DIGITAL PHOTOGRAPHY #101: ISO CALIBRATION
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)
This section is an addendum to ISO Sensitivity and a prologue to the upcoming EXPOSURE: LIGHT MANIPULATION section.
As outlined in ISO Sensitivity, the ISO is the trickiest variable for Exposure to manipulate. The higher the ISO setting, the more flexibility in your Aperture and Shutter Speed settings (explained in EXPOSURE: LIGHT MANIPULATION), but the worse the signal to noise ratio causing degradation of the image.
In this calibration test, we will use the slowest ISO setting as our standard of quality that we are testing against in each succedent ISO level. This will reveal the efficiency of each ISO level on your DSLR camera.
Once you've run this test on your camera(s), you will know exactly how far you can push each ISO level with the expected results.
What we are accomplishing here is a tangible display of image quality through empirical observation.
There are different criteria for ISO level image comparisons. Here, we are using the consistency of a smooth blue sky that can reveal and amplify different types of digital imperfections. Likewise, the even distribution of sun light emphasizes the maximum performance potential of each ISO level.
We will cover histograms in the next section, EXPOSURE -Manipulating the Physics of Light (Exposure Evalution).
I will include a histogram in our test to show that blue sky consists of all three colors in equal proportion (RGB). This is a comprehensive test for ISO calibration.
Let's look at the test, then discuss the results.
(Note: I will post this as a HTML link for convenience and also a high-resolution JPG down-load for a better analysis comparison.)
Hold the CNTL key and hit + or - to control the image size when open.
Click for ISO_CALIBRATION: 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 is the high-resolution JPG to download for better enlargement resolution: ISO_CALIBRATION.jpg (Open, then Right Click and Save Image As)
As you can see, the ISO at higher levels in 2nd generation chips are cleaner than slower ISO levels in 1st generation (common sense, but now proven).
To duplicate this test, simply set your focus to manual and focus close to infinity (auto focus can get confused). Then use manual or automatic exposure while changing your ISO one full stop in-between each frame.
As of 2012, the newest generation of digital cameras are entering the 3rd generation.
There is a small debate that 3rd generation cameras have no mechanical mirrors, but those cameras are still well below the performance levels of current DSLR cameras. (Note: On most DSLR cameras it's called video mode, no mirror.)
Call them what you wish, but I consider 36+ mega pixel cameras with spatial imaging as smooth as medium and large frame film, true 3rd generation digital imaging.
It is important that you do your own calibration testing on your camera to know its capabilities. You can also do tests with patterns and textures for comparison.
Higher ISO levels are beneficial when lighting is limited, but likewise, as long as your camera shoots quality pictures at a slow ISO, it will never be any more obsolete than 35 mm film at the same ISO.
Knowing your ISO limitations gives you the best performance from your camera in any situation.
I hope that you will join us in the next section:
EXPOSURE - Manipulating the Physics of Light
Virtual Studio Photography (VSPHO)
Tags: PHOTOGRAPHY , DIGITAL PHOTOGRAPHY , ISO
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