Canon New FD 35-70mm f/3.5-4.5

Pack one body and walk an unfamiliar city for a day, and this is the lens you want screwed on. It covers the range you actually move through, wide enough for a street corner at 35mm and tight enough for a half-length portrait at 70mm, and it does it in a barrel that weighs almost nothing and takes a cheap 52mm filter you already own. The heavier f/2.8 zooms and the bag full of primes both lose this particular fight. You stop fussing and you shoot.

Optically it is honest about what it is. Stopped down to f/8 it is sharp across most of the frame, plenty for a 6x4 print or a scan you actually look at. Wide open at 35mm f/3.5 the corners go soft and contrast drops a little, and at the 70mm end you are at f/4.5 with some field curvature creeping in. Color and contrast are typical late Canon FD, neutral and a touch cool, with decent flare control as long as you keep the sun off the front element. The bokeh is fine rather than special. This is not a lens you buy for melted backgrounds; it renders out-of-focus areas cleanly and unremarkably, which is exactly what a working travel zoom should do.

The honest weakness is the variable aperture in dim light. At 70mm you are starting at f/4.5, and indoors or at dusk that costs you. On a tripod with a slow shutter it does not matter, but handheld in a cafe you will be wishing for the f/1.8 fifty in your other pocket. Push past f/16 toward the f/22 minimum and diffraction softens everything, so the useful window is roughly f/5.6 to f/11.

It usually turns up in the cheap end of the used case and shoots above what people pay for it. Buyers cross-shop it against the Canon FD 50mm f/1.8 (faster, sharper, one focal length) and against later zooms like the 35-105, which give more reach for more bulk. The reason to keep the 35-70 is that it stays out of your way and adds nothing to the load. FD-mount AE-1 Program and AV-1 shooters reach for it as a do-everything default, and on an adapter it lands cleanly on mirrorless digital because the short range and small front group keep distortion modest.

One metering habit pays off here. Because the maximum aperture changes as you zoom, an exposure that was correct at 35mm f/3.5 is dimmer by most of a stop by the time you rack out to 70mm. Meter at the focal length you are actually going to shoot, set it in Zone Light Meter, and do not trust a reading you took while framed wider. The 52mm thread also makes this an easy lens to feed with a polarizer or an ND grad for bright landscape work, since 52mm filters are everywhere and cost nothing.