Bag vs. normal bellows (4x5)

[CXC]

Through happenstance, I discovered today that I can use my bag bellows with my 240mm lens at infinity (at which I most often shoot). Generally I carry 65/90/159/240/450; this means I can use the bag with 4 out of 5 of my lenses. So I'm gonna try to think the other way around -- the bag should be my normal bellows, which I can swap out to the "extended" bellows when using the 450.

It's one of those combo designs, with a bag in front and 4 or5 accordian folds behind. If yours is similar, don't "sell it short" -- it may be more useful than you realize.

[Clueless Winddancing]

Cambo has had several "designs" of their WA bellows. My very early leather one is flat as a pancake. Later I acquired a virtual box-bag of synthetic material.

[Donald Qualls]

The big issue with using the bag on longer lenses is it's a little more prone to sagging that can vignette on the negative, especially a "medium" extensions. OTOH, this might solve some of my problems with the bellows on my Aletta -- if I had a bag that would let me use, say, a 265 mm and still compress enough to focus a 135 mm to infinity, I could cover every lens I own and get rid of the translucency problem. Gotta check prices on black velvet and start cruising yard sales and thrift stores for a sewing machine (used to own one, but it got left behind in a move).

[Eric Leppanen]

A theoretical concern with using a bag bellows with long lenses with lots of coverage is increased vulnerability to bellows flare. If your 240mm has a large image circle, then in theory the lack of pleats within the bag bellows will allow more excess image circle light to reflect within the bellows and possibly reduce the contrast of your shot. I have never tested for this in practice, and have no idea how much practical effect (if any) such excess light can have.

Using a lens hood will in theory reduce some of this excess light by reducing the amount of off-axis light entering the lens.

[JW Dewdney]

I would think that an accordion bellows would be WAY more prone to reflections - whereas a large bag bellows would pretty much act like a baffle. I have no idea how a bag bellows could reflect light... at least to the extent that an accordion would.

[Donald Qualls]

I would expect a pleated bellows to be better on flare when it's not too extended; the pleats act as baffles. When extended to the point where the pleats begin to flatten, however, I doubt it would be any better than a bag bellows with black velvet on the inside surface (real velvet, not the loop-pile velour we usually see that has a sheen).