You may recall that I recently reported in another thread that my GL-2 appeared to have a bug in its imaging system. Having now received and tested a second camera I can report that this "bug" does, in fact, seem to be intrinsic to the camera's design and was not an isolated manufacturing flaw in my first camera.

In brief, the GL-2's imaging can show a distinct "vignetting" or "key-hole" effect under certain conditions. That is, the corners and edges of the image will noticeably and increasingly darken as the lens' zoom is pushed towards a subject. I've not yet established a definite pattern for this phenomenon but my tests seem to indicate that the effect is most severe when using Tv (shutter-priority) mode under slightly under-exposed conditions. It does not appear at all under "Auto" mode or when shooting well-lit, brightly-exposed scenes.

This attribute seems to be a bug rather than an explicit engineering attribute, since the second unit I've tested displays a much less severe effect than my first. If it were an engineered attribute you would expect the effect to be consistent across each camera.

This vignetting generally remains outside the normal ("action-safe") viewing area of a regular television, although the effect with the first camera I tested did infringe into the action-safe area under extreme conditions. NOTE, however, that this also means that YOU CANNOT GENERALLY SEE THIS EFFECT while you are shooting since neither the lcd nor the viewfinder display much of the image outside the "action-safe" area. Only after capturing your footage or while monitoring the camera with a professional monitor are you likely to see this bug. Of course anyone targeting their footage for full-frame displays (ex: Web streaming or other computer-based displays) should take special note of this attribute.

Since I am not a camera technician I don't know what's causing this problem. But I have reason to speculate that it's not simply the GL-2's lens but rather a combination of the lens and the GL-2's new CCD block. I reviewed some footage I shot with my GL-1 over 2 years ago and, lo and behold, I could detect darkening corners on several shots, although not nearly as noticeable as with the GL-2. This leads me to suspect that the new CCD has a hand in the problem along with the lens' characteristics.

On the whole, the GL-2 produces outstanding images and is the best of its class today, in my opinion, when all of its features and performance are weighed in toto. But if you've purchased a GL-2 you should take time to shoot a test tape specifically to determine if yours exhibits the same vignetting under low-light or slight under-exposure conditions (especially in Tv mode). Unless the problem is very severe on your camera you're probably best advised to simply learn to manage and avoid it since it appears to be the nature of the beast at this stage in the product's life.

If you have a chance to test your GL-2 please take a moment to report your results here. Two cameras do not constitute a categorical finding. Two dozen or more might.

Side note: Kudos are once again due to the folks at ZGC. Upon learning of my discovery last week, they immediately sent a replacement camera to me. No hassle. No yang-yang. Just plain ol' fashioned good customer service. Thank you ZGC!

An interesting, detailed, and well written report, Ken. Many thanks,

Oh well..., that's what you get when you're the first kid on the block to buy one of these new toys. Remember the PD100? And then the new and improved, PD100A?? Yup. I remember...as I kiss my MX300s good night.

Ken

Can you get the camera to do "it" in manual...so we'd know what fstop and gain settings cause the problems? I'd like to test my camera to help confirm or deny what you're seeing. So far I haven't noticed anything like it, and I've shot a lot of low light stuff....but I haven't captured much yet either.

Is this something that you notice "while zooming", as in a change over time that makes it more obvious, or is it something you can hold, and see the vignetting.

"as the lens' zoom is pushed towards a subject"--- does this mean the extreme end of the zoom range, or does it happen in the middle of the range or all the way through?

This sound's a little like a similar issue with the xl1s that was reported on earlier in the year, in that it happens at the most severe end of the exposure spectrum. (although I believe then it was the center of the image was darkening). It was most noticeable "while zooming", and was eventually concluded to be an limitation of the zoom in low light, low aperature, high gain situations.

Barry

The GL-1 and GL-2 have the longest zoom ranges in the industry (20X). The lens is a variable aperture design. In shutter priority the aperture is forced to change as light values change (which frequently happens when zooming the 20X range). My gut instinct says its a combination of extreme zoom range (lens design), variable aperture design and changing aperture that combine to produce the effect. The amount of gain applied only helps make the effect more apparent by making the scene brighter. Old zoom lenses ('60s and '70s) showed this aberration very frequently.

Jeff

Barry:
Try as I might, I could not get the camera to key-hole in manual mode! Nor could I induce the effect in Av (aperture-priority) mode. I could only induce it from Tv (shutter-priority) mode...and rather easily at that. Here are the steps I follow:

1. To avoid the hassle of unloading and capturing from tape connect the camera to a professional monitor that features underscan display. I use a Sony 8045.

2. Set the shutter to, say, 1/60 and aim it into a moderately lit or slightly dim room.

3. Zoom-in towards a subject as if you were snapping focus.

4. If the room is sufficiently dim (but not extremely dark) you should begin to see the effect on your monitor. Tromboning the zoom will reveal that the darkness incroaches further into the image as the lens is pushed closer. If you do not yet see it, try engaging the ND filter.

Jeff:
The fact that I can only reproduce the effect in Tv reinforces your supposition that the lens' automatic aperture adjustment is the agent. When I engage Manual mode right after observing the effect the lens tends to be wide-open and the gain has cranked up as high as 18dB. The Gl-2's 20x lens is, indeed, one long honkin' zoom. Most ENG lenses stop at 19x. So I suppose that some side effects are to be expected, even from the lens gurus at Canon.

All in all, this is probably a very moderate, manageable problem on most GL-2's. But as I noted earlier, the effect is not consistent across all cams. So, under the heading of getting to know your equipment's characteristics and limitations, I encourage GL-2 owners to check their cams for this attribute.

I think the reason that the key-hole effect varies from camera to camera is variables in the manufacture of the lenses themselves. When lenses are tested and evaluated it is not uncommon to see variances in focal length. The 84mm lens might be 83.5mm or 85mm etc. Because the grinding and assembling of the lenses is not a perfect process Canon has design tolerances that allow for some variations. I believe it is these variations that make the effect more pronounced on some models than others. Since it occurs in the overscan (in most cases), I doubt Canon will do anything considering it is an NTSC video camera. I wonder if the increased resolution of the new chips may also play a part?

Jeff

<< Jeff: "Since it occurs in the overscan (in most cases), I doubt Canon will do anything considering it is an NTSC video camera." >>

But the good news is that they've eliminated their horizontal blanking problem from the underscan area! <g>

<< Jeff: "I wonder if the increased resolution of the new chips may also play a part?" >>
After seeing hints of this key-holing on my old GL-1 footage I believe it probably does play a part.

It seems the vignetting is likely caused by the aperture not opening wide enough to keep up with the zoomed-in image, that needs more light. That you can accentuate the effect with the ND-filter, makes this appear to be even more likely. Putting it in aperture-priority eliminates it, as you say. I'd say be careful about zooming in too rapidly or not recording during zooming, until after the exposure is adjusted, unless necessary to catch the content.

Steve McDonald

Steve,
Once this "key-holing" effect kicks-in it is persistent and increases as the lens zooms closer. It does not dissipate when the zoom stops; it remains static in the image. To shake the effect off you have to change to a lighter subject or increase the exposure (shutter speed).

Ken, you'd be inclined to think this vignetting bug might be embedded in the processer's programming, if others reported the same thing. But, as it is, the mystery has yet to be flushed from its lair. Remember the flutter during zoom-in on some XL1s and the viewfinder burn-out that many suffered?

Yes, I sure do remember those bugs. Actually, the 16x on my XL1s still flutters from time to time when auto focus is engaged. I think it's just the nature of Canon's auto-focus processor.

Ken,

Does the GL-2 have an Exposure Compensation dial? What happens if you zoom with the dial engaged (+/- 1/2 EV).

Jeff

Jeff,
Unlike the XL1s the GL-2's AE adjustment is in a menu, although it behaves the same. Making adjustments to it does have a slight impact on the effect but it does not vanquish it. In fact, it looks to me like AE shifts merely accentuate or decentuate the key-hole. It really looks like a mechanical effect rather than a pure electronic/signal effect.

Ken,

To confirm your findings I encounter exactly the same 'feature' with my brand new XM-2.

I noticed it in faily dim lit rooms. It becomes stronger somewhere in the middle of the zoom range.

Since it's not always there, I'm still doing some tests to exactly figure out when it happens. Can you confirm the following:

- it's absent (or minimal) when the whole image (corners and center) is more or less equally lit (dim light).

- It's becomes clearer when the center of the image is lighter than the corners. (e.g. spotlight causing a darker ceiling)

It feels like that the CCD are non-linear. The exposure suddenly drops, whenever the light goes beyond a certain threshold level.

In a certain area of the zoom range, the exposure at the corners drop below this level while the center stays above.

This might be a combination of lens and CCD.

Please let me know your latest conclusions.

Randy,
I exchanged my unit for a new one, which does not display such a marked "keyhole" effect in low light conditions. I concluded that this phenomenon is probably a combination of the lens' design, the new ccd block and perhaps the way the ND mechanism works. It seemed most pronounced after I engaged and disengaged the ND filter. ZGC's lens expert seemed to feel that the lens' design and the new ccd block were the culprits.

Ken,

Based on your reply I decided to return my camera.

My photo shop had still 2 camera's in stock.
They also suffered the same dark corner vignetting!!
It changes a bit from camera to camera but it's there.

And now the strange....

The owner had one demo camera in the showroom.
This one was perfect!!

We concluded that this should be a production line problem, since it seems to be present a certain batches.

Randy

Bumping this thread after a looong time dead, but I've just come across this problem and it might help others considering buying a Xm2.

The reason I'm back here is because I was sitting down today capturing some footage and lo and behold I noticed the problem with my XM2 on this test shot I had done. I then looked over a couple more shots and saw it in them too where I hadn't noticed it before. In the few months I've had the cam what I have shot has been in good light so it's probably masked the problem.

Anyway, after noticing this, I then grabbed my camera and tried it in my room which was mildly lit (100w bulb). Even though the camera can see well enough in that light the keyholing was VERY noticable. At full wide you can see it, and when I zoom, the effect almost disappears around the middle of the zoom range. When the camera gets telephoto though the effect become more prominent. Maybe this is more noticable because the XM2 loses a stop or so when you're at full tele?

One other thing that struck me, was the fact I missed it for all this time. Does anyone think that the issue could get get worse over time? Sounds a bit unlikely to me but I don't know. (The tests I noticed it in were reasonably recent ones)

I'll do some more tests under various conditions this weekend and decide what I do - camera is still under warranty

Cheers
Aaron

Aaron,
Sounds like you've noticed the same problem.

I might not have noticed the problem on my original GL2 so quickly if I had not encountered the precise conditions that cause it so quickly.

No, it's not a progressive problem but it is variable from camera to camera. The replacement that ZGC sent me shows very little of this keyholing problem and only onder rather severe exposure conditions.

Interestingly, I discovered recently that this is not new to the GL series. I've been editing-together a piece I began in 1999, the original footage of which I shot with my GL1. Suddenly in several shots I began to notice the same dark corners beginning to creep into the frame. So I suspect that it's a charcteristic that's been intrinsic to the GL's Flourite lens design and/or the manner in which the iris operates. The GL2's new CCD block and/or exposure programming might have exacerbated the problem in certain conditions.

Thanks Ken. I might take my camera in and see if I can try some others to find one that shows less of a problem.

Do you have an Xl1s? If so, does it exhibit the same problem for you? My search on here suggests that it does a little, but not as much as the GL/XM.

Cheers
Aaron

<<<-- Originally posted by Aaron Koolen : Do you have an Xl1s? If so, does it exhibit the same problem for you? My search on here suggests that it does a little, but not as much as the GL/XM.-->>>

Yes I do have an XL1S. I've not seen this effect whatsoever on any of my XL1S footage regardless of the lens I used or the exposure settings. I believe that it could be induced, as I think that many professional lenses also share this characteristic to some degree. But I've never been able to induce it.

I'm not sure what I hit to make my previous post disappear before I was done typing so the short version here is I also see a keyhole effect particularly as I zoom into the 40x range.

Even worse, I also see a -pulsing- keyhole when NOT zooming, at fully wide anlge, about 1 meter from a poorly lit wall. Not extreme but enough to preclude any serious low light shooting. Return it and gamble on a new one? Who to give feedback to at Canon? The keyhole effect doesn't even require zooming and isn't even steady....

Bud,
To get to 40x you must be using some sort of tele-extender, eh? That would, of course, have the effect of drastically reducing the light into any camera's lens so I guess I'm not surprised to hear that it's more pronounced in such a condition. (BTW, one meter is an extremely close focusing range for the GL2.)

I really can't advise you whether or not it's worth exchanging the camera. I suspect that Canon's response might be cool when you mentioned using an extender. I suppose I would first remove the extender and experiment with the plain lens to decide how pronounced the effect really is.

no extender...I had 100x enabled via the digital zoom and as you zoom with digital zoom enabled you can then see the two different color-coded zoom ranges. I think the first range colored light blue in the lcd is the 40x range. It was that range I was referring to. I notice a keyhole effect prior to entering that zoom range, but as it enters that zoom range the keyhole effect becomes quite pronounced.

You might be noticing it more in the >20 range because it's a digital scaling of the image and not a truly zoomed one. This means that pixels will tend to become more blocky - and depending on the algorithm used and how the keyhole actually covers the pixels, it may get worse with digital zoom.

Ken, thanks for that. I am going to return the camera to see if they can fix it, or give me one that doesn't produce the problem as there have been some that don't display this issue. If not, well, then I'll have to consider my options. By an old XL1 until the Xl2 comes out, or fork out for an Xl1s....or....<whisper under breath> go Sony....<shudder> The new Panny is meant to be out here soon but I was told it'll be around 10k (~US$5500), so a lot more than the XM ;)


Cheers
Aaron

Aaron,
You only live once. Think big. If you decide on Sony, go for the DSR570WS. (Hey, I didn't say CineAlta, did I?)

Ken, be comfortable in the knowledge that if ever DV stopped being your thing that you'd have instant success in the comedy industry!!

That Sony is a loooong way off, much more than I need at present. Just need something that doesn't stick circles around my footage ;)

Cheers
Aaron

This is my second GL2. I exchanged the first one because it was showing the vignetting "feature".

The second one does produce the tunnel effect as well (see attached picture, F1.6, 1/12s, zoom fully out, all factory settings). If you zoom in or go over 2.2 the dark corners will disappear.

http://natzo.com/GL2/F16_12.jpg

The picture is a full frame capture and it’s pretty noticeable. I’m more concerned about TV viewing as I made some tests and was able to see some of the dark area on the TV viewing area.

Canon doesn't want to say anything about that because it’s “only” a prosumer camera!
I understand that it appears only under specific conditions (full aperture, no zoom) but for a $2500 piece of equipment I would rather get an explanation.

I’m trying to figure out if I should return this one again or just keep it, live with it and learn how to light a scene instead of staying focused on such details and shooting white walls ;)

Compared to the GL2 you guys have, does mine produce more or less vignetting ?

I was thinking about switching to another cam but for what ? (in that price range of course) and to get what other problems ? It’s probably all about compromises as no perfect gear exists on this price range.
I still think this cam is one of best bang for the buck with a great zoom and cool manual settings, good sound recording capability associated to a very respectable image quality.

Dany

Dany,
Yes, that's about the extreme that I've seen. I haven't encountered the problem with my GL2 lately, although I know it must still be there.

Interestingly, I attended a premiere showing of a documentary this week. The 40 min. piece was shot principally with a 1/2" Sony DVCam (I believe it was a DSR370 but can't say with certainty). Anyway, at several points I noticed that vignetting appeared in their footage as well! So I don't think it's a phenomenon unique to the GL2 but rather one related to lens and CCD characteristics.

On balance, I've decided that this isn't a major issue for my purposes. When viewed within the context of the camera's abundant good properties I can easly live with, and work around, this odd anomaly. Of course others may decide otherwise.

So from what you're saying I wouldn't a better GL2 (less vignetting I mean) by returning this one.

Also reading Bud Kuenzli's post I've also noticed "a -pulsing- keyhole when NOT zooming, at fully wide anlge, about 1 meter from a poorly lit wall. "

Is this another problem or connected to the first one ?


At least you make me feel better with your story on the DSR370 (about 3 times my cam value).
In this specific case, don't you think it could also come from a wide angle adapter or lens hood ?

Also when you shoot using the "fake 16/9" mode, are you exposed to vignetting ?

To conclude I wanted to say that with the WA58H adapter the vignetting will still occur.
One positive thing about using the WA (beside the good balance it provides to the cam with a large battery) is you will not get the vignetting at all at F1.6 if you agree to have a picture as narrow as the the one shot with the GL2 without the WA... because you need to zoom in to get it framed and vignetting simply disappear when you zoom in.

I think Bud's "pulsing" problem was the same problem. His pulsing probably related to his use of the digital zoom.

Hard to say about the Sony's problem. It sure looked like the same problem (on an enormous screen). I really doubt that it was a hood problem, though. This was an experienced camera operator not likely to make such a boo boo.

I actually use the WD58 adapter on my GL2 most of the time and have yet to encounter the problem with it mounted. Not saying that the adapter is the prophlactic, just that I haven't experienced it.

How close were the serial numbers on the pair of GL2's you've had this issue with.

I checked my GL1 for this issue, and am not seeing it.
Have any clips or photos you want to show for a visual descripton?

Couldn't say, Dan. I didn't record the s/n of the first GL2 that I exchanged for the second. I'd bet that they may have been close numbers, as both came from the same dealer within days.

Day's shot reflects the problem pretty much dead-on.

Aaron and Randy Wisman (XM2) have also encountered this. I think Jeff Donald's supposition of slight variations in lens manufacture hits the nail on the head. Apparently the GL2/XM2's lens' design is such that it's just on the fringe of some boundary optical property. One micrometer of grind variation too much and...

I wasn't using digital zoom at this time!

So what would be your suggestion ? return or keep ?

Thanks to everybody.
Dany

I can't tell you what you should do, Dany. I can only tell you the decision I made long ago and why I made it, which I did above. It's just not a very big issue to me.

If the origin of this "imaging bug" is of a mechanical nature, obviously a lens/camera redesign would be required to eliminate the problem. There's another intriguing possibility...what if the problem was caused by limitations of the camera's current ROM drivers and if that's the case, wouldn't Canon be able to fix it with a drivers/software update?. Since this bug shows up under unique filming situations, not likely to be encountered or noticed under most filming conditions, the only thing that would move Canon to come up with a fix would be if they heard from a lot of their GL2 customers.

I bought my XM2 almost a month ago.

I've found the problem of "key hole" on my camcorder too.
The factory continues to make so priced units with this "bug".
I don't know if they will do something to solve the problem considering that mine is a very new machine.
Is it possible that they haven't yet noted the problem?
I don’t think so.

Anyway, I hope that all these reports from us will lead somebody at the factory to do something.

I can say that at the beginning I worried a lot about this shortcoming.
Now I’m learning to manage it.
In my experience, the “key hole” effect is mostly visible in low light and in particular conditions.
The effect is more noticeable operating the zoom.
It seems that the worst point is in the middle of zoom range.
I've tried to modify the "key hole" in manual mode but no control has effect in it except the zoom.

On the other hand, in most cases the machine makes really outstanding beautiful images (even good photos!)
Colours are never excessive but well saturated and balanced.
Images have a good sharpness and noise is almost invisible even in reasonable low light.

Hope this may help.
Ciao

I don't know...I guess I've been listening to this discussion so long that I'm getting crabby...The so called keyhole problem is nothing more than an "uneveness of field" issue, which effects every zoom lens on the planet...(make that every lens, period). The gl2 as well as gl1 and and xl1s will all exhibit this problem in varying degrees due to the "longer than industry standard" zoom lengths. While we would all like a perfect zoom lens with a fisheye to moon crater zoom range with no vignetting (let's get the term right) or chromatic aberation. I'd also like a lens would bring us (god help us) peace without honor....

But it ain't gonna happen. There is a reason that a good cine zoom lens costs upwards of $20,000, and even then, I guarantee you if you pushed the film 3 stops (equivalent of 18db gain) and then did a rack zoom, you would find some unevenness of field visible in the footage.

The gl2 produces amazing results for a camera with a 20x zoom (oops I guess it's the only one)...I'm not trying to be a cheerleader when I say that perhaps we shouldn't be so amazed at its shortcomings as we should at the fact that the zoom is as good as it is. Canon engineers have pulled off a miracle zoom in my opinion...look at the size of the thing and then compare it to the zoom on the xl1s...(the lens alone is almost as big as the gl2).

I've been in commercial photography for almost 20 years, and I've never seen a perfect lens yet...especially a zoom. All systems have their limitations, and its one of the exciting things about being in this biz...learning what the limitations are, and then figuring out ways to succeed anyway...

This discussion is useful. Hopefully it encourages Canon to continue to advance their technology to produce even better cameras....but the point that is being made...that somehow the gl2 is a defective camera and why isn't Canon doing anything to fix it...I think this is heading down the wrong path.

Barry

Barry,
Thanks for putting the issue in proper perspective.

Barry, very well said!

Too many times people forget that these cameras achieve a level of performance that was attainable in the past only with cameras costing thousands of dollars more.

- don

Since terms are being discussed, I would like to offer two explanations of commonly confused terms, Vignetting and Light Fall Off. At first glance these might seem to be the same. But they have different causes and behave differently when the aperture is stopped down (use a numerically larger F number).

Vignetting is caused by an external source, such as hoods, stacked filters, or wide angle adapters. The effect is similar (dark corners) except the dark corners become sharper (more in focus) as the lens is stopped down.

Light Fall Off is caused by internal design of the lens. It is present in all lenses, but is usually not noticeable if the difference from the center to the corner is less than 1/3 F stop. Light Fall Off is most noticeable at maximum aperture and almost always is decreased by stopping down the lens. It is more common at the wide angle position of the zoom, but can occur at any position. The use of aspherical lens elements helps reduce light fall off.

I just got my GL2 today. It has this keyhole problem.. quite noticeable. It sucks especially for me because I will be doing a lot of greenscreen work. I guess I'll have to keep on experimenting to find ways around it. It seems as if the only way I can get rid of the effect is if I go outside and film. heh. There must be some way I can light the screen to reduce this effect...

Here's what I'm getting at the moment... http://www.scifi-pics.com/images/gl2error2.jpg

What settings produced this? (Shutter, aperture, zoom, etc.) There's alot of grain in that frame, suggesting that it was shot under very low light.

Chroma work will require quite a bit of light meticulously distributed evenly across the background with no reflections back to the talent.

The settings were factory default I think. There wasn't a whole lot of light that was hitting the screen (ok, bed sheet) because I had two 600watt lights directed at white boards which were aimed at the screen (hey, it worked with the canon ZR's, heh) so yes that shot was relatively dark. However, I just did another test with the two lights aimed directly at the screen. The fading was still present, although a little bit less noticeable.

I got my GL2 yesterday and played around. Today, I shot my first video to actually bring into the computer and edit for someone. I'm seeing the keyhole effect, but it looks that it would be off normal televisions. I was shooting for the web, so I planned to crop it anyhow. If this is as bad as it gets, I'll be fine with it.

http://joesacher.com/video/edges.jpg

Settings:
Movie Frame mode
Full Wide on Zoom, with stock lense.
F1.6, 0db Gain
Don't remember shutter, probably near 1/60, as I seem to remember it being just bright enough.

Nice to see that Canon is filling the 720 frame with the GL2, instead of the 706 or so plus black vertical bars that I got out of the GL1 I had used before.

If you read my post above, you'll see that light fall off (key hole effect) will improve as you stop down the lens. You shot with it wide open (F1.6) so that is the maximum effect. It will be less noticeable as you stop down.

Does this happen in Automatic? This does seem to be a problem. Its not like the strap is short or something...its acutally drawing your attention to its imperfection....

I believe it will vary with each lens to some degree. It will occur as you zoom and be more pronounced if the lens is wide open (F1.6, F2.0 etc.). It will occur in automatic or any other mode, if you force the lens to be wide open. If you set the mode to AV (aperture priority) and set the lens to F5.6 or higher, the fall off should not be noticeable, even if you zoom.

So basically, its even worse in low light because of this...

I am wondering if the extra 8X in a Gl2 is worth the quality loss overall to a VX2000?

I will be shooting day and night. Weddings, musicals, graduations, and maybe a short film. I hope Canon addresses this in the next month or so...

I really hate to get a lesser camera for the money.

I am a beginer and basically looking for a point and shoot camera from the go...

I heard that the Gl2 is this camera, but this is a downfall. No way to put it.

I went down into the same lighting I shot earlier today to do some tests. I recorded video a minimum light for Wide, 1/4, 1/2, 3/4, and Full zoom with Image Stabilization on and off. Shot data is in the image for the shot. Here are the results:

http://joesacher.com/video/canon/canon.htm

I expected that the results might improve or stay the same when I turned IS off. In fact, it looks to me that I get less of a keyhole effect with IS on. That is not what I would expect.