Who uses the eyepiece cover [on the strap] if the camera is on the tripod?

I know with film cameras it can be very important to cover the eye piece. On my Sony I don't think it matters as it has an EVF. But on a 7D does it make a difference - when the body is on a tripod.

I'm not talking about massively long 'bulb' type exposures more interested when say using 2 strobes in say a room with light walls.

The 7D manual does advise it - but is that really overkill. So far not had any problems but then I wonder would my images be more acurately exposed if I took that bit of extra care?

It depends.

Never. I once got caught out and couldn't figure out why I had the weird bright spot in my frame. Turned out the sun was shining directly onto the viewfinder.

It's unusual that I will have enough light coming in from behind the camera to make any difference. But when I had the A1 with the built in eyepiece cover I used it all the time.

Does the adapter just protect against light leaks around the mirror? Am I mistaken to understand that on long exposures the mirror is flipped up blocking the eyepiece anyhow?

The viewfinder cover isn't there to block light during the exposure. It is there to block light during the metering portion of the exposure.

If you rely on your cameras built-in meter during exposures, long, short, bracketed or otherwise, blocking the viewfinder is a good thing to do.

If you're shooting in manual mode using a handheld light meter, blocking the viewfinder is unnecessary.

I block it out of habit. Very easy to do on a 1 series body.

long bulb shots yes
and time lapse video a must

I used the cover for my long 10-Stop exposures. Without it in most cases I would get bad light leak.

Never...(especially since I'm using a Crumpler Industry Disgrace strap)...but on my old 1D3 I did use the built-in eyepiece shutter for super long exposure shots...wish more cameras had that!

On many cameras you can clearly see a different meter reading with something blocking the eyepiece (like your head) vs. when it's free in open air.

You don't need it in manual mode, as explained above, but if the camera is metering with your head away from the eyepiece you can just cup your palm over it instead. That's what I used to do with my 5D - the piece of neoprene went straight into a drawer in case I ever wanted to sell the camera.

Remember, with your eye there it's not light-tight so it doesn't have to be perfectly light-tight with normal length exposures.

The issue becomes a real issue mainly when you remote control your camera, or if it's taking photos under control of a TC-80N3 or similar. Then nobody is near the eyepiece.

I've not lost a rubber blanking piece . . . yet. But it's too fiddly, so I black-markered some surgical tape which is stuck to the grip for instant access. I've only used it three times in 18 months, so probably not worth the effort.

Thanks guys
I saw a genuine Canon eypiece cover for £9 delivered so got it as it seemed quicker to get on and off - squeeze and pull. So I'll just block one of them off with some black plastic and thin self adhesive strip.
Even if I lost the original I could just clean it off as a spare.

Very interesting that it's the exposure metering figure that get messed up I thought it was the actual exposure. Great this site you lean something every day!

Have never used it. Not for ND110 shots or bracketed shots or .......

If using E-TTL and bouncing flash from a wall or ceiling behind you, underexposure results if the eyepiece isn't blocked from the preflash.