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Canon XF Series HD Camcorders
Canon XF305, XF205 and XF105 (with SDI), Canon XF300, XF200 and XF100 (without SDI).


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Old January 19th, 2011, 08:42 PM   #1
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Example of parfocal issue

A quick, no frills example of the parfocal issue that many of us (Robert, Steev, Reinhard, myself at least) have experienced with the XF. Please pay no attention to exposure/framing - I just wanted to get an idea for myself if Face Detect was a safer option than manual focus.

The issue is pronounced shooting wide, so these are all shot at f/2.8, ND1, 1/50 shutter, 25p.

Frame 1: Fully Zoomed in, 73.8mm, critical focus achieved

Frame 2: Zoom back to mid-position (15mm) with auto focus (Face detect mode) on

Frame 3: Zoom back to mid-position (15mm) with auto-focus off

Frame 4: Zoom back to mid-position (15mm) with auto-focus off and iris open (f/1.6)

The important comparison is between frames 2 and 3 - both begin at the same starting point, critical focus at maximum focal length, but as we pull wide focus appears to shift behind the subject in manual focus.

In frame 4, the problem is accentuated (ie: it's a complete waste of time zooming in to achieve critical focus, then pulling wide with the iris open - focus will be way off).

Some have noted a) their camera doesn't have the issue and/or b) if it did they would send the camera straight back to Canon.

Reinhard sent his back to Canon Germany who said they couldn't replicate the problem. In my case, when I explained the issue to my dealer yesterday he said it would likely take two weeks to get my camera back, and most likely the technicians will say the lens is performing "within spec".

Is less than perfect parfocal performance acceptable? For me, no, but can Canon claim it is?

I need the camera on a weekly, if not daily basis, so for now I will be sticking with Auto Focus, and only using manual focus when I don't have to make quick changes in focal length.
Attached Thumbnails
Example of parfocal issue-1.jpg   Example of parfocal issue-2.jpg  

Example of parfocal issue-3.jpg   Example of parfocal issue-4.jpg  

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Old January 19th, 2011, 09:28 PM   #2
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Hi, Josh.................

Well, I've looked, scruted and analysed those piccies (as best as these rather tired 'ol eye's will allow anyway) and there sure as heck is sommat going on with that lens, but I'm wondering if there really is a problem with some builds.

To me, everything at the wider lens setting is seriously less sharp than at the full zoomed in setting.

Analysing just what is in tack sharp focus in all four piccies, the only thing I can say 100% is the girls eyes in pic 1.

After that it sort of goes seriously down hill rapidly, no matter what mode you're in.

That the increased DOF at the wider setting doesn't keep things under control makes me wonder if there was a glitch with the production run somewhere and the lens really isn't running to spec.

I'd say "someone" who is experiencing this rather odd behaviour do some pretty precise target based trials to prove categorically that the lens is going off in wider settings (and when I say "off" I mean it's resolving power just seems to dissapear into quicksand).

Canon will only take this seriously when someone proves there is a problem, and I mean prove to the Nth degree.

Geez, glad I haven't bought one yet.


CS
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Old January 20th, 2011, 12:16 PM   #3
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Example of parfocal issue

Wow Josh! I have not had this problem. I did a test with my XF300 Zoomed in focused zoomed all the way out and everything stayed in focus. Josh when you have peaking turned on does it show that it is in focus through out the range?
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Old January 20th, 2011, 10:32 PM   #4
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I wonder if "the parfocal issue" depends on the focus mode (MF / Full MF) and the zoom mode (RING or ROCKER)?

Manual, page 77, Using the Zoom Ring, Notes:
When you set the ZOOM switch to RING, the zoom position will move to the current position of the zoom ring, which will change the picture angle. Also, the picture may become out of focus.

No word about the zoom direction - "Tele to Wide" or "Wide to Tele"...

In "Using the Zoom Rockers" no such the notes.
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Old January 21st, 2011, 03:46 AM   #5
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Thanks Ivan, that's very interesting!! I will check this out tomorrow. I have been using the Ring exclusively (as I much prefer it to rocker). I wonder if those reporting the issue are using he ring, with those saying their cameras are fine using the rocker.

This sounds plausable as the XF300 has a rocker/ring switch and won't let you use both without switching (which is a little annoying).

In my case the issue (using the rocker) is entirely repeatable (and obvious). Tomorrow I will test both in full MF setting and MF using the rocker.

Robert: the problem is generally too subtle to notice with peaking on, but it's pretty clear once I get back in the studio.
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Old January 21st, 2011, 11:33 AM   #6
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josh-

i know this thread is about the parfocal issue u r concerned about but...

...the 1st posted image of the young lady really shows the strength of the xf300/xf305 image quality.

wonderful color, good skin detail right down to her freckles.

i hope u resolve your issue soon so u can return to making lovely images.

be well

rob
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Old January 21st, 2011, 04:08 PM   #7
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Parfocal Accuracy Test on Vimeo

Josh
There is a test Steev Dinkins did on Vimeo.

Link:

He says that Parfocal accuracy on the XF305 varies based on aperture and ND filters applied. Aperture fully open, with a subject in focus while zoomed in, there's a hint of softening when zoomed out. Furthermore, if ND filter 1,2 or 3 are applied and aperture is wide open, this phenomenon is noticeably worse. Its requiring a focus adjustment towards close focusing to truly get the image sharp. Closing down past f3.2 eliminates this phenomenon and focusing is very accurate through zoom range
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Old January 21st, 2011, 08:51 PM   #8
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[Thanks Robert: my testing concurs with Steev's findings]

Okay, I've just done thorough testing of my XF300 and my dealer's XF305 - results were identical with both cameras so I'm inclined this think this is an issue with all XF cameras, not just a few units.

Today I tested parfocal accuracy through the zoom range in four ways:
* Autofocus
* Manual focus using ring
* Manual focus using rocker
* Manual focus using full-time manual setting

Surprisingly, (given I've encountered the issue numerous time in the field) the camera held focus through the range in all instances.

Then I realised I'd encountered the problem predominantly outdoors. I switched on the ND filter and bingo!! The camera consistently lost critical focus when pulling wide, whether zoom, rocker or full time manual were used. This was with the aperture working at f2.8 or wider. (see attached pics of cleaning product).

To confirm it's not an issue particular to my camera, I went to my dealer and used his XF305. It took me two minutes to reproduce the problem (see attached grabs of Mamiya poster). With ND1 engaged, aperture @ f2.8, the camera clearly loses focus through the range.

To those who've said their XF's parfocal performance is perfect, please try the following: Set your camera to ND1@f2.8 and activate autofocus, zoom in fully on a subject and achieve critical focus, pull back to mid way through the range; now repeat with manual focus. Now compare focus in the mid-range shots.

I'm satisfied I can at least put this issue to rest: at wide apertures with ND engaged, the len's accuracy through the range is severely lacking. Outdoors I will either be closing down the aperture from now on or relying on AF :-P
Attached Thumbnails
Example of parfocal issue-xf300tight.jpg   Example of parfocal issue-xf300af.jpg  

Example of parfocal issue-xf300mf.jpg   Example of parfocal issue-xf305tight.jpg  

Example of parfocal issue-xf305af.jpg   Example of parfocal issue-xf305mf.jpg  

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Old January 21st, 2011, 09:10 PM   #9
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Josh, does your dealer back you up? Maybe Canon will listen if one of their retailers lodges a complaint.
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Old January 21st, 2011, 09:19 PM   #10
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Unfortunately they're primarily a camera shop, and say because the issue is happening with both my unit and theirs my camera is not faulty, this will be a known "design limitation", performing within the spec of the lens etc, blah blah...

Basically it renders my standard outdoor proceedure (open aperture for tighter DOF, zoom in for critical focus, pull wide to frame) useless, and also means you can't do creeping zooms in MF unless you close down the aperture.
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Old January 21st, 2011, 09:27 PM   #11
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Josh,
Thank you for your very interesting and illustrative test, clarifying the situation with the problem.

I wonder what happens if you use an external ND filter?
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Old January 21st, 2011, 09:36 PM   #12
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Shooting at wide angle with the iris opened wide is not the optimal setting for any lens. I know with my HPX500, if I shoot wide, the image is soft. That's just the way it is with that camera. Perhaps the Xf300 has the same limitations.

Edit - actually, your images show the video isn't soft - the acute focus actually shifts to another point in the distance. Seems like a back focus issue, if it were an interchangeable lens. Didn't early EX1s have a similar problem? Is there a menu setting that helps correct this?
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Old January 21st, 2011, 11:42 PM   #13
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Quote:
Originally Posted by Glen Vandermolen View Post
Shooting at wide angle with the iris opened wide is not the optimal setting for any lens. I know with my HPX500, if I shoot wide, the image is soft. That's just the way it is with that camera. Perhaps the Xf300 has the same limitations.

Edit - actually, your images show the video isn't soft - the acute focus actually shifts to another point in the distance. Seems like a back focus issue, if it were an interchangeable lens. Didn't early EX1s have a similar problem? Is there a menu setting that helps correct this?
Hi Glen, as noted in your edit, the image is sharp enough (autofocus works fine), but the focus shifts behind the subject as you pull wider with ND engaged. Unfortunately, there is no menu setting to correct this.

Also, the lens actually opens up to f1.6 (where the problem is even more pronunced). These images are wide, but not maximum aperture.

There are 3 situations for me where this is an issue (shooting outdoors, manual focus with ND engaged):
1 achieving critical focus zoomed in, then pulling wide to frame
2 capturing a creeping zoom, either in or out
3 quickly reframing during an interview (ie: I will have to refocus as well as reframe every time)

Work arounds:
1 Use AF face detect
2 Stop down to F/4 or greater
3 Use a screw on ND (as Ivan suggests)

Unfortunately, magnification and peaking are not much help at the wide end: it's only when you get back in the studio that you can tell if critical focus is achieved.
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Old January 22nd, 2011, 12:13 AM   #14
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I wonder why this issue is just now appearing. These cams have been on the market for about 6 months now. I haven't heard of any issue with the focus until recently. When Alan Roberts performed all his critical tests (used by the BBC) he never mentioned the issue. Certainly, he would have reported it. I've seen beautiful images from the XF, at wide settings, and no problems. This makes me wonder if there's some kind of manufacturing problem that has recently come about.

Of course, Canon has looked at one our forum member's camera with this issue and reported it fit for duty. I would suggest all of you with this problem to write to Canon and make your position officially known. Maybe if they get many such complaints they will look into it. Just one camera being sent in for inspection won't convince Canon there's a bigger issue. I doubt they read this forum.
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Old January 22nd, 2011, 02:18 AM   #15
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Glen, I bought my unit back in September I think... Steev bought his a little before me (and reported issue a long time ago)... The XF305 I tested today is hot off the shelf.

It's quite possible to get glorious shots wide with the XFs providing you do any ONE of the following:
A) don't use the NDs
B) use autofocus
C) use manual focus without zooming
D) stop down the aperture

In other words, I can understand why some people have not come across the issue. It's only snagged me from time to time - now I know what's going on I can live with it.

Would Alan Roberts have tested parfocal acuracy with NDs engaged? Is it a problem one would anticipate?

Last edited by Josh Dahlberg; January 22nd, 2011 at 03:55 AM.
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