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How to scan slide film at home using a digital camera

Updated: Feb 13

Positives, positive film, slides or, in some cases, “dias” (from diapositive) are finished images meant for viewing by projecting light through them. Unlike negatives, no further processing is necessary unless the user wants to. Therefore, the goal of digitising slides should be to reproduce what you would see when projecting the slide through a traditional slide project for mounted slides. In this article we will give you simple steps and details to follow for a reasonable starting point, however, for a number of reasons getting a perfect reproduction is unrealistic for the average user. Our goal is to get close to the original without excessive use of technical software or equipment.



Scanning slides is very different from scanning negatives. While negatives are made to compress all the information and nuance from the real world into a wide exposure curve with low density made to be scanned or printed for final interpretation and presentation, slides are made to take a slice of the world and present it with punchy contrast resulting in high density of shadows. What this means, is that the equipment digitising (camera or scanner) has a much easier job capturing the whole spectrum of light recorded on the negative as the difference between lightest and darkest is smaller. The slides on the other hand are much harder to record the full information from as a result of the large difference between light and dark, meaning getting your in-camera exposure is more important.


Looking at the sample images below, you'll see what we mean by slides holding much more density in the shadows. The shot was taken with a silhouetted figure in front of the sun. Ordinarily, you'd expect a solid shape with little to no detail in the shadows. On color negative film, you wouldn't be able to retrieve any information. However, in this case, pulling up the shadows reveals a significant amount of detail.


You must do this carefully to avoid overexposing the blacks and washing them out. Strive to keep your blacks black, but know that detail is retrievable in the shadows. On positive film, the highlights are very sensitive to becoming overexposed, which is why we meter for the highlights in camera when making the shots in the first place. With color negative film, the approach is the opposite. Many suggest that it's better to overexpose than underexpose. This is because reducing exposure or highlights on colour negative film scan can reveal a wealth of information and detail that previously seemed overexposed.





The Setup

To digitise slides, the following equipment is required:


  • Digital camera (recommended: 12MP or higher): For scanning slides we generally recommend a newer camera as these have better noise performance than older models. Models before 2015 might struggle with the high density of slide film

  • Macro lens (must focus close enough to cover the sensor with the frame, such as 1:1 magnification for scanning 35mm film with a full-frame sensor)

  • High quality light source with a CRI rating of at least 95: It should be either daylight balanced (5200k) or tungsten balanced (3200K). A flash or strobe setup is also a suitable light source. We are not that concerned about the white balance rating of the light because the RAW file of our cameras allow for enough flexibility to adjust that later.

  • Film holder for your slides: Many people keep slides mounted in frames, for which you need a special holder. You can find the options for VALOI  here for 360 system and easy35 line-up here: Some people also keep their slides in uncut rolls or cut strips, for this you just need the standard holder for your format.

  • Lightroom or Capture One, or free alternative: Here we will provide you with instructions related to Lightroom, but they should be transferable to most other software

We will assume that you are familiar with your scanning setup. If you are not, you should watch our video demonstrations on using the VALOI easy35 system and the VALOI 360 system . You can find general pointers on scanning film with a digital camera here.

You can find instructions on how to use the VALOI easy35 Slide Holder here and the VALOI 360 Slide Holder here.


The Scan


White balance capture

In this step we will take a blank picture of the light source with average grey exposure to use for white balance reading later. You can use Aperture priority mode on your camera and set the exposure to +/-0 exposure compensation, or, in manual mode, set your aperture at scanning aperture and change your shutter speed until the exposure meter reads +/- 0.

If your light source has adjustable white balance, ensure it is set to the white balance you want to use for scanning:


  • For the VALOI easy35, we recommend the warmest setting as this is closer to the light used on traditional slide projectors. The difference in result is small but noticeable in our testing, showing more true colours throughout the shadows into the highlights.

  • For the Cinestill CS-LITE, we recommend using the “Warm - Slide” setting found on the switch as this is closer to the light used on traditional slide projectors. The difference in result is small but noticeable in our testing, showing more true colours throughout the shadows into the highlights.

  • If you have another light source, make sure you get a consistent setting from session to session.

Ensure your camera is set to RAW mode. The in-camera white balance does not matter.

Once you have set up your light source and camera, capture the blank light source, ensuring that the resulting image is not blown out but closer to middle grey.

We will get back to using this picture in the post processing section.


Scanning Exposure

Reminder: When we scan film, the only exposure change we make is using the shutter speed adjustment. ISO should be kept at the base ISO of the camera and aperture should be adjusted to the ideal aperture of the lens. See more here.


Exposure and Slides

Exposure is one the most important and challenging points of digitising generally, but even more so on digitising slides. This is because slide film is much more dense than negative film, and is therefore more demanding on the sensor. With the wrong exposure your highlights might “blow out” (become completely white with not retained information) or you might end up with too little shadow information, giving you muddy or noisy shadows. The following examples will clarify aspects of exposure and contrast. When whites or lights are excessively bright due to overexposure from the camera or scan, what we refer to as “blown out”, details can be lost, as in the image on the left. Conversely, underexposure can result in an effect called "blocked up," which produces darker images and a loss of detail in the shadow areas.



When you or your camera's metering system attempt to compensate for underexposure, this is achieved by decreasing shutter speed, increasing brightness and exposure, and even elevating shadows (in post). However, when these adjustments are overdone to reveal detail or when underexposure is extreme, it results in muddy shadows. These shadows appear very flat, lack punchiness and are generally disappointing. The image on the right presents a balanced interpretation between shadow and light detail. Notice the extreme contrast, due to the limited dynamic range in slide film, the photographer needs to decide what is most significant and expose accordingly.



There are two approaches to exposure: Manual exposure and aperture priority exposure.


Consistent Manual Exposure

With the camera set to “M” or “Manual”, with this method you control all the three parameters (ISO, Aperture, Shutter speed) manually to achieve the correct result. Here we also assume that you will set it you set the exposure once at the start of the roll and capture the whole roll with those settings. The adjustment here is done using the shutter speed, while the ISO and aperture are left on their ideal settings.


The benefit of this technique is that you guarantee the results come out with consistent black blacks - as in, there will be no muddy areas of black which is common when using automatic metering on under exposed frames. It also ensures that the highlights are not blown out.

The downside of this method is that film that is under exposed will not get any “help” during scanning. In other words, if a frame is under exposed on the film it will remain quite dark on the scan. Generally this is fine as modern digital cameras have a lot of latitude, allowing you to ‘pull’ out shadow detail after the fact. However, you might want to keep an eye on this if you have an older camera.


Consistent manual exposure can be very helpful if you expect your roll to have good and consistent exposure, and particularly if you are using a modern camera with good noise performance. This is our method of choice, as slide film with over exposed blacks looks terrible.

To set the exposure, simply find a nice average frame, preferably with some bright areas, like skies, in it and change the shutter speed until that bright area is not over exposed and the rebate of the film is black. You will find that you can reuse that shutter speed in the future provided the film you use is the same.


Adaptive Exposure with Aperture Priority

With the cameras set to “A” or “AP” (Aperture Priority), you will set the aperture and ISO to the ideal setting, and then the camera will control the shutter speed of the camera based on the light meter reading. Here the shutter speed will change with every new frame as the meter makes judgements. Beyond setting the camera to Aperture Priority, you should also ensure that the metering mode is set to the more advanced metering mode of the camera (often the default). The name depends on the brand, but here are some: Matrix metering, multi-metering, evaluative metering…


Finally, you should decide what exposure compensation to set on your camera. This is a setting that tells the camera to consistently allow more or less light (exposure) to its metering. For example, if at +1 exposure compensation, the camera thinks it should scan at 1/60s, it will actually take the picture at 1/30s (1 stop more light than 1/60). Based on our experimentation, exposure compensation should be between +/-0 and -0.7. The lower exposure can be beneficial because digital cameras “blow out” the highlights easily, but have a much higher tolerance for under exposure, which can usually be recovered in post-processing. The benefit of Aperture Priority is that the settings are automatic and it might help you get more out of under exposed slide film. It also helps even out frames that are of similar decent exposure, but not exactly the same.


The downside of this method is that the camera doesn’t know if your film is under or over exposed ahead of time - it can only measure the amount of light. Since the film can “block up” (shadows with no detail) and “blow out” (highlights with no detail), the camera does in some cases try to pull out information that is not there. This is most common in the shadows, where an under exposed frame will become muddy, without proper blacks. This will then require compensation in post-processing, and can result in highlights blowing out in the scan as the camera tries to compensate for the under exposed slide. In these cases, it is best to use manual metering. Aperture priority can be useful if you have a large set of inconsistent slides or slides from different films, such as in an archive. It can also be useful if you have under exposed slides that really want to draw some information out of, even if the final image won’t look perfect.


Post Processing

The below section will assume that you are just using normal photo editing software. Another alternative to this is using the slide editing modes from FilmLab and SmartConvert.


Colour profile

The colour profiles in editing software are made to handle natural scenes. They are therefore not suitable for scanning slide film which has much steeper contrast curve than the real world or negatives.


For Lightroom, we recommend “Adobe Neutral” with some added saturation or “Adobe Standard” with some negative adjustments of “highlights”. This will get you a relative close result to your slide as seen by your eyes. If you want to dig further into it, using Lightroom, we recommend you find a linear profile for your camera. You can find more information about that on this external site (at the bottom of the page): https://goodlight.us/linear-profiles.html.


For Capture One, there is a built in Linear profile for most cameras and it should be used. This gives you get the best starting point with slides. When importing the images, ensure you apply the correct profile and sync it across all your images to get a good starting point.


White balance application

With the first image you took of your blank light source, use the white balance colour dropper to select the white balance in the middle of this frame. The result should look grey or white, with no obvious colour. Here's an example of a white balance (WB) capture of the easy35 light source on its warmest setting, which is recommended for slide scanning. It should be shot at to +/-0 exposure. The in-camera white balance setting is not significant. The image on the left below shows the out-of-camera scan, while the one on the right displays what it looks like after the White Balance was adjusted using the dropper tool in Lightroom.



Now apply this white balance setting to all your images. For Lightroom, syncing is done as such:


  • While in the Develop module, and ensuring the bottom bar of thumbnails is active:

  • Select all images in the thumbnail bar

  • Click on the blank image where you took the white balance

  • Click “Sync” and uncheck everything but “White balance”

  • Sync with all images

Here you can see the effect of applying the WB from your blank light source to a digitised positive.



Contrast and shadow detail

Slides generally have higher contrast ratios than the real world that cameras are calibrated for. Therefore, despite adding profiles as below, you might want to pull out some shadow detail. Here the exposure of the slide and scan will vary, so setting a fixed amount if impossible. We recommend holding your slide over your light source and matching what you see there by pulling the “Shadows” slider up (brighter). The punchy blacks are one of the reasons slides look so good. So, if you by the end find that your blacks no longer look properly black, compensate by pulling down some black.


Over time you might find that you use the same settings each time. In this case it can be a good idea to make a preset for yourself and just apply that before you do anything else to the files.


Exposure adjustment

As a final step, you should go through your scans and make fine adjustment using the Exposure slider. This is best done while looking at the images, so it might be smart to lay them out on a light table. Generally you will find that washed out colours in the mid-tones can be fixed with adjusting exposure down slightly. Be aware that slide film does not have a lot of latitude, especially for over exposure, therefore some slides have unrecoverable highlights with no information in them. While it doesn’t save information from the scene, it can be beneficial to lower the “white” setting to make them less distracting. Below, you will notice that the white part of the frame has almost no detail. Reducing the highlights significantly improves the glare and washed-out appearance, recovering some detail. However, it doesn't recover the details lost due to overexposure.




Conclusions

Scanning slides is sometimes considered very simple as you don’t have to make any conversions, and if you follow the steps above, in particular the colour profile step, it can be relatively simple. At the end of the day, scanning slides is about matching the original before then editing it to your liking. Despite the common saying that you have to nail your slide in camera, that is not quite true in the modern era of camera scanning. With a camera scan of a slide there is enough latitude to adjust white balance and add or remove contrast.

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