The original design of the OWL has evolved to feature a wider aperture in the back plate - as suggested by Stereo World editor John Dennis. This makes no difference to the OWL's performance in viewing stereo cards, but it enables the viewer to cover the whole area of larger format cards when they are illustrated life-size in book and magazines. Usually these are cards made much later than the "Scenes in Our Village" and "Diableries" cards … for instance Keystone Views, and Underwood and Underwood, and many 21st century stereo pairs now being offered. So the OWL now covers more formats than ever.
The OWL is perfect for viewing side-by-side stereos on the iPAD. The newer versions of the iPad have much better resolution than the previous models, but in my opinion it's still not quite fine enough resolution for our purposes. It would be a lot better if we stereoscopists could use the whole area of the screen for our stereo pairs, but that's very hard. The geometry of the Brewster system - which is really what we are all using, dictates strict limits for the size of our images. Well, we shall see - but in the meantime our OWLs will be a great tool for enjoying electronic stereos on our iPads.
An OWL used to view a classic stereo card from the 1850s
OWL in position for viewing the stereo cards illustrated in "A Village Lost and Found"
This picture demonstrates the method of focussing the OWL. This was a prototype - with nuts and bolts !