Upgrade 4 inch fl Lenses for TDC Stereo Slde Projectors - Matched Pair - vintage

Upgrade 4 inch fl Lenses for TDC Stereo Slde Projectors Matched Pair of Lenses vintage - Excellent Condition Optional upgrade offered at the time of purchase by Bell & Howell for their TDC Stereo Slide Projectors Brightness of image on the stereo screen is always the concern as the projector's polarized filters and the viewers' polarized glasses reduce brightness by as much as 30%. Therefore, the optional 4 inch fl lenses were a distinct improvement over the standard 5 inch fl lenses, because . . . . .  To produce the same size image on the screen, the projector with 4 inch fl lenses is much closer to the screen. And as light falls off inversely proportionally, the result is a significantly brighter image on the screen. Only a few dollars more at time of purchase, the 4 inch fl lenses were suited better for audiences larger than standard home use (classroom and auditorium audiences). But the availability of 4 inch fl lenses is considerably less than the standard 5 inch fl lenses, and the price now for the brighter producing lenses is considerably more than a few dollars. Offered here on 3Dstereo is an outright purchase, but you may contact us for an exchange of lenses which reduces the cost nearly in half.