Should I reverse the enlarging lens when using on a bellows?

I often use a Nikon PB-6 bellows with a 39mm to Nikon F adapter to mount the enlarging lens on the bellows. I most often use the EL-Nikkor 80mm f/5.6 lens and with magnification up to 1:1 or less. Should I try to mount the lens in reverse?

Most high-grade enlarging lenses, such as the 80 mm f/5.6 EL-Nikkor, are of the symmetric Double Gauss design. I've found no advantage in reversing the lens for use on bellows or extension tubes.

I use my forward-facing 50 mm f/2.8N, 80 mm f/5.6N, and 105 mm f/5.6N EL-Nikkors, depending on the situation, with a Fotodiox adapter on my Nikon PB4 bellows unit. The results are quite good.

I’ve tried them reversed but saw no improvement. The lens-reversed setup is somewhat awkward. It’s simpler to use the lens facing forward. This also makes it easy to attach a filter if wanted, likewise for a lens cap while the lens is mounted on the bellows.

Good to know. I haven't tried to mount it reverse because it's difficult to do.

Chan, the rule of thumb is: lens designed for shooting below 1:1 (or for enlarging) is optimized for large subject (print) in front, small negative behind. To get the most out of the optimizations, reverse it when shooting above 1:1 (or making reductions), otherwise use in normal orientation.

When I was reading about using enlarging lenses for macro work (copying film negatives) several authors mentioned the fact that some enlarging lenses are symmetrical -- as @Ian C has already said. For those lenses that are not symmetrical, most websites said there was no benefit to reversing lenses for magnifications less than 1:1, but for magnification greater than 1:1, there might be. Sorry, I can not speak from personal experience; just repeating what I read.

For a while, I did use an enlarging lens on a bellows to copy film negatives with my digital camera and it worked well for that purpose. Because my digital camera has an APS-C size sensor and my negatives were 135 and 120, all of my duplication was done at less than 1:1 magnification.

If an enlarging lens has an odd number of elements, it has an asymmetrical optical design, and will benefit from being reversed at high magnifications.

If an enlarging lens has an even number of elements, it may or may not have an asymmetrical optical design.

There were different versions of the El-Nikkor 80mm f5.6 (six elements in four groups), but they appear symmetrical to me, meaning the glass on one side is a mirror of the glass on the other side. If that is the case, reversing it will do nothing.

Folks, the original Planar, the first 6/4 double Gauss lens, was perfectly symmetrical (identical front and rear cells). By construction it is optimized for 1:1. More modern planar derivatives are based on TTH's Opic, an asymmetrical Planar derivative optimized for distance. The OPIC and derivatives (Dallmeyer Super Six, Schneider Xenon, nearly all f/1.7 - f/2 normal lenses for 35 mm, ...) have unequal cells. This is why modern Planar type taking and enlarging lenses should be reversed when working above 1:1.