Originally posted by marcdsgn At the risk of sounding ignorant, I've often wondered about the practicality of my Sigma hoods. I have three zooms with different ranges, each with a dedicated hood that mounts over the front rim.
But of course, adjusting the zoom means that the end of the lens moves out almost beyond the rim of the hood. To my mind, this defeats the purpose of the hoods ... or am I missing something about the position of the internal lens elements + flare angle + etc??
on any zoom the hood is designed for the shortest focal length, it has to be that way or the lens would vignette. In fact, in the thread on performance of DA lenses on full frame, you can actually see the hood profile in one of the shots.
Having stated the above, I have a different question about the effectiveness of many of my lens hoods, in fact every single one except my sigma 10-20. All my other zooms are full frame lenses, and the hoods must be designed to be compatible with the wider field of view on a film body (I say film because pentax does not make a full frame DSLR) As a result, the performance of the hood is somewhat compromised when shooting with the restricted field of view of an ASP-C sensor. with an optimized hood, you could shoot closer on axis to a bright source without flair. I wonder why manufacturer's don't offer 2 hoods or an optional hood for ASP-C sensors.
As for using the hoods, I use them ewxcept when using the built in flash. Many lens hoods restrict the coverage of the flash.