Hello -

A month has already gone by, and it is time for another Asiva Newsletter? We can’t believe it. We have been so busy here. Well, the first Asiva plug-in for Photoshop has been released. If you haven’t seen it yet you can download a trial version at asiva.com. We have received a good response from Asiva Sharpen+Soften and are hoping Correct+Apply Color will do the same. Look for it to come out soon.

Now don’t get intimidated, we got a little technical with this newsletter. Our Chief Technical Officer and the mastermind of Asiva technologies has contributed his views on the 8 vs. 16-bit debate. We feel he has some insight on the subject many of us have not heard or thought of. He hopes to start a new thought process on the subject.

We are always interested in knowing what you think about the newsletter, it’s topics, and what else you would like to read about. Please keep in contact with us and let us know what you are doing with Asiva and any suggestions you may have for our products. We want to keep and open forum with you. E-mail us at: info@asiva.com.

Until next time,

Shapiro Consulting Group, Inc.

8 bits per channel or 16?

By: Kevin K. Gordon, CTO SCGI

Impassioned arguments have reverberated around forums and discussion groups on the topic of 16 bits per color component image processing vs. 8 bit. One comment referred to the subject as “a huge can of worms”. In fact, bounties have been offered for proof that a 16-bit (per component) representation of an image, enhanced in Adobe® Photoshop® can be differentiated from an 8-bit version. My explanation from an engineer’s standpoint follows and my hope is that you will have a new understanding of an old debate.

As you probably know, for 8-bit component representation, each component (Red, Green or Blue for RGB or Cyan, Magenta, Yellow or Black for CMYK) can have 256 distinct values represented by the whole numbers 0 to 255. For 16-bit component representation, each component can have 65,536 distinct values represented by the whole numbers 0 to 65,535. So for every single 8-bit level, there are 256 levels of a 16-bit representation.

Now, the typical problem with manipulating color image components in 8-bit, is resultant banding. That is, a discernable ramping, or chunky gradation of some tonality may occur when you perform certain types of correction, particularity when you really push the parameters. Even converting a source 16-bit image to 8-bit, could result in some banding, if the program converting the image data does not implement some kind of dynamic rounding or dithering. I have read many complaints about scanner software doing this.

Why?, is the question. The reason is quite simple - its in the math. Operations (as we call them at Asiva), Filters, or Effects all involve mathematical manipulation. Some are simple and other very complex. We all know for 8-bits/component, each component can have 256 distinct values represented by whole numbers. Even when you multiply or divide an 8-bit color component once with a real number resulting, it has to be converted back to a whole number. Depending upon the algorithm, the fractional part could be lopped-off, rounded-down, rounded-up. Nonetheless, the result is not necessarily accurate and will tend to lump values together, as the number of bits gets smaller. This is how Photoshop users, working in 8-bit, come up with the infamous ‘comb histogram’ or non-smooth levels with lots of gaps.

The good news for Asiva® users, Asiva Photo and Asiva Plug-ins, is that all processing is accomplished in 16-bits per component, even if you open an 8-bit image.

Read the rest of this article here.

Asiva Photo Color Information Window and Map Coordinates

Very often after sampling Hue, Saturation or Luminance values into the Maps Window using the Eyedropper Tool, one often finds certain areas or regions of the image are not being affected as expected. Adjusting the Maps blindly or additional sampling could prove fruitless, if not frustrating, if you are unsure about the properties of the color you are trying to effect.

A quick solution is to use the Color Information Window, found under the application’s “Window” menu item. When the Color Information Window is invoked, and the cursor is moved over the image, you will be able to inspect the precise color properties of any pixel in the image (see A in the above image). Sometimes when attempting to define an Operation’s effect more accurately, moving the cursor back and forth over the desired boundary area will expose subtle H, S or V differences that can be exploited to define the effect’s boundaries. Because Asiva is always working in 16 bit space, some of these subtle differences may not be visible to the human eye but are represented as numerical values in the Color Information Window during the inspection process.

The Color Information Window will display the following types of information:
H: Hue
S: Saturation
As: Asiva Saturation (Our own version of saturation)
V: Value (Luminance)
I: Intensity
RGB or CMYK (Depending on file format you are using)

Careful inspection of the values displayed for any particular part of the image will provide the information you need to adjust the curves in the Maps Window to include or exclude specific pixels based on their HSV properties. As you move your cursor over the Map’s curve area, a numerical display at the top part of the Map’s window will display your cursor position in (x:y) coordinates (see B in above image). Depending on which Map you are on, the (x) coordinate will be displayed in degrees (Hue Map) or in percentages (Saturation and Luminance Maps). When you click and drag points in your curve, the coordinates are also displayed next to your cursor icon (see C in the above image). This allows for pin-point adjustment of the curves.

When used in conjunction with the “Eyedropper Tool” this is a very powerful way of inspecting the image and accurately adjusting the HSV maps to select specific colors to be operated on .