The Practical Zone System, Chris Johnson
Digital and Film Photography. The Zone system was developed to help render an image with the correct exposure value to show both the shadow and highlight areas. Pre visualisation is the key. There are similarities and some differences between film and digital photography.
pp113. Digital camera light meters average the brightness of the reflected light to see an exposure that prints as a middle 18% grey or Zone V.
Cardinal rules for digital photography :-
pp113. Digital camera light meters average the brightness of the reflected light to see an exposure that prints as a middle 18% grey or Zone V.
Cardinal rules for digital photography :-
Always use the lowest ISO possible to avoid digital noise in shadows.
Expose for the highlights and process of the shadows.
The RAW image is like your negative, and if it is not preserved the more detailed information recorded will be lost forever. This state can be revisited unlike a latent film image which is lost when developed. A converted RAW image to a JPG format will be 2-4 times smaller and thus can never make a print as large with the same quality. A RAW file also has the metadata attached.
Optimising high resolution and bit depth will give the best quality results in print. p121
These can be considered as Core Digital Values because it is only possible to establish these qualities when the image is captured. Whilst it is possible to increase resolution with computer software (interpolation), it comes at a cost and results in a noticeable loss of image quality. Capture or scan at resolutions and bit depths based upon the type and ultimate size of your final image and never interpolate unless it can't be avoided. p. 122
Adobe Photoshop's interpolation technology has improved to the point where minor adjustments can be made without noticeably degrading your image. This edition is 2007 - Photoshop has made huge improvements in the last 7 years, but that is no excuse for not taking the capturing the optimum at the time of taking.
The RAW image is like your negative, and if it is not preserved the more detailed information recorded will be lost forever. This state can be revisited unlike a latent film image which is lost when developed. A converted RAW image to a JPG format will be 2-4 times smaller and thus can never make a print as large with the same quality. A RAW file also has the metadata attached.
Optimising high resolution and bit depth will give the best quality results in print. p121
These can be considered as Core Digital Values because it is only possible to establish these qualities when the image is captured. Whilst it is possible to increase resolution with computer software (interpolation), it comes at a cost and results in a noticeable loss of image quality. Capture or scan at resolutions and bit depths based upon the type and ultimate size of your final image and never interpolate unless it can't be avoided. p. 122
Adobe Photoshop's interpolation technology has improved to the point where minor adjustments can be made without noticeably degrading your image. This edition is 2007 - Photoshop has made huge improvements in the last 7 years, but that is no excuse for not taking the capturing the optimum at the time of taking.
Consider the final destination of your image - for web production, smaller file sizes are sufficient, but larger ones are needed for quality and large prints.
Histograms.
In Adobe Photoshop pixel tones are numbered 0 (black) to 255 (white). In a black and white image there is one channel called Grey with up to 256 different levels of tone. (p 129). In Colour images there are 3 channels RGB each having 256 levels of red, green and blue. Up to 16.7 million different colour possibilities (256x256x256)
In a histogram, the quantity of pixels with a given tone e.g. 128 (midpoint on the Zone chart) would be shown by a tall line. If only a few, then a shorter line. This becomes a graph of the number of pixels of a given tone.
The Zone System of Digital Exposure: Exposing for the highlights. p138
As more digital noise or banding appears in the shadows one should expose for the highlights. Using Zone system language, place the important Highlight on Zones V!! or V!!! where they belong, minimising the need to stretch out the image's pixels which cause banding and posterization in the shadow areas. This shows as gapping in the resultant histogram (Levels PS) . The reason the shadow areas show as poor quality is because there are less pixels there. Moving the exposure histogram too far to the right results in loss of highlight detail. One point on the Zone scale represents one stop on the camera.
Do as much image correction as possible during the raw conversion stage before editing your image in Photoshop p 154 Image corrections at this stage are much less damaging than in Photoshop editing.
With the use of changing exposure by up to 1 stop, recovery and Fill Light it is possible to recover a little detail if your image is not too over or under exposed.