A cloth is more effective than a folding hood, but when I shoot 4x5", I often use only the folding hood and maybe a hat to provide a little extra shade, in part because I tend to choose 4x5" over a larger format in situations where I want to work more quickly and to be aware of my surroundings (i.e., not under the darkcloth in a crowded place). The folding hood is easier to use if you have a fresnel screen.
I have a Robert White viewing bellows with magnifier for my camera. At first I thought it was a bit difficult to use compared to using a darkcloth and loupe but now I am not sure.
I have been using it for about a month now and it seems to be doing everything that I could with a darkcloth and loupe. About the only area where I sometimes remove it is when I want to check deep in the corners with a loupe. (not that often for me).
The three key advantages I see for this is.
1. No need to remove, quick set up and adds protection to the groundglass
2. My head is always in plain sight so I do not feel like somebody could sneak up and grab something or perhaps accidently fall over me.
3. The lousy wind is not an issue any longer when focusing. Still not desired when shooting but at least the dark cloth is not closing in front of my eyes as I try to focus and adjust.
4. I do not believe that I will now be fogging the groundglass during winter shooting. (unproven but a reasonable guess)
As of late I am starting to get really comfortable with the viewing bellows and doubt very much that I will be using a darkcloth much into the future.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.
I tried the folding hood and the reflex viewer approach to avoid my large heavy hot darkcloth, but despite it's disadvantages I found a darkcloth is the best approach for me for many reasons.
So I finally made a home made one which is nylon silverized fabric on the outside and black cotton on the inside so it is lightweight and reasonably cool in the sun. I have fit it to the camera and put velcro at various places to hold in the dark yet keep to minimum size and weight. It also serves to cover the pinholes in bellows and act as lens shade when folded forward.
Other than having it redone so it doesn't look so amatuerish I am very happy with it. Wish it was heated and airconditioned but that might increase the weight.
Black sweatshirt is what I use. Hey if you want to go High Tech you could slide a white T shirt over the black sweat shirt to reflect the sun light. Since I do a lot of 8X10 I stick my head in the head hole backwards and wrap the waist band around the back of the camera. My wife is embarrased for me. I look like a goof doing that.
He is no fool who gives what he cannot keep..to gain that which he cannot lose. Jim Elliot, 1949
All three of my LF cameras have folding hoods. They are really nice for (A) a quick overview of the composition and (B) coarse focus. They are useless for critical focus, and with small-aperture wide angle lenses.
Nothing is as easy as composing and focusing with a 300mm/f:4.5 on the 5x7", but try a 90mm/f:8.0 on the same camera and I ned something else.
So I always carry a black T-shirt. Mine's a Levis, it is particularly "dense". Besides, it was on sale...
I have rarely had any reason to complain about the heat inside the T-shitr. But that's probably because I live in Norway
I had been using a BTZS focusing cloth for 3 years and just recently switched to the QuietWorks BlackJacket http://www.quietworks.com. It is lighter weight material than the BTZS and folds much more compactly. It is essentially an oversized "shirt" with gigantic sleeves designed to eliminate the light, but still allow easy access to the GG, and with a "collar" that has an adjustable elastic band. It also has "leather" around the collar so it doesn't slip off the camera. The BTZS's elastic collar is not adjustable and tended to slip off my camera. This new cloth stays in place very well. It has a black interior and a reflective surface and is not as "hot" as the BTZS. It does an excellent job of eliminating stray light and you can hold it up with your head while composing much better than the heavier BTZS. Since it is lighter, it may be a bear in the wind but I haven't used it under windy conditions, yet. I've only used it during three outings, so the final verdict is not in, but so far I like it very much and it will most probably replace the BTZS as part of my kit. It's not cheap: $75US.
Two black T shirts, one inside the other. Wear it through the neck hole and cover the back standard with the waist hole. Try it and see by yourself. If you like, then proceed sewing the edges. So simple and extremely efficient, without extraneous light and wind problems.