Fujinon Feedback/Back focus. at DVinfo.net

Michael Knight · December 19th, 2006, 01:03 AM

Just a quick note.

Got our lens back from Fujinon today.

They found no problems with the lens...nor was it a pre-production model ....so it must have been OE (that's an acronym for Operator Error) which more than likely was in the back focus adjustment being done with too small of a chart.

Nevertheless, if anyone can run me through the "professionals" back-focus process I'd appreciate it. We did this using a monitor today, and it seems okay now.

However, absent a chart, we simply zoomed in on a vertical straight edge 16ft away, then pulled wide and adjusted the back focus.

But are there other things one should do to ensure the lens is good at all focal lengths/stops?

Michael Knight.

Greg Boston · December 19th, 2006, 09:12 AM

Quote:

Originally Posted by Michael Knight

However, absent a chart, we simply zoomed in on a vertical straight edge 16ft away, then pulled wide and adjusted the back focus.

The usual recommended distance is 3 meters. So, roughly 11 feet. A good sized Siemen's chart will make the task much easier.

-gb-

Bob Willis · December 19th, 2006, 01:05 PM

Use the ND filter wheel to make sure you are nearly wide open on the lens. That gives you a shallow depth of field to more acurately focus the back flange distance.

Michael Knight · December 19th, 2006, 10:02 PM

Much appreciated.

Siemens chart is on the way.

Then watch me spin some wheels.

Michael Knight.

December 19th, 2006, 01:03 AM	#1
Michael Knight Regular Crew Join Date: Oct 2006 Location: Mossyrock Wa USA Posts: 65	Fujinon Feedback/Back focus. Just a quick note. Got our lens back from Fujinon today. They found no problems with the lens...nor was it a pre-production model ....so it must have been OE (that's an acronym for Operator Error) which more than likely was in the back focus adjustment being done with too small of a chart. Nevertheless, if anyone can run me through the "professionals" back-focus process I'd appreciate it. We did this using a monitor today, and it seems okay now. However, absent a chart, we simply zoomed in on a vertical straight edge 16ft away, then pulled wide and adjusted the back focus. But are there other things one should do to ensure the lens is good at all focal lengths/stops? Michael Knight. __________________ All media since 1960. Formerly CP16/Nagra. Currently learning F350/Fujinon HSs18 x 5.5BRM, Mac G5 Quad and FCP Studio.

December 19th, 2006, 10:02 PM	#4
Michael Knight Regular Crew Join Date: Oct 2006 Location: Mossyrock Wa USA Posts: 65	Much appreciated. Siemens chart is on the way. Then watch me spin some wheels. Michael Knight. __________________ All media since 1960. Formerly CP16/Nagra. Currently learning F350/Fujinon HSs18 x 5.5BRM, Mac G5 Quad and FCP Studio.

December 19th, 2006, 01:05 PM	#3
Bob Willis Major Player Join Date: Oct 2006 Location: Albuquerque, New Mexico Posts: 292	Use the ND filter wheel to make sure you are nearly wide open on the lens. That gives you a shallow depth of field to more acurately focus the back flange distance.