Comments about Seculine Seculine 77mm Vivicap, White Balance Filter + Lens Cover:

It works using custom white balance on my t2i. I tried it outdoors, indoors, at work, in the garage, and the white balance came out much better than I expected in different lighting situations. Can be used as a lens cap and just point to light source or if you have multiple sizes on lenses, you can just buy the largest you need and use it as a "filter" holding it in front of the smaller lenses.

Like others have noted, the wire center pinch mechanism is a little obtrusive. I removed them, but then the peripheral pinch meachnism no longer worked, so I had to put them back. That's the only reason I am giving 4 rather than 5 stars.

Comments about Seculine Seculine 77mm Vivicap, White Balance Filter + Lens Cover:

It does not get any easier than this. With the Vivicap on, set the lens to manual focus, point at the light source used and snap a picture. Then go in to the camera's custom white balance menu and select the photo taken. On my Canon EOS 7D it just takes a few seconds. Just remember to re-enable the auto-fucus if you plan to use it.

This is a huge time-saver and saves me the time of trying to dial-in the white ballance at the shoot or having to do it manually in Photoshop later.

The only reason for not giving the 5 stars is the metal wire clips for removing the cap when a lens hood is installed can be easily bent when bumping the front of the lens and rather would have liked some made out of the plastic the rest of it is made of. If I could give it 4.5 stars, I would have.

Comments about Seculine Seculine 77mm Vivicap, White Balance Filter + Lens Cover:

I use this on my 17-35 Nikon lens and find I get a much closer white balance reading than any of the presets on my D700.
I let it permanently attach itself to an old clear filter then just screw it on and off the lens.