How to scan slides with a camera
To scan slides with a camera, put each slide over an even, high-CRI light and photograph it in RAW with a macro lens, at 1:1 for 35mm on a full-frame sensor. Expose for the highlights: the clearest parts of a slide are the brightest, and once they clip in the capture they are gone. A slide is already a positive, so it needs no inversion, only a crop, levels and colour.
What you need
The basic setup is the one in how to scan film with a camera. For slides, add:
- A holder for mounted slides, or a strip holder for unmounted film. See below.
- A daylight-coloured light with a high CRI. Its colour matters more for slides than for negatives, because the slide is the final colour.
- An air blower and an antistatic brush. On a slide, every speck of dust stays in the picture.
The adapter holds the slide at a fixed distance in front of the lens, so there is no stand to align. If your adapter has no light of its own, put an even, daylight-coloured light behind it.
Mounted and unmounted slides
Mounted slides sit in card, plastic or glass frames. A holder for mounted slides keeps each one in the same place, so you can swap them fast.
- Different mounts hold the film at slightly different heights. Refocus when the type of mount changes.
- The mount covers the edges of the frame a little. Frame the capture with some of the mount showing, and crop later.
- Glass mounts protect the film, but they trap dust and can show Newton rings where the film touches the glass. Clean the outside of the glass before each shot.
Unmounted slides come back from the lab as strips in sleeves, like negatives. Scan them in the same strip holder you use for negatives. You see the whole frame, edge to edge, and there is no mount to cast a shadow.
Slide copy adapters
A slide copy adapter puts a holder at a fixed distance in front of the lens, so there is no stand to align.
- Nikon ES-2. It mounts on the AF-S DX Micro NIKKOR 40mm f/2.8G, the AF-S Micro NIKKOR 60mm f/2.8G ED, the AF Micro-Nikkor 60mm f/2.8D and the NIKKOR Z MC 50mm f/2.8. Nikon says it does not fit its 105mm macro lenses, which focus too far away. The set comes with the FH-4 holder for strips and the FH-5 holder for mounted slides.
- Valoi easy35 v2. It has its own light, and its slide scanning kit adds a holder for 50 × 50 mm mounted slides to the strip holder. Valoi says the slide holder suits plastic and sturdy card mounts from 1.5 to 4 mm thick.
- Negative Supply. It makes mounted slide holders for 35mm, for 6x6 slides from 120, and for 127 and superslides.
If your adapter has no light of its own, put an even light behind it, not a window or the sky, so the colour stays the same from slide to slide.
Expose for the highlights
On a negative, the brightest part of the capture is the clear film base. On a slide, it is the clearest highlight in the picture: a sky, a white wall, a reflection. If those clip, they turn into flat white with no detail, and you cannot get it back.
- Set the camera up: manual mode, RAW, base ISO, f/8.
- Use a flat picture style. The camera draws its histogram from its own preview, not from the RAW data. Nikon suggests its Flat Picture Control for slides, and keeping other in-camera enhancement to a minimum.
- Find the brightest slide on the roll, the one with the most clear highlights.
- Set the shutter speed so the brightest highlight sits just left of the right edge of the RGB histogram, in all three channels. Turn on the highlight warning and make sure nothing inside the picture blinks.
- Keep that exposure for the roll. Give a dark slide more light only if nothing in its picture clips, and make a note of it.
The full method is in exposure, white balance and RAW settings for film scans.
The density range of slides
Slides hold a longer range of densities than negatives. Their deepest shadows let very little light through. When you protect the highlights, those shadows land near the bottom of your camera’s range, where the noise is.
- Base ISO gives you the most range, so do not raise the ISO.
- Expose as far to the right as the highlights allow. Every bit of extra light helps the shadows.
- For a very dense slide, you can shoot two or three exposures and merge them in an app that makes HDR images. Save the merge as a 16-bit TIFF.
The colour of the light
A negative’s colour is set in the conversion. A slide’s colour is already on the film, so the light you scan it with shows directly in the result.
- Use a high-CRI, daylight-coloured light. Lights made for scanning list a CRI of 95 or more, at a daylight colour of about 5000 to 5500 K.
- Set the white balance from the bare light. Nikon suggests this for slides with one strong colour: measure a custom white balance with no slide in the holder. Then keep it for the whole roll.
- Some lights have a slide mode. CineStill recommends the warm setting of its CS-LITE for slides processed in standard E-6 chemistry.
- Turn off the room lights. Light from a lamp or a window reflects off the film and the mount and mixes its colour into the capture.
Old slides may have faded or shifted in colour over the years. That is in the film itself, not in your light. You correct it after the scan.
Dust
Dust blocks light. On a negative, it turns into white specks after conversion. On a slide, there is no conversion, so dust stays as dark specks and hairs.
- Blow both sides of the slide with an air blower before each shot.
- Use an antistatic brush for dust that clings. Do not wipe the film.
- Handle slides by the mount, or unmounted film by its edges, with lint-free gloves if you have them.
- Check the first capture of each session at 100%, so you find dust on the lens or the holder early.
Some flatbed and film scanners remove dust with an infrared channel. A camera cannot do that, so cleaning before the shot matters more. See dust on film scans for prevention and removal.
Common problems
- Blown-out skies or white areas. The capture clipped. Lower the exposure until nothing inside the picture blinks.
- Noisy, blocked shadows. The slide is dense. Expose further right if the highlights allow it, or merge two exposures.
- A cast that changes from slide to slide. Auto white balance, or room light mixing in. Fix the white balance and darken the room. See colour casts in film scans.
- One slide sharp, the next soft. The mount type changed. Refocus.
- Rainbow rings. A glass mount. Remount the slide in a plastic or card mount, or scan it unmounted.