didnt Pentax super multicoat all air glass surfaces starting back in the early 70's. including rear elements? jco -----Original Message----- From: Pentax-Discuss Mail List Sent: Jun 17, 2022 11:37 AM To: Subject: Re: sample photos. - smc pentax A 100mm F2.8 MACRO at middle distances w/K-1   On 6/16/2022 10:17 PM, Alan C wrote: > The problem is related to lack of Multi-coating on the rear element > which was absent on pre-digital lenses. More commonly this gives rise > to ghosting (back-and-forth reflections) when these old lenses are > used on digital camera because the sensors are much more reflective > than film. The difference between the Sigma 170-500 APO & the later DG > version is indicative. > I suspect that is a possibility, I suspect the "multicoated" lenses of the day may not have been as multicoated on the rear element. I use quite a few legacy glass and the A100/2.8 macro is the only one I've noticed hot spots on, which is why I thought it might be related to the FREE design and the flat rear element.   Anyway, according to John, the problem doesn't exist, so it's all good.   bill -- %(real_name)s Pentax-Discuss Mail List To unsubscribe send an email to pdml-leave@pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.  

Well, that's what I thought, which is why I suspect the sensor reflections are related to the FREE optical system, which, if I am remembering correctly the A100/2.8 macro is the only lens with this designation. Anyway, it's no big deal if it doesn't affect you but for what I was doing with the lens the issue rendered it unusable. On Fri., Jun. 17, 2022, 3:31 p.m. JC OConnell, <hifisapi@gate.net> wrote: > didnt Pentax super multicoat all air glass surfaces starting back in the > early 70's. including rear elements? > jco > -----Original Message----- > From: Pentax-Discuss Mail List > Sent: Jun 17, 2022 11:37 AM > To: > Subject: Re: sample photos. - smc pentax A 100mm F2.8 MACRO at middle > distances w/K-1 > > On 6/16/2022 10:17 PM, Alan C wrote: > > The problem is related to lack of Multi-coating on the rear element > > which was absent on pre-digital lenses. More commonly this gives rise > to > ghosting (back-and-forth reflections) when these old lenses are > used on > digital camera because the sensors are much more reflective > than film. > The difference between the Sigma 170-500 APO & the later DG > version is > indicative. > > > I suspect that is a possibility, I suspect the "multicoated" lenses of the > day may not have been as multicoated on the rear element. I use quite a few > legacy glass and the A100/2.8 macro is the only one I've noticed hot spots > on, which is why I thought it might be related to the FREE design and the > flat rear element. > > Anyway, according to John, the problem doesn't exist, so it's all good. > > bill > -- > %(real_name)s Pentax-Discuss Mail List > To unsubscribe send an email to pdml-leave@pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. > > > -- > %(real_name)s Pentax-Discuss Mail List > To unsubscribe send an email to pdml-leave@pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions.