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Skype for Business–Thumbnail Image Quality Issues

Over the weekend I was scanning a few message boards and came across a post asking

Why does the image of a person look ok sometimes but pixelated at other times for the same person?

To clarify the problem is when a user answers a call from a person and the picture of the caller is expanded and displayed in the conversation window.

Unlike most quality issues within Skype for Business, this problem is not down to lack of bandwidth or some other Skype for Business trick to ensure best possible experience. The actual cause of this is simple.

Back in the days before Exchange 2013, Lync didn’t really have a plausible Photo store worth having anyway. We were limited to using Active Directory based photos or using a web site hosting images of each user. Most organisations used AD based photos, and in so doing limited the quality to a 96 x 96 pixel image of no more than 100KB in size.

So give you an idea of what this looks like, here is an image at 96 x 96 pixels


The first problem is that people usually use pictures taken in landscape format, rather than portrait. The problem with is that when resizing to equal aspect ratios for horizontal and vertical axis is that they are not uniform. So converting a 1200 x 600 image to 96 x 96 pixels means that the horizontal axis is resized out of proportion to that of the original resolution. This makes the resized picture seem thin and long. As you can see in the above example it is pretty hard to make out any type of facial definition and is about as much use as a thumbnail image as a blank placeholder. A picture taken in portrait mode fairs better with resizing due to the 1:1 aspect ratio. So when resized to 96 x 96 pixels it comes out a bit clearer


But the story does not end there. In the Skype for Business client will actually retrieve the AD thumbnail photo and resize further to 48 x 48 pixels to get to the address book thumbnail display size of this:


Look familiar?

When this person calls you, or you call them, the conversation window expands this 96 x 96 pixel image into 648 x 648 pixels, and herein is the problem… The result blurred image!



The introduction of High Resolution images in Exchange 2013 allows users to upload their own images to Exchange. This means that they are able to upload an image with a resolution of 648 x 648 pixels. As with AD, the same rules apply, the image should be in portrait mode to get the best resize scaling. There is no value in uploading an image to Exchange higher than the resolution of 648 x 648 pixels as that is the largest size Exchange supports. If you upload an image of greater resolution it is going to be resized to this anyway. If you do not properly format and scale the high resolution image then you are reducing the potential image quality.

Here is a example of a high resolution image at 648 x 648

Image result for man portrait

However, High Resolution photographs are not the complete answer to these photo quality issues. When you upload the image to exchange a few things happen:

  • Exchange will resize your picture if over 648 x 648 to 648 x 648 pixels, so make sure that your image will scale to this resolution in the first place!
  • Exchange will store a picture in Active Directory Thumbnail attribute of 64 x 64 pixels!
  • Exchange will also store a 96 x 96 version to be used in OWA, Outlook, Skype Web App and the Skype Client

So even though you think you have solved your picture resolution woes, there is one more thing to consider and this is the reason for the image quality problems even with High Resolution photos.

Skype for Business will attempt to retrieve the high resolution photograph of the user as stored in Exchange using Exchange Web Services. If there is a problem with EWS or Skype’s ability to access EWS at the time of photo retrieval, the Active Directory thumbnail image of 64 x 64 pixels is used instead. Therefore, when the conversation window expands, it is blowing up the 64 x 64 pixel image to 648 x 648 pixels, giving you the same experience as if you were just using AD pictures…. errr because at this moment you are! Smile

So if you are experiencing issues with your high resolution photo’s quality, then this will be the reason behind it. The resolution will be to figure out why EWS and Skype are not behaving themselves for you!

1 Comment

  1. Photos in portrait mode, when resized to 1:1, will not look like that. You will look ver fat!
    And the picture you say it’s 648×648 it’s actually 770×535.

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