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03-27-2014, 01:49 PM   #16
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QuoteOriginally posted by stevebrot Quote
This always sort of puzzles me since the same lens when manually focused will be accurate 100% of the time.

What are the manufacturers or service techs adjusting when you send a lens in? Are they tweaking the drive response or just replacing potentially worn parts?

I am curious too as to how are you measuring and applying your adjustments? Are you saying you have a way of measuring 10 Ám (1/100 mm) back focus at the focal plane and that you have some way of adjusting your lens so that this is no longer the case?


Steve
Not quite - the micrometers are referencing my adjustment steps in my k-x. It takes 10 micrometers to correct the focus to be "accurate" on the short end, and about 70 on the long end. I found the numbers using two methods, first method was using the focus adjustment and finding the high and low value when the camera starts registering focus, and the second was using a ruler at 45 degrees and aiming at the middle.

I assume the techs are tightening up tolerances so that the lens elements cannot shift as much when being moved into position.

03-27-2014, 01:51 PM   #17
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QuoteOriginally posted by stevebrot Quote
...
Found it! It takes awhile to load, but it is only too cool when it does. The accompanying lecture notes are also one of the best descriptions I have read as well.

Autofocus: phase detection

Here is the corresponding applet and discussion for CDAF:

Autofocus: contrast detection


Steve
Thanks for the links. There are even more applets on the courses site. Now I got lost in the Internet again checking those apps and lots of further Stanford links. Education looks extremely different to what we have here in Germany. Is it usual on most US universities to address the Professor by his first name? There seems to be a lot less distance between schoolars and teachers than what I experienced. Sorry for the OT...
03-27-2014, 04:39 PM   #18
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QuoteOriginally posted by delegopa Quote
Thanks for the links. There are even more applets on the courses site. Now I got lost in the Internet again checking those apps and lots of further Stanford links. Education looks extremely different to what we have here in Germany. Is it usual on most US universities to address the Professor by his first name? There seems to be a lot less distance between schoolars and teachers than what I experienced. Sorry for the OT...
Addressing people is much more casual here. You can typically call pretty much anyone by first name, even the CEO of your company or a professor. You rarely use the last name, maybe for medical doctors.

Gruss aus Los angeles
03-27-2014, 04:41 PM   #19
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QuoteOriginally posted by JinDesu Quote
the micrometers are referencing my adjustment steps in my k-x
Ok...I see. You got the Ám figures from the debug mode display for global AF bias.* Out of curiosity, which number did you settle on and how is your focus with your other lenses?


Steve

* The K-x does not support body-to-lens AF calibration per se. Some users with older cameras have found some satisfaction by tweaking the global AF system bias as accessed through the hidden "debug" system settings menu. That calibration is expressed in Ám units, presumably +/- the focal plane. Any adjustments effect all AF lenses used by the camera. Per-lens AF adjustment on the newer bodies is done through the regular menu system using arbitrary units (+/- 20) and is only applied to the lens in question.

---------- Post added 03-27-14 at 04:56 PM ----------

QuoteOriginally posted by delegopa Quote
Is it usual on most US universities to address the Professor by his first name?
Not usually. When I was at university, it was customary to address the professors as "Doctor". That being said, many (most?) of the lower-division courses and labs are actually taught by graduate students or lower-level instructors. In those cases, dealing on a first-name basis is not unusual. In secondary and elementary schools, last-name basis is the rule.

In industry, it depends how initial introductions are done and the presence of a working relationship. A few years ago I was writing software here in the U.S. for a company that is headquartered in Austria. I was introduced to the company president by first name during one of his visits here and have remained on a first-name basis to this day. I am afraid that I truly shocked his administrative assistant when I was in Linz on business and asked if <first name> was in. She gathered herself after a few seconds and responded that yes, Herr <last name> was in and would see me in a moment. Oooops!


Steve

03-27-2014, 06:23 PM   #20
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QuoteOriginally posted by stevebrot Quote
Ok...I see. You got the Ám figures from the debug mode display for global AF bias.* Out of curiosity, which number did you settle on and how is your focus with your other lenses?


Steve

* The K-x does not support body-to-lens AF calibration per se. Some users with older cameras have found some satisfaction by tweaking the global AF system bias as accessed through the hidden "debug" system settings menu. That calibration is expressed in Ám units, presumably +/- the focal plane. Any adjustments effect all AF lenses used by the camera. Per-lens AF adjustment on the newer bodies is done through the regular menu system using arbitrary units (+/- 20) and is only applied to the lens in question.

Steve
I gave up setting it for the Tamron. I just work around it. All my other lenses are in line with each other (Sigma 50 F1.4, FA* 24 F2, Sigma 105mm F2.8 Macro, Sigma 50 F2.8 Macro, and DA 40mm XS). Humorously, in line means -80 micrometers for all lenses. I think that my k-x's AF calibration was damaged a long time ago from a fall, and so the 0 point is -80 micrometers.
03-28-2014, 05:30 AM   #21
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QuoteOriginally posted by delegopa Quote
Thanks for the links. There are even more applets on the courses site. Now I got lost in the Internet again checking those apps and lots of further Stanford links. Education looks extremely different to what we have here in Germany. Is it usual on most US universities to address the Professor by his first name? There seems to be a lot less distance between schoolars and teachers than what I experienced. Sorry for the OT...
Well...even out getting drunk with our professors in the '80s we'd still call them Dr. (name)...most of them. Some preferred first names. We're pretty casual here in the US. Sometimes it's Dr. or Prof. (first name).
03-28-2014, 08:33 AM   #22
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Thanks to all for the look over the pond : )
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