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 to the first section on:
The Digital Darkroom – Creative Cropping
Part 1: The Editing Environment
Part 2: Getting a Digital Editor
Part 3: Creative Cropping
Part 1: The Editing Environment
DIGITAL IMAGING ARCHITECTURE is a primer to this section.
Physical Pixels come directly from the camera’s sensor data. In short, when the capacitor’s voltage is analyzed (see ISO Sensitivity), the conversion to data becomes a single Physical Pixel based off of the Physical components of the sensor. Then the values of each Physical Pixel are converted to what I like to call Spatial Pixels. Spatial Pixels compose the image that reflect the actual Spatial Resolution and overall Apparent Image Quality (advanced overview link).
File formats like RAW and TIFF store the physical pixel information which makes the file size quite large. But when edited and compiled for viewing or printing, the information is converted into Spatial Pixels. On digital cameras that offer only JPG output files, the images have already been compiled into Spatial Pixels and the original Physical Pixel data is destroyed.
The Spatial Pixel is calculated from a complex algorithm of averaging other like colored pixels (RGB) on a grid pattern from the same physical region called demosaicing. The most common demosaicing algorithm used on virtually all digital cameras is called Bayer Interpolation (the JPG standard).
The net effectiveness of the Bayer Interpolation algorithm is not 100% efficient and there are variations of performance between camera models. Hence: There needs to be an industry standard for Spatial Pixel efficiency and the Apparent Image Quality for performance comparison.
With each new generation of digital technology, the efficiency of digital imaging is improving.
Part 2:
As this section is on digital image editing, I know some of you have image editors and some don’t. I personally use Photoshop, but if needed, here are a couple of freeware/shareware photo editors you can download.
You will need to copy and paste the URL as I have removed the hyperlink per GroundReport’s guidelines.
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Microsoft Picture It! is easy to use and comprehensive, it comes free with other Microsoft applications. If you don’t already have it, this download is only a 30 day free trial. Likewise, make sure you un-click the free tool bar it wants to install (unless you like that stuff). I believe the newest version is 10, this is version 2. Tip: I found some “open box” on Amazon for $39 (version unknown).
http://english.eazel.com/lv/software/download/kl659357.htm (Again, cut and paste)
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PhotoScape is freeware/shareware, limited in scope, but handy:
http://www.filewin.com/Photoscape/?p=US
It will simply download a file called: installer_photoscape_English.exe
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For GIMP:
http://gofree.com/download/Windows-Software/Graphic-Design/gimp.php?gclid=CPixuurPhrECFeUBQAod7FamDA
GIMP is impressive for Freeware, but a definite learning curve with its functionality.
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Because of the diverse differences in photo editors, I will be describing the functionality of what we want to accomplish, not the actual key strokes of any given editor. However, I will give visual examples. Once you know what you wish to accomplish, there are hundreds of YouTube videos showing key stokes for various editors (Photoshop being most common), but try playing with it first.
Part: 3 Creative Cropping
Creative Cropping allows you the artistic freedom to create a customized image from your original picture. A major advantage to high resolution cameras is the creative cropping it allows. That is to say, it is beneficial to shoot a picture with added space around the subject or the over-all landscape so it can be cropped in The Digital Darkroom.
Professional photographers have always used the fullest benefit of high resolution film to allow for creative cropping.
Here is a quick review of Pixel Resolution for the beginner:
Pixel Resolution is measured in Spatial Pixels per inch (I will simply refer to them as pixels as we now understand that they have been converted from Physical Pixels). In the simplest example, 100 DPI (dots or pixels per inch) means 100 pixels across the horizontal edge times(x) 100 pixels up the vertical edge of a 1×1 square inch image = 10,000 pixels per square inch. Extrapolated to a 4×6 image, 24 square inches times(x) 10,000 pixels = 240,000 pixels for the entire image at 100 DPI.
Note: Previously outlined, DPI (Dots Per Inch) refers to printed resolution. PPI (Pixels Per Inch) refers the actual digital image resolution, the terms are interchangeable in our context.
You can download this previously posted 16×20, 324 DPI poster to experiment with. After you open it, just right mouse click and copy with “save image as” (any name you like):
16×20 MOUNT EVANS POSTER: 324 DPI x 320 square inches = 33.59 mega pixel image (Note: It’s JPG compressed to file size 11 meg.)
This image was Bicubic Interpolation enlarged, explained below.
Here it is as the original from the EXPOSURE section:
Hold the CNTL key and hit + or – to control the image size when open.
Click HERE for high-res PICTURE: 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.
Before we crop, let’s clarify:
As this is a 16×20 image at 324 DPI, it is also an 8×10 at 648 DPI. As 8×10 and 16×20 are the same Aspect Ratio (5:4), I could take this digital negative to a professional printer and make either size. Of course, the 16×20 would print at the 324 DPI resolution, but the 8×10 would automatically be reduced from 648 DPI to the maximum printing resolution of 350 DPI.
You are welcome to crop it any way you like for practice. But first, always make a copy of your original to work on. Always keep the original untouched for future needs.
If your editor allows you to specify the resolution when you crop, you can keep it the same or increase/decrease the resolution with the crop.
If your editor does not offer the resolution setting, you will have to go back after the crop to reset the resolution if needed. (More on resolution enhancement in the next section.)
However, every change in resolution slightly degrades the over-all picture quality, so if you need to do it twice, start over (if you have an undo crop feature, that counts as starting over).
Likewise with JPG files, every time you save and close, then re-open and save again, the image is degraded. So try to do all of your editing in the same session (you can save as often as you like while editing, it is just closing then re-opening and saving again that degrades the image in JPG).
We’re using Picture It Express 10 this time, I cropped this into a 4×6 post card. I cropped it out of the original 16×20 (JPG link above). Picture It does not change the actual pixel count, so the area I cropped in a 3:2 aspect ratio came out to be exactly 3.904×5.858 inches at the original 324 DPI resolution. When it prints at a slightly larger 4×6 image size, the resolution will decrease proportionately to 316 DPI.
Hold the CNTL key and hit + or – to control the image size when open.
4x6EVANS click here: 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.
Now is a good time to bring up Bicubic Interpolation image enlargement. Bicubic Interpolation is another incredibly sophisticated algorithm that is used to increase pixel count resolution for enlargements.
Poster size prints need higher pixel resolution than most digital cameras can provide. A 24×36 (3:2 aspect ratio) poster at 300 DPI would need almost 78 mega pixels. The Leaf Aptus II at 80 mega pixels (at $8,000 for just the image sensor, not a whole camera) could make a 24×36 poster without resolution enhancement. So utilizing digital enlargement works well to supplement image density until more digital cameras have higher pixel resolution someday.
Note: There are other enlargement schemas, but Bicubic Interpolation is the most common.
For me personally, so that I do not need to enlarge more than once if possible for creative cropping, I enlarge all the images that I will be editing while still in a RAW file format. Photoshop allows for this process while in the RAW/NEF editor for the best quality pixel resolution enhancement (NEF is Nikon’s RAW format). (More on RAW next section.)
But even for JPG format, Bicubic digital enlargement is a great way to increase the performance of your digital camera’s images in The Digital Darkroom.
Let’s practice on another high resolution image.
As you recall from the last section (DIGITAL IMAGING ARCHITECTURE), this example was modified in Photoshop for Creative Cropping for a 3:2 aspect ratio to a 5:4 aspect ratio.
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.
This time we will take another image from that same photo shoot and crop it without modifications to the image. Again, the image pixel density was already enhanced before conversion to the JPG format, so we will not need to modify the resolution for our training purpose (Resolution Enhancement, next section).
Here is the high resolution JPG image. After you open it, just right mouse click and copy with “save image as” (any name you like):
This is an 8×12, 375 DPI JPG image = 13.5 mega pixel image (compressed to a 5 meg file in JPG) .
Here are the results of two comparison pixel density formats (below).
Comparison #1:
Hold the CNTL key and hit + or – to control the image size when open.
Click for TRANSFORMERS: 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.
Comparison #2:
Hold the CNTL key and hit + or – to control the image size when open.
Click for 375 TRANSFORMERS: 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.
We already had ample resolution for these samples. But in our next section (Resolution Enhancement) we will take a look at image resolution enhancement algorithms.
Here is a glimpse into the next section:
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If you wish to make prints, my rule of thumb is print at 300 DPI, 240 DPI minimum for good quality. 350 DPI is the maximum resolution that most professional print sites can produce.
You ask: Why not print at 300 DPI or even 350 DPI at all times?
Space and time is the answer. The space to save them on disk and the time it may take to download the images on-line.
Both of these pitfalls have become less important with cheap hard disk space and faster Internet connection speeds. Therefore, make 300 DPI your standard as you will see virtually no difference between 300 and 350 DPI.
Note: If you start making enlargements the size of posters, file size may become a real factor, so you may want to make your minimum 240 DPI.
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See you next time,
Virtual Studio Photography (VSPHO)