Letus35 FE removing inner lens at DVinfo.net

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Old November 8th, 2006, 12:20 AM   #1
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Location: Phoenix, Arizona
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Letus35 FE removing inner lens

If anyone can help me out, it would be much appreciated...

I have dust speckles on the inside of the lens where the mirrors are located. The red circle is where the lens is located.


Is there anyway to pull that lens off without breaking it so I can clean the backside of it?
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Old November 8th, 2006, 03:27 AM   #2
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The lens is a bi-convex glass element mounted in a threaded filter rim. It is an interference fit inside a precisely machined hole against an internal shoulder machined into the front of the flip enclosure.

The junction of the front tube and the flip enclosure is an interference fit, secured by an adhesive bond of the tube over an external shoulder machined into the front of flip enclosure.

Unless there is a compellingly urgent reason for disturbing the assembly, I would counsel leaving it alone.

You will also have to redo the adhesive and/or drill and tap screwholes if the disturbance refinishes the plastic shoulder to a less secure fit. I don't know the type of adhesive material Quyen has used. He is your best counsellor on this.

Your knowing of this lens suggests you have already had the groundglass mechanism and the front lens mount support removed from the tube to look inside.

You can check to see if the specks of dust on that lens are causing a problem by attaching the appliance as normal to the camcorder to look through this lens with the front groundglass/lens mount support assembly removed.

You will have to keep the camcorder focus the same as when the groundglass was in place as it might also be able focus sharply onto the surface of the lens which of course will disclose the motes of dust.

With normal focus on the groundglass plane, the dust motes may not be apparent but this test will likely tell the truth of the matter.

If there is a slightly darker patch, then obviously there is some cleaning to be done, but if there is not, best leave it.

If you have gone so far as to remove the tube from the flip enclosure and now need to remove this lens, you will observe a threaded shoulder on the rim of the lens.

By gently prising with two small jeweller's screwdriver points poked into the waste groove adjacent the shoulder where the threads have been cut and gently levering outwards a little at a time and moving around the lens, you should be able to tease it out and clean it.

You risk chipping the edge of the glass element inside the rim if it is very tight in the hole which is why a little and often is better than too much with brute force.

Take care not to place this lens face-down onto a hard surface as the curve of the glass protrudes beyond the face edge of the rim and it will get scratched.

Before attempting any dismantlements, make fine accurate reference marks across all joints.

If there is dust on the lens, there may well be dust on the surface coated mirrors as well. Do not be tempted to clean this off with a damp cloth or damp or dry cotton tips.

Surface coated mirrors can be easily injured. I don't know an appropriate method of cleaning them except perhaps by very light brushing with a soft lens brush and fine air jet. Don't blow by mouth on them as you will get moisture spots or condensation which will leave stains.

Hopefully someone else will contribute advice as I would like to know what is best as well.
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Old November 9th, 2006, 02:10 AM   #3
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Thanks Bob... How do you know so much about these adapters?
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Old November 9th, 2006, 05:15 AM   #4
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The knowing of adaptors? - cumulative experimentation, driven by penury, in home building one and wasted time going down dead-ends others have already eliminated.

There's two factors at play in regards the Letus which is otherwise not my business to stick my nose into.

I demoed my own adaptor and when asked about it, I referred the persons to technical literature at P+S and dvinfo and on the strength of info then posted here the item was purchased.

So when the persons bought them in and then experienced difficulties, I became sort of obligated to put things right, having sent them off on this adventure instead of redesigning, making and selling them XL versions of my own adaptor.

The more practical reason for me knowing a bit about the inner workings is that the entrails of one of the devices saw the light of day after spontaneously separating from the camera and heading for a hard landing on the floor.

When you are a long - long way from product support you tend to do stuff yourself as long distance freight tends to damage things en-route.
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