If the viewfinder's own symbols and focus markings look soft while saved photographs look sharp on another display, check viewfinder diopter adjustment. This control changes how you see the finder. It is different from focusing the taking lens on the subject. Do not blur, sharpen, or regenerate a correct photograph to compensate for an eyepiece viewing problem.
Use an internal reference before the scene
The subject can genuinely be out of focus, so it is a poor first reference for setting the eyepiece. Instead inspect the viewfinder's display and focus-point markings using the camera manual's procedure. Nikon's D3500 instructions tell the user to adjust diopter until the focus points appear sharp. That is a specific observable target, not a guess about the scene's detail.
If you wear glasses, use the normal viewing arrangement in which you photograph. Avoid changing glasses, lens focus, and diopter simultaneously. The exact adjustment range and mechanism differ by camera. Never force a control beyond its range; a persistent viewing issue can require appropriate accessory or service advice rather than a software workaround.
A three-view comparison
This is a proposed checklist, not an optical test performed for this article. First, record whether the finder symbols are clear. Second, take a photograph of a stationary textured object using the camera's normal supported autofocus method. Third, open the actual saved original on a separate familiar screen at a useful scale, without applying a new sharpening preset.
Keep a note with three separate entries: finder markings, scene appearance in the finder, and detail in the saved file. Adjust only the diopter according to the manual and repeat the observation of the markings. You are checking the viewing path, not attempting to prove that one camera's autofocus system is accurate under every condition.
Choose the right next step
If the markings become clear and the saved file remains sharp, there is no need to alter the image. If the markings are clear but the saved subject is soft, investigate actual capture focus, subject movement, and exposure time. If the exported copy alone is soft, compare it with the original at matching display size before changing the camera.
A small camera preview is not sufficient for judging identity details needed in a professional portrait. Check the eyes, hairline, and any defining marks in the saved source. Conversely, do not reject a usable photo simply because a shared camera's finder was adjusted for another person's eyesight. Keep the distinction between viewing comfort and recorded information.
For an Imagild reference, use the actual image file rather than a photograph taken through the viewfinder or a screenshot of its display. Preserve the original and select a source whose required details are clear in the file. This avoids spending a creative generation on a problem that belongs to the camera's eyepiece, while keeping real capture softness available for separate diagnosis.