Capture: Camera, Scanner Settings
Setting the camera or scanners color space
Most cameras have a menu setting for color space
1. ProPhoto RGB (Largest Color Gamut)
2. Adobe RGB
3. sRGB (Color gamut matches CRT monitors)
Choose the largest color gamut available for your camera, however
some cameras use sRGB as a pre-set You can determine what color space
is preserved in your photos by looking at your cameras EXIF data, In
Photoshop the menu item is File > File Info... Camera Data 2 You can
also look at the EXIF Meta data in the Adobe Browser or Bridge under
the Meta data Tab.
3 Digital Cameras File Formats
All files on a PC need to have a three letter extension that tells
the computer the nature of the data,whether it is an executable program
(.EXE), or a picture file, for example like:
| pic-01.jpg |
pic-02.tif |
pic-03.raw |
There are many other picture file formats, but digital cameras save picture data in either .raw, .tif or .jpg formats.
The extensions can be written with upper or lower case letters.
Rule #1: Never throw away data Always use the camera or scanners
largest resolution --as measured in pixels, with the least amount of
compression.
Most Digital Cameras save the picture data only in .jpg format.
JPEG (.jpg)
Joint Photographic Experts Group - The name of the committee that designed the standard image compression algorithm.
JPEG (.jpg) is designed for compressing, either full-color or
grey-scale digital images of "natural", real-world scenes, to save
space on the computer and internet transmission time. It is a "lossy"
type of storage because even in its highest quality mode the
compression scheme throws away data.
Some cameras can also save using the .tiff (.tif) format.
TIFF (.tif)
- Tagged Image File Format -
An uncompressed image file format that is lossless and produces no artifacts as is common with other image formats such as JPG
Most higher end cameras (SLR's) can save picture data using a file
format called "RAW" Almost all camera manufacturers have their own
proprietory "raw" format.
RAW (.raw)
- RAW files contain the raw unprocessed data imaged by the camera or
scanners sensor usually at 12 - 14 bits per channel Usually using a
lossless compression routine is applied to the data to reduce filesize
without compromising quality.
Which one do you use? It's Dictated by intended use!
1. RAW if you are a serious photographer or it's a "money" shot, or
you are trying to capture a scene where there is a large dynamic range
The raw data includes data spanning at least 2 f/stops and your choice
of white balance, and more...
For more info about RAW Format, read The following Article: The RAW Truth, by Michael Tapes
2. .TIF if you need to preserve detail.
3. .JPG
If you are shooting for the internet, you only intend to make small
prints up to 8 x 10 or you are going to hand the photo off to a client
WITHOUT PREPROCESSING. Always(Use high, super fine, quality....)
Caveat. Every time a picture is saved in .jpg format, data is lost, in
other words the compression artifacts get worse every time the picture
is saved in Jpeg format...
Sample of JPG Compression Artifacts
Comparison of Compressed jpg and uncompressed Tif File
Note the JPG banding in the clouds
Exposure! It's all about exposure.
Rule #4: Never Throw Away Data
The Light Meter Reading ---Finding Mid Gray.
 |
 |
Real Time Camera Histogram
in Record Mode
|
Recorded Histogram in Display mode |
When your camera does a meter reading, it is trying to determine what is midgray (18% gray) In a photograph,
in the view and place the mid gray in the middle of the dynamic range
of the light falling on the sensor. If you plot horizontal
brightness levels from dark at 0 (black) to bright at 255 (white), and
plot in the vertical the number of pixels at each light level, you
would have a graph that is called an histogram.
"There is no such thing as a bad histogram."
The Vertical Axis
shows the number of pixels
at each level of brightness
The Horizontal axis has a scale of 0 - 255Â (left to right) with
0 = black and 255 = white. As a result, on the histogram, mid
gray would have a value of 128.
Almost all cameras can display the pictures histogram in playback mode, some can show histograms in record mode.
There is no such thing as a good or bad histogram, however, one that
shows most of the pixels in the middle is a better exposure than one
that has the pixels clumped toward the black or white end of the plot.
 |
 |
 |
| A Normal Histogram |
An histogram of an underexposed picture |
An Histogram of an overexposed picture
|
| Just right |
Not enough |
To much |
With a little practice, you will be able to tell if your photo has good exposure values by looking at its histogram.
But, the digital
information we really need to know about a picture when we are "image
processing" is What pixels are white, What pixels are mid gray, and
What pixels are black.
EV - Exposure Value, Exposure Compensation
TIP
Use +/- exposure compensation when the resultant photograph is too bright or too dark.
EV - Exposure Value --- the ability to override the auto exposure system to lighten or darken an image
HOW TO:
USING EXPOSURE COMPENSATION
Look in your camera manual for a section on exposure compensation.
Many cameras let you select a setting from -2 to +2 stops in increments
of 1/3 of a stop. The camera's LCD monitor will display the result of
the changes. If you select a +ve value, the scene will look brighter.
If you select a ve value it will look darker.
ISO (ASA) Light sensitivity of the sensor
Another way of controlling light is to change the sensitity of the image sensor to light.
Most digital cameras have an automatic ISO function and the camera will choose the appropriate ISO setting to set mid-grey.
Some digital cameras allow you to choose 2 or 3 settings say 100 ISO, 200, ISO and 400 ISO
By using more sensitive settings you can set faster shutter speeds and or smaller apertures...
Cameras with lower and higher ISO settings are generally more advanced.
Speed Rating
International
Standards
Organization
|
Gain in light 50 = 0 |
Sensitivity |
Contrast |
Grain (Noise) |
50 ISO
|
|
low
|
low
|
low
|
| 100 1SO |
1 f/stop
|
medium
|
medium
|
medium
|
| 200 ISO |
2 f/stops
|
medium
|
medium
|
medium
|
| 400 ISO |
3 f/stops
|
high
|
high
|
high
|
 800+ ISO
|
4 f/stops
|
very high
|
very high
|
very high
|
When in Doubt about the exposure...Bracket!
When the dynamic range in the scene exceeds the capability of the camera...Bracket
Photoshop has the ability to merge the braketed shots!!!
WHITE BALANCE For proper colour balance the camera needs to know what pixels are Grey, Black and White
White Balance - Refers to adjusting the relative brightness of the red,
green and blue components so that the brightest object in the image
appears white.
AWB - Automatic White Balance. A system for automatically setting the
white balance. A digital camera has to be told what is white in order
to correctly display other colours cast in the same light.
Most digital cameras automatically calculate white balance, however
sometimes these auto systems can be fooled, especially if a subject is
dominated by one colour.
Manual white --- Some cameras allow one to choose typically lit
conditions such as full sunlight, cloudy, fluorescent, and incandescent.
Some digital cameras also allow a manual "white preset" you set the
white balance from a sheet of white paper or a card. Yet, another item
for your camera bag.
Colour Temperature Each type of light or colour temperature can also be represented numerically.
Here are some colour temperatures of typical lighting conditions: Type of light Colour temperature
Incandescent/Tungsten (Light bulb) 2500K - 3500K
Twilight 4000K
Fluorescent 4000K - 4800K
Sunlight 4800K - 5400K
Cloudy daylight 5400K - 6200K
Shade 6200K - 7800K
Calibrating your Monitor and Printer
Or, how do you know that the color you see on the screen is what the camera captured and
why doesn't my printed colors match what I see on my computer screen???
- Simple Calibration (You have to start somewhere)
-
- Photoshop installs a program called Adobe Gamma
- It isn't the best way to calibrate your monitor, but it is better than nothing.
- --- On a Mac the calibration program is part of the OS
- Look in the Utilities Drawer for ColorSync Utility.app
Huey or Spider?
- Better yet Purchase a monitor calibration tool like Huey or Spider and use the manufacturers paper
-
- (Printer Manufactures calibrate their printers for optimum output to their own brand of paper and ink).
- Or, use specialty papers with color profiles for your printer
- Have someone else make your profiles
- Even Better yet Calibrate everything! Do it yourself.
-
- The Monitor, the Camera, the scanner, and the printer
-
- Caveat, this is a expensive and very, very time consuming process
More later on Printing with profiles
Introduction to PhotoShop Image Processing
First steps
Before we can actually do image processing we need do the following:
In PhotoShop or PhotoShop Elements
1. Set Color Management.
Set the following In Photoshop look for the menu item "Edit/Color Settings..." on the Mac the menu is "PhotoShop/Color Settings"
Click on the button that says "Full Color Management"...
 In Photoshop or other programs choose Adobe RGB
the rest we explain in class...
2 Setting the eye dropper sampler
Choose sample sizeÂ
3 by 3 Average
The eye dropper is found in the tool bar. Select it by cvlicking on it.
Then look for the options tool bar. If it is not visible the menu item is
Windows > Options
In the options bar click the check mark and choose 3 x 3 Average 3.
3. Setting Black, Mid-gray and White values for layers and curves
In photoshop ElementsÂ
Look Under the Enhance menu select Adjust Lighting > Levels
In Photoshop CS, CS2, etc
The menu is
Layer > New Adjustment Layer > Levels...
Keyboard shortcut:
on th PC is Control L,
 Mac it's Command L.
To set the black point double click the Black eye dropper
- Change
- R setting to 10
- G setting to 10
- B setting to 10
then click okay To set the White Point
double click the White Eye Dropper
- Change
- R setting to 240
- G setting to 240
- B setting to 240
then click okay To set the Gray Point double click the Grey Eye Dropper
- Change
- R setting to 133
- G setting to 133
- B setting to 133
then click okay
Now click okay in the requester will pop up that asks if you want to "save the new target colors as defaults?"
Click Yes
Now were ready to Image Process.
Rule #4: Do not
assume..that if the picture you are photographing doesn't turn out, you
can fix it in Photoshop, ImageFX or some other
image processing software. You will be sorely disappointed! Remember,
with a digital camera, you don't use film... you can shoot until you
run out of storage memory and you can always delete (heaven
forbid)Â failed pictures.
Always remember this Absolute Rule: Do Not, not ever, Throw Away Data!
- Use contrast and brightness controls carefully and sparingly as
these tools changes whole pixel values... you actually wind up throwing
away information when you save the result. In other words, the data you
changed using contrast and brightness is a one way street...there is no
way to get back to the original data set.
- Use and exaggerate color balance controls: R, G, B, or Hue / Saturation, or CYMK
- These functions control or manipulate data in the colour look up
table, only changing their values not not throwing them away. You can
reset or revert the "color look up data" back to its original state,
even after you have saved the changes.
- Do Not Throw Away Data
- Never change image resolution.
- Yep, you got it, Do Not Throw Away Data.
Level Controls
You can use "Levels" to adjust color tone The test picture was shot in
Guadalajara, Mexico on a dark sunless street, right around sunset,
using a Nikkormat FT2 with a Vivitar f/2.8 28 90mm lens on KodaChrome
64 slide film.
Ugh, it's way dark...The fix is to work with the mid grays. this is
done using the "Levels" function and the sliders under the histogram's
bell curve.
Here's what the controls do in The "Levels" Dialogue box
Don't forget to flatten and save the "enhansed" picture.
For an excellent getting up to speed tutorial on using PhotoShop go here...
http://luminous-landscape.com/tutorials/instant_photoshop.shtml
Here's the details about the curves Dialogue box...
Layers
How it works...
http://www.photoshopcafe.com/tutorials/layers/Layers.htm
A tutorial for fixing Under oand over exposed photos
Overexposed Instructions
