Paint flaking in mirror chamber
 

I've just bought a Letus Extreme from a mate but it seems to have the black paint peeling off like spidery cracks on the right hand side of the mirror chamber which can be seen when looking through the adaptor. Is there any way that I can blow the paint out of the adaptor? Can I open the adaptor? Or do I need to have it serviced? if I do need it serviced, where in Sydney Australia can I get it done?

Don't forget that you're roughly half way between Sydney and Brisbane. Plenty of good tech guys in Brisbane.

Andrew

That's not entirely true Andrew - 90 minutes to the Harbour Bridge from here, and 7 hours to the NSW/QLD border! Still, if it means I get my Letus fixed I'd be more than happy to make the trip

Shaun.


See other post on removing the achromat for the link to one of these opened up.

Are there actually loose flakes of paint drifting around or sitting on glass inside?

If not I would counsel against opening it up. Getting all the prism faces clean after you sully them with fingerprints is as Chris Soucy describes - a real mission. What you are seeing may be milling marks in the metal surfaces.

Thanks Bob. The paint isn't drifting it does appear more like cracks on the prisms, although the previous owner didn't have them when he first bought the adaptor and has never dropped the adaptor or had any big knocks. I haven't been able to mount the adaptor onto my camera yet as I still need to buy a new lens adaptor, so I don't know whether I can zoom past them or not. I'll check out the other post

Shaun.


If they are prism cracks they will be bright and there might be rainbows. Hopefully there aren't any. It would take a fairly heavy knock in transit to crack one and likely it will be a corner off one of the smaller prisms. If it is not too bigh a chip, blacking the chip should help if there are any flares.

Let us know how you get on.

here are some photo's - it's not really clear but on one side you can see some paint/matt surface missing and these cracks/paint flecks/?? come out from that - they look like thin wires or circular cracks but they're not.

you can zoom in past them, (they just show on the edge on one side) but if we can get rid of them - great.

I've leave Shaun to pull it apart - if I tried they'd be 4 or 4 pieces left over and the thing would never work again

Paul.


That is not a good look. Those are prism cracks to me, I think on the heel of one of the small prisms, the lower one possibly where it fits over the centre spine or in centre of the big prism on the front. It is a bit hard to pick it. The cracks will be most likely very shallow flakes coming away.

If you could get an insurance claim for shipping damage I would do so. That seems to be impact damage. It looks like it has copped a hard enough thump to slam the prism against the spine and flake the glass at the corner.

It might also be the beginnings of bond separation between two prisms but I think it is flaking glass.

The moment you try to pull it apart, the flakes of glass will fall right out when you disturb the prism.

It might be remotely possible to put some UV-cure optical adhesive on the cracks, pull a vacuum on the whole adaptor, let the pressure return and take the adhesive into the cracks, clean off the excess with solvent, clean the optical surfaces spotless, then shine the UV light onto the adhesive to set it off.

If the adhesive is carried into the cracks by returning atmospheric pressure, the cracks should largely disappear. I don't know what Windscreens O'Brien uses. Might be UV cure and vacuum infusion. I doubt you would be able to use the image area where the cracks are. There would be an optical abberation of some kind unless you zoom past it. Disappearing the cracks will reduce any added flare they would otherwise cause in that portion of the image.

Those other marks seem like milling marks in the metal case to me.

Paul.


Furthur to my previous post, if you use the damaged Letus without immobilising the loose flakes of glass somehow, tiny fragments may come away and get on the back of the condenser or anywhere in the path to become a nuisance.

They may also migrate in between the centre spine and surfaces furthur into the active image area and grind between the metal and glass surfaces.

So it is a bit of a dilemma as to intervening and possibly aggravating a problem or leaving best be.

If loose bits get into the active areas and you intervene, take care when cleaning them off.

Don't blow them off because a piece of glass in the eye is not funny. Don't wipe them because they are hard particles and will scratch and gouge the other glass. Use a damp cotton bud to pluck them off.

Make sure there are no other loose flakes inside when you polish stains off the glass otherwise they may pick up onto your lens cloth and then scratch your glass.

If the flakes come off and you have an open chip in the prism which is causing flares, try painting the inside of the chip with black permanent marker pen to see if that fixes the flare.

The inner surfaces of the metal casework you may find have been coated with a light grease against corrosion and to trap any loose dust or swarf which might have been missed in pre-assembly cleaning. This stuff will come off onto your fingers and folds in the lens cloth.

If you are cleaning prism faces in-situ, you may find it more helpful to cut a small piece off the lens cloth and hold that bunched in a pair of plastic medical tweezers for spot cleaning of prism faces. Cut some cardboard shields out of Weetie packet and use them to stop the lens cloth from touching greased surfaces.

If you get a greasy stain, cut a sugar cube sized piece out of a kitchen sponge, Oates or similar soaky type, not the open foam yellow stuff.

Dampen it, put a drop of Cussons or similar dishwash on it, squeeze it into the damp to mix it in. Without the sponge being drippy. wipe the stain with it until cleaned, then use another piece also damped with plain water to wash off.

Then use another damped one with ordinary bathroom cake soap rubbed against it, then wash off again, then dab dry with a piece of kleenex tissue ( not the aromised ones as they may contain oils ).

Then polish final stains with a lens cloth. You can also use cotton buds but they tend to come apart and leave whiskers behind.

Great pics Paul. I tried to get some photos but they didn't turn out as good as yours. I think the insurance claim is the way to go (I got your phone message BTW - I'll speak to you in person soon). Bob, you are a wealth of information. However, everything you suggested is way beyond me! I'll se how Paul's insurance claim goes. I don't want to have to give up an owning a Letus after only having it for a few days!

This is true, but using rubber gloves is essential - helps grip too. The Letus Elite at least, has an oily coating inside, presumably to catch any spcs of dust or larger bits of dirt floating around inside it. It can be a mission if you touch this and get it on any of the many pieces of glass inside. It all depends on how brave and how patient you are. These things are fairly simply put together really. I spent 6 hours cleaning mine the other day. Took every bit of glass out and vacuumed the housing. I got sick of of dirt getting on either one of the prism faces or the GG. Since I do this often, I built myself a dust free chamber with an extract. Makes it easier.

Tough break on the cracks though. No pun intended,

Rubber gloves? Wash them first so you don't get talc coming off them onto the glass.