I love taking pictures and am a stickler for quality, sharpness and detail in the pictures my family enjoys on our walls, scrapbooks, computers and devices. It's not uncommon to find me retouching an image for days until I get it just the way I like it. My recent acquisition of a Zune had me pretty excited about the ability to showcase pictures to family and friends. I loaded up a few hundred images and started viewing slideshows and selecting images for the background. The quality was fine, but in comparison with the sample images which ship on the device mine looked out of focus and not quite as crisp. I knew some of my originals were every bit as sharp and detailed. So I decided to run a few tests to see if I could figure out how to tweak my images for maximum enjoyment.
I wanted to share my images with the general public, so no copyrighted material or people for which I would need signed releases. The quandary here is that humans (generally speaking) tend to notice quality issues with faces more easily than any other type of image, especially if we know the individual personally (as will be the case with many of the images on my Zune). Therefore they can be the best subjects for evaluating quality. So I tried to pick a couple of images which would give me enough detail to mimic what I observed with crisp closeups of people. I evaluated about 15 images total and selected these as representative of the overall results:
Test Image 1 is of a hat sold in the company store about a year ago. It has lots of fine threads which don't travel in straight lines, and the intricacies of the weave lends itself nicely to mimic the wisps of hair, the eyelashes, eye details, facial hair and other details you commonly see in faces. Things for which a single pixel missing or out of place can mean a world of difference in perceived quality. This particular image is particularly sharp around the stars and R.
Test Image 2 is a picture I took while hiking the Badaling section of the Great Wall of China several years ago. This picture has and incredible amount of fine detail both in the inorganic (building) and organic (stone work, trees, snow in the distance). This picture provides interesting challenges for resizing because of the detail (and the type of detail, as we will see).
Cropping and Resizing
There were three individual tests with each image and in my tests the end result was a typical (and some might say predictable) good, better, best paradigm...
- Good: Import pictures at their original resolution and aspect ratio and allow the Zune software to crop and resize during the sync process. This is the out of box experience which I describe above as OK but not quite as good as the sample images provided.
- Better: Crop originals to a 4:3 aspect ratio (keeping original resolution) before importing into the Zune software and syncing with the Zune device. There was a noticeable uptick in perceived quality taking this approach.
- Best: Crop and resize to the optimal resolution and aspect ratio outlined below in a third party tool like Digital Image Pro, Photoshop or Paint.NET. I used Photoshop for all of the tests except the first where I compared all three programs to see if there were large differences in their resizing algorithms (which there really wasn't except if you went looking for the differences). For each export of the JPEG the highest quality option was used (12 in the case of Photoshop) to try and keep artifacting to a minimum).
The best resolution for most pictures (especially those involving faces) is going to be 640 x 480. While not a face, the image for Test Image 1 shows distinct differences at the pixel level between 320 x 240 and 640 x 480 on the Zune device, closely resembling my observed results with actual faces. You can test this out for yourself by copying these images to your Zune and playing a slide show -- look for pixels to appear which provide more definition in the weave of the embroidery. For faces the difference between the two resolutions can be a glimmer in the eye (or not) and the other nuances we observe in the human character. Also, 640 x 480 is going to look better if you are using the TV out functionality on the Zune.
However, there are always exceptions to the rule. If a picture has many hard edges or patterns involving straight lines 320 x 240 may be perceived as better due to moire' patterns. In Test Image 2 the bricks in the building at 640 x 480 introduce an unpleasant moire' pattern on the device not observed when the 320 x 240 resolution was displayed.
It does NOT seem to make a difference what DPI you use for display on the device. I tested at 45, 72 and 96 DPI and could not discern a difference on the device between the three at comparable resolutions. As a result I'm only posting the 96 DPI images for you to download and test for yourself, because...
Even though this was a test of pictures on the device you have to go through the Zune software to get the images to the device. So why not take a look at the results there. So I did and observed the following:
It DOES make a difference what DPI you use for the Zune software for when it generates thumbnails. 96 DPI renders better in the Zune software than others and in some cases beat the thumbnail generated by the Zune software from the original high resolution image.
Resolution also seems to matter in the Zune software, and it seems somewhat at odds with what is optimal for the Zune device in most cases. 320 x 240 @ 96 DP Iooked best in the software but 640 x 480 (no matter the DPI) generally speaking looked best on the device. I guess it's hard to have your cake and eat it too. For comparison look at the suite of images in Test1. Again, this will be highly dependent on images -- it's hard to tell the difference between the various choices in Test2. Judge for yourself...
You will want to maximize use of the pixels on the Zune. Slide shows look best when all of the pictures are landscape (640 width x 480 height). Otherwise the portrait images (480 width x 640 height) are displayed significantly smaller in a horizontal letterbox format. Here is some ASCII art which hopefully illustrates the differences...
[ || ]O vs. [| |]O
It's nice not having to swivel the Zune 90 degrees while cycling through a slide show -- but you are using only 1/3rd the amount of pixels you could be for portrait images. The only time you would not want to do this is for images you plan to set as the background -- the Zune device will automatically crop the landscape picture on the sides to display as the background, perhaps obscuring important information (like those faces).
If you want your pictures to look their absolute best on the Zune device always use third party software to crop and resize to the following specs before importing into the Zune software and syncing to the Zune device:
- Slideshow Pictures: 640 x 480 (Landscape)
- Background Pictures: 480 x 640 (Portrait)
...and by all means use the highest quality JPEG export setting your software provides.
I hope you are enjoying your Zune as much as I am.