I also believe lossing of coating on back or front element will cause
similar effect but may be in most case you will only get a small area
coating off so with same area on front and rear element the effect on front
lens will be less as the front glass is much larger.
On the other hand I can't agree with the flare and ghosts, if you wear
glasses you will know, a non coated glasses will have very high flare and
ghosts in severe backlight situation and it is only one element, right? Ok,
today most glasses are coated and you will not notice this.
C.H.Ling
> -----Original Message-----
>
> There are long answers, but here's the short answer.
>
> Front surface: Light never enters the lens, so cannot cause
> flare or ghosts. Only a slight loss of light, 4% at worst. This
> 4 0s the per-surface reflection from uncoated glass. This is
> log2(1-0.04)= 0.06 stop, which is a negligable loss.
>
> Rear surface: Up to 40f the light coming out of the lens (on
> its way to the film) is instead reflected back into the lens,
> where it bounces around causing flare and ghosts. However, most
> modern lenses have very good internal baffles, and the coatings
> of internal len surfaces will have survived, so most of this
> reflected light is simply absorbed.
>
> So, I bet that loss of either front or back or both coatings
> makes little difference in practice in that one will get ghosts
> in situations where one would already get ghosts, and flare isn't
> likely to be much worse.
>
> Joe Gwinn
________________________________________________________________________
This email has been scanned for all viruses by the MessageLabs Email
Security System. For more information on a proactive email security
service working around the clock, around the globe, visit
http://www.messagelabs.com
________________________________________________________________________
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|