How perspective, lenses, and hand size make handheld photographs unreliable for numerical size estimates.
A handheld photo has no dependable scale
A hand may provide a visual impression, but it is not a standardized measuring reference. Hand dimensions differ between people, and the photograph rarely establishes the relevant hand measurement. Even if a viewer assumes an average hand size, that assumption cannot produce a reliable product dimension.
Perspective changes apparent proportions
Camera distance, lens characteristics, viewing angle, cropping, and the relative positions of the hand and product can all affect apparent scale. An object closer to the camera may look disproportionately large, while a wide-angle view can alter relationships between near and distant features. A tightly cropped image can further conceal the perspective cues needed to recognize that distortion.
For this reason, a handheld image can help show general appearance, grip context, or how visible features relate to one another. It cannot, by itself, establish a numerical overall length, blade length, handle length, or storage fit. SEWARD’s Terms of Service says photographs help comparison while directing customers to check dimensions and other model-specific details on the individual product page.
Use a defined measurement instead
For numerical comparison, use a specification or measured image that identifies the unit, endpoints, product state, and a dependable scale. Confirm that the selected variant and the pictured item are the same version. If two references conflict, preserve both sources until their measurement conditions can be reconciled.
When no dimensioned source is available, state that the size cannot be calculated from the photograph. Do not assign a range based on the person’s hand, familiar-looking objects, or screen pixels. That restraint does not make the image useless; it simply keeps an appearance reference from being mistaken for measurement evidence.