Originally posted by malenisjaj I don't get that 1.5x? Does the hood needs to be one and the half times longer than focal length?
No. You want a hood that is deep enough to properly shade the lens while also not intruding into the field of view. For most lenses, the size that was appropriate for 35mm film is good enough for APS-C. At the wider end (say 35mm and shorter), however, you may wish to use a deeper hood than was originally intended for your lens. The reason being that most hoods designed for wide angle (35mm and shorter) lenses on 35mm film are too shallow to effectively shade the lens. With APS-C you have the advantage of being able to use a somewhat deeper hood.
BTW...don't bother with "tulip" hoods unless they were originally dedicated for your lens. As fpr the "vented" style hoods, they will work, but were intended for use on rangefinder cameras where the "vents" provide a means to not have the hood block the viewfinder. They will work on your camera, but are not worth paying extra for. They also do a poor job at blocking dust.
Regarding materials. I prefer rigid metal since they provide good protection for the lens. Almost all feature matte paint coupled with some form of flocking or light baffles on the inner surfaces to dampen reflection. The collapsible rubber kind tend to be somewhat shallow and offer little protection, but they are more compact in the bag. I would not buy a filter-mount plastic hood due to durability concerns.
Steve
Last edited by stevebrot; 02-14-2014 at 10:00 AM.