Re: Testing Focal Lengths of Lenses

[Jook Leung <jook360@xxxxxxxxxxxxx>]

Hi George,

Yes, after reading Bill's post, his points are well reasoned and as he also
said, confirmed by Mr Seitz. So you maybe off the hook in collecting
everybody's lenses.:-)

I've found my 50mm/1.4 Nikkor to be very sharp using the suggested numbers.
My 28PC Nikkor is okay.

I also use a Sigma 14EX whose results could be better.
A 390 degree image is short enough to scan on my Leafscan45.
Caution: Sigma lenses focus past infinity!
I never try to focus with the 14mm, and consider everything beyond 3 meters
is at infinity, so I tape the lens at infinity. Conventional hyperfocus
depth of field rules do not apply here.

To recap, is it correct to say that a calibrated fl is only good at one
focus setting? This is because the image size will change with the lens
focus.


When I did lens testing, I looked for image sharpness and did not try to
measure
aspect ratios! I also set the 220VR to take 90 degrees so that I could fit
many trials on a roll. But such short starts and stops may cause problems.
In the end, I didn't have a powerful enough magnifier to really see
differences between tenths of a fl, but maybe quarter and thirds.

Jook



>Dear Jook,
>   I am not so certain after reading Glickman's posting that this is the
>right way to go...what do you think?
>George :-)
>
>

. . . . . . . . . . . . . . . . . . . . . . . .
J O O K   L E U N G
360VR Photography - Panoramic Photography for Virtual Tours
44A Honeck Street, Englewood, NJ  07631
Email: jook@xxxxxxxxx    Web:  http://360vr.com
voice: 201.894.5881  fax: 201.894.5882  mobile: 201.679.6177