Forum: Pentax SLR Lens Discussion
06-14-2015, 04:57 PM
|
|
I'm not terribly familiar with the whole process. It seems to me that the Pentax TCs were pulled off the market (or at least discontinued) due to this issue.
Keep in mind I was quoting Pentaxus who used the term "radioactive." However, the rare earth elements and radioactivity are linked apparently, based on this article: Radioactive lenses.
I still have one of those old lens brushes with a well-protected cartridge radian strip that when active can help blow off any dust. It shows an expiration date of Aug 1976, so I feel pretty much unthreatened. The brush itself is really excellent! I suspect it was pulled off the market well before that expiration date.
|
Forum: Pentax SLR Lens Discussion
06-11-2015, 05:57 AM
|
|
You might be overlooking the rather obvious reason for that. Everyone left Chernobyl because they found a nicer place to live and work. Yes, radioactive coating technology is something that could be done, but the costs of taking appropriate precautions would be extremely high.
|
Forum: Pentax SLR Lens Discussion
06-10-2015, 08:57 PM
|
|
No hard-and-fast rule exists. The majority of older lenses do not have a significant problem with reflection off of the sensor, but a few have hot spots and some others have generally lower contrast. This tends to relate more to the shape of the rear element, and not so much the coatings - which have been quite good on better lenses since the late 1970s (especially so with Pentax). Very recently, the HD coatings have been another step up, but not a game-changer.
As a very general rule, the DA lenses tend to give slightly higher resolution than the FF (FA) lenses - whether film or dSLR era. The newer lens designs also tend to have better overall contrast - sometimes referred to as micro-contrast.
Also as a very general rule, the prime lenses today are not significantly different than the designs from decades ago. Over time, zooms have improved. Exceptions to the rule exist, such as the A-series 35-105 f/3.5 which is still a very good optic from 50mm upwards. Newer zooms for crop sensors that start at ultra-wide (anywhere from 8 to 16) tend to be better than older film designs because providing a wide perspective was a high priority for shooters entering the crop-sensor digital age.
As a general rule, really poor lenses from the film era are worse than the worst modern lenses. On the other hand, some film era gems remain vastly under-valued if you know the market.
Question anyone who views digital or film era lenses as always one thing or the other.
|