About Films(II):The Structure of Films

Hi guys! It’s scheduled to introduce positive films this week, but before that I would like to replenish some information about the structure of photographic films, and the main difference between negative films and positive films, to make you know better about them.

         Both positive and negative films are composed of three layers of light sensing gelatin (乳膠), which sense the color blue, green, red respectively. Between first and second sensitive layer of is yellow color filter layer, which absorbs all the blue light after getting through the sensitive layer. Thus, there were only green light and red light passing the filter layer. With the same principle, the other two sensitive layers absorb different lights and then the light are absorbed by the filter layer.

     

      There are also developer in light sensing latex, which will be the complementary color when the film is processed. This kind of film is called “negative film”. As for positive film, it needs reversal development (反轉顯影) to become the same color of the scenery.

    

       Hope you can have a better understanding of photographic film’s structure. The picture I’d like to share with you today is a Japanese man and a shrine. This was also taken in Japan, after the man had worship a deity. The man’s back gave tranquil atmosphere to the photo, and I couldn’t help thinking he must be a good-looking gentleman!

About Films (I): Negative Films

       Today I’m going to introduce an important part of film photography, films. Without films, there will be no pictures. (Well…it’s not informational at all.) There are many kinds of films, and in this and next post I will tell you the two main categories, negative films and positive films respectively. And in next post I will tell the difference between the two.

   

Negative Films

Negative films is the most commonly used kind of film, as we’ve seen in daily lives. Not only it is cheaper than others but many other reasons make it so widespread. First of all, its tolerance is higher than other kinds of films ( e.g. positive films), so it could be post-producted (後製) in the darkroom if you didn’t let the right amount of light onto the film. Secondly, it’s easy to process and the cost of the processing is inexpensive. Thirdly, it can be converted onto the graph at a lower price, makes it more easily for spreading. As a result, negative films are widely used due to its convenience and price.

At the end of the post, I want to show you a picture taken in 21^st Kanazawa Art Museum, Japan. It was a girl by the famous work, the swimming pool, and she was pulled by her parent while she was about to get into the pool. It was an amazing contrast!

Photographic processing

As a film photography lover, learning how to process films is one of my goals. So I’d like to share some related information to you.

The picture below is the steps of film processing. The process can be divided to three parts, which are exposure process, chemical process and refinement process. There are several steps in each of them. During the first and second process, the film must be prevented from being exposed to the light.

(Ref: wiki)

1.      Exposure

When we are taking a shot, the film in the camera will be exposed to light. It’s important to control the right amount of light, or the pictures may be too bright or too dark.

2.      Developer bath

Photographic developer, a mixture of chemical compounds, transforms the latent image to the visible image. When photographic films are soaked in the developer, the silver ions exposed to light before will be turned into silver. If the bathing time is longer, the image will be darker. Therefore, time needs to be controlled in this step.

        Ag⁺   (light) → Ag

3.      Stop bath

The usage of this step is to stop the developer from working. Instead of using acid in the step, water-washing is allowed.

4.      Fixer bath

Fixer bath is to dissolve the rest of the silver halide on the film. With this step, the image will be stable and won’t be affected by light anymore. We usually use Sodium thiosulfate (硫代硫酸鈉，俗稱海波) for fixer bath.  

5.      Washing

To remove the rest of fixer on the film, the film has to be washed by a large amount of water, usually taking more than five minutes.

6.      Drying

After all the steps above, the film must be dried in dust-free environment. Then you will see the photos taking by yourself!

As always, I will put my picture to this blog every week. The photo was taken at Tamsui MRT station, and the woman in the black cloth was an unexpected character. What was she looking at, and what was she thinking about? With the appearance and the following questions about this woman, the photo gets more interesting!

Here is a video about film processing:

https://www.youtube.com/watch?v=Vu0Ul_wsYO8

Brief history of photographic film

       Hello guys! Let’s talk about a brief history of photographic film today. It originated in England in the early 18th century, and has been through several huge changes.  

1. Calotype (卡羅法):Invented by William Henry Fox Tablet in 1835, the  Calotype process is paper negatives with 
        Silver(I) chloride (AgCl,氯化銀).                                                                                                                                                                                                                                                          

2. Wet Plate Processing (濕版火綿膠攝影法): It’s a less expensive film and its light sensitivity was a lot better.    

                                                                                                (Calotype[1]) 

                                                                                      (Wet Plate Processing[2])

3. Color photographic film: The first color photographic film was invented by German physicist Maxwell in 1861.

4. Flexible photographic roll film: The Kodak company produced a new type of light-sensitive material in 1888. Different from the original film which was a coating on a paper base, the new image-bearing layer was transferred to a hargelatin support. Then the first transparent plastic roll film was devised the next year. From then on, the type of photographic film was confirmed.

    Hope this information will let you guys know more about photographic films. In the end, I would like to post a picture taken in my hometown, Hsinchu, It's the intersection I will pass through everyday. Although it was taken by cellphone, it's still a nice photo:)

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[1]http://www.upagallery.com/blog/2014/7/24/photographys-parallel-histories

[2]http://zhejiang.kaiwind.com/jctp/201407/09/t20140709_1753648.shtml

    photo by Alex Timmermans