Convert NEF to WebP

Nikon bodies carry a colour space setting in the shooting menu, and plenty of them are left on Adobe RGB because somebody once said it was better. Adobe RGB describes a wider range of colours than sRGB, and it does it by assigning different meanings to the same numbers — which is fine as long as every step of the chain knows which space it is working in.

This conversion does not carry a colour profile into the output. Browsers treat untagged images as sRGB. So an Adobe RGB preview converted here arrives on the web page with its numbers reinterpreted, and the result is exactly the complaint people describe: flat, slightly desaturated, greens and reds noticeably weaker than what they saw on the camera. The fix is upstream — set the camera to sRGB for web work — or in an image editor that can convert the profile properly before the file gets here.

Bytes, and the metric they are measured on. WebP typically delivers the same visible quality in a quarter to a third fewer bytes, and on an image-led page the Largest Contentful Paint is an image, so that saving lands directly on the number somebody is being held to.

It is also safe now in a way it was not a decade ago. WebP is supported in every current browser and standardised as RFC 9649, so serving it needs no fallback chain and no discussion about old Safari versions.

Set the maximum width to the largest size the site will serve and convert once per size if several are required. A responsive image set typically wants something like 800, 1,600 and 2,400 pixels; producing those three from the NEF each time is better than producing the largest and scaling it down elsewhere, because each scaling step is another re-encode.

Resist the temptation to deliver the full 8,256-pixel preview and let the CMS handle it. Some do this well; many store the original and serve it unchanged to a phone, and then the page weight the brief was about arrives anyway.

No raw development happens here. Your Nikon writes a finished JPEG inside the NEF at the moment of capture, and the converter finds it, keeps the largest one above 640 by 480, and re-encodes that as WebP. The Picture Control the camera was set to is baked into it.

For a delivery job this is usually acceptable and occasionally not. If the client has approved a graded look, the grading has to be done from the NEF in a raw developer and exported before it comes anywhere near this page. If the brief is "the pictures from the shoot, on the website, by Friday", the camera’s rendering is what everyone has already seen and agreed to.

The camera compressed the preview once; converting to WebP decodes and compresses it again. Two passes is one more than ideal and considerably fewer than most delivery pipelines actually run, where an image is exported, uploaded, re-encoded by the CMS and re-encoded again by a CDN.

The practical rule is to convert from the NEF every time. Converting from a WebP you delivered last month, or from a JPG somebody emailed back, adds a pass for nothing. At the default quality of 82 and at web dimensions the second pass is invisible; the fifth is not.

The re-encode drops the metadata: no EXIF, no lens or exposure data, no capture time, no GPS coordinate, no copyright field. For public web images most of that is a benefit — a photographer with a GPS-equipped body should not be publishing coordinates by accident.

The exception is attribution. If the delivery agreement says the files carry a copyright notice, that has to be written into the WebP afterwards with a metadata tool, because nothing in this conversion will put it there.

The output keeps the source name, so DSC_4102.NEF becomes DSC_4102.webp. That is helpful for reconciling a delivery against the originals and unhelpful on a live site, where a descriptive filename is one of the few things a search engine can read about an image.

Renaming is a step for whoever owns the site rather than part of the conversion, but it is worth flagging in the handover. A delivered set of DSC_ filenames tends to go online exactly as delivered.

Drop the whole selection and take the finished set as a ZIP. Each file extracts and encodes separately with its own progress, and because the work runs on your machine there is no queue and no per-file cost — a hundred frames is a matter of minutes rather than a plan upgrade.

Input files are accepted up to 100 MB on the free tier, comfortably above even an uncompressed D850 NEF at around 90 MB. WebP itself tops out at 16,383 pixels on a side, which no Nikon body approaches unless you have stitched a panorama first.

The conversion is JavaScript and a WebAssembly encoder running in your browser. The NEF files stay on your disk and the WebP files are written on your disk. Nothing is transmitted, and you can confirm that in the network tab rather than taking it on trust.

For work under embargo, under a client agreement, or simply not yet announced, that is the difference between a conversion tool and a disclosure. It also means the job runs at full speed on a bad hotel connection.