Resetting Aperture / Backlash?

[Sawyer Thurston]

Hello, Im reading a book and Im hoping someone can give me more details on a few sentences I read.

 

It says, When setting the aperture on a lens, never go backward. Most apertures have a certain amount of backlash that must be compensated for. It is necessary to go to a larger stop, open the lens all the way up and then reset the stop.

 

So if I start at 2.8 to 5.6 Im fine, but if I wanted to go from 5.6 to 4, I should first reopen to 2.8 before moving to 4?

 

Is this a common practice I missed? What is the backlash they speak of? Thanks!!

[Bruce Greene]

I've never done this, but it makes some sense :)

[Robin R Probyn]

I don't think anyone does this.. ? was the author a DoP .. I doubt it.. big time DoP,s pull Iris open during shots

[Dom Jaeger]

Modern cine lenses don't have much backlash in the iris, if any, but it's probably good practice to set the iris from one direction. A bit like always tuning a guitar up from flat.You can check backlash just by looking at the iris and seeing how much you can turn the iris ring before the iris changes.

[Art Adams]

In older lenses there's some play to the aperture ring. If you always open it all the way and close down to the desired stop, you err on the side of overexposure, which is easier to correct than if you go the other way and underexpose.