chalk tip #18: using ImageScope to measure viewing response time

Today’s chalk tip is one of my favorites.  Did you know you can use ImageScope to measure viewing response time?

ImageScope can randomly access views of a slide and measure how long it takes to retrieve and display them.  Here’s how you can do this:

1. On the Windows taskbar, click Start | Run.


2. Type “imagescope /t” into the Run dialog box, like this:

 

ImageScope will start and open a blank window. You will see that it includes a Testing menu:



3. Open an image from the server for which you want to test viewing response time.  You can do this by signing on to Spectrum, listing or searching for slides, and then clicking on a slide thumbnail.  If you want to test with an Aperio server, you can select a slide from http://www.aperio.com/gallery.


4. Zoom in all the way, e.g. click the 20X button:



5. From the Testing menu, select Timing:



6. In the Timing Interval dialog box enter the number of seconds between each view, then click OK.  Generally the default value of 5 seconds works well, so you can just click OK.



7. The timing test will start!  ImageScope will begin randomly fetching views from the slide at the time interval you’ve specified.  The Elapsed time to retrieve and display each view will be displayed in the lower right corner of the status bar, along with the Average response time (both in seconds).



8. The timing test will continue until you stop it by selecting Timing from the Testing menu again.

A few notes about measuring viewing response time in this way:

• The viewing response time is generally a measure of network bandwidth, not server speed.  It takes a lot of bandwidth and very little computing speed to serve digital slides.
• The bandwidth at the server usually determines the viewing speed, but in some cases it can be the bandwidth at the client.
• The response time depends on the size of the window.  The larger the window, the more data have to be retrieved, transmitted, and displayed for each “view” of the slide.

Cheers and have fun measuring response time!