quality. Either elements had to be cemented into fewer groups or the number of elements kept low. An uncoated air-glass interface reflects about 4% of the light, making it impossible to build an objective like the M.Zuiko 90 mm f:3.5 with 26 such interfaces: \(0.96^{26} = 0.346\).

Pupil ratio

The pupil ratio is the ratio between the apparent diameter of the diaphragm opening measured at the back (exit pupil) and front (entrance pupil) of a lens. For lenses of simple construction the ratio is 1.0 and does not vary when the focus point is changed by moving the whole objective away or towards the film or sensor. The Zuiko 50mm f:3.5 Macro was the first Olympus objective with a group that moved with respect to other groups to implement corrections that make the lens perform well at a very broad range of focus distances. This is an objective where focusing is implemented by moving the whole optics, and the lens as a whole extends by 15mm, and the optics move even further, when changing the focus from \(\infty\) to 0.22m to achieve \(0.5\times\) magnification. Larger magnification can be achieved by inserting a macro extension tube between the objective and the camera.

In modern objectives containing multiple groups that move with respect to each other, not only pupil ratios frequently differ from 1.0, but in addition, the pupil ratio can change when the focus point is shifted. When the Four-Thirds mount was announced and Olympus advertised the first FT objectives, a feature that was highlighted was that these new objectives, designed specifically for digital cameras, were telecentric on the sensor side. This would be relevant for the exit pupil if the rear element of the objectives moved during focusing, which is not the case for the three M.Zuiko Macro objectives. Neither the front nor the back of these objectives moves, focusing is achieved entirely by movement of elements or groups internal to them. The pupil ratio is difficult to measure in telecentric lenses because of parallax likely affecting differently the measurements of entrance and exit pupils.

Effective aperture

The usual calculation of effective aperture seems not to be applicable to modern and complex objectives like the M.Zuiko 90mm f:3.5 Macro based on the apparent pupil ratio measurements. This is not surprising as the M.Zuiko 90 mm is most likely of a telecentric design as most MFT and FT objectives are. This lens has an internal focusing mechanism, thus the position of the front and rear elements of the lens does not change. In principle, deviations could be accounted by incorporating the pupil ratio. This approach, breaks down in the case of telecentric objectives because of the impossiblity to correctly measure the pupil ratio by sight using a ruler. We can compare the specifications given in the manual, provided either as effective aperture values or as required exposure compensation, to the theoretical values computed.

Table 1: Effective aperture at different magnifications for M.Zuiko 90mm f:3.5 Macro. Nominal aperture, true effective aperture (from lens specifications) and theoretical aperture (based on optics formula valid for simple lenses using the uncertain measured pupil ratio). This approximate pupil ratio, measured with a ruler, at maximum aperture and farthest or \(\inf\) focus is also reported. This objective has a switch to enable a S-MACRO (super-macro) mode, whose magnification, in part overlaps with those available in the normal modes.
Magnification f.nom f.eff f.theor mode pupil ratio
\(2.0\times\) \(5.0\) \(8.0\) \(16.6\) S-MACRO \(\approx 0.86\)
\(1.0\times\) \(5.0\) \(6.3\) \(15.4\) S-MACRO \(\approx 0.48\)
\(0.5\times\) \(5.0\) \(5.0\) \(7.9\) S-MACRO \(\approx 0.85\)
\(2.0\times\) \(3.5\) \(-\) \(-\) other \(\approx 0.86\)
\(1.0\times\) \(3.5\) \(4.5\) \(7.9\) other \(\approx 0.86\)
\(0.5\times\) \(3.5\) \(4.0\) \(5.7\) other \(\approx 0.86\)
\(0.25\times\) \(3.5\) \(3.5\) \(4.6\) other \(\approx 0.72\)
focus at \(\infty\) \(3.5\) \(3.5\) \(3.5\) other \(\approx 0.82\)

Using manual focus and the non S-MACRO modes, on an uniformly illuminated surface (a computer monitor) the EV from the auto-exposure changes very little, agreeing with the effective f-values reported in the documentation. This is for a macro objective very useful behaviour, because if we do the computations backwards we see that at \(1\times\) magnification the M.Zuiko 90mm, behaves as an f:2.0 objective would. In S-MACRO mode exposure changes as magnification increases, and the exposure is almost the same at the same magnification and nominal f-number. So, also in this case the M.Zuiko 90mm f:3.5 is behaving as an objective with a larger maximum aperture.

Diffraction limits the maximum resolution achievable at small effective apertures, i.e., as the effective f-number increases, not according to the nominal f-number. From the perspective of macro photography that the maximum nominal aperture is f:3.5 is of little importance, as the effective aperture is large enough to allow accurate focusing and because in most cases a smaller aperture is needed to increase the depth of field by partly closing the diaphragm.

In the M.Zuiko 60 mm f:2.8 the decrease in effective aperture is less than expected but more than in the M.Zuiko 90 mm f:3.5, so that at \(1\times\) magnification, the effective aperture of the 90mm f:3.5 objective is larger than that of the 60mm f:2.8 lens. In the S-MACRO setting of the 90 mm lens, with a nominal aperture of f:5.0, the effective aperture is only slightly smaller than in the 60 mm f:2.8. Thus, at magnifications of \(0.25\times\) or more, the 90 mm f:3.5 objective has a larger effective aperture than the 60 mm f:2.8. The 60 mm f:2.8 is an excellent macro objective, but it lacks the optical image stabilization, the large working distance and the fast auto-focus of the M.Zuiko 90mm f:3.5.

Table 2: Effective aperture at different magnifications for M.Zuiko 60mm f:2.8 Macro. Nominal aperture, true effective aperture (from lens specifications) and theoretical aperture (based on optics formula valid for simple lenses). The approximate pupil ratio, measured with a ruler, at maximum aperture and farthest or \(\inf\) focus is also reported.
Magnification f.nom f.eff f.theor mode pupil ratio
\(1.0\times\) \(2.8\) \(5.6\) \(12.4\) - \(\approx 0.29\)
\(0.5\times\) \(2.8\) \(4.4\) \(5.4\) - \(\approx 0.54\)
\(0.25\times\) \(2.8\) \(3.8\) \(3.7\) - \(\approx 0.74\)
focus at \(\infty\) \(2.8\) \(2.8\) \(2.8\) - \(\approx 0.75\)

In my experience, all three objectives, the 30 mm f:3.5, the 60 mm f:2.8 and the 90 mm f:3.5 handle without problems the 80 MPix high resolution mode of the OM-1 camera at least at their optimal f settings. The 90 mm outperforms, at the magnification I tested, the other two objectives at smaller apertures. In the case of this objective, the large pupil ratio seems to explain the rather similar effective aperture at \(1\times\) magnification compared to the other two objectives. This small objective is difficult to use at high magnification because of the small working distance. However, at moderate magnifications it performs well. All three objectives perform very well fully open with a flat focus plane.

Table 3: Effective aperture at different magnifications for M.Zuiko 30mm f:3.5 Macro. Nominal aperture, true effective aperture (from lens specifications) and theoretical aperture (based on optics formula valid for simple lenses). The approximate pupil ratio, measured with a ruler, at maximum aperture and farthest or \(\inf\) focus is also reported. This objective has no magnification or focusing distance scale, preventing measurements at intermediate settings.
Magnification f.nom f.eff f.theor mode pupil ratio
\(1.25\times\) \(3.5\) \(7.1\) \(6.4\) - \(\approx 1.5\)
\(1.0\times\) \(3.5\) \(5.6\) \(-\) - $$
\(0.5\times\) \(3.5\) \(4.5\) \(-\) - $$
\(0.25\times\) \(3.5\) \(4.0\) \(-\) - $$
focus at \(\infty\) \(3.5\) \(3.5\) \(3.5\) - \(\approx 2.9\)

Modern objectives are complex. The M.Zuiko 90 mm f:3.5 macro, released in 2023, has 18 elements in 13 groups, and some groups move relative to others, during focusing, for the S-MACRO mode, and for optical image stabilization. The M.Zuiko 60 mm f:2.8 macro, released in 2012, has 13 elements in 10 groups, internal focusing and no optical stabilization. The M.Zuiko 30 mm f:3.5 macro, released in 2016, has seven elements in six groups. The Zuiko OM Zuiko 50mm f:3.5 Macro, released in 1973, has five elements in four groups. At moderate magnification it has surprisingly good resolution, a flat focus plane, and no distortion. If properly focused (I use the digital magnifier in camera) it performs very well also with the diaphragm fully open.

Table 4: Effective aperture at different magnifications for OM Zuiko 50mm f:3.5 Macro, released in 1973. Nominal aperture, true effective aperture (from lens specifications) and theoretical aperture (based on optics formula valid for simple lenses). The approximate pupil ratio, measured with a ruler, at maximum aperture and farthest or \(\inf\) focus is also reported. This objective has no magnification or focusing distance scale, preventing measurements at intermediate settings. Magnification of \(1.0\times\) using 25mm macro extension tube.
Magnification f.nom f.eff f.theor mode pupil ratio
\(1.0\times\) \(3.5\) \(7.1\) \(-\) - \(-\)
\(0.5\times\) \(3.5\) \(5.6\) \(5.3\) - \(\approx 1.0\)
\(0.25\times\) \(3.5\) \(4.5\) \(4.4\) - \(\approx 1.0\)
focus at \(\infty\) \(3.5\) \(3.5\) \(3.5\) - \(\approx 1.0\)

In the M.Zuiko Macro objectives the pupil ratio seems to change with focusing distance. In the OM Zuiko 50mm f:3.5 Macro from the 1970’s, the the pupil ratio is constant and equal to 1. While the three M.Zuiko objectives have an internal focusing mechanism, the OM objective extends when focusing. This objective has a maximum magnification of \(0.5\times\) by itself but can be used together with macro extension tubes with good results. The use of macro extension tubes with the M.Zuiko lenses is problematic given their construction, and Olympus/OM-System does not offer extension tubes. The M.Zuiko 90 mm f:3.5 can be used with teleconverters to increase the magnification to \(4\times\) that given the small sensor which yields the same field of view as \(8\times\) magnification on a camera with a full-frame sensor.

In all M.Zuiko objectives, except the 30 mm f:3.5, the specified effective apertures are wider than the theoretical ones, but my estimates of the pupil ratio are very uncertain. With such complex lens designs it is difficult discover how the wider effective apertures are achieved given that measuring the pupil ratio becomes very difficult.

The M.Zuiko lenses do have microprocessors and built-in memory with stored information used in-camera for various corrections. Controls are implemented by wire and thus it would be possible that the aperture position or size changes concurrently with the internal focusing mechanism, but this is unlikely.

Depth of field

I have been unable to find information on the depth of field for the M.Zuiko 90mm f:3.5 Macro objective, like that published by Olympus for the M.Zuiko 60mm f:2.8 Macro, M.Zuiko 30mm f:2.8 Macro, and the old Zuiko 50mm f:3.5 Macro. The tables take into account the image size, using 1/60mm for M.Zuiko and 1/30mm for Zuiko OM. With a pixel pitch of \(3.37\,\mathrm{\mu m}\) a minimum value to use would be \(10\,\mathrm{\mu m}\) while 1/60mm is \(16.6\,\mathrm{\mu m}\) and 1/30mm \(33.3\,\mathrm{\mu m}\). In the case of sensor-shift high resolution mode, it would sensible to base DOF on a smaller circle of confusion of \(\approx5\,\mathrm{\mu m}\). Table 9 Provides estimates of depth of field as a function of effective aperture. Using the values from the section above, including the decrease in f-number due to camera settings, and looking up the DOF from Table 9 based on the magnification in use should provide a reasonably good estimate. Of course, it is also possible to preview the depth of field through the camera, but the difference in resolution between the electronic view finder and actual image must be remembered. The higher the image resolution, the narrower is the apparent depth of field.

I am working on this section. Experimentally measuring depth of field is beyond my capabilities and equipment.

Settings

Focus bracketing is controlled in the OM-1 camera by two settings: 1) focus differential expressed in what seems an arbitrary but monotonically increasing number in the range 1 (narrow) to 10 (wide), with default 5 and 2) depth of the stack as the number of frames in the range 1 to 15 or 999 (default 8 for stacking and 99 for bracketing).

Additionally, a delay or “charge time” between frames, to allow a flash to get ready in the range 0 to 30 s with 0.1, 0.2, 0.5, 1, 2, 4, 8, 15 and 30 s as possible values (default 0 s). With Olympus/OM-System flashes including the older FL-36R, the necesary delay is managed automatically at the setting can be left at zero. TTL-flash control is not supported in sensor shift high-resolution mode or focus bracketing, and with Olympus/OM-System flashes the switch to manual is automatic. When using third-party flashes like the Godox X-system, the flash control mode does not switch automatically to manual mode, and if left in the TTL setting, only the first photograph is well exposed, with subsequent flashes triggered at full power. My experience is with a Godox AD200 flash and a Godox Xpro O trigger.

For in-camera focus stacking, in the OM-1, the maximum number of frames is 15, and frames are captured both in front and behind the starting focus point. For focus bracketing, the maximum number of frames is 999 and all frames are taken moving the focus point away from the camera, starting from the initial position. The initial position is restored at the end of the bracketed series.

Focus differential

The focus differential setting in 1 to 10 is not expressed in a fixed scale. The actual shift of the focus point for one unit of focus differential is a function of the focusing distance, current diaphragm setting (nominal f-value) and possibly objective type or focal length. This makes estimating the depth in mm or m covered by a bracketed set of images difficult. On the other hand, it seems to keep the focus depth setting nearly proportional to the observed depth of field available with the settings currently in use. This is in fact excellent as it makes the suitable setting rather independent of the camera settings. The 1 to 10 scale for a given camera setting seems to be nearly linear in distance. In long stacks the step length seems to slightly increase as the focus point moves away from the camera.

I have not found detailed information in the camera manual or on-line except for the Focus Bracketing Reference Sheet for the OM-1 with the M.Zuiko 60mm f:2.8 Macro lens from Chris McGuinnis.

Because of this, I have done some measurements for the OM System M.Zuiko 90mm f:3.5 Macro PRO on the Olympus OM-1 Digital Camera. Because of diffraction, f-values between 3.5 and 8 yield higher resolution than smaller apertures. In the high-resolution mode of the camera, diffraction will be more limiting than at the base resolution.

The first tests confirmed that at a given camera setting, the displacement increases linearly from 1 to 10. Thus, it is enough to measure the step size and only one focus differential setting, for each camera setting of interest.

Table 5: M.Zuiko 90mm on OM-1. The depth of field (DOF) was computed based on the effective f-value (Table 9). Focus differential, or step size, is less uncertain as it is based on the measurement of the accumulated distance shift for multiple steps divided by the number of steps.
Magnification f f.eff DOF (mm) FD = 1 (mm) frames (mm\(^{-1}\))
\(2\times\) \(5.0\) \(8.0\) \(\approx 0.126\) \(\approx 0.015\) \(\approx 67\)
\(8.0\) \(13\) \(\approx 0.2\) \(\approx 0.03\) \(\approx 33\)
\(22.0\) \(35\) \(\approx 0.52\) \(\approx 0.070\) \(\approx 14\)
\(1\times\) \(3.5\) \(4.5\) \(\approx 0.19\) \(\approx 0.035\) \(\approx 29\)
\(8.0\) \(10\) \(\approx 0.42\) \(\approx 0.075\) \(\approx 13\)
\(22.0\) \(28\) \(\approx 1.1\) \(\approx 0.200\) \(\approx 5\)
\(0.5\times\) \(3.5\) \(4.0\) \(\approx 0.5\) \(\approx 0.275\) \(\approx 4\)
\(8.0\) \(9.1\) \(\approx 1.1\) \(\approx 0.330\) \(\approx 3\)
\(22.0\) \(25\) \(\approx 3.3\) NA NA

Table 5 shows computed values for DOF. These roughly matche what I see in the photographs of a high resolution scale, with marks every \(0.1\,\mathrm{mm}\), on a plane slanted at 30 degrees. In most cases, at magnifications of more than \(0.5\times\), FD = 2, seems to ensure a reasonable overlap of the sharp regions in successive frames, while FD = 5 leaves a slightly out-of-focus band between successive frames. Thus, it seems that FD = 3 matches approximately the actual DOF. FD = 1 or FD = 2 should be good for focus stacking. At the highest magnifications it may be possible to to use FD = 3 or FD = 4 with a very stable copy stand in a vibration free setting. Most likely the very small step sizes have to do with to tolerances and disturbances in the step size-

Conclusion

With modern lenses, it is better to rely on manufacturers’ specification- and instruction-sheets to obtain the effective f-values than to rely on tables or simple formulas that ignore the pupil ratio. As measuring the pupil ratio of some modern telecentric objectives is difficult, the use of formulas that take it into account the pupil ration, may also fail to provide a reliable estimates of the effective f-number at different magnifications.

Depth of field at high magnification can be predicted using formulae, but it is necessary to keep in mind that one has to use the effective f-number for the computations of table look-up.

Deciding on the focus differential to use and number of frames should be simpler than how it looks like, but lack of detailed information hinders it. It seems that the only way out is to follow McGuinnis example and rely on experimentation to work out some guidelines. The preliminary measurements that I have done, are not enough.

Appendix

Computed effective f-number for ideal lenses

The table below gives approximate effective f-numbers assuming ideal lenses with a pupil ratios of 1.5, 0.86 and 0.50 As shown above, the real pupil ratio of modern lenses is not constant. If is also clear above, that the actual effective apertures given by manufacturers for complex objectives differs from that based on the simple equations used to describe ideal simple lenses.

Table 6: Effective f-numbers for an ideal objective with a pupil ratio of 1.5 computed for magnifications between 2x and 0.05x and nominal f-values between 1:2.8 and 1:22.
2x 1x 0.5x 0.25x 0.1x 0.05x
f:1.4 3.27 2.33 1.87 1.63 1.49 1.45
f:2 4.67 3.33 2.67 2.33 2.13 2.07
f:2.8 6.53 4.67 3.73 3.27 2.99 2.89
f:3.5 8.17 5.83 4.67 4.08 3.73 3.62
f:4 9.33 6.67 5.33 4.67 4.27 4.13
f:5.6 13.10 9.33 7.47 6.53 5.97 5.79
f:8 18.70 13.30 10.70 9.33 8.53 8.27
f:11 25.70 18.30 14.70 12.80 11.70 11.40
f:16 37.30 26.70 21.30 18.70 17.10 16.50
f:22 51.30 36.70 29.30 25.70 23.50 22.70
Table 7: Effective f-numbers for an ideal objective with a pupil ratio of 0.86 computed for magnifications between 2x and 0.05x and nominal f-values between 1:2.8 and 1:22.
2x 1x 0.5x 0.25x 0.1x 0.05x
f:1.4 4.66 3.03 2.21 1.81 1.56 1.48
f:2 6.65 4.33 3.16 2.58 2.23 2.12
f:2.8 9.31 6.06 4.43 3.61 3.13 2.96
f:3.5 11.60 7.57 5.53 4.52 3.91 3.70
f:4 13.30 8.65 6.33 5.16 4.47 4.23
f:5.6 18.60 12.10 8.86 7.23 6.25 5.93
f:8 26.60 17.30 12.70 10.30 8.93 8.47
f:11 36.60 23.80 17.40 14.20 12.30 11.60
f:16 53.20 34.60 25.30 20.70 17.90 16.90
f:22 73.20 47.60 34.80 28.40 24.60 23.30
Table 8: Effective f-numbers for an ideal objective with a pupil ratio of 0.5 computed for magnifications between 2x and 0.05x and nominal f-values between 1:2.8 and 1:22.
2x 1x 0.5x 0.25x 0.1x 0.05x
f:1.4 7.0 4.2 2.8 2.10 1.68 1.54
f:2 10.0 6.0 4.0 3.00 2.40 2.20
f:2.8 14.0 8.4 5.6 4.20 3.36 3.08
f:3.5 17.5 10.5 7.0 5.25 4.20 3.85
f:4 20.0 12.0 8.0 6.00 4.80 4.40
f:5.6 28.0 16.8 11.2 8.40 6.72 6.16
f:8 40.0 24.0 16.0 12.00 9.60 8.80
f:11 55.0 33.0 22.0 16.50 13.20 12.10
f:16 80.0 48.0 32.0 24.00 19.20 17.60
f:22 110.0 66.0 44.0 33.00 26.40 24.20

Computed DOF for ideal lenses

In the normal mode, information is reconstructed from each group of four pixels, and consequently the effective pixel resolution is less, by approximately a factor of three (Table 9).

Table 9: Theoretical depth-of-field (mm) for an ideal objective with a focal length of 90 mm and a sensor with a pixel pitch of 0.0035 mm and a circle of confusion three times it, computed for magnifications between 2x and 0.05x and effective f-values between 1:2.8 and 1:128, assuming a pixel pitch of 3.34 micrometers as in the sensor of the Olympus/OM-System OM-1. (For the sensor-shift high resolution mode at 80 MP the depths of field values need to be divided by 4.)
2x 1x 0.5x 0.25x 0.1x 0.05x
f:3.5 0.0551 0.147 0.441 1.47 8.09 30.9
f:5.6 0.0882 0.235 0.706 2.35 12.90 49.4
f:8 0.1260 0.336 1.010 3.36 18.50 70.6
f:11 0.1730 0.462 1.390 4.62 25.40 97.1
f:16 0.2520 0.672 2.020 6.72 37.00 141.0
f:22 0.3470 0.924 2.770 9.24 50.90 195.0
f:32 0.5040 1.340 4.030 13.40 74.00 284.0
f:64 1.0100 2.690 8.070 26.90 149.00 577.0
f:128 2.0200 5.380 16.100 54.00 302.00 1240.0

As in the sensor-shift high-resolution mode information is acquired for all colours at each pixel position, we set the circle of confussion the the pixel pitch (Table 10).

Table 10: Theoretical depth-of-field (mm) for an ideal objective with a focal length of 90 mm and a sensor with a pixel pitch of 0.0035 mm used for circle of confussion, computed for magnifications between 2x and 0.05x and effective f-values between 1:2.8 and 1:128, assuming a pixel pitch of 3.34 micrometers as in the sensor of the Olympus/OM-System OM-1. (For the sensor-shift high resolution mode at 80 MP the depths of field values need to be divided by 4.)
2x 1x 0.5x 0.25x 0.1x 0.05x
f:3.5 0.0184 0.0490 0.147 0.490 2.70 10.3
f:5.6 0.0294 0.0784 0.235 0.784 4.31 16.5
f:8 0.0420 0.1120 0.336 1.120 6.16 23.5
f:11 0.0578 0.1540 0.462 1.540 8.47 32.3
f:16 0.0840 0.2240 0.672 2.240 12.30 47.0
f:22 0.1160 0.3080 0.924 3.080 16.90 64.7
f:32 0.1680 0.4480 1.340 4.480 24.60 94.1
f:64 0.3360 0.8960 2.690 8.960 49.30 189.0
f:128 0.6720 1.7900 5.380 17.900 98.80 380.0

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