Film Scan Using DSLR

Foreword

On the Internet, I have found many articles on the topic of film scanning using DSLR. They suggested very simple or very cumbersome methods, but some issues were not given due attention. In this article, I would like to talk about my considerations in the field of film scanning, a little deeper into the theory, and consider a home-made installation for scanning. In my opinion, I managed to make a fairly simple and inexpensive installation, using which you can get the most information from the film and minimize post-processing.

Why is it necessary?

Scanning the film in the manner described below will allow you to get the maximum information from the image, the ability to adjust exposure, white balance, contrast, etc. When scanning a film in a photo salon, the machine automatically selects contrast, white balance, exposure, often doing it wrong.

Installation

I used the Canon 5d markII as a camera, although you can use any DSLR with interchangeable lenses shooting in RAW. I also needed macro rings with a total length of about 9 cm, an Industar 61 L / Z-MS lens, an M42-EOS adapter, a 49mm filter (any one is suitable), parts of the photoelectric enlarger (you can try another one) and electrical tape.

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First, we will extract the necessary parts from the enlarger. In my case, I used the FED enlarger. We need only a film broaching device. Next, we put on the macro rings and the adapter on the lens. Then we unscrew the filter glass from the light filter, we use only the case. We wrap it on the lens. We insert a macro-ring into the filter housing (threaded forward) and fasten with electrical tape. Then we join the free end of the macro rings with the device for drawing the film from the enlarger. I used electrical tape for sealing, wrapping it in 2 layers at the junction. The length of the macro rings is selected empirically. For cameras with a crop factor of 1.6, you will need fewer rings between the camera and the lens, and more macro rings between the lens and the film. The result is a setup that is worn on the camera just like a lens. In my case, everything is very tight,

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Light source

We will need a light source. It should have a high color temperature, and should have an even spectrum of radiation. Why so? The higher the color temperature of the light source, the more information we can extract from the film in the future and the easier it will be processed. Moreover, there is an interesting feature - for images on film made with artificial “warm” lighting, a very high color temperature of light is not required even when digitizing. The high color temperature of the light source when digitizing is needed for images with a colder white balance, for example, taken in sunlight in the afternoon. This is due to the white balance of the images themselves on the film. So, in order to achieve the desired white balance when processing the obtained images, we need a light source with the highest possible color temperature. Therefore, incandescent lamps (2200-2800K) do not suit us, we need a colder color. You can try turning to fluorescent lamps, there are lamps of color temperature up to 6500K, but there is another problem - they have a very uneven spectrum with large dips. This is not noticeable to the eye, there are cones in the eye responsible for the perception of red, green, and blue. But they perceive the total intensity of each of the 3 colors, without taking into account the unevenness of the spectrum. A fluorescent lamp has only a few sharp peaks in the spectrum, which our imperfect eye perceives as white light. The same process takes place in a digital camera - the intensity of 3 colors is also perceived, and if their intensity is the same, then we get white. But when light is reflected or passes through something, then part of the spectrum is absorbed, and the remaining unabsorbed light is the color. For example, blue paint absorbs light in the blue spectrum less than in others, so it is blue. The absorption spectra are also very uneven. Often the same colors in sunlight and fluorescent light have different shades.

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An example of paints illuminated by sunlight and a fluorescent lamp.

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Elements of the picture in sunlight and fluorescent lamp light. It is

theoretically possible that the paradox is that with white light, white paint will be completely black if their spectra do not match, or for example, green if they match only in the green part of the spectra. That is why it is very important to use an even-spectrum light source. The xenon flash lamp also has a not very even spectrum, but does not have such strong dips as a luminescent one, and has a temperature of about 5500K. A compact disc can be used as the simplest spectroscope; its mirror side not only reflects, but also at a certain angle spreads the light into spectral components.

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As a result, during a long search, a cloudless daytime sky was determined ideal for our case, it has a color temperature of about 12000K and has a fairly even spectrum.

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spectrum of the sky

Another plus is that a scattering filter is not required. Another very good and obvious option is the sun itself, but here you need a matte filter for dispersion, and in color temperature it is significantly inferior to the sky.

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sun spectrum

habrastorage.org/files/5a2/831/8c4/5a28318c44c54b5fb28839d858ba1471.jpg
examples of spectra from the Internet

But unfortunately the weather is not always clear outside the window, and not even always the day. Although film photography is not for those who like to rush. However, there is another option - adjust your monitor to a specific color temperature. for example, to achieve the same 10000K on the monitor is quite possible, but the monitor has quite obvious disadvantages - relatively low brightness, and uneven spectrum, uneven spectrum of the monitor can be seen again using the CD-ROM. For my monitor, I found a spectrum on the Internet.

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As you can see, it is not uniform, but also does not have strong interruptions.

How to adjust the white balance on the monitor? If so, turn on the color temperature mode on the monitor and set the highest, for example, 10000K.

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In Photoshop, create a white background. Next we need a digital camera. I have an alternative Magic Lantern firmware installed, this greatly simplifies the matter. We set the same color temperature as on the monitor in the manual white balance setting mode. We direct the camera to the monitor, so that a white background completely covers the frame field on the camera. I can immediately see the histograms of the channels.

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You can also use Vectorscope. You can immediately see that the red color is higher, to fix this, go to Curves in Photoshop and slightly lower the red curve.

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Now it is clear that the intensity of all channels at 10000K is the same.

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We take a picture, look again at the histograms - all channels are the same.

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Now the monitor corresponds to a source of 10000K. But still the best source of light is a cloudless daytime sky.

Shooting

I will describe the shooting process. We set the manual mode on the digital camera. Be sure to use RAW. ISO is minimally low, for example 100. White balance is not important for us - it is set in Raw post-processing. The aperture on the lens closes f / 8 to increase sharpness. We charge the film with the photosensitive layer to the camera, and the substrate to the light source. The mesh-sensitive layer of the film can be easily identified by slightly scratching the film with a knife. We turn on the Liveview mode, set the shutter speed so that it would not overexposure or darken the image too much (ettr). We use crop mode for focusing. Focus on the grain of the film. Take off. My exposure time when shooting against the sky is 1/2 - 1/20 seconds, and when shooting against the background of the monitor it can reach 10 seconds per frame.

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Treatment

For processing, it is best to use Lightroom, although the same thing can be done with adobe camera raw.
First, crop.

Then, in the camera calibration tab, select camera standart.

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In the Tone Curve tab, invert the RGB curve (you can make a preset).

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Add some contrast there in the RGB curves.

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Set the white balance. The value of Tint most often has to be set between -40 and -25. (If the light source was not at a sufficiently high color temperature, the white balance slider would

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rest against the left edge, and we would not be able to set the balance) Remove some red from the shadows and add some red in the highlights.

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And then we make the final image adjustment.

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Hirez 4388 x 2925
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But for example, the same image with a lower exposure

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as you can see in the overexposure, all the information is saved

Here are some more examples of photos scanned by this method.

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List of useful articles on this topic.


en.wikipedia.org/wiki/%D0%A6%D0%B2%D0%B5%D1%82%D0%BE%D0%B2%D0%B0%D1%8F_%D1%82%D0%B5%D0 % BC% D0% BF% D0% B5% D1% 80% D0% B0% D1% 82% D1% 83% D1% 80% D0% B0
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en.wikipedia.org/wiki/%D0%91%D0%B5%D0%BB%D1%8B%D0%B9_%D1%86%D0%B2% D0% B5% D1% 82
en.wikipedia.org/wiki/%D0%9C%D0%B5%D1%82%D0%B0%D0%BC%D0%B5%D1%80%D0%B8%D1%8F_%28%D1%86 % D0% B2% D0% B5% D1% 82% 29

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