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Old May 20th, 2002, 03:32 AM   #1
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critical focus and the color evf and zebra bars

I remember reading that although achieving and accurate critical focus was difficult using the XL1s's color EVF, it could be done by using the zebra bars, as they "snap into focus", I believe it was. Can someone clarify? I tried it out, and all I noticed was that the area around the zebra bars (I think it was purple, and no, I'm not smoking anything) got smaller as the focus got more . . .um. . .focused.
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Old May 20th, 2002, 08:11 AM   #2
 
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zebra is electronically superimposed on the image.....there is nothing to focus, so what you heard was urban legend
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Old May 20th, 2002, 08:43 AM   #3
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No, it's not an urban legend. However, the comment I made about "snapping into focus" was in reference to the 16x manual lens.

I find when using that lens the change in appearance of the zebras is a good way to know when you've hit focus.

I don't remember the change being so obvious with the auto lens, but it's been a long time since I've used one.

Mike Avery
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Old May 20th, 2002, 02:05 PM   #4
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Ah. Okay. Well, I'm planning on getting that manual lens. . .so I guess it'll make sense then. Thanks.
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Old May 20th, 2002, 02:16 PM   #5
 
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The zebra is not designed to facilitate focusing and won't work for this purpose.

Last edited by Chris Hurd; May 20th, 2002 at 09:36 PM.
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Old May 20th, 2002, 02:41 PM   #6
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Bill, here's the deal with that... we all know that zebra bars are used for exposure control, and we know that the zebra bars not designed to facilitate focusing. As you state, they most definitely are not intended for that purpose. *However* the tip is that the zebra bars themselves change in appearance slightly when an image snaps into focus. It's unintentional and not by design, and if Mike Avery sees it using the 16x manual lens then I'm inclined to believe him.

As for myself, this is how I know my viewfinder diopter is in perfect focus. Sometimes it's hard to tell if the EVF has proper focus because of the low resolution of the LCD screen. So I'll purposefully overexpose the image to show the zebra pattern, and focus the viewfinder diopter using these bars. Hey that's not what they're for, but it works!
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Old May 20th, 2002, 02:43 PM   #7
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I feel I have started some sort of conflict. Now gentlemen, let's please not come to blows. I'll not have the two or three of you hitting each other with Canon XL1ses. . .they're just too expensive. Use an SVHS cam.
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Old May 20th, 2002, 02:46 PM   #8
 
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Well, it seems I may owe everyone an apology. I've been reading "focus" as in lens focus....not, diopter focusing of the viewfinder. For this error on my part, you have my deepest apologies. Chris, thanx for clearing my clouded perception. Sorry for giving the impression that "we're coming to blows". It isn't that, at all.

In fact, I can see how using the zebra stripes for diopter focusing may work quite well.
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Old May 20th, 2002, 03:08 PM   #9
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Wait. Now I'm confused. We're talking about the "diopter" is it . . .the actual viewfinder glass? I thought we meant the lens of the camera. Nevermind then. Guess it's another 1500 for the b&w viewfinder for me! Boy Howdy!
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Old May 20th, 2002, 04:34 PM   #10
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How is this for a rationalization.

Note that auto focus is judged by contrast. Contrast is highest at best focus. But contrast being higest means whites are whiter (like with good laundry detergent) and blacks are blacker.

Now whiter whites can mean pushing narrow white portions of the image into zebra, causing zebr to appear if the white level is at the threshold of zebra.

In summary, do not count on it work at all (or evenmost) times and places.
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Old May 20th, 2002, 06:39 PM   #11
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I am talking about focusing the lens by using zebras. Yes, I understand it might not make sense to an opto-mechanical engineer, but to my eye it works.

I can definately see a change in the zebra pattern when I hit focus, and at least one other conributor to this forum has noticed the same thing.

It's not the only tool I use to focus, but it helps.

Mike Avery

Last edited by Chris Hurd; May 20th, 2002 at 09:37 PM.
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Old May 20th, 2002, 08:19 PM   #12
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So you were talking about the lens focus earlier, then?

You said that was not your only method of focusing. What else do you use? Still talking about the color viewfinder, just for clarification.
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Old May 20th, 2002, 09:16 PM   #13
 
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There is a great deal of mis-information floating around this internet. I would just like to make sure that an innocent newbie reading this thread sees the diffrerence between opinion and a phenomenon based on a known principle of optics.

Last edited by Chris Hurd; May 20th, 2002 at 09:37 PM.
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Old May 20th, 2002, 09:35 PM   #14
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Thread closed.

Let's just say that the zebra bars are first and foremost a measure of exposure and leave it at that. Thanks,
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