A regular acrylic is very translucent and optically pure. It has no coatings, matte finish and tint. It is more optically pure than glass excluding very expensive low iron. Regular glass has a green tint which can be seen if a piece of glass is laid on white printer paper. A standard acrylic works fine if the print is a standard photographic print process or archival inkjet or if it is not required to last past 10 years or if the display is not in direct sunlight. A standard acrylic is also better because it can be reprinted.

The other types:

Another type is UV filter acrylic which blocks 98% of the UV radiation. This is better as it reduces fading on all kinds of photos in frames. It also has a slight yellow tint (probably half the tint of glass) which can create a slight warming effect. If displaying a photo frame in a brightly lit room or if required to last for 10 years, then consider this type of acrylic. Regular photographs can last for 10 years with hardly any fading depending on the type of light they are displayed in. It also depends on how much fading one can accept. Even with UV filter acrylic it fades unless kept in dark.

The finishes:

Then there is non-glare acrylic, which has a matte finish on one side to reduce glare from light. This is an extremely high quality product and causes a minute loss in sharpness even with a thick mat. Some non-glare acrylic or Plexiglas products originate a noticeable loss of sharpness even if it is against the print. This version of non-glare has no UV-filtering making it optically pure i. e. without tint. Non-glare will reduce the glare of light considerably and make the picture frame much more presentable in poor lighting environment. The only shortcomings are high cost and a minor loss of sharpness. The best way to display an image is with a standard or UV acrylic and proper lighting so no glare is created. There are other options also available to choose from for acrylic frames. One can make the best use only if one can understand the way it needs to be displayed.