Life is a series of moments that leaves us with memories, both splintered and whole.
If you are just joining us, the PRELUDE & SYLLABUS section is the logical starting point for the series.
Welcome to Digital Photography #101
by Virtual Studio Photography (VSPHO)
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Welcome back, we are now experienced with the settings on our Digital Camera to get a proper EXPOSURE.
As mentioned in the PRELUDE & SYLLABUS section, we are entering the final segment of the Technical side of digital photography and also starting the transition into the Creative aspects. Now we need to understand the basic principals of digital imaging beyond Aperture, Shutter Speed, and ISO Sensitivity.
From our previous section on 35mm FILM versus DIGITAL IMAGING, we are now in full control of our digital image utilizing a Photo Editor. There are different nick-names for a Photo Editor, my personal favorite is "The Digital Dark-Room."
We will cover digital editing in The Digital Darkroom in the next section. This section is the primer for digital editing.
Again, for easier future reference, let’s break this into parts:
Part 1: Aspect Ratios
Part 2: Common Digital Camera Sensor Aspect Ratios
Part 3: Pixel Resolution and Spatial/Image Resolution (Image Quality)
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Part 1: Aspect Ratios
The first technical and creative parameter of any image is the Aspect Ratio. When we look at any picture, the first visual impression is the dimension of the image. The most common picture dimension is that of the snap-shot. 35mm film has a dimension of 24mm tall by 36mm wide (when holding the camera in a normal horizontal position). For many decades we have seen prints that reflect this exact Aspect Ratio (Example: 4×6 prints).
A brief summary, if we reduce 24mm x 36mm to their least/lowest common denominator, (2×12 = 24mm and 3×12 = 36mm) we have an Aspect Ratio of 3:2. This produces the common 4×6 print.
The format 3:2 is simply a 1.5 aspect ratio (3 divided by 2). It is a Run over Rise ratio, differentiating it from Rise over Run in math that establishes the slope of a line.
Aspect Ratios are in the format such as 3:2 (which also equals 2:3). Both are interchangeable to reflect image orientation. The first number refers to the Horizontal run in Width in relation to the second number, the Vertical rise in Height in a two dimensional image.
Some photo editors (like Microsoft Picture It) use 3:2 (6×4) to reflect a Landscape orientation (wider than high) and 2:3 (4×6) to reflect a Portrait orientation (higher than wide). However, with Landscape or Portrait orientation, we simply refer to a 4×6 print as a 4×6 and an 8×10 print as an 8×10…
Here are the Aspect Ratios that are utilized in Photography (more sizes available but seldom used):
1:1 most commonly associated with a 6×6 inch prints.
3:2 makes 2×3 (wallet size), 4×6, 8×12, 10×15, 12×18, 16×24, 20×30 or 24×36 inch prints.
4:3 makes 6×8, 9×12, 12×16, 15×20, 18×24, 21×28 or 24×32 inch prints.
5:4 makes 8×10, 16×20 or 24×30 inch prints.
6:5 makes 10×12 or 20×24 inch prints.
7:5 makes 5×7 or 10×14 inch prints.
14:11 makes 11×14 and 22×28 inch prints.
We will cover creative cropping to different Aspect Ratios in the next section on The Digital Dark Room. But here is an example of a 3:2 (actually a 2:3 portrait orientation) Aspect Ratio that was Photoshop modified to allow cropping into a 5:4 Aspect Ratio for a 16×20 enlargement.
Hold the CNTL key and hit + or – to control the image size when open.
Click for ASPECT_RATIO: Then hit the "back arrow" at top left of page to return. If the picture comes up BLACK, just hit the screen REFRESH icon. Round Arrow upper left of screen.
Trivia: Traditional analog television had an aspect ratio of 4:3 (12:9 expanded for comparison).
In comparison, HDTV has an aspect ratio of 16:9.
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Part 2: Common Digital Camera Sensor Aspect Ratios
When we take a picture with any camera, the camera’s sensor dimensions determine the initial aspect ratio. As mentioned, 35mm film has an exact aspect ratio of 3:2. Digital cameras have two primary Aspect Ratios.
DSLR cameras stay very close to the original 3:2 aspect ratio. The sensors vary in actual size depending on the brand, model and sensor type (CMOS or CCD), but the aspect ratio will be close to 3:2, but not necessarily exact. (We will cover cropping for perfection to correct this in the next section).
Most compact digital cameras have a sensor chip with a 4:3 aspect ratio. These have both a smaller physical size and shoot a smaller image (pixel resolution) for manufacturing cost reduction. Newer models always have an increase in pixel density (resolution) that helps offset this limitation, but they still have less overall resolution and image quality compared to their more expensive relative, the DSLR. This is common sense, but for the price and convenience, most compact digital cameras still shoot amazing images.
Note: As you can see from the list above, the 3:2 and 4:3 aspect ratio sensor chips also have the most variety of print sizes to choose from with little or no cropping necessary. (Creative Cropping next section.)
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Part 3: Pixel Resolution and Spatial/Image Resolution (Image Quality)
We’ve previously mentioned Pixel Resolution (Pixel count), Bit Depth and Spatial/Image Resolution. Now let’s define how they apply to the quality of our images.
We also outlined some of the basics of Digital Imaging Architecture in ISO Sensitivity. Tiny capacitors store electrical current converted from light. The accuracy of the electrical conversion that is delineated by the computer code (algorithms) into data, determines the quality of our image.
The Pixel Resolution (Pixel count) is only part of the equation. If the Pixel Resolution is too low for the image size, it gets digitally grainy even worse than film. As previously outlined, 240 dots per inch is the industry standard for magazine images.
Professional print sites print up to 350 DPI. A good rule of thumb for printing your photos at any size is 300 DPI (more on the subject in the next section).
So here is a 4×6 image sized at both 240 DPI and 30 DPI.
As you use "CNTL +" to enlarge the image size, the difference will become even more dramatic.
DPI TEST To reduce the image size use "CNTL - ." Hit the "back arrow" at top left of page to return. If the picture comes up BLACK, just hit the screen REFRESH icon. Round Arrow upper left of screen.
Next is the Bit Depth.
As we have previously outlined, JPG is the current industry standard for printed pictures. JPG has an 8 bit color depth = 256 gradient levels in all three color channels (RGB). Top DSLR cameras have bit depths from 12 to 16. The average compact digital camera has a bit depth of 8.
Here is a high pixel resolution (300 DPI) image in both a bit depth of 8 and 4. An 8 bit color depth has 256 gradient levels per color channel (RGB). A 4 bit color depth has only 16 gradient levels per color channel (RGB).
Hold the CNTL key and hit + or – to control the image size when open.
Click for BIT_DEPTH: Then hit the "back arrow" at top left of page to return. If the picture comes up BLACK, just hit the screen REFRESH icon. Round Arrow upper left of screen.
This demonstrates the term " Posterization." When there is not enough information to distinguish different levels of intensity in color, the image colors bleed together and lose their Spatial/Image Resolution. (Although the Pixel Resolution remains the same.)
We forced this Posterization with a reduced bit depth of 4. But the same principal applies (to a lesser extent) to even high end digital sensors when high bit depths like 12, 14 and 16 try to differentiate minute voltage levels in capacitors when shot at high ISO speeds. (see water glass example in ISO Sensitivity)
Another important aspect of our image quality (the Spatial/Image Resolution) is the contrast and focus between each pixel. As we outlined previously, Digital technology is already exceeding the limitations of 35mm film.
35mm film needs no definition for resolution as it is inherent with the film speed, nor can you vary the resolution. Hence, with film, if you need higher resolution past ISO 25 (very slow film), you have to go to a larger format camera (much more expensive and harder for developing and prints).
Therefore, the newest consumer level DSLR camera at over 36 mega pixels exceeds 35mm ISO 100 film on every level (performance, long term costs, convenience and versatility in The Digital Dark Room).
As outlined above, Pixel Resolution is only part of the equation. For low end to middle range digital cameras, pixel resolution does not necessarily mean the best image quality. With DSLR cameras, you pretty much can’t go wrong, especially with prices coming down in the past few years.
Less expensive digital sensors do not have the ability to delineate the finer differences of the visible light spectrum.
Between inferior digital sensors and lenses, images with the same high Pixel Resolution can have a much different Spatial/Image Resolution.
But as technology develops exponentially fast, we will see steady improvements in digital imaging at all levels.
With that, it is important to note that the lenses we use on our digital camera are just as important as the sensor chips. Without a clear focus of light, our sensors can not parallel precise image reproduction.
In this next example, the image on the right is an over-exaggeration of an inferior sensor coupled with an inferior lens. But it is a great example of an inferior Spatial/Image Resolution. (Kind of like an old driver’s license picture.)
Hold the CNTL key and hit + or – to control the image size when open.
Click for SPATIAL_RESOLUTION: Then hit the "back arrow" at top left of page to return. If the picture comes up BLACK, just hit the screen REFRESH icon. Round Arrow upper left of screen.
I’ll leave you with my own definition of Spatial Resolution:
"Spatial Resolution is the minute detail of subtle differences in light that produce intrinsic detail."
So I think of Spatial Resolution as the Dynamic Range within the Dynamic Range. Dynamic Contrast in the HD monitor industry is more like expanded Dynamic Range. Spatial Resolution deals more with the subtleties of realism that can evoke feeling and emotion.
Hold the CNTL key and hit + or – to control the image size when open.
Click for REALISM (digital style): Then hit the "back arrow" at top left of page to return. If the picture comes up BLACK, just hit the screen REFRESH icon. Round Arrow upper left of screen.
I hope you’ll join us in the next section as we continue to develop our creative skills in digital imaging with Creative Cropping in "The Digital Darkroom."
Virtual Studio Photography (VSPHO)