I recently completed a roof project for a relative. This was roof #3 for the home- tore off the previous two layers. The home is about 40 years old with roof trusses and 1/2 (maybe 7/16) plywood sheathing, no clips. Plenty of roof and eave ventilation. As expected, the roof deck seemed to be quite brittle. A 220# guy with a bundle of shingles in hand could have stepped through the roof quite easily.
DSLR Definition: Digital Single Lens Reflex Camera. The Nikon D3000 is a DSLR camera. A DSLR, or digital single lens reflex camera is an advanced type of digital camera that provides high-level image quality, performance levels, and manual control options, typically much better than what you'd receive with a fixed lens camera.
A DSLR with this feature is often known as an HDSLR or DSLR video shooter. The first DSLR introduced with an HD movie mode, the Nikon D90, captures video at 720p24 (1280x720 resolution at 24 frame/s). Other early HDSLRs capture video using a nonstandard video resolution or frame rate.