Image Circle & Aperture Diameter

Image circle versus aperture

The image circle is the circular field a lens projects onto the image plane. To cover a centred rectangular sensor right into its corners, its usable diameter must be at least the sensor diagonal:

Required image-circle diameter = √(sensor width² + sensor height²)

The entrance pupil is the apparent aperture opening viewed through the front of the lens. Its diameter at infinity focus is calculated from the optical focal length and f-number:

Entrance-pupil diameter = focal length ÷ f-number

A 50 mm f/1.2 lens has an entrance pupil of approximately 41.67 mm. Full frame requires an image circle of approximately 43.27 mm. A pupil smaller than the required image circle is entirely normal: these are different quantities on different planes. The ratio in this calculator compares diameters only. It does not establish sensor coverage, brightness, lens compatibility or image quality. Neither the front-element diameter nor the physical iris diameter can generally be inferred from this calculation.

See Edmund Optics on f-number and effective aperture for the focal-length / effective-aperture relation and its infinity-focus assumption.

Sensor dimensions and sources

The presets use representative active imaging dimensions, not universal dimensions for every camera in a format. Every diagonal in the table is calculated from these dimensions.

• 1″ type: 13.2 × 8.8 mm, as specified in the Sony RX100 VIIA help guide. The historical “1 inch” format label does not mean a 25.4 mm sensor diagonal.
• Micro Four Thirds: 17.3 × 13.0 mm, as shown in the Micro Four Thirds system catalogue.
• APS-C: 23.5 × 15.6 mm, using the Nikon D3300 specification as a representative example. APS-C dimensions vary by camera.
• Canon APS-C: 22.3 × 14.9 mm, using the Canon EOS Rebel T7 specification. Some Canon models differ.
• Full frame: nominal 36 × 24 mm, described in Nikon’s DX and FX format guide. Actual active dimensions can differ slightly.

Reading the 3D diagram

The open lens barrel reveals curved glass elements and an adjustable iris. Drag the scene to orbit, scroll or pinch to zoom, and choose Reset view to return to the starting camera. When the 3D canvas has keyboard focus, + / − zoom and R or Home resets the view.

Use the Sensor format dropdown and Lens slider in the viewer’s top toolbar to choose a sensor and step through 24/1.4, 35/1.4, 50/1.2, 85/1.4, 135/1.4, 200/2, 300/2.8, Sony 400/4.5, Nikon 400/4.5, 400/2.8, Sony 600/6.3, Nikon 600/6.3 and 600/4, in increasing focal length with slower lenses before brighter lenses at the same focal length. Each stop selects focal length and aperture together. The default is FE 50mm F1.2 GM.

All thirteen lens presets use dedicated cross-section reconstructions and link to manufacturer specifications in the table. Lens selection keeps your chosen sensor unchanged for size comparisons. The tool does not establish actual image-circle coverage or mount compatibility.

Light enters from the right, with the sensor on the left. Most presets show a translucent teal volume marking the envelope of incoming scene directions. Shorter focal lengths open that envelope into a wider view; longer focal lengths narrow it. Moving bands indicate direction, not light speed. The 50mm, 85mm, 135mm, 200mm, 300mm, 400mm and 600mm presets use estimated refracted rays or a volume following those rays, described below.

The volume extends to a miniature landscape with a cabin, trees and mountains. The sensor displays a perspective view of that same scene, inverted through 180° to illustrate image formation. Changing the sensor or lens changes the framing of the projected image. Use Inspect sensor image for a close-up of the projection, Inspect scene to examine the landscape, or Expand for a larger view. This image is rendered with an ideal perspective camera; it is not ray-traced through the decorative glass, and it does not simulate depth of field, aberrations, exposure or vignetting.

The Sensor / entrance pupil board on the wall behind the lens superimposes the sensor rectangle, required image circle and entrance pupil at one fixed scale. The board is part of the 3D scene, so it moves in perspective as you orbit. Changing the lens changes only the pupil on this board; changing sensor format changes its rectangle. These overlaid quantities come from different optical planes, so they remain a size comparison rather than a coverage test.

The lens model changes with each preset, from compact primes to larger telephoto housings. The 600 mm f/4 preset has a calculated 150 mm entrance pupil, shown on the comparison board; this does not set its physical iris diameter. The sensor stays at a fixed position and the camera does not automatically zoom as you change lenses. Orbiting pivots around the aperture. Camera zoom, orbit, pan, reset and viewport resizing can change the apparent size; changing the lens alone does not. The viewport keeps a 16:9 aspect ratio during resizing and preserves the camera angle and zoom.

The 600 mm f/4 model follows the Sony FE 600 mm F4 GM OSS cross-section: a large front element, a long open front barrel, three fluorite elements (gold), an XA element (coral), and the compact rear assembly with ED glass (mint) and a filter. Sony’s specifications list 24 elements in 18 groups including the filter, 449 mm length, 163.6 mm diameter, and an 11-blade iris. The reconstruction uses those outer dimensions and revolves the illustrated element contours into 3D. Surface curvature, glass thickness, spacing and physical iris dimensions are approximate: the published optical diagram is not a numerical optical prescription. Its estimated ray trace uses these approximations; the sensor image remains an ideal perspective rendering.

The 400 mm f/4.5 preset follows the Sony FE 400mm F4.5 GM OSS layout, including the large front element, long front air space, three Super ED elements (blue), and ED glass (mint). Sony’s specifications list 22 elements in 16 groups, 108 × 242 mm, and 11 aperture blades. Its calculated entrance pupil is 88.89 mm. The tapered ivory barrel, black grips and collar foot follow the body photograph. Sony’s lens configuration and material key identify Super ED and ED glass, without supplying a numerical prescription.

NIKKOR Z 400mm f/4.5 VR S

Focus playback moves one estimated internal element, with the same offset applied to glass, rays and volume. Nikon confirms STM autofocus but does not identify that element in the source. Its membership and bounded travel are estimates; the sensor, iris, mount and VR assembly remain fixed. Nikon’s 16 mm mount register and fitted quartic surfaces are retained. This range does not reproduce Nikon’s minimum focusing distance; finite-focus blur and clipping remain, and the sensor preview is separate ideal perspective rendering.

The Nikon preset is a separate optical design from the Sony 400mm f/4.5. Nikon’s specifications and construction diagram identify 19 elements in 13 groups, including one ED, two Super ED and one SR element, a 104 × 234.5 mm body and nine diaphragm blades. Its calculated entrance pupil is 88.89 mm. In the cutaway, gold identifies SR, red Super ED, and pink ED glass.

The fitted surrogate targets +400 mm effective focal length and near-axis focus at the fixed sensor, 16 mm behind the Z-mount flange, following Nikon’s mount specification. Displayed glass and Snell-law rays share the same fitted surfaces. The iris position and physical opening are inferred; the entrance-pupil diameter does not supply that opening directly.

The single-wavelength estimate uses assumed ED and Super ED proxies and independently fitted indices for unidentified glass and SR. Nikon describes SR as specialized short-wavelength refractive glass; its chromatic behavior is not simulated here, and the fitted index is not an identified Nikon grade. Rays are clipped by the glass, inferred iris and complete inner barrel/mount. Residual blur and clipping remain. Rays / Volume use the same paths, independent of sensor crop; the landscape preview stays separate ideal perspective rendering. This is an approximate optical surrogate, not Nikon’s prescription or a measurement of image quality or usable coverage.

The inferred physical iris has a radius of approximately 10.99 mm. All 101 axial samples reach the sensor, with maximum transverse error approximately 0.028 mm. Across 17 signed fields through the nominal full-frame corner, admitted-ray error stays below 0.375 mm, with RMS below 0.2 mm and at least 58 of 101 samples transmitted per field. These limits describe this fitted surrogate, not Nikon’s measured performance.

Estimated Sony 400mm f/4.5 refraction

This preset enables focus playback with two moving cells. Hands-on coverage reports two independently driven focus groups; the animation’s element assignments, opposed directions and travel curves remain estimates. Both cells share their motion with the rays and volume, with the iris, mount, housing and sensor fixed. Finite chiefs pass through the iris center. Near–Infinity does not reproduce the minimum focusing distance, and close-focus blur/clipping remain. The sensor image stays separate ideal perspective rendering. Calibration figures below describe infinity focus.

This preset supports Light: Rays / Volume, using its own independently fitted surfaces, not a stopped-down version of the 400mm f/2.8 model. Displayed glass and vector-Snell rays share the same fitted geometry. The surrogate has +400 mm effective focal length and near-axis infinity focus at the fixed sensor, 18 mm behind the E-mount flange. Unknown glass indices are bounded to 1.45–1.90. Super ED uses the 1.43875 OHARA S-FPL53 proxy; ED uses 1.48656. These are single-wavelength assumptions near 588 nm, not identified Sony glass grades or a simulation of chromatic correction.

The physical iris is unmarked and remains inferred, with radius approximately 11.45 mm. Finite chief rays are solved through its center; each field samples the full nominal entrance-pupil offsets around its own chief. Glass openings, the iris and the complete inner barrel clip paths physically. All 101 dense axial samples reach the sensor, with maximum transverse residual approximately 0.001 mm. Each nominal full-frame corner field transmits 67 of 101 dense samples, with maximum error approximately 0.133 mm from a chosen rectilinear image target. That target is an imposed surrogate constraint, not a measured distortion characteristic.

The display samples 21 rays per field, equally divided between the axis and two fixed opposite full-frame corner directions: 47 of 63 reach the sensor plane. Equal counts do not represent relative brightness. The sampled sensor envelope is approximately 43.43 mm across, versus the 43.27 mm full-frame diagonal; it includes residual blur and does not establish usable image circle or illumination. Sensor selection changes the crop and required-coverage guide, not the lens rays or transmitted-ray volume. The sensor image remains a separate ideal perspective rendering. These diagnostics describe the fitted surrogate, not Sony’s actual optical performance.

The 600 mm f/6.3 model follows the Sony FE 600mm F6.3 GM OSS layout, with a large front element, three blue Super ED elements and one mint ED element. Sony’s specifications list 24 elements in 17 groups, a 108 × 263 mm body, and 11 aperture blades. Its calculated entrance pupil is 95.24 mm. The ivory barrel, ribbed rings and collar foot follow the lens photo. Curvature, clear openings, spacing and physical iris dimensions remain approximate; the configuration diagram is not an optical prescription. The fitted surrogate shares its glass surfaces with Snell-law rays and their transmitted volume, with +600 mm effective focal length and near-axis infinity focus at the sensor, 18 mm behind the E-mount flange. It remains an estimated single-wavelength optical model, with residual blur and clipping.

The Sony 600mm f/6.3 preset enables focus playback with two estimated moving cells. Firsthand coverage reports two independently driven groups; this visualization’s exact element assignments, directions and travel curves remain estimates. Both cells, rays and volume share the motion. The iris, mount, sensor, housing and other elements stay fixed. Near–Infinity does not reproduce the manufacturer’s minimum focusing distance, and the sensor preview remains separate ideal perspective rendering.

NIKKOR Z 600mm f/6.3 VR S

The Nikon preset also enables focus travel and playback, moving one estimated internal element. Nikon documents STM autofocus but does not identify that element in the source. Its membership and travel remain estimates. Glass, rays and volume move together while the PF element, other glass, iris, VR optics and sensor stay fixed. The 16 mm Nikon mount register and existing quartic/PF surrogate are retained. This range does not represent Nikon’s minimum focusing distance; finite blur and clipping remain.

This separate Nikon preset follows the NIKKOR Z 600mm f/6.3 VR S construction diagram and specifications: 21 elements in 14 groups, including two ED, one SR and one Phase Fresnel (PF) element, nine diaphragm blades, and a 106.5 × 278 mm body. Green marks PF, yellow ED and pink SR. Its calculated entrance-pupil diameter is 95.24 mm.

The equivalent ray surrogate has +600 mm effective focal length, with near-axis focus at the fixed sensor 16 mm behind the Z-mount flange. Displayed glass and traced rays share the fitted geometry. The physical iris is inferred, with radius approximately 12.63 mm; it is distinct from the entrance pupil. All 101 axial samples reach the sensor, with maximum transverse error approximately 0.033 mm. Across 17 signed fields through the nominal full-frame corner, admitted-ray error stays below 0.471 mm, RMS below 0.178 mm, and at least 67 of 101 samples pass at each field. These are surrogate results, not measured Nikon performance.

Nikon’s PF element uses diffraction. Its phase prescription is not published in the construction diagram, so this single-wavelength visualization uses a smooth equivalent refractive fit. It does not simulate actual PF diffraction, chromatic correction, efficiency or flare. Glass grades and fitted surface terms are estimates, not Nikon’s prescription. Full glass, iris and barrel clipping remain active. The display transmits 47 of 63 equally sampled rays; equal field counts do not represent brightness. Sensor crop changes the active sensor and coverage guide, while Rays / Volume retain the same optical paths. The sensor preview is separate ideal perspective rendering, and the sampled envelope does not establish usable image-circle coverage.

Estimated 600mm refraction

The 600mm f/4 preset includes a focus slider with Near on the left and Infinity on the right, plus Play focus and Reset to infinity controls. An illustrative internal cell moves while rays and their volume are recalculated through the same translated glass surfaces. The sensor and mount stay fixed. Cell selection and travel are estimates, not Sony’s focusing mechanism or minimum focusing distance; finite rays retain residual blur and clipping. The sensor preview remains an ideal perspective image and does not change focus with this slider. All thirteen presets now support estimated focus travel.

Use Light: Rays / Volume to switch the 600mm f/4 view. Volume is the default. Volume revolves the sampled outer envelope of the transmitted ray paths around the optical axis, preserving their bends and narrowing through the rear assembly. Stopped rays are omitted from the volume. Moving bands animate along the transmitted rays. This envelope illustrates the bundle’s extent; its brightness does not represent irradiance. The choice is remembered while switching lens presets; the toggle appears for the 50mm, 85mm, 135mm, 200mm, 300mm, 400mm and 600mm presets.

The sensor-plane guides compare gold dashed: required sensor coverage with teal: sampled ray envelope. For full frame these diameters are approximately 43.27 mm and 45.62 mm respectively. The smaller rear filter opening lies on a different plane and is not the image circle. The teal guide does not establish usable image-circle coverage or image quality. Changing sensor format changes the gold requirement and sensor rectangle; the lens, traced rays and teal envelope stay fixed.

The 600mm view traces 63 rays in a plane through the optical axis: parallel bundles for an on-axis object at infinity and two opposite field directions. The two off-axis directions are fixed at the nominal full-frame corner angle for 600 mm. Selecting another sensor changes the crop and framing readouts, not the lens or these ray paths. These bundles are separate from the finite miniature landscape. Each ray intersects the displayed approximate surface curve and bends according to Snell’s law. Shared traced faces use a direct glass-to-glass interface. A ray that misses a clear opening, reaches a glass edge or is blocked by the inferred iris stops; it is never squeezed into a smaller rear element. Teal rays reach the sensor plane; amber rays terminate earlier. Reaching that plane does not establish that the ray lands within the sensor rectangle.

The fitted surrogate uses a single reference wavelength of approximately 588 nm. Its effective focal length is +600 mm, with near-axis infinity focus at the sensor. The sensor stays 18 mm behind the mount, consistent with Sony’s E-mount flange distance. Element order and axial vertices retain the reconstructed layout; surface sags and unidentified glass indices are adjusted to meet those optical constraints. The rendered glass uses those same fitted curves. Some inferred clear radii are slightly expanded to admit the axial 150 mm bundle. This is one possible optical approximation, not a recovered Sony design.

Illustrated material	Assumed refractive index	Basis
Unidentified glass and XA	Fitted separately per element within 1.45–1.90	Broad assumed optical-glass range; individual grades are unknown
Filter	1.51680	SCHOTT N-BK7 as a crown-glass proxy
ED	1.48656	SCHOTT N-FK51A as a low-dispersion proxy
Fluorite	≈1.434	Crystran calcium fluoride data, rounded visible-light approximation

These are assumptions, not identified Sony glass grades. XA specifies an aspherical element, not a refractive index. Fitted curves use parabolic sag; they do not recover Sony’s aspheric coefficients. The drawing does not mark the iris, so its location remains illustrative. Its fitted radius is approximately 16.94 mm, chosen for the axial 150 mm entrance-pupil bundle; this is not a Sony stop measurement. The iris blocks rays but does not bend them. The on-axis sample spans ±75 mm; its largest sensor-plane error is approximately 0.11 mm, despite exact first-order focus. Off-axis rays retain blur and clipping, so neither this spread nor the sampled pass count predicts Sony’s image quality or coverage. Dispersion, coatings, reflected branches, diffraction and the real focusing mechanism are omitted. The sensor image remains a separate ideal perspective rendering.

The Sony FE 400mm f2.8 GM OSS preset reconstructs the shorter 400 mm lens, with three fluorite elements (gold), ED glass (mint), a long open front section and a rear filter. Sony’s specifications list 23 elements in 17 groups including one filter, a 359 mm body length, 158.1 mm diameter, and 11 aperture blades. Its optical diagram supplies the layout and glass key. The reconstructed curves and fine rear interfaces are approximate. Its calculated entrance-pupil diameter is 142.86 mm, distinct from the illustrative physical iris.

Estimated 400mm refraction

The Sony 400mm f/2.8 preset also supports focus playback. Sony documents XD motor drive; the visualization moves one inferred internal element, with estimated direction and travel. Glass, rays and volume share that motion while the mount, housing, iris, sensor and other elements remain fixed. Near–Infinity does not represent Sony’s minimum focusing distance. Existing field-sampling limits, finite blur and clipping remain; the sensor preview stays independent ideal perspective rendering. Calibration figures below describe infinity focus.

The 400mm preset also supports Light: Rays / Volume, with Volume selected by default. It has its own fitted surfaces and per-element glass assumptions, calibrated to +400 mm effective focal length and the same fixed sensor plane 18 mm behind the E-mount flange. The element order and axial vertices retain the reconstructed 400mm layout. The rendered glass and Snell-law trace share its fitted curves; the 600mm coefficients are not reused.

Fluorite, ED and filter indices use the single-wavelength proxies above; unidentified indices are fitted separately within 1.45–1.90. The iris position is unmarked in the drawing and remains inferred. Its fitted radius of approximately 27.31 mm admits the axial 142.86 mm entrance-pupil bundle. Small inferred clear-radius expansions stay inside the reconstructed housing.

All 21 axial samples reach the sensor, with maximum transverse error approximately 0.01 mm. Off-axis bundles retain blur and clipping. The sampled sensor-plane envelope is approximately 46.58 mm across, compared with 43.27 mm required for full frame. These are surrogate diagnostics, not predictions of usable image circle or Sony image quality. Changing sensor format affects the crop and gold requirement, while the ray paths and teal envelope stay fixed. The house image remains a separate perspective rendering.

The FE 300mm F2.8 GM OSS preset has its own compact body and optical layout. Sony’s specifications list 21 elements in 17 groups including the filter, 265 mm length, 124 mm diameter, and 11 aperture blades. Unlike the larger Sony models here, its specialty glass comprises three Super ED elements (blue) and one ED element (mint). Its calculated entrance pupil is 107.14 mm. Curves and spacing are reconstructed from the diagram and remain approximate; the physical iris dimensions and location are illustrative.

Estimated 300mm refraction

The 300mm f/2.8 preset supports focus travel and playback. Sony’s focus-drive diagram shows two XD motors around one unit; it does not establish individual moving elements. This visualization moves one inferred two-element cell, with estimated direction and travel. Rays and volume follow the same moved glass; the mount, sensor, iris and other elements stay fixed. Near–Infinity does not represent Sony’s minimum focusing distance. The original field-fan approximation, blur and clipping remain, and the sensor preview is separate ideal perspective rendering. Calibration figures below describe infinity focus.

The 300mm preset supports Light: Rays / Volume, defaulting to Volume. Its independently fitted surfaces give +300 mm effective focal length and infinity focus at the fixed sensor, 18 mm behind the E-mount flange. Displayed glass and rays share the same curves, preserving the element order and axial vertices of the reconstructed layout.

The three Super ED elements use 1.43875 as a representative single-wavelength index, from OHARA’s S-FPL53 catalog entry. This is a proxy, not an identification of Sony’s glass grade. ED and filter indices remain 1.48656 and 1.5168; unidentified glass indices are fitted within 1.45–1.90. Dispersion is not simulated. The unmarked iris remains inferred, with a fitted radius of approximately 21.58 mm admitting the 107.14 mm axial entrance-pupil bundle.

All 21 axial samples reach the sensor, with maximum transverse error approximately 0.034 mm. Off-axis bundles retain blur and clipping; 49 of the 63 sampled rays reach the sensor. The sampled envelope is approximately 53.25 mm across at the sensor, compared with the 43.27 mm full-frame diagonal. These are surrogate diagnostics, not measurements of usable image circle or Sony image quality. Sensor selection changes the crop and required guide; the lens rays and their volume remain fixed. The house image is a separate perspective rendering.

The Sigma 135mm F1.4 DG ART preset reconstructs its optical diagram, highlighting four FLD elements (gold) and two aspherical elements (coral). Sigma’s specifications and construction diagram list 17 elements in 13 groups and 13 diaphragm blades. The model uses the Sony E-mount body dimensions, 111.7 × 137.5 mm. The supplied optical diagram has no mechanical outline or physical scale, so the black housing, glass dimensions and spacing are illustrative. The aspherical labels identify the elements; they do not supply exact surface equations. Its calculated entrance pupil is 96.43 mm.

Estimated 135mm refraction

The 135mm f/1.4 preset enables focus playback with two moving cells. Sigma documents a floating focus system with two independently driven HLA groups. The INF/MOD mechanism diagram identifies both moving groups behind the iris: the single element moves toward the sensor while the following two-element group moves toward the scene. The animation follows that membership and those directions; travel distances, timing curves and exact iris dimensions remain estimates. Glass, rays and volume share the motion, with the housing, mount, iris and sensor fixed. Near–Infinity does not represent Sigma’s minimum focusing distance. Close-focus blur/clipping remain; the sensor preview is separate ideal perspective rendering. Calibration figures below describe infinity focus.

The 135mm f/1.4 preset supports Light: Rays / Volume, defaulting to Volume. Its independently fitted surfaces give +135 mm effective focal length and near-axis infinity focus at the fixed sensor, 18 mm behind the E-mount flange. Displayed glass and traced rays use the same curves. The four FLD elements use the assumed 1.43875 low-dispersion glass proxy linked below for the 200mm; this does not identify Sigma’s glass grade. Both aspherical bodies have separately fitted material indices within the same 1.45–1.90 bounds as unidentified glass. The aspherical labels do not supply exact aspheric coefficients; this single-wavelength approximation does not simulate chromatic correction.

Each off-axis bundle is aimed so its chief ray passes through the aperture-stop center. The fit tests a broad pupil region at both nominal full-frame corner directions. The diagram draws 21 samples in each of three directions: one axial and two opposite corner fields. These equal counts do not represent relative brightness.

The optical drawing supplies no measured glass scale. One tiny overlap in the reconstruction is removed before fitting; glass dimensions and the unmarked iris location remain estimates. The rays also stop at the reconstructed inner barrel and mount opening. The inferred iris radius is approximately 21.60 mm, admitting the axial 96.43 mm entrance-pupil bundle. All 21 axial samples reach the sensor, with maximum transverse residual approximately 0.014 mm. Off-axis blur and clipping remain: 45 of 63 sampled rays reach the sensor plane. The sampled envelope is approximately 43.85 mm across there, versus the 43.27 mm full-frame requirement. Its extent includes residual off-axis fitting error and does not establish usable image-circle coverage or Sigma image quality. Sensor selection changes the crop and requirement, while the ray paths and their volume remain fixed.

The default FE 50mm F1.2 GM preset follows its stepped barrel and optical layout, with three XA (extreme aspherical) elements highlighted in coral. Sony’s specifications give 14 elements in 10 groups, 87 × 108 mm dimensions, and 11 aperture blades; Sony describes the three XA elements. Its calculated entrance pupil is 41.67 mm. Surface curves, thicknesses, spacing and physical iris dimensions are schematic approximations; the highlighted XA surfaces do not reproduce a numerical aspheric prescription.

The FE 35mm F1.4 GM preset follows its compact barrel, large central gap and 14-element glass layout. Sony’s specifications list 14 elements in 10 groups, a 76 × 96 mm body, and 11 aperture blades. Its two XA elements and one ED element are highlighted in coral and mint. The calculated entrance pupil is 25 mm. Curves, thicknesses, spacing and physical iris dimensions remain schematic approximations.

The Sigma 200mm F2 DG OS Sport preset reconstructs its 19-element layout, with two FLD elements in gold and two SLD elements in blue. Sigma’s specifications list 14 groups, 11 diaphragm blades, and a 118.9 × 203 mm Sony E-mount body. The calculated entrance pupil is 100 mm. The body has an ivory paint texture, ribbed grip, curved markings and controls informed by a product photo. The removable hood is omitted to expose the glass. Mechanical details, glass scale, spacing, curves and physical stop dimensions remain illustrative; stabilization is not simulated.

Estimated 200mm refraction

The 200mm f/2 preset enables focus travel and playback. Sigma documents HLA autofocus. One moving element is provisionally mapped from a matching Sigma patent layout; the retail identification and travel remain estimates. Glass, rays and volume share the motion. The iris, mount, sensor and stabilization elements stay fixed. Near–Infinity does not reproduce the manufacturer’s minimum focusing distance. The existing field-fan approximation, blur and clipping remain; the sensor image is separate ideal perspective rendering. Calibration figures below describe infinity focus.

The 200mm f/2 preset now supports Light: Rays / Volume, with Volume selected by default. It uses its own fitted curves and per-element material assumptions, constrained to +200 mm effective focal length and near-axis infinity focus 18 mm behind the E-mount flange. The displayed glass and Snell-law rays use the same surfaces. The optical drawing does not establish exact physical glass dimensions; the reconstructed glass scale and unmarked iris position remain estimates.

The two FLD elements use a representative low-dispersion glass index of 1.43875, based on OHARA S-FPL53; FLD is glass, not crystalline fluorite. The two SLD elements use 1.48656, the SCHOTT N-FK51A proxy linked in the index table above. These are assumed substitutes near 588 nm, not identified Sigma grades. Unidentified glass indices are fitted within 1.45–1.90. The trace does not simulate dispersion or stabilization, and is not Sigma’s optical prescription.

The inferred iris radius is approximately 24.10 mm, admitting the axial 100 mm entrance-pupil bundle. All 21 axial samples reach the sensor, with maximum transverse residual approximately 0.0034 mm. Off-axis blur and clipping remain: 49 of 63 sampled rays reach the sensor plane. The sampled envelope is approximately 59.57 mm across there, versus the 43.27 mm full-frame requirement. These are fit diagnostics, not measurements of Sigma image quality or usable image circle. Changing sensor format changes the crop and required guide; the rays and their volume remain fixed.

The FE 85mm F1.4 GM II reconstruction follows its 14-element layout, with two coral XA elements and two mint ED elements. Sony’s specifications list 11 groups, an 84.7 × 107.3 mm body and an 11-blade diaphragm. The pupil is 60.71 mm, calculated at f/1.4. Its supplied body photo guides the textured black finish, focus and aperture rings, markings and controls.

Estimated 85mm and 50mm refraction

The 85mm f/1.4 GM II preset also enables focus travel and playback. Sony confirms two XD linear motors. The animation moves one estimated internal cell; the source does not establish its exact elements or a second floating group. Its membership and travel remain estimates, with the iris, mount and sensor fixed. Glass, rays and volume use the same motion. The Near–Infinity range does not represent Sony’s minimum focusing distance; close-focus blur and clipping remain, and the sensor preview stays separate ideal perspective rendering.

The 50mm f/1.2 preset enables focus playback with two moving cells. Sony confirms a floating focus system with two independently driven groups. The visualization uses separate estimated travel curves; the exact element membership and motion are not Sony’s prescription. Both cells, their rays and their volume use the same offsets, with a fixed iris, sensor and mount. The Near–Infinity range does not represent Sony’s minimum focusing distance. Close-focus blur and clipping remain, and the sensor preview stays separate ideal perspective rendering. Calibration figures below describe infinity focus.

The 85mm f/1.4 and 50mm f/1.2 presets now support Light: Rays / Volume, defaulting to Volume. Each has an independent fit of its 14-element layout, with shared displayed glass and Snell-law surfaces. Their effective focal lengths are +85 mm and +50 mm, with near-axis infinity focus at the same sensor, 18 mm behind the mount.

The 85mm retains its two ED elements using the assumed N-FK51A index of 1.48656 linked above. Its two XA elements and the 50mm’s three XA elements have independently fitted unknown indices within 1.45–1.90 near 588 nm. XA identifies shape, not a glass grade; true aspheric coefficients and chromatic correction remain unknown.

Surrogate	Nominal entrance pupil Ø (mm)	Inferred clear iris Ø (mm)	Maximum axial residual (mm)	Maximum admitted-ray error across checked fields (mm)
85mm f/1.4	60.71	≈39.88	≈0.0011	≈0.038
50mm f/1.2	41.67	≈40.52	≈0.016	≈0.32

The iris positions are inferred from the layouts, and their sizes follow a dense axial ray sweep rather than the entrance-pupil formula directly. All 101 axial samples pass for each lens. Tilted bundles are aimed through the iris center, then clipped by the actual glass, iris and full inner barrel. Across 17 signed field angles, each sampled with 101 nominal pupil positions, at least 42 rays pass for the 85mm and 48 for the 50mm. These sampling counts do not describe brightness or measured vignetting.

The display draws 21 rays in each of three fixed scene directions. Respectively, 37/63 and 39/63 reach the sensor plane, with sampled envelopes approximately 43.28 mm and 43.39 mm across. Residual blur and clipping remain; neither envelope establishes usable image circle or Sony image quality. Changing sensor format crops the image and changes the required-coverage guide without changing the lens rays or volume. The sensor image remains a separate ideal perspective rendering.

The FE 24mm F1.4 GM reconstruction has 13 elements, including two coral XA and three mint ED elements. Sony’s specifications list 10 groups, a 75.4 × 92.4 mm body and an 11-blade diaphragm. Its pupil is 17.14 mm. The textured body details follow the supplied photo. These reconstructions approximate curves, spacing, iris dimensions and unseen mechanical details; they are not numerical optical prescriptions.

Estimated 24mm and 35mm refraction

The 24mm f/1.4 preset enables the Near–Infinity slider and focus playback. Sony specifies a DDSSM focus drive. The visualization translates one inferred rear assembly; its precise element membership and travel are estimates, not recovered Sony mechanics. Glass, finite-distance rays and their volume move together while the sensor, mount and iris remain fixed. Tilted chief rays are aimed through the iris at each position. Near focus retains blur and clipping, and the displayed range does not represent Sony’s minimum focusing distance. The sensor preview remains separate ideal perspective rendering. The calibration figures below describe infinity focus.

The 35mm f/1.4 preset also enables focus travel and playback. Sony documents two XD linear motors. The model moves one inferred rear assembly; two motors do not establish two independently moving focus groups. Its element membership and travel remain estimates, with a fixed sensor, mount and iris. Rays and volume use the same moved surfaces and finite-distance chief aiming. Close focus retains blur and clipping; its range does not represent Sony’s minimum focusing distance. The infinity calibration remains unchanged.

The 24mm f/1.4 and 35mm f/1.4 presets support Light: Rays / Volume, with Volume selected initially. They have independent +24 mm and +35 mm effective focal lengths and near-axis infinity focus at the fixed sensor, 18 mm behind the mount. Displayed glass and Snell-law rays share the fitted surfaces.

Their ED elements use the assumed N-FK51A index of 1.48656 linked above. Unidentified glass and XA indices are independently fitted within 1.45–1.90 near 588 nm. Each XA face also has a bounded, inferred fourth-order sag term to improve the wide-field estimate. These terms and glass assumptions do not recover Sony’s prescription or predict its image quality; dispersion is omitted.

Surrogate	Nominal entrance pupil Ø (mm)	Inferred clear iris Ø (mm)	Maximum axial residual (mm)	Maximum admitted-ray error across checked fields (mm)
24mm f/1.4	17.14	≈31.47	≈0.021	≈0.22
35mm f/1.4	25.00	≈33.32	≈0.011	≈0.14

The iris positions are inferred, and their clear sizes follow 101 actual axial stop crossings rather than the entrance-pupil formula directly. All 101 axial samples pass for each lens. Tilted chief rays are aimed through the iris center before the full nominal pupil is sampled and clipped by the glass, iris and inner barrel. Across 17 signed field angles, each with 101 pupil samples, at least 47 rays pass for the 24mm and 39 for the 35mm. These sampling counts do not measure brightness or vignetting.

The display draws 21 rays in each of three fixed directions. Respectively, 39/63 and 37/63 reach the sensor, with sampled envelopes approximately 43.43 mm and 43.50 mm across. Residual blur and clipping remain. The envelopes are not usable image-circle measurements; the full-frame requirement is 43.27 mm. Changing sensor format crops the image and changes the required guide without changing lens rays or volume. The landscape preview remains separate ideal perspective rendering.

The diagonal field of view is calculated for an ideal rectilinear lens at infinity focus:

Diagonal field of view = 2 × atan(sensor diagonal ÷ (2 × focal length))

At a fixed sensor size and focal length, aperture changes the entrance pupil but not this viewing angle. The presets change both focal length and aperture together. A larger sensor captures a wider angle at the same focal length. The angle describes framing, not a lens’s measured usable coverage. This is the same geometric relation used in the Field of View Calculator.

A real scene consists of many ray bundles from different directions. All thirteen presets now use fitted ray diagrams and volumes derived from transmitted paths, with the assumptions described above. The optical bench uses physical sensor and nominal pupil diameters alongside estimated glass and housing geometry. Perspective affects their apparent sizes because they occupy different planes; use the Sensor / entrance pupil board or the tables for direct diameter comparisons. A real lens has distinct principal planes and entrance/exit pupils; its physical iris can differ from its entrance pupil, and its physical length and back-focus distance need not equal its focal length. The diagram does not recover the lenses’ actual entrance-pupil planes.

The dashed circle at the sensor marks the required coverage, not a measured or simulated usable image circle. The fitted diagrams do not establish real-lens vignetting, aberration performance, distortion, diffraction, transmission or usable coverage. Sensor shift, lens shift and tilt can require extra coverage beyond the simple diagonal.

For a framing comparison, try the Field of View Calculator. To explore diffraction separately, use the Diffraction Calculator.

Comparing sensor and pupil sizes

The Sensor / entrance pupil board behind the lens shows the selected sensor as a teal rectangle, its minimum required image circle as a dashed circle, and the calculated entrance pupil as a gold circle. All three use the same millimetre scale, with room for a 150 mm pupil. Changing the lens changes only the pupil circle; the sensor stays the same size until you choose another sensor format. The tables below the viewer compare all five sensor formats and all thirteen lens presets.

This comparison deliberately places quantities from different optical planes together. A pupil smaller than the sensor diagonal does not imply vignetting; a pupil larger than it does not prove coverage. Actual usable image circle depends on the lens design and image-quality criterion.

On devices that cannot run the interactive 3D scene, the numerical results and comparison tables remain available. Reduced-motion settings pause the light animation initially.