OT: Speck of dirt inside my Z1 lens

NickHope wrote on 7/27/2008, 11:06 PM
I'm a couple of weeks into a 2-month stint on a boat in Tonga shooting humpback whales.

Somehow a speck of pale dirt has got inside the lens of my Sony Z1 and is showing up as a black spot in the lower right corner on all my wide-angle shots of the whales and, in my view, ruining them.

It looks to me like the dirt is in the front of the lens system, on the front of the front-most curved element. When I zoom and the internal components move backwards the speck stays in place. The speck moves toward the centre of the field of view as I zoom in and then totally blurs/vanishes at 70% zoom. The sharpness of the speck varies with the iris and it moves around a bit, possibly because I have steadyshot on.

Is it possible to disassemble the lens system enough in the field to remove this speck of dirt?
How does that front flat glass element remove and how difficult is it?
Would one access it from the front or from the rear?
Are specialist tools required?
How big is the risk of trashing the whole lens/camera?
Are lens exploded drawings or service manuals available online?
Are any photos of a disassembled FX1/Z1 lens available online?

There are no Sony places or techs in Tonga and time is too limited to send the camera overseas for cleaning, so a DIY job is the only option. We have lots of tools/engineers/patience/time on the boat and could even make tools for the job if required.

The small white speck can be seen on the photo below.

Any advice would be greatly appreciated.

Thanks!

Comments

farss wrote on 7/28/2008, 12:54 AM
Pulling a lens apart without the right tool(s) in the humidity of Tonga could be asking for a lot more trouble. The tool needed doesn't look all that fancy and I have even seen them on eBay and for sale online.
Even with the right tool I'd be nervous about doing it although just the front element mightn't be too risky.

However before even contemplating such drastic action I'd try dislodging it from the glass. Lots of shaking might do it. Once you get it off the glass it'll hopefully stay out of the way until you can get it serviced. If lots of shaking doesn't do it you could try compressed air around the rim of the glass. Enough might get inside the lens to blow the grot out of the way.

Another idea. If the front element is a plastic lens it could be a static charge that's holding the grot in place although that would seem unlikely in the humidity of Tonga. Maybe the reverse idea would work. Take the camera into very dry air and try creating a static charge to move the grot out of the way.

That's about all I can think of. I would be very wary of pulling the whole lens assembly apart. There's sensors, encoders, motors, gears, springs and electronics in there.

Bob.

Grazie wrote on 7/28/2008, 1:41 AM
Take the camera into very dry air and try creating a static charge to move the grot out of the way.

I like that idea!

How about actually doing some plastic rod or candle stick static charging? Rubbing a Biro cover over and over on a dead cat and try and set up a charge? Then pointing this at the speck and seeing if you can dislodge/move it to the periphery? Now, I have absolutely NO idea if this would create any damage to any electrics within!! Perhaps try an experiment on a lens filter and see if that gets some attraction?

Can you hire another Z1 there? Would your insurance cover your hire?

Grazie
farss wrote on 7/28/2008, 4:09 AM
"Can you hire another Z1 there?"

In Tonga I doubt it.
But 4 hours flying time from Sydney, tropical island, WARMTH. Got 4 Z1s not doing much, I'm tempted to hop on a plane and deliver one myself.

Bob.
Serena wrote on 7/28/2008, 5:25 AM
Taking the lens apart is, I think, a bad idea. I'm surprised it shows as a defined black spot, because the speck in the photo is very small. First you need to shoot at wide aperture to soften the image of the speck and since it will be stationary in frame (unless you're zooming) look to fix in post.
richard-courtney wrote on 7/28/2008, 5:30 AM
"Rubbing a Biro cover over and over on a dead cat"
sounds good to me in any situation......

If you hold the lens near a CRT does the speck move?
Should be a strong charge.
JJKizak wrote on 7/28/2008, 5:31 AM
Try cleaning the front of the lens first even though it doesn't appear to be on the front of the lens. Sometimes there are "anomolies". That means there is something on the front of the lens but you can't see it. This was the case with my Canon XL1s. Being in the jungle it could be some form of bug juice.
JJK
farss wrote on 7/28/2008, 6:02 AM
That's a very good suggestion. I get to clean a lot of lenses and I've found specks on the front of lenses that are very difficult to remove. Worst cases I needed lens tissue rather than cloth or a fingernail.

Then again I've never had something get stuck on the inside of the lens. I've heard of bits of paint flaking off inside the lens but if it's stuck to where it should be so badly that it comes off then it's hard to imagine how it'd get stuck to clean glass. The only thing you usually have to worry about inside a lens is fungus but let's hope it's not that.

Bob.

ECB wrote on 7/28/2008, 11:20 AM
The spec of dust you show should no be in focus at the film plane. Worst case it should just cause light scattering and a loss in contrast. But the spec is so minute you would never measure the loss in contrast let alone see it. I would look for something else causing the spec to appear on the film plane.

Ed B
JackW wrote on 7/28/2008, 4:13 PM
Dead pixel?

Jack
johnmeyer wrote on 7/28/2008, 4:20 PM
The one time I attempted to open and repair a lens, I ruined it.

I also agree with the several people who said that a speck you see should not actually show up in the frame: I've filmed with dirt on the lens and been amazed and grateful when I later discovered that my footage was pretty much OK (perhaps not as sharp as it might have been, but definitely no spots).

In addition to a dead pixel, perhaps it is dust in the sensor? I have certainly seen this on my Nikon still camera which has removable lenses. I have the FX1 and its lens doesn't remove, and I think that is true of the "big-brother" Z1 as well, but perhaps some defect has allowed dust to get in.

This is clearly something which is going to require a Sony tech and something approaching a clean room.
farss wrote on 7/28/2008, 5:03 PM
I've slept on this and looked at the picture again.
It looks like something I've seen several times before. Yes indeed, I've yet to see those tiny white dots show up on the image. However this camera is being used in an underwater housing and most likely has an auxillary lens in it. Just how that impacts how the light hits the front element of the camera and hence that white dot I have no idea.

Perhaps more to the point though. That white dot sure doesn't look like it's inside the lens, if it was it'd be very hard to photograph, the coating on the lens reflects too much light. Now if that white dot is anything like the ones I've had to deal with they're darn hard to get rid of, as I said before more agressive cleaning could be in order. There's also the possibility that it isn't anything on the lens at all, it could unfortunately be a divet in the lens coating. I've found this on some of our cameras and I can't see how it's happened either, without taking the lens hood off the lens is well protected. Maybe something eats into the coating, I'd expect a hit from a sharp object to do more damage.

Bob
NickHope wrote on 7/28/2008, 7:05 PM
Thanks for all the suggestions everyone. Brilliant forum as ever!

This is definitely no dead pixel and I'm 99% sure it's not on the front flat element but down inside on the foremost convex element. I'm also pretty sure it's this spot causing the dark area on the footage because of how the spot moves on the footage relates to how the zoom works.

I'll go back to the boat and give the front another very good clean just to check, and I'll try some of these static ideas. We have a CRT TV on there. I've already given the front of the cam a good shaking/bashing and that hasn't helped. I also tried compressed air around the area but to no avail.

I found exploded service drawings of the Z1, and also that series of pics of the camera that a guy totally disassembled but in both cases the lens unit remains as single unit and is not shown disassembled.

Assuming I'll have to live with it, I'll definitely turn steadyshot off so that the spot doesn't move around. My choice is then whether to go wide iris and blur the spot, or stick to small iris and keep the spot small and sharp and more easily removable in post. My housing has an 80-degree plano-concave port/lens that makes the depth of field IN FRONT of it very long in either case. But the iris definitely has an effect on the sharpness of this spot on the footage.

I'm limping along in the slowest internet cafe on earth here but I'll report back tomorrow and try and post a couple of stills from the footage.
farss wrote on 7/28/2008, 9:29 PM
Looking more closely at your photo (don't have a Z1 at home) I fear you're right, the front element of the lens doesn't come out easily at all and it looks like it would be a major job to get inside of it. I've never even heard of a Sony repair centre repairing a lens. When we've had any damage to one it's been a complete new lens assembly.
Where I went wrong was some lenses retain the front element with a screw in ring that can be unscrewed with a tool not unlike the one used to take the back off a watch. That's clearly not the case with these lenses.

Bob.
ECB wrote on 7/29/2008, 6:35 AM
I will be very surprised if the dust speck you identified is causing your problems. Lens designers make sure the focal planes in the lens never are located on the surface of any of the intermediate elements to avoid the whole dust issue.

If you could find a negative ion 'gun' Zerostat and bombard the front element with negative ions and the charge may dislodge the dust particle. In any event I would never disassemble the lens.

EB
NickHope wrote on 7/29/2008, 6:49 PM
I tried the TV thing last night but there's really no static on the front of the screen, I guess because it's humid here on a boat in Tonga.

Looks like I'll wait until I get back to civilisation and see what Sony can do about it.

In the meantime here are some pics showing that it's definitely showing up in the footage. Some might say that I'm being fussy but that speck definitely bothers me and would be a problem for stock footage purchasers. I'll be looking to correct it in post with a mixture of techniques.

blurry (larger iris)



sharper (smaller iris)



zoomed about 30%

Tim L wrote on 7/29/2008, 7:34 PM
Nick,

I assume you have confirmed its not something on your housing -- that you see the same problem with your camera outside of the housing, right?

The fact that the defect changes with lens zoom and iris would seem (to me, an amateur) to confirm it's something in the optics path, and not directly on the sensor. Plus it would be color specific if it was on one of the three CCD's.

Come on -- isn't there anybody here with an FX1 or Z1 thats willing to glue a small grain of sand to your lens just to help confirm Nick's problem??? Anyone???

(By the way, Nick, it looks like you have a very interesting career...)
farss wrote on 7/30/2008, 4:08 AM
Nick,
my offer to try to get another Z1 to you still stands. You'd probably need to meet a flight at the airport which could put a serious dint in your shooting schedule unless you've got a runner you can trust.
PM me if you think it's worth the effort of me pushing it at my end.

Bob.
JJKizak wrote on 7/30/2008, 5:27 AM
My .02 cents says your not cleaning the lens hard enough. I had the same thing with my Canon XL1s. Clean the living crap out of it (hard rubbing) and if that doesn't work send that one in to be fixed and get another spare. (or a spare lens assembly). And make sure your viewfinder is clean as sometimes stuff gets reflected back especially if your eye is away from it and the sun is busting into it directly. But under water wouldn't seem like a problem. Then again those pressure changes might have busted something loose.
JJK
Serena wrote on 7/30/2008, 6:01 AM
OK, not a spot which is sharply defined and looks much the same as a spec on the screw in filter (I've had that) -- fairly annoying. Using wide aperture is recommended, which is also better in terms of diffraction softening of the image. Fixing in post shouldn't be a problem.