OT: Spots on Lens ( no not Spot Spot )

MUTTLEY wrote on 9/11/2004, 11:15 PM
Recently had a shoot for a music video and for some shots used my 3x wide angle lens for the XL1s. As I had it on a crane on the back of a moving pickup truck it was all I could do to keep the band in the shot and did not notice the spots on the screen. Sure did notice them once I imported the footage to Vegas though. Here are a couple screen shots:

Lens Spots Screen Caps

So I thought someone ( me ) had just overlooked cleaning the lens. Today I sat down with it, some Optic Cleaner, a Promaster cloth, and a Lenspen and gave it a good going over. Put the lens on the cam and hooked it up to an external monitor and they were still there. Hard to see unless you whack out the focus and have some lens flare, but they're there all right ... and a lot of em. Not sure what to think or what could have caused this. My unschooled guess is that it could have been caused inside the lens by humidity ? I can see small dots in or on the lens under bright light but hard to see with the naked eye. Actually can't tell for sure if its on the surface or inside.

So has anyone had a similar issue ? Kinda freaking out cuz its not a cheap lens. And while its a long shot, any suggestions to at least minimize the damage in post ?

-Ray

www.undergroundplanet.com


Comments

Grazie wrote on 9/11/2004, 11:38 PM
Mutts . .you aint gonna like this . . Er .. did you have a "filter" over your lens? . . "As I had it on a crane on the back of a moving pickup truck " . . . do you think it could be the unthinkable . . ? .. Sand pitting on the lens surface? . . WDs need BIG covers . .. I haven't got one for my Canon WD58h .. MUST get one . .. Is it possible you shot footage with abrasive sand, grit or dust coming at the naked lens?

Sorry mate . .. In the UK we do have a firm that can resurface lenses . .. maybe an option IF IT IS THIS?!?!?! But check it out first . .

.. . oh dear . ..

Grazie
MUTTLEY wrote on 9/12/2004, 12:30 AM
No, I didn't have a frigging filter on it. Though I did just buy one for my new 20x lens and I'll be buying one for this one as well. It was at the Austin Studios, same hanger than Mike Judge just used for his next movie. Was pretty clean and I honestly dont think it was from this shoot, the spots are there from the first shot.

With all that said your point is well taken my friend, believe you me. If I can get this fixed ( somehow ), trust me I'll never have a lens without a filter again even if that wasnt the cause.

- Ray

www.undergroundplanet.com
apit34356 wrote on 9/12/2004, 5:40 AM
Carefully inspect the lens body end(both ends), use mag lens to inspect surface for fine flim deposits from cleaning or being touched.
JJKizak wrote on 9/12/2004, 6:42 AM
Clean the viewfinder. Also air bubbles in the lens. Also random light spots in low light conditions. Avoid excessive bright light.
It's in the Canon XL1-s manual.

JJK
farss wrote on 9/12/2004, 7:47 AM
First of all are you 100% certain it's the lens?
I'm not 100% certain from your screen shots just what I'm looking for, there does seem to be some errant flare but depending on the lens coating and many other factors I've seen this in many shots, certain types of CCDs also produce these kinds of artifacts or something similar.
I don't really have that much experience so I could be wrong but before I freaked out too much I'd try another lens, you maybe chasing a ghost.
If you were using a standard lens then yes a filter of some form is a wise idea. One reason why many prosummer cameras don't have interchangeable lenses is to avoid the risk of grot getting onto the CCDs and or the back element of the lens. Also there's some nasty fungus that grows inside lenses. Zooms cannot be made airtight which is another problem. High quality fixed lenses and rifle scopes are filled with dry nitrogen to get around the problem.
If you live or work in areas of high humidity look into storing any geatr at risk in zip lock plastic bags with silica inside and replace the silica regularly.

Bob.
Randy Brown wrote on 9/12/2004, 10:30 AM

I don't see anything other than lens flare (unless it's the spot just to the left of the front man's floor monitor).
You may be aware of this forum Mutt but I would post this issue at the XL1 forum
Randy
apit34356 wrote on 9/12/2004, 11:31 AM
"If you live or work in areas of high humidity look into storing any geatr at risk in zip lock plastic bags with silica inside and replace the silica regularly." farss' advice should be on equipment labels. Going from air conditioning hotel room to the humid outside is another reason why equipment has problems.
Stonefield wrote on 9/12/2004, 11:46 AM
I see the spots you're referring to...Looks like muck on the REAR element. In order to see something like that on the front element, you'd have to be shooting almost macro photography and this is a long shot. Give the rear lens element a careful wipe if ya haven't already.

if not, it's inside somehow. That's happened to me with my Nikon gear. And that unfortunately has to be taken in for servicing.

rmack350 wrote on 9/12/2004, 11:51 AM
Possible causes are blemishes on the lens or spots-specks on the CCD. It's a wide angle lens so the back element might well be the bad spot. Wide angle lenses have tons of depth in front of the lens but almost none behind the lens-which is why backfocus is most critical at wide angles. And it's almost impossible to set backfucus on an XL1 if you're just using the color viewfinder.

Anyway, shoot a new test against black and with flares. Also look down the lens when this test is set up and see if you can see these spots. Shine a flashlight down there.

Maybe put another lens on as well and shoot the same test at that lenses widest angle

Good Luck

Rob Mack
JJKizak wrote on 9/12/2004, 1:32 PM
Like I said before, the Canon manual explains the problem and says to use different exposure settings. Those are light spots caused by bright spot lights at certain exposure settings in low light, not the spot lights themselves but the small light spots around the spots.

JJK
rmack350 wrote on 9/12/2004, 10:04 PM
Hey JJK,

Not that I own an XL1s but I downloaded the manual anyway because I was curious. I found the bit about compression/decompression bubbles in the lens after an air flight. I also found the bit about using a lens hood to cut down on lens flares (although an attentive grip does a better job).

Maybe you can give me a page number or some good search terms. Just curious what they have to say.

To me it all looks like lens flare-which you can't ever get rid of when the lights are in the shot. However, from the conversation it sounds like there are blemishes on the lens or CCD that are making things worse. I'm curious to learn if it's something beyond this obvious stuff.

Obviously with the lights in the shot it could be a smudge on any element all the way down the barrel of the lens. It could even be a reflection off a shiny surface down by the prism or CCDs

Rob Mack
rmack350 wrote on 9/12/2004, 10:16 PM
Ah...

found the next one. Page 109:

"About the CCD
Due to the construction of the CCD, in low-light recording using the slow shutter or gaining up, small specks of light may become visible in the viewfinder. In such cases, increase the shutter speed, reduce the gain or use an additional light source such as a video light."

Fair enough. Quite possibly the CCD is freaking out in addition to all the pbvious lens flare. Another thing is bugging me as well though. When I first saw the stills I thought Ray was using a star filter but he says the lens was bare. Hmmmm. Wonder where that's coming from then?

Rob Mack
Grazie wrote on 9/12/2004, 10:35 PM
Rob - I need Ray to "circle" the items under discussion. I took the lens flare as being wished. I never thought that it was this that Ray was having a problem with. So, yes, Ray, please "annotate" the areas with which you are having a problem. . .. It would kinda "throw" some light on it - yeah?

Grazie
MUTTLEY wrote on 9/12/2004, 11:58 PM
Grazie, you nailed it. The lens flares are intentional, the spots are not. The problem is only with the 3x lens, other lens flares from the same shoot with a different lens look great.

I've posted a pretty big clip from the vid if you really aren't getting what I'm saying, if you can't tell with the pictures this should clear up any confusion:

Zipped Lens Spots Video Clip

Also this was shot with my last XL1s and I just upgraded to an XL2 ( WHOOOHOOO !!!! ) , same thing with the 3x lens on the XL2 body. As I mentioned in my first post, I cleaned both front and back of the lens thoroughly, multiple times, to no avail.

- Ray

www.undergroundplanet.com
apit34356 wrote on 9/13/2004, 12:47 AM
video showns definely spots, either surface damage,like Grazie's suggestion or air bubbles in the glass or between glass mating surfaces. if glass got super hot, glass mating surfaces can separate. to test further, if you have a slide projector, put light thru lens onto a large wall, record pts. a laser source can be used also. lens can be rebuilt, mating surfaces - not bad, len element more costly. But if the len was made with poor glass, check with manufacturer first, maybe a bad batch of glass was sent out.
JJKizak wrote on 9/13/2004, 5:38 AM
I sometimes get a lot of spots that look like dirt on the lens but I can't see any dirt spots or any dirt on the CCD. The spots come into play when aiming into almost direct sunshine and sometimes if shooting blind without looking into the viewfinder. I would clean the lens but did not help. Then I noticed the ND filter seemed to reduce the problem but not eliminate it. Then I checked the viewfinder lens and the spots on the video seemed to correspond with the spots on the viewfinder. That makes me wonder if the viewfinder lens is uncovered and light shines into the viewfinder if that somehow gets planted into the video.
Anyway the light spots are probably not related to what I am seeing in my videos. The manual says on shooting spot lights to use certain settings.

JJK
farss wrote on 9/13/2004, 6:37 AM
Sure looks like light bouncing around in the optics. And thanks to Mutley today I was checking out one of cameras and I thought hm, looks like an odd flair and guess what , dint in the front element of the lens, deep enough to knock out a piece of the coating so we just bought another camera, cost over half the price of the camera to replace (cheap cammy though).

They look to me like separation between the coating and the lens. I'd suggest you dig aorund the Cannon XL1 forums. That camera had lots of problems and I seem to recall some issues with the lens. I really think you need to talk to a lens techo, mostly we're just speculating.
Apart from that it isn't THAT objectionable, if it's only affecting shots with bright spotlights almost incident to the lens it's not that bad. I know it'd bug me forever it was my cammy but will the average viewer ever notice?

Bob.