Meeting 4

Batti il ferro finche' e' caldo

Topics: Class Prep #1 (artist examples), toning grayscale, noise reduction, rotating a picture

Brief presentation/discussion of examples of work found by students for the Class Prep assignment.

Files needed from the server:

Simple Toning in Grayscale:

Levels vs. Brightness and Contrast
Open musicians.tif (Exercises 1) for in-class exercise.

Image>Adjustments>Brightness/Contrast vs. Image>Adjustments>Levels.
(Levels is almost always preferred over Brightness/Contrast adjustments -- but there was a change to the control back in CS3 to make the Brightness/Contrast tool more useful. Still, Image>Adjustments>Levels is preferred if only because of the histogram provided in the dialog box.)

NOTE: When toning on a flat LCD screen, the tilt of the screen affects picture tones. In the VisCom Imaging lab, we used to have a tiled screen background image that helps you tilt the screen properly for more accurate toning of pictures. Click here for a web page that explains how to do it. This information was also published as an article in More Mastering Digital Photography, Preston Publications, 2004. It's not a pretty picture, but it will alert you to a mis-calibrated screen which is VERY useful for imaging and publishing creatives.

One thing to watch when toning is that you don't fall into the trap of adjusting the picture tones with multiple iterations of Levels, and clicking OK each time. It's best to obtain optimum picture tones in a single edit of a picture to minimize histogram "combing" and ugly posterization. Posterization effects will be most apparent in the darker tones of a picture.

TIP: Hold the Option key (Alt key on a PC) when you use Levels adjustments to see what parts of the picture get "clipped" when making adjustments to the white slider and the black slider.

Noise Reduction

Noise in pictures is defined as unwanted variations in tone or color at the pixel level. In film photography, it was called "film grain". It becomes more objectionable as exposure decreases - usually because the user has chosen a high exposure ISO settings in the camera. It also affects areas that have dark tones in digital picture more than lighter areas.

All things being equal, digital cameras having sensors with larger effective light collection area per pixel are less likely to produce noise. Of course increasing the area of each pixel sensor reduces the megapixel count on a sensor - a tradeoff. Most small consumer cameras combine a small sensor with a high megapixel count, making them most susceptible to noise.

Noise also increases when making very long exposures in dim light. The culprit is photodiode leakage current and it produces a salt-and-pepper type of noise. Sometimes a technique known as "dark frame subtraction" can help with this type of noise.

More information about noise can be found online. A good overview can be found at Wikipedia.

Gray square, no noise (all pixels the same color)	Gray square, noisy (random variations in pixel colors)

TIP: When scanning prints, textured print surfaces (matte or "pearl" surfaces, or fake canvas textures, etc.) often produce speckles and other unwanted artifacts in the picture. The cause is scanner light reflecting from the small "facets" that make up the texture of the paper. These artifacts are a form of noise. If you have a choice, choose a glossy print surface to achieve the smoothest scan.

The old way to reduce noise in a photo or scan was Filter> Noise>Despeckle. Back in 2005, Photoshop CS2 introduced a new Reduce Noise filter. (Filter>Noise>Reduce Noise...) It was much more sophisticated than the older Despeckle filter, and gave the user greater control over noise reduction.

Choose Filter>Noise>Reduce Noise on the darker parts of the musicians.tif file. Be sure to magnify a part of the picture to examine by clicking the little "+" sign at the bottom of the filter's preview.

To maximize the noise reduction, increase Strength and decrease Preserve Details in the dialog box. Use a modest amount of Sharpen Details to recover some sharpness lost when noise is reduced.

TIP: The last-used filter will be inserted at the top of the Filter menu list. If chosen, it will apply the filter again with the last-used settings. If you want to use different settings, do not choose it. Instead, navigate to the original location of the filter and choose it there to be able to adjust settings.

Reducing Visible JPEG Artifacts

The Reduce Noise filter can also reduce jpeg artifacts in pictures...

Open venezia hit hard.jpg from Exercises 3.

Zoom in on the face to see blocky aggregates of pixels. These are jpeg artifacts from a #2 quality jpeg compression. Remember that saving as a jpeg actually changes a picture's information with the amount of change determined by the user. Because I chose a very low quality setting, the picture shows serious degradation.

Open the Reduce Noise filter and experiment with Remove JPEG Artifact check box in addition to the rest of the controls.

Rotating a picture

Method #1:  Select>All (or type Command-A), then choose either Image>Image Rotation. This is by the numbers in degrees.

Method #2:  Select>All, choose Edit>Transform>Rotate. This method is visual, but some of the picture will be cropped away. (Helpful Tip: drag non-printing guidelines from rulers if they are visible to ease the task of alignment for either horizontal or vertical lines. To make rulers visible, choose View>Rulers or type a Command-R).

Rotate View Tool: CS4 introduced a new Rotate View Tool which rotates the view of the picture ONLY, but does not alter the picture itself. In other words, it doesn't change the rotation of the picture when printed. In CS6, it's found nested with the grabber hand tool.

It is meant to aid illustrators working with a tablet creating sketches onscreen, working in a way as if they rotated their art paper on the desk when working. For a short online video on how this feature is meant to be used, go to:
http://www.vimeo.com/2218899

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Technical Exercises 1:

Place files in the Turn-in_01 folder  - Due by Friday January 27 at midnight

For Technical Credit: 1) Fix flaws in fade left.tif using the rubber stamp tool. Do not remove the lettering - just the squiggles. Submit this as a TIF file. 2) Retouch and tone musicians.tif in Exercises 1 (tone, remove the lamp on the wall, crop). Submit this as a JPG file. Naming Your Assignment Files: When submitting files, be sure your LAST name is the first part of the filename so you get can get credit for your work. Continue this practice throughout the quarter. If you have a very common last name, please add your first initial to the end of your last name. -- i.e. "smithk_musicians.tif" or "jonesw_musicians.tif". Don't submit your pictures together in folders! Let me repeat that....DO NOT put your files in a folder for submission. It wreaks havoc with the Macintosh server's permissions for files within a folder you make and I may not be able to manage the files within the folder. Also, do NOT do a "Save" or a "Save As" from Photoshop directly into the turn-in folder. The file name only gets placed onto the server, but the contents (picture) amy be missing - it's an empty,  zero k file without any data. Save to your desktop first, then drag-copy the file to the server.               Retouch out the squiggles found in the original, but leave the word "Pizzaz!"   Tone, crop, and rubber-stamp out the lamp on the wall behind the musicians.

How to submit files to a "drop box" folder...