JJC WB-F1 Durable and Lightweight Universal White Balance Filter for Lenses up to 95mm Diameter, Certified 18% Transmission for Metering

it works really well, however my unit just came damaged and I didnt have time to send it back! so buy at your risk! hopefully if they see this, they would be kind enough to do something about it, with that being said it works well as expected.

Does not give a proper wb as much as a grey card.

This product does its job pretty efficiently and helps you record accurate colours under most lighting conditions. Its a must have if you're very particular about accurate colour rendition.

If used properly its a great helper to get your colors as real as possible

There's almost nothing I like better than finding a (much) less expensive item that works as well - or in some ways better - than the name brand item. I've wanted an Expodisc for years, have heard good things about them, but have never bought one for 2 reasons. 1) I couldn't stand to pay that amount of money on a piece of plastic (although I didn't mind spending $3400 dollars on a 5D Mark III - haha - great investment!); 2) the Expodiscs are sized to fit onto your lens, but I have 5 different lens sizes, so I could only use it on one of my lenses and would have had to buy 5 different sizes in order to utilize them. But I haven't had very good luck with using gray cards for custom white balance, and that has been a continual frustration for me, so I came back to Amazon resigned to finally buying and Expodisc. I found this little gem instead, read the reviews (don't we just love Amazon for that reason!) and decided that the price was so reasonable it wouldn't be much of a risk. I LOVE IT. Very easy to use, fits all of my lenses and the white balance has been spot on. I haven't used it outside yet, only in several challenging indoor lighting situations, which is usually where I need custom WB the most, but the WB has been perfect every time. I have also been using it to set my exposure and it's great for that as well.As far as the reviewers who said it was too big? I don't feel that way at all as it is one of the smallest, lightest pieces of equipment in my bag and I don't see how it wouldn't fit in ANY bag because it's so slim. I could see that's it's maybe a bit too big for some pants pockets, but geez, if you can't find a way to carry this thing around, you must not be very committed to accurate white balance. And that's all I have to say about that.Oh, and for another similar substitute for a name brand item that I have used for years and LOVED - check out this flash:http://www.amazon.com/Neewer-Speedlite-Panasonic-Fujifilm-single-contact/dp/B004LEAYXY/ref=sr_1_1?s=photo&ie=UTF8&qid=1452365121&sr=1-1&keywords=neewer+flash

How to use:(1) Put the white balance disc over your lens.(2) Aim your camera at the light source and take the picture in RAW (shooting RAW is the best for color correction).(3) When using the white balance selector in Lightroom, remember to put the dropper over a white area (or an area that should be white) that is the light coming from the light source. (Or use whatever is the Lightroom equivalent for this in your photo editing software.)When you follow these steps, it works great! Attached above is the before and after. It's proven to be highly accurate when I used the same color temperature and tint settings for other pictures that were taken with this sort of light source.