T354 - Week 3 - Spring 2007

Notes/Announcements:

• Put your homework into our T354 Oncourse Resources folder. "Week 3/"your IU login"/
• For future work remember clip art is not allowed - create 100% original works
• Remember to use size and contrast to draw the viewer's attention to your message. If you have a complex background image, you can screen it down, lower the contrast, blur it, etc.
• Remember to adhere to the safe text area. Foreground text needs to be visible and have adequate background space so that it has room to "breathe".
• Photoshop Quiz in one week (Next Monday)

Agenda:

• Look at artwork
• Finish up Photoshop
• Previewing on an NTSC monitor.
• Alpha Channels
• In-class exercise
• Quick peek at After Effects

Photoshop (continued)

Video monitoring & output

No matter what colors or brightness levels you use in Photoshop, the images you create on your desktop will always look crisp and sharp on your computer monitor. Unfortunately, in the real world, graphics for TV must typically be compressed, output to video, stored on tape, played back, uplinked, downlinked, aired and finally received and viewed on a TV set. When we finally see them on TV they look quite different from the original computer output display.

To ensure their images will appear properly on TV, many professional graphic designers work with an actual video output which displays their Photoshop, After Effects, or Motion work. so they can view their work on a TV screen, and not just their computer displays. Don't feel confident that your work is ready for prime time until you view it on a TV set.

Some companies make real-time video output devices so you can see your Photoshop or After Effects composition on a video monitor while you work. Decklink (a video IO card for computers) provides a real-time display as does AJA. Even Adobe's After Effects, and Apple's Motion and Final Cut Pro lets users view their work in real-time through the firewire port. In other words, you can hook up a camcorder or deck with a firewire cable to view your work on a video monitor connected to your gear.

In class exercise (5 pts):

(The instructor will present the work on the projector for this exercise.)

Start a blank document in Word or TexEdit. Look at all of the graphics that your classmates created for their week 2 homework. Which of the two would you use and why?

Boese, William
Boyle, Patrick            
Cohen, Ryan            
Crowell, Scott
Day, Isaac            
Hemsworth, Jonathan
Hunnicutt, Joshua D            
Mager, Tyler            
Mattei, Jennifer
Mountsier, Ricky            
Panovich, Katrina
Pund, Evan
Schmittler, James
Schoenbaechler, Gregory
Smithson, Alan
Stum, Chad

Leave a copy of your comments in your week 3 folder and call it "observations".

Thursday ---------

Channels and Alphas and Bits, Oh My

First let’s start with channels. Video graphics are typically defined in three colors: Red, Blue and Green. In Photoshop you can easily see this in the channels window. In fact if you toggle the three channels on and off you may even come to understand that they are in essence three separate black and white images.

Color channels are created automagically when you select a color mode in Photoshop. The color mode determines the number of channels. When you start a new RGB image, it creates three channels, one for each color plus a composite RGB channel. If you make a new file in a CMYK color space, Photoshop creates four channels (Cyan Yellow Magenta & Black) plus a composite CMYK channel.

You can view your channels in your image by looking at the channel window in the lower right hand corner of your screen. If you can't see it select "Windows -> show channels"

Masks let you isolate and protect areas of an image. They work like stencils. When you select part of an image (say with the magic wand tool) the area that is not selected is masked, or protected from editing.

Quick Mask mode lets you create, view and edit a temporary mask for an image. The good thing about editing your selection as a mask is that you can use any paint tool to modify your selection. You can enter Quick Mask Mode by clicking on the button near the bottom of the toolbar.

When you paint with black, you are adding to the mask. When you paint with white, you subtract from your mask.

Masks and selections can be permanently stored with your artwork by saving them as alpha channels.

Alpha channels

Alpha channels can define parts of an image to be transparent. To understand this, it helps to quickly review bit depth. Bit depth or pixel depth refers to how much color information is in a particular image. 8-bit images contain up to 256 colors or shades of gray (like a GIF graphic). 16-bit images can have thousands of colors and 24-bit images more than 16 million.

The RGB files you create in Photoshop have three 8-bit channels. (3 x 8-bit = 24-bit).

An alpha channel is another 8-bit channel. Think of it as an extra black and white image stored along with your graphic. To make one simply save a selection or a mask as an alpha channel. In Photoshop you can save selections as alpha channels by looking under "select" -> "save selection". Or you can go to the channel palette and click on the "save selection as a channel" button.

Look at an example of a lower third graphic with an alpha channel.

• The black parts are transparent
• The white areas are opaque
• Grays are semi transparent

Since it's an 8-bit channel (think grayscale image), you have 256 steps from black to white. That's 256 varying stages from opaque to transparent.

Adding this additional 8-bit information to your 24-bit image creates a 32-bit image.

An image can have up to 24 channels. (Color or alpha channels) So it’s possible to save multiple alpha channels for varying applications. But while you can have multiple alpha channels in a Photoshop document, a PICT file can only have one alpha channel.

In-class exercise (5 pts):

• Create a basic, but nicely designed 720 x 480 pixel (4:3) lower third or keyable title TV graphic.
• Make an alpha channel for your graphic. Examine it to see how it looks. Try compositing it with your video or another image.
• Once you've mastered that try something a little more challenging: Add an element that has a gradient or feathered element with a corresponding alpha channel. Try to create a soft drop shadow that keys properly.
• When you are finished, save a copy of the PICT with an alpha channel into your own folder in the "Week 3" folder named "alpha.pct".

Straight & Pre-Multiplied Alpha Channels

Alpha channels can be saved as straight or premultiplied.

Straight (also known as unmatted) relies solely on the alpha channel to determine opacity.

Premultiplied (also known as matted) store information in the alpha channel, but also factor in transparency information into the R, G & B channels. In premultiplied files, the nicely feathered semi-transparent edges will become mixed with the background color.

Programs like After Effects interpret alpha channels as either straight or premultiplied. Using the wrong interpretation or premultpilying with the wrong color can result in undesirable white fringing or halos around the perimeter of the alpha.

Vocabulary

• Codec – Short for compressor / decompressor. Manufacturers have unique, sometimes proprietary ways to store and retrieve digital video and audio files. Examples include Sorenson, Avid and Media 100. Each has a unique way to compress and decompress the digital data.
• D1 – a.k.a. ITU 601 - This digital video format reached by the CCIR (Consultative Committee for International Radio). It specifies technical parameters and sets standards for international digital video.
• Opacity - (the level of transparency. Objects that are 100 percent opaque are solid, objects that are 0 percent opaque are transparent.
• Alpha channel – (see above)
• Straight - (see above)
• Premultiplied - (see above)

Homework (Due at the beginning of next week's lab):

You have been hired by a production company to design a package of graphics for their new TV talk/magazine show. They want you to make a title graphic, a graphic to promote the show, and a lower third key graphic to ID their guests with. The company has requested PCT versions of each graphic at 720 x 480.

There should be some visual and artistic consistency between the three graphics. For instance if you use a yellow crescent moon over a deep blue background in the title, you might consider adding that as part of the lower third to ID the host with.

Remember- the major design elements need to come from you! In other words please don't rely on other people's images or artwork as the major emphasis in your design. If you do include images or artwork, it must be cleared and have legal integrity.

• Title Graphic: This full-screen graphic needs to contain at least two separate pieces of artwork or images, and any text you want.
• Promo Graphic: This should be a full screen graphic and contain the vital information you'd expect to see in a promo: plug (reason to watch), title, time etc. The message should be clear & easy to decipher.
• Lower third video graphic: This key graphic will ID a MCU of the host or guest. Your PICT file should have a clean alpha channel in it.
• Since these graphics will be similar in style, you can use one critique form for all three graphics.

Since these images all have the same "look" you can use a single critique form- just be sure to identify all three file names and sizes.

Don't forget to study for next week's Photoshop Quiz!

Starting next week we'll start After Effects. Don't forget to get the book "Creating Motion Graphics with After Effects, 4th Edition".

 

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