(Vitaliy, I have no idea where to post this; sorry if this is not the right place)

I was reading the other day about de-clicking old Nikon lenses, and people's comments about how they'd like to slightly tweak the iris "on the fly" to adjust for minor light changes. Since I have a photographer background, the first thing that came to my mind is "Why would you want to do that? Doing so will change the depth of field!". Ok. Tweaking can be interpreted as "less than a click", that is, less than 1 stop (or 1/2 in some brands). But still, my question to you guys is "Why?" Is it because it is the only basic parameter (Aperture/SSpeed/ISO) that you can change on the fly, and not via camera menus? (You wouldn't want to change the SSpeed anyway.... And for the sake of this discussion, let's pretend we are on the less noisy side of the ISO values). What are the benefits of changing Iris? If you could decide to change Iris vs ISO (which takes me back to "Panasonic: Auto-ISO in Manual Movie Mode, por favor...!!!"), which one would you choose?