XL1 / XL1S focus hunting backfocus problems

[Mark Solleveld]

Hi Rob,

it would definitely be nice if you could have a look at it. The thing is that in case of shooting with a tv-presenter I always used to set focus on his/her eye, then zoom out and after that everything stayed in focus, even if the presenter comes very close or even walks further away.. I really hope that the cam is ok..

If you like to please email me: marksolleveld@zonnet.nl
I live in Soest by the way..

thx all for your help

[George Goltz]

Would appreciate some imput.

I have been doing a fashion show for a school past 3yrs, using the XL1s standard lens, and have been really dissapointed in final video as far as the focus hunting.
The models walk down on a runway approx. 50ft long they stop in the middle and at the end, camera is positioned 25ft and 90degrees from the runway at midpoint. lighting of course is not ideal and not very bright at all, need to videotape from start of walk to midpoint then to far end of runway and back to start. Camera constantly hunts, last year I tried to pan very slowly and not zoom did help a little but very frustrating at least. camera is tripod mounted, iam using an 7"external monitor , tried to use lens in manual and push focus button constantly,but how do you pan,view monitor, zoom and push focus at the same time "not doable"
any ideas?

[Ken Tanaka]

Hello George,
Well you've just discovered how the role of "focus-puller" came to exist in motion picture production. Focusing while keeping pace with framing and motion is a real challenge.

Use of manual focus is essential, especially in dimmer light. (All auto focus mechanisms require a moderate amount of light and contrast to operate well.) Unfortunately, using of the standard 16x lens for manual focus is a challenge because the focus ring is electronic rather than mechanical. This makes repeatable focus moves almost impossible.

I recommend rehearsing, as best as possible, with your focus before the show. You have the advantage of already knowing where the models will move. Have someone follow that same path on tthe stage/runway and rehearse the manual focus motions required to keep them sharp. (That's what's done on film productions.) If at all possible, rent/purchase one of the manual lenses available for the XL1s. These have mechanical focus rings and witness marks. You can use a white pencil to mark your range on the lens barrel.

I also recommend setting your exposure such that your iris is as closed as possible (i.e. maintain a slower shutter speed or even boost gain just a tiny bit). This will create a deeper depth of field and help to keep subjects in better apparent focus.

Good luck.

[Bill Edmunds]

I do not own a Xl1s (yet). I was playing around with a friends XL1s and noticed that even the slightest touch seemed to send the lens focus off a bit (in manual focus). If I remember correctly, it seemed that even changing the gain settings would change the focus (manual focus). Is this right? Shouldn't the lens hold focus better than that? Does this unit still have back focus issues?

[Ken Tanaka]

Bill,
In my experience the 16x auto lens will hold focus when the lens is in Manual Focus mode and when the camera is in Manual exposure mode. If the camera is in a program exposure mode, such as Av or Tv the focus may drift as the camera adjusts the free parameters.

All lenses can have back-focus issues. The 16x auto lens reportedly continuously adjusts its own back focus, hence the lack of a manual adjustment such as those found on the 16x and 14x manual lenses. However, as with any other aspect of a gizmo I am sure that this facility can go haywire and require servicing.

We have had many people report focus problems with the 16x auto lens. Most were due to auto-focus matters. Some were due to operator errors. But, like UFO reports, some were inexpicable. Search around here and you'll likely find enough of each to fill your afternoon's reading.

[Robert Schofield]

Hi

I use the XL1 in full manual mode (and I am positive it IS in full manual mode!).

If I'm focusing a frame I'll usually zoom all the way in to my subject, focus, then zoom back to ensure a sharp focus.

When I pull back the focus though the whole shot goes in and out of focus like mad.

Is this an issue with my camera (i.e. does it need servicing), or a common general issue?

Thanks in advance!

[Ken Tanaka]

If the camera's exposure mode is in Manual mode and your manual is in Manual Focus mode, then the chances are that that the lens' back-focus is out of adjustment. If you are using a 16x manual lens (you didn't specify your lens) then follow a standard back-focus adjustment procedure. If you are using the standard 16x auto lens you will have to send the camera and lens to Canon for service. The 16x auto lens has a system that continuously adjusts back-focus but it can go awry.

One maneuver you may want to try before sending the camera for service (if you are using the 16x auto lens) is to unmount the lens, remove the main battery and back-up battery. Wait a moment and reassemble. Then see if this made any improvement. It's a long shot but worth a try.

[Robert Schofield]

Yeah it's the standard auto 16x lens. Thanks for the info I bought the xl1 second hand and the guy said it had been serviced by canon last year, which I guess means it wouldn't harm to send it in anyway.

Thanks for the advice. If you could offer any info on the technicalities of this "back focus" it'd be appreciated too!

Cheers.

[Don Palomaki]

You might try call canon as ask when it was last serviced. I believe that they do keep records.

[Ken Tanaka]

Robert,
As you may know, camera lenses are composed of many optical elements arranged serially to perform various refractory gymnastics on light as it passes through the lens assembly. The rear-most element of a zoom lens is responsible for ensuring that the resultant image strikes the objective point (in this case, the prism or CCD block) in focus throughout the focal length range of the zoom lens.

Since this "last word" element can get out of position (millimeters count here) with use (or when the lens is mounted on different cameras) many, probably most, professional zoom lenses feature a device known as a "flange back" that enables the user to make fine ajustments to the position of this element. This adjustment, known as "back focus" adjustment, basically calls for zooming close-in on something, focusing, then pulling wide to check for consistent focus. The flange back is loosened, then rotated ever so slightly to bring the object into crisp focus, then locked. The process is repeated until crisp focus is restored throughout the zoom lens' range.

The XL1 system's 16x auto lens provides no such flange-back facility to enable user back focus adjustment. I suspect that Canon's reasoning was that, with the camera is selling into the relatively unsophisticated consumer and prosumer markets, such a facility might only lead to unnecessary service expenses as users started to tinker with this foreign gizmo.

Gee, reading this made it sound really clinical, eh? Well, I hope this is helpful.

[Ken Tanaka]

Robert,
I just recalled that Chris Hurd wrote an article on this general subject quite some time ago. You can find it here, in the main section of DVInfo. I think you'll find it particularly interesting since it discusses your specific problem.

[Robert Schofield]

Wonderful stuff. Thanks ever so much for all your help guys!

[Edris Kamali]

Hi;
I have a Canon XL1s camera and used it only once. Every time I zoom-in or zoom-out the picture became out of focuss for one second. I usually record in Auto mode. I hope someone help me with this.

thank you

[Chris Staab]

Focusing will be a bit of an issue until you get used to your camera. Unless you decide to.....

A) purchase the optional monochrome viewfinder

B) purchase a lens that has true focusing capabilities.
(notice the stock lens rotates through and beyond a full 360)

C) Both A and B


I know that sucks to have to do this, but I chose (C) and couldn't be happier.

[Alexis Vazquez]

Chris, can you explain the relation between the focus problems and the monochrome viewfinder, also a little more indepth about the lens.

I'm sure new users will apreciate, me also.
AV