[Leica] RE Tale of Two Telyts Part Deax - The Evil Twin (bob palmieri)

[hoppyman at bigpond.net.au (G Hopkinson)]

Bob, I looked again at this effect for my own education.

I am more than ever convinced that this is a digital artifact we are seeing.

 

When you enlarge the image so that the individual pixels are very blocky,
(say 500%)you can see that the purple is a discrete and very even line at
the edge of the blown highlight.

Yet it is not present at all on the (very fine) highlight on the vertical
edge of the leg. If this was an aberration in the analog info, I would have
thought that there would be some other traces of it in the other areas.

Along the edge of the log where the highlight is completely white the fringe
is just about a perfect diagonal 4 pixel wide line. (1/1000th inch line in
the scanned slide?????)

 

I'd really be interested to hear the definitive outcome of this

 

Cheers,

Hoppy

Happy to be proven wrong, but love to learn

 

Bob, pardon me if this is a silly question.

Is this aberration definitely visible on the film?

(I assume its transparency film)

After your image is captured on film, obviously it must then be scanned to
produce your digital image for posting. I wondered if the aberration was
being introduced at that (weak link) point by the scanner?

 

Cheers,

 Hoppy

(who'd like a focomat in his coolscan)

 

-----Original Message-----

 

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Message: 20

Date: Thu, 6 Jul 2006 10:41:31 -0500

From: bob palmieri <rpalmier@depaul.edu>

Subject: [Leica] Tale of Two Telyts Part Deax - The Evil Twin

To: lug@leica-users.org, leicareflex@freelists.org

Message-ID: <0c6a689957fb15b7e15c496265b09547@depaul.edu>

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Folks -

 

As promised, here's an example of a disturbing symptom I encounter
occasionally with the 400 Telyt.

 

Here's a snap of a blue heron impersonating a stick:

 

http://gallery.leica-users.org/album409/Camoflage_Heron_Crop

 

 

And here's a 100% pixel crop showing heavy purple fringing around the feet
and along the top edge of the log (in areas of serious

overexposure):

 

http://gallery.leica-users.org/album409/Camoflage_Heron_PurpleCrop

 

 

I've seen the same effect on Kodachrome, so I don't think it's one of those
artifacts of digital sensor architecture (despite all the talk you hear
about purple fringing in digicams.)  My questions are as

follows:

 

1. Is this just a classic case of chromatic aberration in a simple achromat?
(I hear tell that the Anomalous Dispersion glass (whatever that is) in this
design is supposed to control this kindof thing to a pretty acceptable
level.)

 

2. If so, is it really possible that the results in the normally exposed
areas can look as good as they do (not that this snap is the best example;
things were getting pretty dim at the time and the shutter speed was
probably quite low) with a level of CA this high?

 

3. Does someone who uses both this lens and the probably staggeringly
CA-free 280 APO (Doug??) ever see this effect in their 400 shots and not in
those shot with the APO ?

 

Inquiring minds want to know...

 

Bob Palmieri