Archived posting to the Leica Users Group, 1998/06/15

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Subject: [Leica] Re: Photos on the Web and seeing subtle differences
From: "Robert G. Stevens" <robsteve@istar.ca>
Date: Mon, 15 Jun 1998 18:35:11 -0300

Hi Lugnuts:

There was a thread a few days ago regarding the ability to see subtle
differences in lenses as mentioned in some tests.  I just got a used
Noctilux and decided to test it against a new style 50mm Elmar. My
conclusion was that it is possible to see differences, if the scans are
done to enough resolution and just a small portion of the larger scan is
displayed at web resolutions.  These differences may not show up on some
lower resolution video modes. 

I took two pictures with each lens with the camera mounted on a tripod.  I
did not shoo a test pattern, but my back yard.  It has some big pine trees
which can really show the resolving power and contrast of a lens.  The day
was overcast and fairly even soft light.  These pictures were taken with an
M6 and the film was Kodak Gold 100.  I must admit, this is the first print
film I have ever used in the M6, but I was taking some pictures of some
friends that visited my parents last week and slides would not do them much
good.

As for the method.  The negatives were scanned at 2700dpi on a Canon 2700F
scanner.  A section showing some shadow detail differences was cut from
these 2700dpi scans and then reduced to 72dpi for monitor viewing.  The
original files were then resized to 480X320 and 72dpi.

The resulting files show that the Noctilux vignettes at F1, but seems fine
at 5.6.  This can be seen even at monitor resolutions.  You can ignore any
color differences, as the scanner was set to auto colour correction.  Now
for the fine details as you would see through a loupe.  In the files
elmar5.6detail.JPG, and noct5.6detail.jpg, you can see the very slight
increase in the detail of the area of tree trunk in the shadow of the table.  

These files are posted to some web space that my ISP provides.  I apologize
for not having a HTML page, but if you cut and paste these links into your
browser, you should get these images.  Some email programs will just let
you click on these links below.

http://home.istar.ca/~robsteve/noct-f1.JPG
http://home.istar.ca/~robsteve/elmar2.8.JPG
http://home.istar.ca/~robsteve/noctilux5.6.JPG
http://home.istar.ca/~robsteve/elmar5.6.JPG
http://home.istar.ca/~robsteve/noct5.6detail.JPG
http://home.istar.ca/~robsteve/elmar5.6detail.JPG

You may want to open these in pairs in multiple browser windows, so you can
have them side by side or quickly click from one to the other.


Thanks for your time and excuse the bandwidth if it doesn't interest you.
It is raining today and I didn't have anything better to do.

Regards,

Robert Stevens