Folding TLR lens cap -- why does it fold?

<p>I am going to feel stupid here...<br>

What is the purpose for the hinge in the lens cap for TLR camera? I have the Minolta Autocord and just came across an original lens cap. I use one of the inexpensive plastic lens caps. Why does the original one fold? To cover one lens and leave the other open? To fold and thus be smaller?<br>

I feel a "d'oh" coming in...</p>

<p>I have a folding metal cap for my Rolleiflex, but your Autocord probably works the same way. If you think about it, the purpose of the hinge is straightforward.</p>

<p>If the cap was rigid, you could fasten it to the bayonet on the top lens, but you wouldn't be able to swing it in place over the bottom lens, because the bottom cap would collide with the lens mount. Since the two lenses are in the same plane, you need to be able to do one, then the other. </p>

<p>In fact, you only need ten or twenty degrees of flexion, but the gnomes of Brunswick made it so it would fold up 180 degrees, which is better because you won't break the hinge.</p>

<p>Odd fact about Rollei lens caps: apparently the convex mirror on the surface of the lens has the same focal length as the lens, so you can use it to line up a self-portrait of yourself or a small group. This is a clever, although completely useless, feature.</p>

<p>The cap folds to allow the cap to rotate so to fix to one lens bayonet rim as so not to pop off. Once fixed in position, it can be simply folded to cover the other lens. It's a very secure way of keeping the caps on the lenses.</p>

<p>The viewing lens has a bayonet mount. The cap folds so it can be attached to the top, then snapped over the taking lens.</p>

<p>I've never had mine fall off, and you know immediately if it's attached to the camera. Leica caps (brass, lined with velvet) don't fall off either, but don't pass enough light to take a picture. Nikon caps ... let's say I always carry several spares.</p>

<blockquote>

<p>"This is a clever, although completely useless, feature."</p>

</blockquote>

<p>Maybe not entirely useless. <a href="https://www.google.com/search?q=vivian+maier+self+portrait&newwindow=1&biw=1073&bih=617&source=lnms&tbm=isch&sa=X&ei=bcAQVbj7OtKnyAT8xoKoCw&sqi=2&ved=0CAYQ_AUoAQ">Vivian Maier made many self portraits with her Rollei TLR</a> and other cameras. I doubt anyone knows whether she used the mirror lens cap for alignment. She left no diaries, notes, or hints, and there appear to be no photos of her taken by other photographers who might shed some light on her technique. She may have been very good at aligning the camera without using the mirrored lens cap.</p>

<p>Ah, many thanks. It turns out the lens cap I bought doesn't fit, that's why I was confused. The viewing lens bayonet works fine, but there is no "snap" into the taking lens, just sits there. (The cap says Minolta but apparently not for an Autocord). </p>

<p>Lex, I assume you saw the documentary on her life. What a fascinating and sad story. In many ways, I guess we are all "walking wounded," some just more than others.</p>

<p>Todd I think this is normal for the Autocord cap. Mine is the same.</p>

<p>By the way, it never clicked with me why they are invariably hinged, until I read your post. Its like a lot of things, it's obvious, when you think about it.</p>

<p>With a bayonet fitting cap, the top part (viewing lens cover) <strong>has</strong> to hinge out in order to be able to rotate the bayonet fitting of the taking lens. Try removing it without hinging the top part back!</p>

<p>And now I see that Dave and Edward already posted this.</p>

<p>Post-war excess inventories of tiny hinges? (I actually agree entirely with Rodeo Joe)</p>