"Perfect" negatives exist only as a technical concept based on arbitrary and subjective values, or as perceived as perfect by someone for an individual printing style in a particular medium. "Perfect" really means you made a negative that prints the way you want it to, on what you want to print it on. "Perfect" in the case of negatives should be redefined to be "perfectly controlled"
Like I said, I don't have two identical examples of hits and misses, but here are images where an exposure error in relation to my speeds and processing would have made a clear difference. These negatives were shot on J&C 100 (IRRC) rated at 64 (my tested speed for this film with PMK)Two were processed normally (my tested normal), in PMK. The third was shot and processed N+1. (N+1 means I exposed and processed the negative to "expand" it. "Expansion" or "contraction" of negatives is one of the most basic and important reasons for using The Zone System, and getting a handle on this is largely what all the testing is about. Many people who poo poo this stuff have no idea that it is possible to control tonal relationships independently from overall contrast, except with color filters. Filtering is useful, but is limited, and the most control over the process is best arrived at with a full tool box.)
Although the development was "normal" the effective development on the first two images was N+1, meaning the highlights pulled up, but the low values remained near where they fell in the scene, because of reciprocity failure, as the exposures were long. This means the negatives were "expanded", an effect we test and plan for if we desire more separation of higher values from lower values than the scene possess. The Zone System is one of the methods that can be used to control the relationships of highlights and dark areas, not just arriving at an average exposure for a specific scene, but choosing an exposure and development to modify the relationships of the values found in that scene, beyond the natural contrast that exists within the composition with the conditions present at the time of exposure. Being able to move specific tonal values offers far more control of an image than merely adjusting the overall contrast with paper grades, or contrast filters, with the averaged contrast and tonal relationships present in a "box speed and developed" negative.
The manufacturer has to put something on the box, and recommend some kind of development, and the numbers and recommendations that are usually arrived at are those that offer the most forgiving performance for an average situation, not the best performance for a specific situation, because it is impossible for them to predict specific situations. (one can, of course, consider forgiving performance at the expense of other factors to be paramount). The "forgiving exposure and development" is the method that you, Ray, are using and espousing, and is why you can blow an exposure, probably by a stop or more, especially with regard to over exposure, and get away with it. You aren't using all the film's capability, so there is room built in for error. What you are giving up in return for that is control of the tones within the negative, and the maximum lattitude the emulsion can deliver. A box speed and developing regimen is literally a "one size fits all approach" There is nothing inherently wrong with that, but some of us desire negatives that fit better, with the maximum lattitude the film can deliver.
It's very much like a car. The average sedan gets ok mileage, handles ok, has a decent ride, and predictably average acceleration, because these characteristics are the compromises needed to mass produce and market the car. If that's what you want, that's what you drive. Some of us like to tinker and modify the sedan, push its perfomance to the maximum without regard to comfort or mileage, and drive it on a closed course at the absolute limit, with no margin for error. We do this because we want or need this kind of performance. Dismissing it out of hand, as you have tended to interject into exposure disscussions, is telling somebody who desires to race that they should drive a box stock sedan on race day, because the big brains in Detroit said that's how the car should be.
In the first two examples the lighter values received more exposure in the highlights because the film was faster where the light was more plentiful. This was, as mentioned, accomplished as a side effect of reciprocity failure, but it can also be accomplished by modifying exposure and developing times, and it is mostly done that way. The ability to control tonal relationships through exposure and developing is what we test for. Had I followed box speed recommendation, and processed for this average, none of these images would exist as they are.
If you combine the effect of the expansion of the upper zones as intended, and note where the highlights of these images fall, and also note that the highlights, and their relationship to other areas are extremely important elements of these images, its easy to imagine the havoc a one third stop error would have wreaked. There was no margin for error in these exposures, as the highlights in each are taken right to the limit. I might have gotten lucky with a WAG, instead being able to predict my results with a fair degree of accuracy, but not likely. Exposing at box speed using an incedent reading and processing according to the manufacture would have resulted in flat negatives with blown highlights, that couldn't in any case be coaxed to these kinds of light versus dark relationships without appearing very hard in contrast, or, for the last example I could have sat around on the beach at the Great Salt Lake, eating brine flies and cheetos for a few weeks, waiting for the conditions that would mimic the result of the expanded exposure and developing method, that would allow me to expose and print according to the manufacturer, to get the same result.
If you are only using a portion of a films capability, an exposure error can be easily forgiven, and go largely unnoticed and therefore be ignored. However, if you seek to gain every bit of lattitude you can get, and take an emuslion to its absolute limit, you have to do better than a WAG, or your gonna have allot of unprintable failures. A "shoot and develop for box speed" photographer probably would have stood in the conditions where I made the waterscape negative, and said with conviction that it couldn't be made to look like I made it look.
Here the three images that tell the same tale. The waterscape is an example of expansion by development.
On the prints there are far more details in both the shadows and the highlights than a computer monitor can display.