Purpose of foam inside mirror assembly?

[sean_r2]

<p>I've recently acquired two old Canon manual film cameras, and the little foam strips on each of them is totally shot. I wanted to find out: What was this for? Is it something critical that I need to get replaced? If so, what type of foam would work the best (I wouldn't even begin to know where to guess what type of foam they used to be, as they were super old and crackly before falling right off at the slightest touch).</p>

 

[Mike Howard]

<p>Yes, they should be replaced, but more importantly, all traces of the old need to be removed so they don't contaminate the rest of the camers, especially the shutter. </p>

<p>The foam pieces dampen the action of the mirror, reducing the vibrations caused by mirror slap. The best replacements for these are those made by our good friend John Goodman. They are available on That Auction Place who shall not be named, do a search for Interslice, which is his company name on That Place that Shall Not be Named. He includes good instructions and everything you need. Here is a link to one such kit: Well, apparently, we can't link to auctions, so just do a search for "interslice" and you'll find him.</p>

<p> </p>

[chongspics]

<p>I bought a foam seal kit fro John, couldnt have been more pleased.</p>

[Lou_Meluso]

<p>Sean, there is a good chance that if your mirror bumper is bad, then your seals are ready to be done too. Most likely you can use a full CLA (clean, lub and adjust) from a professional camera tech although some of the more handy folks try a home CLA. Not me, although I have had some luck with John's foam kits with other classic cameras and fully recommend them. They have very complete instructions that must be followed to the letter. Getting old foam bits on your mirror or focusing screen is BAD news. Proceed with care!</p>

[photom]

<p>The purpose of the foam is to dampen the mirror slap and more importantly make it easier to create a light tight seal around the mirror when it is down.</p>

[h_s1]

<p>Sean, others have responded about what is its purpose. And you also know by now that if mirror foam is disintegrating and sticky, then there is quite a good chance that film doors seals also need replacing.</p>

<p>Based on others suggestions, I tried to contact the foam seller on ebay but didn't get a response for some days so I just wnet ahead and did this myself (you can search the archive here) after reading some article online using the following procedure:<br>

1. Got some foam pads from an arst and craft store (they are around 2~3mm thick, so they are just right for us, just one foam pad is more than enough), 6 or 8 ply pure wool, naphtha (Ronsonol from a hardware store), and cement glue (or any other glue that is good with fabric and metal). Also, a sheet of felt(from the same crafts store, or felt stickers).<br>

2. Removed the bad seals and foam. This is most crucial and time consuming part of the project and you need to very very careful and patient while removing the mirror foam lest you damage the focusing screen. Basically, I inverted the camera with the lens off, used naphtha and ear buds to wet the mirror and tooth picks (perhaps cut with a knife to make a sharp blade like edge on one end) to remove the older foam. Do not use too much naphtha at one time, but go through several iterations to completely remove the foam. Similarly, remove the seals from the back and from the film door's edge on the hinge side.<br>

3. Cut a 2mm wide foam sufficiently wide for the mirror foam base and stick it in place of the old mirror foam.<br>

4. Cut the wool and stick its one end on one end of the ridge in the back of the body. Twist and tighten the wool yarn and keep inserting and sticking it to the rest of the ridge using the glue (I used a paper clip to insert the wool). The upper ridge needs to lengths of yarn for a break where the frame counter comes out of the body.<br>

5. Similarly, remove the strip of foam from the film door near its hinge. Cut a suitable length of felt and stick it in its place on the film door.</p>

<p>Here is the post I used for the procedure:<br>

http://www.photo.net/classic-cameras-forum/00SVtt</p>

<p>Here is my post:<br>

http://www.photo.net/casual-conversations-forum/00VQqN</p>

<p>And to clean your mirror (if your foam is bad, mirror will also have the sticky mess on it), this might help:<br>

http://ghaint.no-ip.org/~sahambi/photography/Canon_FTb/ (has pictures)<br>

http://www.acecam.com/cameras/842.html</p>

<p>After this, your camera will have new seals and mirror foam and you are done.</p>

<p>Post here or pm me if you want further details.</p>

<p>Good luck.</p>

<p> </p>

[bob_miller4]

<p>Is there a replacement for the foam and seals that does not deteriorate over time?</p>

[h_s1]

<p>Well, using wool yarn instead of foam in back seals is one option. I recall reading some place that this was more common in the earlier times, till the camera manufacturers realized using foam is economically cheaper. Apparently, using black wool, felt and velvet is fairly common DIY repair in movie cameras.</p>

<p>I have noticed that in cameras the foam is the one to go, whereas the felt and velvet strips are usually in good shape (at least in cameras from around 1967).</p>

<p>This made me think that if I were to use felt strip, perhaps folded in a "u", sewn at the open end "u" to make it around 2 ~ 3 mm thick and then pasting it in place of mirror damper foam might do the trick. This might need another "u" over it to make this 'tube' like thing wider. Further, pasting a layer of velvet to face the mirror slap might improve this a bit further. I assume a fabric like this would outlast a foam, or perhaps there are special foams that do not deteriorate over time (or take much longer).</p>

<p> </p>

[Lou_Meluso]

<p>From a previous discussion with Jon Goodman, the new foam products have a different chemical composition and do not deteriorate in the same way or time frame as the original materials. The new foam will last much longer, but I suppose all thing must pass eventually.</p>