On 1 Jun 2003 12:31:04 -0700, brianc1959@aol.com (brian) wrote:

>d_ruether@hotmail.com (Neuman - Ruether) wrote in message news:

<3edc0101.1742037@newsstand.cit.cornell.edu>...

>> On 31 May 2003 19:22:56 -0700, brianc1959@aol.com (brian)

>> wrote:

>> >"Joseph Kewfi" <Joe_Kewfi@iol.ie> wrote in message news:

<bbb44a$9ht$1@dorito.esatclear.ie>...

>> >> How does this lens rate: distortion/sharpness for architectural photography

>> >> ?

>> >As David Ruether has pointed out, the 20/2.8 has wavy-line distortion.

>> > It also has noticeable color fringing. The 17-35/2.8 AFS at 20mm is

>> >better in all respects (except size, weight and cost!) from f/4 to

>> >f/22.

>> >Brian

>> >www.caldwellphotographic.com

>> I have never noticed serious color-fringing with this Nikkor

>> or with any other on film at good stops, viewed with good

>> 5-15X magnifiers, though others report this (and show it)

>> in digital images. Are you finding CF in digital images

>> only, or on film also?

>Hi David:

>The color fringing is on the order of 20 microns near the edges of the

>frame, which would not be easy to see with a 5x magnifier. At 15x the

>fringing is several times larger than the resolution limit of the eye,

>so it should be visible if you know where to look. I have only used

>the 20mm AFD on a D1x camera, but the magnitude and type of color

>fringing (blue-green-red "rainbow" type as opposed to magenta-green or

>cyan-red) matches my analysis of the Nikon patent on this lens. By

>the way, according to the patent prescription the color fringing

>increases until you get to around 16-18mm from the image center. Then

>the fringing actually decreases before dramatically increasing at the

>extreme corner at 21.6mm. In the extreme corners the orientation and

>coloration of the fringes also appears to change from blue-gree-red to

>yellow-blue. If you decide to undertake a careful study on film I

>would be very curious to know if you see this phenomenon.

>

>The color fringing is certainly not caused by the sensor, because

>lenses like the 55mm f/2.8 Micro Nikkor which have a very similar exit

>pupil location do not show even a trace of color fringing.

>

>With lenses I've used on both film and digital, such as the 28/3.5 PC

>and 24/2.0 the orientation and magnitude of color fringing is the same

>regardless of the imaging medium. The grain structure of film does

>seem to reduce the obviousness of the aberration, but its still there.

>

>Brian

>www.caldwellphotographic.com

Thanks for the information. I guess I will need to look

more closely at those 20mm corners on film...;-)