Best practices for optimizing the quality of your images best-practices-for-optimizing-the-quality-of-your-images

Source image format:

• Using lossless formats like PNG, TIFF, or PSD ensures that the image quality remains high without any compression artifacts.
• These formats preserve all the original data, making them ideal for editing and further processing.

Source image size:

• Starting with a high-resolution image provides more detail and flexibility.
• When images need to be displayed at different sizes (for example, across devices or screen resolutions), having a larger source image allows for better scaling.
• For images that support zoom (like product photos), aim for dimensions of around 2,000 pixels or more on the longest side.
• Logos or banners that don’t require zoom can be uploaded in the largest size needed for their intended use.

Best practices white paper Adobe Dynamic Media Classic Image Quality and Sharpening Best Practices applies to Experience Manager as well.

Watch Use Image Sharpening with Experience Manager - Dynamic Media.

Simple sharpening ( &op_sharpen) – Similar to the sharpen filter used in Photoshop, simple sharpening applies basic sharpening to the final view of the image following dynamic resizing. However, this method is not user-configurable. The best practice is to avoid using &op_sharpen unless required.

Unsharp masking ( &op_USM) – Unsharp masking is an industry standard sharpening filter. The best practice is to sharpen images with unsharp masking following the guidelines below. Unsharp masking lets you control the following three parameters:

• &op_sharpen=amount,radius,threshold

  • amount (0-5, strength of the effect.)
  • radius (0-250, width of the “sharpening lines” drawn around the sharpened object, as measured in pixels.)

  Keep in mind that the parameters radius and amount work against each other. Reducing radius can be compensated by increasing the amount. Radius allows finer control as a lower value sharpens only the edge pixels, whereas a higher value sharpens a wider band of pixels.

  • threshold (0-255, sensitivity of effect.)

  This parameter determines how different the sharpened pixels must be from the surrounding area before they are considered edge pixels and the filter sharpens them. The threshold parameter helps to avoid over-sharpening areas with similar colors, such as skin tones. For example, a threshold value of 12 ignores slight variations in skin tone brightness to avoid adding “noise,” while still adding edge contrast to high contrast areas, such as where eyelashes meet skin.

  For more information about how you set these three parameters, including best practices to use with the filter, see the following resources:

  • Best practices white paper Adobe Dynamic Media Classic Image Quality and Sharpening Best Practices applies to Experience Manager as well.

  • Watch Use Image Sharpening with Experience Manager - Dynamic Media.

  • Experience Manager also lets you control a fourth parameter: monochrome (0,1). This parameter determines if unsharp masking is applied to each color component separately using the value 0 or to the image brightness/intensity using the value 1.

This parameter controls JPG encoding quality. A higher value means a higher-quality image but a large file size; alternatively, a lower value means a lower quality image but a smaller file size. The range for this parameter is 0-100.

To optimize for quality, do not set the parameter value to 100. The difference between a setting of 90 or 95 and 100 is almost imperceptible. And yet 100 unnecessarily increases the size of the image file. Therefore, to optimize for quality but avoid image files becoming too large, set the qlt= value to 90 or 95.

To optimize for a small image file size but keep image quality at an acceptable level, set the qlt= value to 80. Values below 70 to 75 results in significant image quality degradation.

As a best practice, to stay in the middle, set the qlt= value to 85 to stay in the middle.

Using the chroma flag in qlt=

• The qlt= parameter has a second setting that lets you turn on RGB chromaticity downsampling using the value ,1 or off using the value ,0.
• To keep it simple, start with RGB chromaticity downsampling turned off (,0). This setting usually results in better image quality, especially for synthetic images with lots of sharp edges and contrast.