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Techniques: The Zone System and Exposing for Detail (Part 1)

Ansel Adams - National ArchivesIn the last Blog, I talked about Ansel Adams and his contributions to photography. Over the next two weeks I’m going to be expanding on one of those contributions.

The Zone System (and exposing for it)

The zone system is the way he ensured that he could correctly develop the photo he had envisioned in his head when the shutter was pressed. by planning out the whole process and leaving room for correction of details, highlights and shadows latter in the lab. This would help him to latter dodge and burn images in the lab without loosing the details in his photos. In his words “Expose for shadow, develop for the highlights.”

This rule is important in film photography as when you are later developing a photograph, you will find that with any type of film, black and white, colour negative you will loose detail in the image when shadows are under exposed. However, you will not lose as much when overexposing film. This is because when scanning or enlarging film, an over exposed film can be exposed or scanned for longer to find the detail lost in an over exposed highlight, whereas for an under exposed shadow you often cannot expose it for shorter periods to gain that detail which has been lost.

Now colour positive film or slide film Is the opposite because opposite nature of this film, you will need to under expose or expose for the highlights to the keep detail.

Digital photography is the same as slide film in this respect, as when a photograph is overexposed there is no detail to recover as the data is simply not there. As to why this is though, when you take a digital image, the sensor in the camera is exposed to light for the time that the shutter is open. Each individual spot on the sensor then records the amount of light it receives during this time, filling up like a bucket, starting empty (true black) then filling until its full (true white) however once it is full the bucket can’t take any more and so wont record anymore. Because of this there is a maximum amount of light the sensor can take before it just sees white, but, until it is there will be a variance between the pixels around it, which we can use to extract more detail.

So to ensure that you do not lose detail in you photos give yourself room to play with in a lab or in photoshop (or other program). When using slide film or digital cameras, expose for the highlights (p.s. this doesn’t mean the sun).

Now tune in next week for part 2 of this blog where we will dive into the zone system and using it and how this applies to photography and working all the way through to the final print.

(P.S. If you find this blog interesting and are keen on learning more about the techniques and thought processes of professional photographers but want to learn in a more hands on environment, PhotoCo offers courses for what ever level you are be it in a group or a one on one. Have a look here to find out more).