The original black-and-white image of Czeslawa Kwoka is that of a young Polish girl, one of the hundreds of thousands of children murdered by the Nazi regime. The record of her arrival at the Auschwitz extermination camp in December 1942 shows a frightened-looking girl with coarse-cut hair and a wounded lip, an injury caused by a guard just moments before being photographed.

The image, originally in black and white, is even more striking when viewed in color, thanks to the work of Brazilian artist Marina Amaral, who digitally colors old photographs with remarkable precision and realistic tones. For the artist, the colorization of Kwoka's photo made the girl appear to be a real human being: "A 14-year-old girl, not just a statistic."

Read more: Colorized photo of girl at Auschwitz strikes chord on social media

'People understood the message'

In recent weeks the image has gone viral on social media after having been shared by the Auschwitz-Birkenau Museum in Poland, which once housed the largest of the Nazi extermination camps.

In an interview with DW Brazil, Amaral says she chose Kwoka's photo to color because she was impacted by the expression on the girl's face. "When I first saw her, I could not forget her. I wanted to humanize her and tell her story," she recalls.

But the huge response was a surprise, says the artist, who has since gained prominence in the international press. "It was completely surprising, I received messages from all over the world. I was very happy when I realized that people understood the message and felt the same way I did."

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Painstaking process

Amaral began to casually use Photoshop as a child. Years later, in 2015, when she came across a collection of World War II color photos in an online history forum, she decided to try the technique. "I started practicing without having any idea which way to go, and I didn't stop. Since then, I have been able to develop my own techniques, and eventually, unexpectedly, it has become my career," says the self-taught artist.

The image coloring process is done entirely in Photoshop, manually, and can last for weeks. "While a simple portrait can be done in 40 minutes, a more complex and detailed photo can take up to 40 days," she explains. Some 98 percent of the photos she uses are in the public domain, made available by government agencies, libraries and museums. The rest of the photographs are offered by collectors, historians or institutions.

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Variety of images

When choosing the images, the artist also takes into account the visual impact that the photo will have, but the historical context of photography is the determining factor. "Unfortunately I'm a bit limited, because there are themes I'd love to explore, but I just cannot find the photos under the conditions I need, in the public domain and in high resolution."

According to Amaral, this is why her portfolio has very few records related to her homeland. "I would love to do a series about Brazil's participation in World War II, for example. I received very interesting material recently, and I'm talking to some people to try to bring this idea to life," she says.

Amaral's work mainly involves images from the first half of the last century, when color photography was still taking its first steps. In addition to historical events such as the Holocaust, she also colors portraits of personalities such as Martin Luther King Jr., former US President Abraham Lincoln and German physicist Albert Einstein.

One of her most recent works was in Germany: a series of old photos depicting 10 important moments in the history of German football. The black-and-white images were first shown in color at an exhibition at the German Football Museum in Dortmund.

Read more: Auschwitz museum plans traveling exhibition

Colorizing is 'an obsession'

The colorization of black and white photos is nothing new. Today, there are hundreds of tutorials on the internet, forums with tens of thousands of subscribers and even an algorithm that does the work by itself. But for Amaral, "coloring old images is not just a hobby, it's an obsession." US tech magazine Wired concurred, calling the Brazilian the "master of colorization."

Before beginning the colorizing work, she conducts a rigorous research process to render the colors as close to reality as possible. For this, she also counts on the help of historians and specialists, who analyze the most relevant details of the photo – from the clothes to the decorative elements.

Read more: How Germany deals with Nazi propaganda films today

"Research is the most important part of the process because these photographs are historical documents, and I have to respect as many features as possible," explains the artist. There are cases, such as certain locations, military uniforms and medals, where it is possible to reproduce the exact colors by utilizing visual descriptions made in periodicals, documents or books.

The coloring of the photo of Czeslawa Kwoka, for example, was based on two details: the color of the uniforms used by the prisoners in Auschwitz and the color of the triangle stuck to the garment. "These triangles could be of various colors, because they were used to identify each prisoner according to the group to which he belonged," says Amaral. In the Polish teenager's case, the triangle was red, indicating that she was a political prisoner, and carried the letter P, for Polish.

'Most important photo I've ever taken'

Kwoka, who was not Jewish, was deported from the Zamosc region of southeastern Poland to Auschwitz. She arrived in the Nazi camp on December 13, 1942 along with 318 other women, including her mother, Katarzyna, who would die two months later. The 14-year-old girl was murdered on March 12, 1943 with a lethal injection into the heart.

"Czeslawa's photo is certainly the most important photo I've ever taken," says Amaral. "When I got the color of her face back, I managed to show the blood on her lower lip, the marks, the fear in her eyes." The man who photographed Kwoka – Auschwitz survivor Wilhelm Brasse – said the girl had been beaten by a guard who was annoyed because she did not speak German. Besides Jews, Christian citizens of Poland were also persecuted by Nazi Germany. It is estimated that the regime was responsible for the deaths of at least 1.9 million non-Jewish Poles during World War II, whether in battles or extermination camps.

Kwoka image led to more

With the impact generated by the photo of Kwoka, the artist had the idea of creating a project entirely aimed at recovering stories and photos related to the Holocaust. The Auschwitz-Birkenau Museum has come on board and will make available its archives and a research group to assist her in the project.

Now Amaral is preparing to launch her first book, "The Color of Time: A New History of the World 1850-1960", which is set to launch in European bookstores in August. The work is a partnership with British writer, historian and TV presenter Dan Jones, and brings together 200 photos she restored that cover world history during the period from 1850 to 1960.

"Dan and I met on Twitter, and shortly afterwards he invited me to create the book," says the artist. The bestselling British writer wrote captions that explain the historical context of each of the images. "Most of these photos have never been seen in color before," says Amaral.

Amaral says that the goal of her work is to bring people closer to the realities of the past. "The fact that we live in a world so filled with visual stimuli creates a deeper connection when we see those color photos," says Amaral. "In that way it is easier to create an empathetic connection with the historical characters, and they no longer seem like fictional characters who only exist in books."