I too have the PortaTrace 18x24 model. In fact, it's brand new from B&H. It's the 4-tube stainless steel version. I was a bit less than satisfied with the fit and finish at first. And the light distribution had noticeable - to me, anyway - hot lines along the tube lengths.
But I'm a tinkerer always looking to improve things a bit. So I purchased a couple of 4-foot aluminum U-channel pieces and just today miter-cut them down and assembled them so as to raise the height of the plexiglass over the tubes by only 7/8 of an inch. This small adjustment made a huge difference in the eveness of illumination from below. It also served to noticeably lower the brightness level, which I found excessive.
Tomorrow I'll cut some custom white reflector pieces and insert them at an angle over the now bare left and right inner sidewalls of the box. This should help alleviate the somewhat darker left and right edges. The upper and lower edges, along with the bottom, are already pure white.
That ought to do it, I hope. 18x24 is big enough to display four 8x10 negatives at once. And with the above improvements, I should be able to reliably compare overall negtive densities for all four at a single glance. And my Kodachrome slides - the reason I purchased it in the first place - already look just wonderful.
Last edited by Ken Nadvornick; 11-02-2008 at 12:36 AM. Click to view previous post history.