Lens-mount designation ... what do they mean?

[Aryajaide]

Very informative, Don. Thanks a lot. My knowledge had just increased 'by that much'. Now.....to digest all that.....

[DWessel]

Good post, Don.
The only area where I would take issue is the reference to Digital Coatings.
This is marketing speak designed to encourage people to replace their existing film lenses.

If people were to pick up some of the old Konica/Minolta "film" lenses and experienced the chromatic aberations, is there any way to add a coating or filter to combat that effect?

[DonSchap]

Normally CA (chromatic aberration) is in the design of the lens. It is the way light gets through the glass medium at different wavelengths and winds up looking split on the sensor. Most high-end lenses take this very seriously and use elements (composed of fluorite) in them that have differing dispersion rates and when ASSEMBLED into a compound lens, realign the different colors into the same spot on the sensor.



Now, you are going to have to explain to me HOW you can do that with a simple layer of optic juice, because I am having some difficulty seeing it.

Purple fringing is similar to color aberration, but it takes place not at the sensor, but inside the "micro lenses" of the sensor itself. Green is correctly channeled through the lens, but red and blue are incorrectly focused and result in the purple color around highlights. Haven a good lens on the camera will reduce the effects of purple fringing, but the best remedy aside from construction of that "good lens", is the use of a demosaicing algorithm in the processing portion of the camera's output.

In other words, we are in an area that requires quite a bit more thought than just a "coating." If only it were so easy to solve.

[Peekayoh]

If people were to pick up some of the old Konica/Minolta "film" lenses and experienced the chromatic aberations, is there any way to add a coating or filter to combat that effect?

CA's are the result of poor lens design. Stands to reason that a cheap lens is likely to be worse than an expensive one.
If you pick up a good Minolta lens, CA's will be well controlled and won't be a major issue.
Plenty of new digital lenses are worse than some old Minolta glass.
The good news anyway is that CA's are reatively easy to deal with in post processing.

[DonSchap]

Okay ... in a nutshell, because a picture is worth a thousand words ...

Here is the 100% crop of a TAMRON AF 70-300mm f/4-5.6 LD @ f/4.5 w/ a circular polarizer (a good one!) (the typical "branch against the bright sky" scenario)



And here is the reason you buy a TAMRON SP AF 70-200mm f/2.8 Di LD @ f/4.5 w/ a circular polarizer (a good one!)



As far as Chromatic Aberration goes, it really doesn't get much clearer than that, my friends.

Now, the purple fringing can be cut down by tightening up your aperture, but then you change things like DOF and, of course, the amount of light the camera will see, creating a more silhouette effect.

TAMRON AF 70-300mm f/4-5.6 LD[/SIZE] @ f/8 w/ a circular polarizer



TAMRON SP AF 70-200mm f/2.8 Di LD[/SIZE] @ f/8 w/ a circular polarizer



Oops ... this went a little "Off Topic" ... good stuff, but let's get back to those crazy lens mount differentiations.

[DonSchap]

How about a lens mount "bump", for the new guys?

[seanhoxx]

And how about a bump fpr Tokina, come on guys, A-mount!