[Leica] RE:Re:Tale of Two Telyts Part Deaux - the Evil Twin (Hoppy's Observation) (bob palmieri)

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

Folks, I 'm pleased there is some interest in this. Since it is about the
Telyt's performance I think it can also be considered a Leica topic.
So, just to add a little more to the thread:

I assumed that the image was from a transparency original, which was then
being scanned. Bob, is that right?
If it is via a digital back on a Leica SLR then all bets are off. Not that
I'm not interested, just that my assumptions would be wrong and then we'd be
talking about the digital back and Telyt combo. I have no experience there
whatsoever, except greatly admiring (birdman)Doug's superb images.
Having said that I guess that the same phenomenon could be present, except
introduced by the digital back rather than the scanner.


>From both Bob and David's observations, it sounds as though some aberrations
can be visible on film with the some Telyts and on more than one film,
dependent also on the contrast in the subject lighting. This aberration MAY
be what we are seeing or it MAY be what I theorised about.

So Bob, please, is this specific original a transparency?
If yes, can you see the fringing with a good loupe? That would obviously
prove that I was mistaken.
If the original is a transparency that does not have the fringing, then it
has to be from:
Scanning software or
caused during the down-sampling process to produce the small jpeg for the
gallery.

Cheers
Hoppy, off with the pixels?

------------------------------

From: David Young <telyt@telus.net>
Subject: Re: [Leica] RE Tale of Two Telyts Part Deax - The Evil Twin
        (bob palmieri)

>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


Hi Hoppy!

I'd be interested, too!

However, before you write off this as a digital problem, please note 
that I get the same results with the Telyt 400, in similar 
situations.  Moreover, it is exacerbated by the use of my old SL 
style 2x converter, which I use with the Telyt 400, most of the time.

Because of the tendency of digital to suffer blown highlights, it is 
more noticeable, perhaps, with digital (I've had the problem with 
both the Canon 20D and R8/DMR), it is still noticeable with film.

I do not get the same problems, in similar situations, when using, 
say, the 80~200/4 Vario, even with the same 2x converter added, no 
matter if it's film or digi.

That being said, in more evenly lit, or more normal contrast 
situations, this is not a problem for the Telyt.


David Young,

------------------------------

Message: 10
Date: Sat, 8 Jul 2006 09:46:57 -0500
From: bob palmieri <rpalmier@depaul.edu>
Subject: [Leica] Re:Tale of Two Telyts Part Deaux - the Evil Twin
        (Hoppy's        Observation)
To: lug@leica-users.org
Cc: Joe Biegel <jbiegel@alum.rit.edu>
Message-ID: <efa260d5f48d7538e0a8882f1ac1e484@depaul.edu>
Content-Type: text/plain; charset=US-ASCII; format=flowed

(Joe, you might wanna read this one backwards, if you know what I 
mean...)

On Jul 8, 2006, at 12:03 AM,Hoppy wrote:

> 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
> Hoppy
>
> 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?
>  Hoppy
>
> -----Original Message-----
> ------------------------------
> 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
>
>
> 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


Hoppy -

This is indeed a very interesting observation in your part.  Although I 
can sorta visualize a way in which the digital representation of an 
analog phenomenon could take on this characteristic I also thing you 
may be onto something here.  Plus, I'm impressed with your persistence.

So, I'm gonna forward this thread to an imaging scientist friend and 
see what he has to say.

Bob Palmieri