Lens Explorer

Image circle coverage, MTF, fall-off, distortion, transmission and chromatic aberration — one lens selection across every view.

Lenses. Select them once in the sidebar: the Image circle view draws their circles against the selected formats, the curve views plot whatever data each lens has (the / marks on a row: image circle / curves). Lenses are grouped by family; ALPA, Sinar and Cooke each form one group. Class filters by coverage (MF Ø < 165 mm · LF ≥ 165 mm · ULF covers 8×10) or by use (enlarger, macro).

Image circles are quoted at infinity (usually f/22, per the brochure), macro lenses at their design magnification (@ 1:1 in the name). Hover a circle or a selected row to preview its coverage; click a circle or the row's to pin its info box.

Curves come from manufacturer datasheets: vector charts extracted programmatically (250+ points per curve), raster brochures and web GIFs read by a vision model (≈ 11 points per curve), one sheet's Zemax screenshots traced by pixel colour (Silvestri Apo-Silvetar — computed design data, flagged in its note); the links and the info box under the chart name every source. MTF: solid = radial, dashed = tangential; a selected lens starts with its panel closest to infinity at the highest f-stop, the chevron opens its panel / curve list. Panels marked * carry verified labels where the sheet's print is wrong (the source note says how). With two or more lenses on the MTF chart, the first legend line says how far their curves compare: the frequencies all their sheets carry, whether f-stops or focus distances differ, and whether the makers differ — Schneider and Rodenstock chart with different conventions, so gaps under about 2 points between their lenses are ties (the tooltip explains).

One coordinate system. MTF, fall-off and distortion share the absolute axis — image height in mm, degree-based distortion converted with f′(1+β)·tan w, percent-only sheets placed with their own u′max — and one x range per selection, so a feature sits at the same place on every view; relative mode is % of each sheet's field. Transmission and chromatic aberration share a 370–710 nm axis.

Diffraction limit (MTF view): the MTF a perfect lens with a round pupil would reach at each shown panel's working f-number, at 540 nm (Schneider's printed white light averages 539–540 nm) — a dotted line per frequency. The f-number follows each sheet's convention: k (1 + |β|) on Schneider's sheets, the printed f-stop on Rodenstock's and Leica's (their close-focus curves fit only that way), and the film-side k (1 + 1/m) for enlarging lenses at an enlargement m. It is the on-axis limit: off axis a lens's pupil changes shape, and a few sheets print curves that rise a little above it mid-field (the Xenars, by up to about 4 points). cos⁴ law (fall-off): the natural vignetting of a simple lens, cos⁴ of the image-side field angle from f′ (1 + |β|) — retrofocus designs beat it, a curve below it adds mechanical vignetting. Depth of focus (chrom. aberration): the band ±2 λ N² at a chosen f-stop — colour focus shifts inside it are not visible.

Formats are shared: the selected formats are the rectangles of the circle view and the corner markers on the mm axes of the curve views; a custom W×H can be added. Max shift (rise / fall in mm) raises what a format demands of the lens — the circle view draws the swept footprint, the corner markers move out, and the coverage filter judges lenses against it.

Twins. ALPA-market and Sinar (Sinaron) lenses are OEM lenses under another name: every row of one optics shows all its curve data, series from a rebrand's own sheet are tagged · ALPA (LINOS reprints · LINOS); Rodenstock's 2008 renames (Apo-Sironar digital HR → HR Digaron-S, …) are paired the same way. Specs (weight, filters) stay per row; the info box links the twins.

Specs. Where shown, weight (g) and filter threads are read from the documents below — lenses none of them covers simply show no value. Weights are for the lens in the mount the source quotes (Copal for the Schneider line sheets, the ALPA helicoid included in the ALPA tables), so the same optics can weigh differently on two rows.

Library: the archive's PDF index as a view; its / icons select that lens here. ?lens=<id> deep-links, the URL hash carries the state.

The datasheets and tables the data was read from are linked as provenance; they remain the property of their publishers. The app and the digitized data are CC BY-NC 4.0: free to share and adapt, with attribution, not for commercial use (see LICENSE).