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[ In Focus ] |
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Adobe Photoshop CS3 Extended gets technical
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by Wayne Cole
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I was using my recently arrived Adobe Creative Suite 3 Production Premium package when, in Photoshop CS3 Extended, I saw a new menu. Because a good portion of my “day job” income is from photo analysis of incident scenes, incident simulation, and controlled testing videos and stills, the Analysis menu not only caught my eye, it gave me a little touch of the kid-at-Christmas feeling.
The process I usually employ is to export video captured by Avid Media Composer for import into Bauhaus Mirage, where I go through the video frame-by-frame entering the pixel coordinates of interest into a Microsoft Excel spreadsheet. In some cases, the motion in the video requires two passes to be made, one to get the coordinates of the point of interest and one to get the coordinates of a reference.
Some known “real world” measurement must be extracted from the video to scale the pixel data to real world values. This may take the form of measuring sticks, checkered tape, round center of gravity targets, or the pixel dimensions of some object of known size in the scene.
In severe cases, a third pass through the video has to be made because the camera motion also causes the scale object (which is ideally in the same plane as the measured object) to change size with each video frame. I then use the spreadsheet to calculate the position of the point of interest relative to some reference in each video frame.
At this point, the data collection is complete and motion analysis, which usually involves the use of a mathematical tool like Maple or MathCad, can start. The time-consuming tedium and exacting mouse work it takes to get to this point is hard on the eyes, mouse-hand, and deadlines. I’ve been on the lookout for an easier and faster way to get from capturing the video to the actual analysis.
Video Import And Measurement
Adobe seems to have read my mind when they developed the extra features that can be found in Photoshop CS3 Extended. First is the ability to import video into the new video layer type.
To view and manipulate the clip, Photoshop includes a scaled-back After Effects timeline complete with transport controls, time scale options, and onion-skinning capability. Key to my workflow is that Photoshop can import QuickTime reference files and maintain links to the actual media.
Then there is that wonderful Analysis menu. The first item in the menu allows an analyst to set the scale required to convert from pixels to real world units.
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| The new Analysis menu in Photoshop CS3 Extended gives you access to tools that help simplifiy measurements within your video. |
With the Measurement Scale dialog active, simply drag the ruler along the length of some known dimension. Photoshop sets the measured number of pixels in the dialog, and you set the known distance the ruler spans. Photoshop uses this information to calculate the scale and report subsequent measurements in real world units.
The next step is to select the data you want recorded in the measurement log using the Select Data Points dialog. These “data points” are actually columns in the log. They identify certain common data, or data for selection tools, ruler tool, or count tool that you want to see or not see in your log.
For my test analysis, I stretched the ruler tool out on the first frame of video from the reference to the point of interest. I used the Ctrl-Shift-M combo to record the measurement to the log, advanced to the next frame, adjusted ruler end points, and recorded the next measurement.
I repeated this for each frame of the test video, then exported the Measurement Log. The log imported directly into Excel, where I had the X- and Y-components of the measured positions calculated in seconds from data that Photoshop captured for each measurement.
You can do more than measure simple lengths. Any of Photoshop’s selection tools, including the magic wand and smart selections, can be used to designate an area from which Photoshop will calculate area measurements based on the current scale data.
Tools like the color range selector will often generate multiple selections in an image. In such situations, the Count tool can be used to count these distinct selection areas. Medical, astronomical, and other engineering applications often use “false color” imaging to detect items of interests. The color selection/count tool combo can be a real productivity boost to the poor interns and grad students who have to count such items manually.
Photoshop CS3 Extended Adobe added an interface to MATLAB, a popular data analysis and algorithm development tool. It also added access to DICOM files, a popular medical imaging format containing imagery and metadata. Forensic video analysts will find the new image stacking feature helpful. Image stacks can blend or average a series of images to smooth out noise and bring up detail in areas of interests.
More To Come … Please
While these technical imaging tools are a great addition to Photoshop, there is room for improvement in future releases. First, the measurement log is not saved with the image. If you don’t export the log before closing the image file, you will lose all your measurements. I believe many analysts would favor saving measurement logs within the Photoshop file with the image as a way of simplifying data management.
Also, because Photoshop has the awareness of timeline frame numbers and/or frame times for which a measurement was logged, it should be able to save these parameters with the measurement data. That would be a big boost for users who would use Photoshop for dynamics analysis on video clips or frames from high-speed cameras.
Security analysts would like to be able to work with video layers field by field in addition to frame by frame. As many multi-camera security systems record a different camera feed to each field, this is necessary to avoid missing critical information. And the addition of the ability to de-multiplex a multi-camera video stream to separate video layers for each camera completely within Photoshop would make security analysts positively swoon.
The technical imaging features are only available in Photoshop CS3 Extended, not in the base version. If you purchase Photoshop as part of any of the Creative Suite bundles, you need to be sure you get a premium level bundle or the Master Collection to get the extended Photoshop.
The price difference between the base and extended versions of Photoshop is $350 for new purchases and $150 for upgrades. If you are involved in technical imaging, especially if you have pressed earlier versions of Photoshop into service, the extended version should be high on your list to evaluate.
Wayne M. Cole, CCV, CLVI, and member of the AGCV Board of Advisors, is also the owner of IHP, a video production company located Santa Barbara, CA. Contact him at wcole@ihpweb.com.
MORE INFO
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