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Old March 8th, 2003, 08:12 PM   #1
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Calibrating Back Focus 16x manual lens

I just read Kens article on the 16x manual servo lens. I'm concerned about calibrating back focus. This is somthing I never did when I attached my new lens to my XL1s. As I recal the directions were a little sketchy. Is there an article or directions with a good explination on how to do this. I figured it was factory set and I didn't need to do anything but the article states that the back focus should be calibrated after mounting the lens on a different camera. (now I can't find the directions that came with the lens) I must get more organized one of these days!

Thanks in advance, and great article Ken, also great article about the B&W Viewfinder!

Dan O'Bannon
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Old March 9th, 2003, 10:41 PM   #2
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Hi Dan,

This is really a fairly simple thing to do.

Here's how:
First, turn on the Color Bars on the XL1S and adjust your the viewfinder diopter so it is in sharp focus. If you are using the FU-1000 B&W viewfinder, turn up the peaking control.

Place the XL1S on a tripod. Next, focus the lens on a focus chart placed as far as possible from the camera. I use a Putora 7A9 "Magic Chart" which I purchased from ZGC.
http://zgc.com/html/7a9_test_chart.html
If you don't have access to such a chart, then you can download a copy of the Sieman's Star Chart from cameraman extradinaire Ron Dexter's site:
http://www.rondexter.com/focus_pattern.pdf -or- you can use a page from a magazine if need be.

1) Set the iris to manual.

2) Open up wide on the aperature. If the test chart is too bright and overexposed with the wide-open iris, adjust the lighting on the chart so that you have a balanced exposure.

3) Zoom in all the way with the lens onto the focus chart and focus on the chart.

4) Next, zoom out all the way to the widest setting on the lens. The focus should remain sharp. If it isn't, then loosen the back focus ring retaining knob on the lens and adjust the back focus ring until the focus is sharp.

Repeat the last two steps until the focus is consistently sharp at both full tele and full wide positions. After doing so, tighten the back focus ring retaining knob so that the back focus control is locked and cannot move.

- don
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Old March 9th, 2003, 10:55 PM   #3
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Dan,
Very glad you enjoyed the articles! Don's procedure is precisely it.

My close vision is not what it used to be, so I struggle a bit with back-focus adjustment through the color lcd viewfinder. If convenient I'll either use the FU-1000 (best) or an external monitor.

I also struggle with using fine-focus charts. They're great tools but can be hard for me to judge when I zoom-out. Full-page, gigantic type ads found in the newspaper (you know, those "One Day Only Sale!" ads that stores run) have worked best for me.

Good luck!
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Old March 10th, 2003, 08:35 PM   #4
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Thanks alot Don and Ken, You guys are GREAT!

Is the color chart the best thing for focusing my eye to the view finder?? Im concerned that what I see through the lens might not be in sharp focus because I'm not 100% sure my viewfinder is in focus to my eye.

My wish list was an onboard (menu) viewfinder focus wheel for my bad eyes. Any sugestions on that?

Thanks again, Dan O'Bannon
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Old March 10th, 2003, 08:49 PM   #5
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Dan,
The best way to focus your viewfinder is to turn your EVF displays on (ie, the date/time display, et.al.) and use those character displays to focus the eyepiece. Since those characters are reflected from the LCD screen you're assured that your eyepiece is in good focus.
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Old March 11th, 2003, 03:40 PM   #6
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Thanks Ken, I've been using the EVF display but there is always a question (maybe a little more or a little less) would it help to turn peak up all the way and then focus? I'll try it my self but don't have the camera set up right now.

thanks again, Dan O'Bannon
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Old May 25th, 2005, 09:40 PM   #7
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focusing manual lens

I'm trying to follow the advice of others on focusing the my Xl1s with a manual 16x lens. They say to zoom all the way in on a chart, then focus it.
Ok, then I zoom all the way out and it becomes out of focus. Then I adjust the back focus to get the image focus but then if I zoom back to the chart for a close up, it's out of focus. Does anyone know what I'm doing wrong? Could you help please.
scott
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Old May 25th, 2005, 10:46 PM   #8
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When you zoom back in and its out of focus..... refocus again zoom back out and adjust the back focus again. repeat this process until correct.It may take a few times
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Old May 25th, 2005, 11:00 PM   #9
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[Thanks jack,
The more I try the worst it gets. I've gotten to a point that it won't focus when it's totally zoomed in. I'm such a rookie at this. I'll give it a try again
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Old May 25th, 2005, 11:05 PM   #10
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Jack,
Also do I touch the micro focus at all while going back and forth adjusting the back focus?
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