I have two PREMO (Rochester Optical Company) folding cameras circa 1895, one is a 4x5 PREMO Senior, the other a Long-focus 5x7. Both are typical brass-bound, leather-covered cameras. Both are "drop-bed, self-casing" cameras, with rack-geared front focus rail (lens standard slides onto, then clamps to a brass slide, that in turn, has a rack-gear & knob that pulls out of the right side of the bed). I've shot about six photos with the 4x5, and am pleased enough with the image quality so far, both with color (Portra 160) and B&W (FP-4). However, if I pull the front standard out, and lock it to the rail with the scale pointer at Infinity, then use the knob to rack the focus-slide out for closer focusing, when I push the knob back in, the bellows tends to pull the whole focus slide back towards the film plane... it doesn't seem like there's a lock on the focus mechanism, or it's not working. Anybody know "if" and "how" the front focus lock is supposed to work on these things ?