Like anybody, of course, he had wondered what happened during the mysteriously guarded transition from plate to print, but never enough to step across any darkroom's forbidden doorsill to have a look.
* * * * * * * * * *
Pynchon has a lot going on in this sentence but first and foremost is his alluding to transubstantiation except in reverse: instead of an object becoming flesh, flesh, in photography, is transformed into an object. He couches it in the "mysteriously guarded transition from plate to print" but that's just allowing Merle to ease into the subject of flesh to print. In the span of two lines, Merle has expanded his idea of photography from an idiot's game to a religious concept.
"mysteriously guarded transition"
Merle will step back slightly from this characterization in the next half of the sentence when he admits that he's in control of where and when he could learn this secret but here, at the start, he sounds like he's a subscriber to the Proverbs for Paranoids. Something guarded must have guards. Rather, Guards, capitalized. As in They. Them. The Masters controlling the information.
"but never enough"
People often become obstacles to sating their own curiosity (and that's if they can even bother to find themselves curious about the nature of things at all). Ignorance comes in many forms but the withholding of information from yourself is the foundation of one of the most common. The most common probably stems from people simply not understanding complex answers to questions and seeking the safety of a simple solution. These are the people who believe they're smarter than the most intelligent people because they have common sense. Common sense feels like intelligence but it's actually just a smokescreen to understanding. Common sense says the sun revolves around the Earth because that's a common and easily digested common observation. But what common sense often just hides is ignorance based on a lack of understanding a complex world where observation isn't the only answer.
Before you think I've gone off on a tangent, let's observe this: photography becomes an easy allusion to discuss light and vision, a comparative to human perception and observation.
"darkroom's forbidden doorsill"
Pynchon uses "doorsill" purposefully since it's a synonym for threshold, or the point of beginning. The term "darkroom" indicating ignorance and the lack of knowledge, forbidden because the knowledge remains particular to those who study photography and their apprentices. With Roswell's loss of apprentice, Merle has filled the vacuum to be allowed this knowledge. He steps over the threshold to begin his new life as a photographer, a capturer of moments, one who sees and observes particularly well.
"have a look"
Once again, it's observing that's important, with the basic understanding that light is essential for "looking". Perhaps this encounter with photography and the need to understand how light can be used to save images in time and space was needed for Merle to encounter and fall in love with Erlys, a name that means "the light" in Norwegian. Remember, this is the story about how Merle fell in love with Erlys Mills!
