If you want to obtain critical focus with enlarged live view on either Nikon, which I use, or Canon, which many of my friends use, you do need some sort of magnifier. I started with one of the old loupes I had used with my 4x5 and while it worked, the Hoodman blocks out light very nicely and fits the entire screen. I even added their device which attaches to the hot shoe and holds the Hoodman in place, no hands. This has proven really helpful when using manual focus tilt-shift lenses as then both hands are free to manipulate the lens. I believe it is a worthwhile product. I too have looked at the Zacuto, but Lloyd's latest recommendation is a $700+ flashlight, and the Zacuto is quite expensive. My philosophy is to spend serious money for things are in the light path, eg lenses, filters, and bodies, and to try and cut back a bit on others unless the convenience is really worth it or the price is reasonably small.