The Old Faithful
The Lens Cap Strap Holder
$15, Photojojo.com
A true photography staple. Pick your lens size, add to cart, then slide this snap-in holder on your strap. It doesn't get easier than this.
The Adaptable One
ReadyCap
$19.99, ReadyCap.com (adapter rings $3.99 each)
If you carry around more than one lens (and more than one lens size), the ReadyCap might be for you. Adapter rings screw on and off the strap-secure holder to fit mutliple sizes.
The Universal One
Cap Gorilla
$14.99, CapGorilla.com
If you want one holder to hold them all, the CapGorilla can stash away any cap up to 105mm without any adapter pieces whatsoever.
The Hidden Gem
Stow-Away Lens Cap Holder
$15, FullFrameInnovation.com
Ok, so it's not really hidden, but this lens cap holder goes where no lens cap holder has gone before: To the tripod mount at the base of your camera.
The DIY One
SkottiRotta Lens cap holder template
Free, Benvelo.com
Use this template and the pastic from a shampoo bottle to create this handy little hook for your camera strap to hang your lens cap (retrofitted with a short cord, which is also covered in the tutorial).
(Images: As credited above)
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Really?! No mention of one of these elastic tethers? Like the most basic and makes it literally impossible to lose your cap. Under $4 at Target. http://www.target.com/p/universal-lens-cap-keeper-1-x3-75-x5-4/-/A-13724289.
I have one of the ReadyCap holders... It's different than the rest because you can carry filters on it as well. I chose the ReadyCap holders after I watched this video that someone had posted on youtube http://www.youtube.com/watch?v=Q7_OwbbSUv8 The video is a comparison of various holders.
Lens Cap Strap Holder: for every Cap a new holder? Not very practicable
ReadyCap: Adaptable, ok, but everytime I change the lens I have to switch the adapter ring? Like the above, not very practicable
Cap Gorilla: One size fits all. I only hope the cap does not get lost while moving
Stow-Away Lens Cap Holder: Unpracticable for everyone using a adapter plate or a sun sniper.
SkottiRotta: drilling holes in every cap? Not really ...
Pockets work really well too. The key is to put the cap in your pocket. And then put back on the camera when you're done taking photos.