I've had a few people voicing concerns over the lightness of the comic clean sketch. The reason the sketch is so light isn't because I didn't adjust the levels enough in Photoshop. It's due to the grade of lead that I used.
Lead comes in various levels of hardness and softness. Harder lead makes a lighter line, while softer lead leaves a much darker mark. Here's an image of the lead scale which I snagged from Pencils.Com.
The reason I drew the page sketch with a harder lead was because of my initial plan. I was working with the idea that the pencils would need to be erased so, I wanted a lighter line. As a result, I used the 2H lead. I've been going back over the lines today to darken them using an HB. (Own a No. 2 pencil? That's an HB.) I use an HB when I don't plan on inking or erasing the lines.
You can see the difference in this scan. The lighter lines still need to be redone.
While I occasionally use a 2B it's rare. Unfortunately the softer the lead, the easier it is to smudge. I'll be doing all future pages with the HB lead. That way if we decide to go with the clean sketch option the lines will be richer. If we go with the ink option, well, that's what erasers are for.
edit: Here's the finished page darkened with the HB pencil. Personally I like it and am very pleased with the results.
"Every line tells its own story, even the very tentative ones."
-- Gillian Redwood