hood vignetting first makes itself visible in the form of slight light falloff in the image corners and its first seen/worst at wide open. In many cases, slight vignetting at wide open ( seen as slight corner light falloff) goes away completely with stopping down or with lens extension/close focussing ( no occurance of vignetting whatsoever). That's why when you calculate your "ideal lens hood" size you have to assume wide open and infintity because THESE are worst cases most likely to cause any vignetting, not stoppped down and close up. Bottom line is if you are unsure about a given hood on a given shot, stopping down will minimize any vignetting, possibly eliminate it completely. And so will closer focusing especially extremely close. jco
-----Original Message----- From: Paul Stenquist [mailto:[EMAIL PROTECTED] Sent: Sunday, December 25, 2005 2:07 AM To: pentax-discuss@pdml.net Subject: Re: Lens Hoods - know your worst case Perhaps, but if you don't stop down, you can't see the vignetting in the image. Not enough DOF. Try it, you can see for yourself. Paul On Dec 25, 2005, at 12:30 AM, J. C. O'Connell wrote: > Correction, the worst case for hoods ( most likely > to cause vignetting) is not close focus and small > apertures, it is with lens at infinity (widest angle > of view) and wide open ( optical path closest to > hood). It seems to me a common myth that stopped way > down and lens set to mimimum focus would be worst > case but that's backwards.... > jco >
