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139Q very Sweet

Hi Wang,
I am very interested in your comment about replacing the mirror bumper foam with silicone rubber. This surprises me because the silicone rubber I am familiar with is much denser than open cell foam. I have replaced the mirror bumpers on a couple of cameras with the foam strips that come with light seal kits (such as available on e-bay). This foam is very soft and readily compressible. Where did you find this silicone rubber that you are using?

Also you left us hanging with your final sentence about reducing the weight of the mirror flap. Details please.

Thanks,
Mike
 
Let me explain the use of silicone rubber in reducing the vibration created by the impact of the mirror flap. The transparent rubber I use is called Cica-care manufactured by Smith and Nephew at Hull in England. If you remove the white plastic sheet with red imprints,you could stick this sheet on scar. It effectively reduces the redness and the size of the scar. It is available pharmacies in Hong Kong and UK. Since it is so common to treat scar in this way,this kind of products could be easily obtained at drug stores in other countries. It is a large sheet and you could cut it to whatever size you like. It has two surfaces with one sticky and non-sticky side. The sticky side is uncovered when you remove the plastic white sheet.
330075.jpg
 
You could cut this sheet into small cubes with 6 surfaces. It will have 5 sticky sides and one non-sticky side,this is because the surfaces created by cutting are sticky too. You can stick it to the roof of the mirror chamber as in the diagram. The non-sticky surface is responsilbe for the contact to the mirror.The body showed is an RX. Photo taken by 50mm 2.5 Canon lens on a 10D at f4 1:1 magnification. Apart from the cropping factor of the camera body, the image is not cropped.
330078.jpg
 
Here is another image of the rubber cube from Makro-Planar 100 2.8 on a 10D f4 magnification 1:1. Again the image is not cropped.
330081.jpg
 
This time the RX is put on B-mode with the mirror flap lifted up on its own when the button is pressed. You can see the collapse of the silicone cube,it absords considerable energy from the impact of the mirror flaps. The problem of the sponge provided by the manufacturer is that it does not collapse enough to receive the impact.You can see this in your own camera/cameras.
330084.jpg
 
Two cubes of silicone can last for rolls of film. I have tried the silicone with longer lengths,but the absorption of impact is not as good as the length I showed on the photos.
The use of silicone in the way I showed in the photos reduces vibrations more effectively than the sponge provided by the manufacturers. I have been using the B mode to test this and the mirror impact is less noisy and creats less vibrations. The length of silicone use is also an important determinant of the impact absorption.
 
Thanks Wang for that explanation together with the excellent graphic photographs illustrating the procedure. I may give it a go.
John
 
Yes, thank you Wang for the explanation and the very good illustrations. I can't wait to hear about reducing weight of mirror.
Mike.
 
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