Common problems that are addressed by adjusting the tonal scale are as follows:
1. The image is too hot when the white areas are “blown out”, or there are no image details in the highlights.
2. The image is murky when there is not enough contrast between the darkest black value and the lightest white value.
3. The image displays a colorcast when there is evidence of a hue in areas that should be neutral gray or white.
4. The middle gray area of the image is too dark or too light, which usually corresponds (especially) to the skin tones being too dark or light.
Examine this first photo from 1826 entitledView from the Window at Le Gras, Nicéphore Niépce
Exposure times were a LOT longer in the early days of photography. Silver halide crystals that constrict to create an "exposure" hand't fully been developed. People would have to sit still for very long amounts of time to have a portrait made. This particular photo took 8 hours to expose. It exhibits a very high contrast and limited tonal range.
Migrant Mother, Dorothea Lange, 1936. Silver gelatin print.
This photograph was commissioned by the Farm Security Administration (FSA). Florence Owens Thompson looks towards the future with worry, as her children bury their heads into her shoulders. The FSA was part of The New Deal, a set of programs initiated by Franklin Delano Roosevelt to stimulate and revitalize weak economies from 1933 – 1938. The FSA hired photographers, such as Lange, Walker Evans and Marion Post Wolcott to document America after the Great Depression. Notice how the range of tonal values expresses the details in Florence’s face and the blanket on her lap.
IN CLASS:
Part 1--Downloading images to the computer.
To send the images from the storage device within the camera to the computer, the camera is connected to the computer via a USB cable. Alternatively, a card reader can be used to connect the memory card to the computer and read it like a small hard drive (similar to a jump drive).
If you connect your camera to the computer through the USB cable, then you will use an application to read the images. On a Mac, iPhoto may automatically launch. It will read the images and place them in a folder. Alternatively, you can create folders and drag the files into that folder manually if you prefer. I, personally, like bringing the photos into folders, which I can open in Bridge (then in camera raw) to edit. Then organize based on size. I shoot in raw. You might want to save images into your folder in 300dpi and 72dpi folders for print and for web.
Part 2--Making minor adjustments
Download the following image to your desktop:
1. open the a purple flower by Fred Benenson in Photoshop. Then close the blog and follow along with me.
2. Whenever an image is scanned or captured digitally, the process of digitizing a three dimensional reality into a two dimensional file results in a loss of contrast. Unsharp Mask is a filter that is commonly used to compensate for this loss. Click Filters > Unsharp Mask. This filter looks at edge areas where there is contrast and increases the contrast of those pixels. Be sure that the preview button in the Unsharp Mask dialog box is checked.
The larger the file size, the larger you will set the threshold, radius and amount. With smaller file sizes (anything less than 30 megs) you will probably leave the threshold at 0, the radius lower than 1.0 and adjust the percentage by eye between 20 and 250 percent. You will know when you’ve gone too far, the increased contrast will result in an image that looks pixilated and forced. Applying this filter should produce a minor modification.
If the image needs to be rotated or cropped, you can do that now.
Demo "Cropping tool"
Demo "Image Rotation"
it is a good idea to check the Image Size also (Image>Image Size) to evaluate the resolution settings. Ask yourself, at what size do I plan to print this image? If the resolution is too low (many digital cameras record very large images, but the resolution is set at 72 dpi), be sure to uncheck “Resample Image” before adjusting the resolution to a higher number. You should see that as the value of the resolution (measured in dots per inch) increases, the width and height of the file decreases and the amount of pixel information (in the top boxes, which should be grayed-out) remains the same. If all of this is not happening for you, and you are trying to increase the resolution of the file, something is wrong! Our image has a resolution of 240 dpi, so it is unnecessary to change.
Part 3--Understanding the Histogram
1. Click on Image > Mode > Grayscale to convert the image from RGB color mode to Grayscale. (Click OK through the "Discard Color Information" dialog box.) Save the file as flower_gray.psd.
2. Click Window > Histogram.
The overall graph displays the amount information within the image (y-axis) at the various levels of gray from black (on the left side of the x-axis) to white (the right side of the x-axis). There are 255 levels of gray in any 8-bit image. Consumer scanners and digital cameras capture 8-bit images. There are professional scanners and cameras that capture 16-bit images, yielding more options for adjusting the tonal range; but for the beginning digital media student, we will remain focused on 8-bit images.
Does the histogram start and end at the beginning (dark values) and end (light values) of the x-axis? This would mean that there actually exists image information in the darkest shadow areas and the lightest highlight areas. If the graph seems to end before the edges of the box containing the histogram, the graph is “clipped” and there is no information at one (or both) end(s) of the spectrum. There is probably a noticeable lack of contrast in the image if the graph is clipped.
Where on the x-axis of the graph is most of the image information stored? In other words, where are the spikes in the graph? This should make sense in terms of how dark or light the overall image appears.
Does the histogram have any gaps where information does not exist? This means that there is no image information in areas where gray values between black and white are expected. This is usually a result of “over-tweaking” an image with tonal adjustments, as opposed to something that will be noticeable from a scan or digital camera capture. Sometimes this is a reasonable result of increasing contrast in an image, especially when certain areas are particularly hot (bright or blown out highlights).
Adjusting the histogram with the use of Levels or Curves
Click Image > Adjustments > Levels, which is used to control tonal adjustments specifically in the shadow and highlight areas, and a histogram dialogue box will appear.
Tonal manipulations occur as a result of adjusting the numbers associated with each slider. If the objective is to make the image look abstract through high contrast, push the sliders towards each other. If the objective is to make the image seem true to life, the sliders should be used carefully. Adjust the sliders to your taste and click OK. Adjusting with Curves-Click Image > Adjustments > Curves. Once again, the histogram is presented in the Curves dialog box. Curves, like Levels, can be used to adjust the tonal scale within the image.djust each of the red, green, and blue graphs so that there is image information where the deepest shadows and lightest highlights appear. To do this, start by using the pull-down Channel menu from within the Curves dialog box to select “Red” (CMD+1). Use the input sliders on the left and right sides to move the edges of the endpoints of the line graph to the point where image information exists. Use the pull-down Channel menu to select “Green”Use the pull-down Channel menu to select “Blue”, and adjust. Click OK. Adjusting the Curves (or Levels, either palette could have been used for this last exercise) manually for each color channel produces a better result than simply doing this one time for the composite RGB channel.
Targeting Saturation Levels
Click Image > Adjustments > Hue/Saturation. Use the pull-down palette on the word, "Master," to work specifically on the magenta areas of the image.Use the Saturation and Lightness sliders to modify the image.
Working in Selective color. Image/adjustments/selective color.
Use the Saturation and Lightness sliders to modify the image.
Homework- create a surreal image (at least 3 images authored by you--either through scanning or photography). Your final project should be (11x17) (300dpi) -- either landscape or portrait.
Targeting Saturation Levels
Click Image > Adjustments > Hue/Saturation. Use the pull-down palette on the word, "Master," to work specifically on the magenta areas of the image.Use the Saturation and Lightness sliders to modify the image.
Working in Selective color. Image/adjustments/selective color.
Use the Saturation and Lightness sliders to modify the image.
SURREALIST COLLAGE!!!
IN CLASS ASSIGNMENT:
Research an artist that works in Surrealism. This should be an artist that will inspire the project you are creating in some way. Then, write a short word document (no more than one page) double spaced/12pt. font review discussing their work. Download several images of their work. Include this research on your blog and add to the research you will be turning in. You may use a contemporary or historical Surrealist artist. Create several quick sketches in class that we can discuss before you go and make the work.
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