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Look closer before you draw a conclusion / KitForma

Lens Sample Check: Matched Photo Crop Comparison

A practical workbench for checking a lens sample. Match the same detail across controlled photographs, inspect enlarged crops and record repeatable differences. Your files stay in your browser.

Open the workbench Understand the details

No account neededRuns in your browserFree to use

Local evidence / clear next steps01 → 02

Controlled capturesSame target · same settingsSelected by you

Compare matched cropsAligned viewsObservation, with uncertainty

Your originals stay unchanged. Keep a report of what the check found.

From question to next step

Lens Sample Check

Start with the details you know. Unknown answers stay unknown. Try the example to see how the check works.

Your inputs

Required fields are marked with an asterisk.

01

Comparison workflow

The pair requires two separate captures. Digitally rotating one photo does not test a lens.

Normal camera orientation photo

JPEG, PNG or still WebP; up to 24 MiB and 48 MP. Use identical export dimensions and processing.

Camera physically rotated 180° photo

JPEG, PNG or still WebP; up to 24 MiB and 48 MP. Use identical export dimensions and processing.

Photo with the target at top left

JPEG, PNG or still WebP; up to 24 MiB and 48 MP. Use identical export dimensions and processing.

Photo with the target at top right

JPEG, PNG or still WebP; up to 24 MiB and 48 MP. Use identical export dimensions and processing.

Photo with the target at bottom left

JPEG, PNG or still WebP; up to 24 MiB and 48 MP. Use identical export dimensions and processing.

Photo with the target at bottom right

JPEG, PNG or still WebP; up to 24 MiB and 48 MP. Use identical export dimensions and processing.

I kept the camera, lens, zoom, aperture, exposure and ISO fixed, with focus locked across this set.

I used a supported camera, a static detailed target and stable lighting, without obvious motion or heat shimmer.

I exported every image with the same crop, size, sharpening and noise reduction, without AI enhancement.

Loading the local tool… Your files stay in this browser.

Your report

A practical interpretation of your evidence.

02

Make the next step clear.

Your findings, assumptions and next steps will appear here after you run the check.

Lens Sample Check · https://lenscheck.kitforma.com/ · KitForma

01

Interactive matched crops and zoom

02

EXIF consistency with unknowns shown

03

Private, downloadable comparison evidence

Go one level deeper

Understand the evidence.

Focused guides explain the rules, the edge cases and the checks worth doing before you act.

Field guide / 01

Capture a controlled lens sample comparison

Choose a repeatable scene, lock the capture settings and separate camera motion from optical differences.

Read the guide ↗Field guide / 02

Align photo crops before comparing lens detail

Use target matching, rotation and a common crop scale to make the visual comparison meaningful.

Read the guide ↗Field guide / 03

Why a soft corner does not automatically mean a faulty lens

Understand field curvature, alignment, image processing and the limits of browser sharpness measurements.

Read the guide ↗

Good questions

Before you start

Can this prove that my lens is decentered?

No. It helps you document and inspect repeatable differences in controlled photographs. Misalignment, focus, field curvature, movement, atmospheric shimmer and processing can mimic an optical problem. A persistent difference is a reason to repeat a careful test or seek professional evaluation.

What do edge energy and tonal deviation mean?

Edge energy is the average central-difference image gradient measured on a 256 × 256 crop. Tonal deviation describes the spread of brightness. Neither is calibrated MTF or a lens sharpness rating. Sharpening, noise and different subject texture can raise both values.

Why does the tool withhold my comparison?

The tool withholds interpretation when the target alignment is unconfirmed, known EXIF settings or image dimensions differ, crops are too small or nearly featureless, transparency is present, clipping is substantial, or brightness differs strongly. The visible crops remain useful for finding what needs correction.

Can I use RAW, HEIC or TIFF files?

Use browser-decodable JPEG, PNG or still WebP exports. RAW, HEIC and TIFF are outside this tool’s supported scope. Export the full set using identical crop, size, sharpening and noise reduction. Missing EXIF is reported as unknown, including when an export strips it.

Are my photographs uploaded or saved by KitForma?

The tool reads and measures your selected photos on your device. Its downloadable JSON contains the selected camera settings, crop coordinates and measurements; it omits image pixels, GPS fields and filenames. Keep the original files separately if you want to repeat the comparison later.

Should I rotate the second picture by 180 degrees?

Physically rotate the camera for the second capture if using the normal/180° workflow. Camera orientation metadata can already make both decoded images upright. Use the crop rotation control only when necessary to match the target. Digital rotation of a duplicate photo adds no optical evidence.

The evidence behind the check

Sources & assumptions

Rules are reviewed against the references below. Manufacturer updates, firmware and your exact setup can change the result.

Lensrentals: Setting up an optical testing station ↗
Controlled setup, alignment, field curvature and limits of practical lens testing. Browser pixel statistics are KitForma measurements, not Lensrentals optical tests.
Lensrentals: Testing for a decentered lens ↗
Why optical asymmetry requires a careful method and follow-up. This browser tool does not reproduce a calibrated optical bench.
MDN: createImageBitmap ↗
Browser image decoding and orientation behavior; browser-rendered exports may differ from RAW development.

Reviewed 2026-10-13. Read our methodology or report an issue.