My lens cocking tool just arrived and I've given it a try. I must say, it doesn't actually feel safer than using a coin for me so far. A couple of things I don't like. (I'm going to refer to the bit on the lens with the slot it in as the "screw head", because it looks like one and I'm not sure what else to call it).
- I feel like I have to hold the tool at the very end near the screw head when using it. Trying to use any of the length of the tool means you've got this bit long lump of metal "secured" by your fingers at one end and the screw head at the other, the moment you get any "angle" on the tool it can slip off of the screw head, and then it feels a lot like I'm waving something quite jabby at the rear element of my lens.
- When keeping the tool short, things are more secure, but the tool covers the whole of the screw head, that helps with grip, but it makes it far harder to assess the amount of "turn" I've put it. When you do it with a coin you can easily see the angle of the slot and the red dot you are turning to, that's harder with the tool.
- I feel like the above also means there more of a risk of "over tightenting", which feels very bad. Obviously there's just the potential of doing something nasty to the internal spring, but also, I worry about wear/"stripping" the slot.
- The tool is kind of OK if I put the lens on a non-slip surface and can be sure I'm keeping the tool vertical, but if I needed to do something in the field, that wouldn't be an option.
I feel like using a soft "copper" coin is safer? I can hold the coin to lower the risk of slipping and knocking the element, I can gauge the turn better, and it feels like I'm more likely the tear up the coin than the slot (the slot being worth literally thousands of times more than the coin!).
When "exercising" my lenses, I tend to do it with them off the body. I've taken to using a coin to cock them because that's just a lot quieter than having the lens on the body (the dog tends to sleep in my office with me, and I always feel terrible if she gets up because her "spare human" is messing about with his noisy cameras again).
I'll keep the tool around, especially if I need the other end of it one day, but I think I'll stick with the coin.