A GL-2 Imaging Bug / Attribute

[Ken Tanaka]

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.

[Randy Wisman]

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

[Aaron Koolen]

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

[Ken Tanaka]

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.

[Aaron Koolen]

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

[Ken Tanaka]

<<<-- 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.

[Bud Kuenzli]

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....

[Ken Tanaka]

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.

[Bud Kuenzli]

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.

[Aaron Koolen]

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

[Ken Tanaka]

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

[Aaron Koolen]

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

[Dany Nativel]

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

[Ken Tanaka]

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.

[Dany Nativel]

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.