There will be variation between Kodak's, Ilford's, and each of our own results. You have to test yourself if you want to find out your answer to this question.
The number one thing you must also do is to learn to meter "properly" and consistently. You can throw various EIs and development at a problem that simply boils down to metering technique. I would start with a good old grey card (or incident meter). If you can add a spot meter on top of this in order to really get a handle on things like luminace range in your composition, you are going to have an even easier time with your tests.
This is one test method I like. It is long and wordy, but pretty darned simple to do. Once you do it, you are set up very well as long as you meter in a consisent manner.
On a tripod, shoot a scene that has a luminance range that is about 6 EVs ("stops") from the darkest area in the composition that you want to show texture (*not* detail; texture), to the lightest area in the composition that you want to show texture. The easiest way I have found to do this without purpose-made test charts is to set something up using light and dark fabrics draped over opposite shoulders of a person, and also have them hold a grey card. Get fabrics with a texture that is visible through your lens. You don't want fabrics that are too smooth, as your test prints will be harder to judge.
Meter the grey card, both cloths, and take note of these readings. If they are not exactly 6 EV apart, it is fine, as long as you have notes of what they really were. One thing you DO NOT want is for the dark fabric to measure more than 3 EV lower than the grey card, however. If you have an incident light meter that you intend to use with this film, take a reading from on top of the grey card and notate that as well. (All the calibration will be done using a reflected meter, but you want the incidennt reading just to figure out how far you will need to tweak your EI when you use the incident meter instead of the reflected one.)
Use a moderate shutter speed, not a super fast one, as super fast or slow ones have a greater likelihood of being significantly off in my experience. Use box speed. If your apertures can be set in half stops, make five exposures. One one stop under your meter reading, one 1/2 stop under, one at the reading, one 1/2 stop over, and one one stop over. If your apertures can be set in 1/3 stops, make seven exposures, and do the bracketting in 1/3 stops instead of half stops.
Process these five (or seven) negs, as well as a totally unexposed neg, the way you intend to process in the future. After they are all dry, print the blank frame at your most common print size so that it is *just* below the threshold of maximum black after dry down. (Obviously, you will need a maximum black refernce print as well. To get this, process a piece of paper with the room lights on so that it is fully exposed.) Once you are in the ballpark, you will need to bracket print exposures by seconds to do this accurately. Once you have this print time and aperture, print all of the other negs at this same exact print time. Hold processing until they have all been exposed. Process them all at the same time if you can, or at least half at once, followed by the other half. (This will reduce the impact of print developer exhaustion. It is not a huge deal with only a handful of prints in a tray with a few liters of developer, but you are trying to minimize as many variables as possible in the testing phase.) Dry the prints and view them in the type and intensity of light in which your prints will most often be viewed.
Label the back of each print as follows for 1/2 stop aperture precision:
Darkest print: EI 200
Next darkest print: EI 100+1/2
Print made from meter-recommended exposure: EI 100
Next lightest print: EI 50+1/2
Lightest print: EI 50
...and for 1/3 stop aperture precision:
Darkest print: EI 200
Next darkest print: EI 160
Next darkest print: EI 125
Print made from meter-recommended exposure: EI 100
Next lightest print: EI 80
Next lightest print: EI 64
Lightest print: EI 50
Take out your notes. Look at the reading of the dark fabric compared to the grey card. How many EV apart were the two? If they were three EV apart, look for the print that *barely* shows texture on the fabric. Texture and detail are different. You are not looking for discernible details, but for the first hint of something other than flat tonality.
If the readings were 2-1/3, 2-1/2, or 2-2/3 EVs apart, look for the same thing, but not at the point at which the texture *just* becomes visible. If 2-2/3, you are going to be very close to being able to see detail. You will have to use your judgement as to what you personally want to call the crossover point between detail and texture". For "detail", you should be able to see the fabric threads clearly, not just as a kind of fuzzy field.
If the dark fabric and the grey card were 2 EV apart, you want to pick out the print that shows the first sign of what you call "detail".
So, depending on how far apart the black fabric measured from the grey card, you will pick out the print that "properly" rendered the black fabric as it "should" appear in reference to the gray card. The EI on the back of this print will almost certainly be a better working EI than box speed for you in most situations. If you tested with 1/2 stop precision, and picked one of the prints with a "+1/2" after the EI, use the EI before the "+1/2", and when setting your exposure, always stop down 1/2 stop past what your meter recommends. Or, if your light meter will allow it, set it in between the same EI and the next higher doubling of it. For instance, if you got "EI 100+1/2", set your EI halfway in between 100 and 200 (which is also halfway in between EI 125 and 160).
Then, lay all the prints out again. This time pick out the one that rendered the light cloth where it "should" have been rendered given its EV spread from the grey card. Do the same thing you did to determine the proper rendering of the dark cloth, comparing texture and detail. Detail should be present if the grey card and the light cloth were 2 EV from each other. Only texture should be present if they were more than 2EV from each other. If they were more than 3 EV from each other, this next part is probably best suited for a separate test, unfortunately, though you can get close.
Now that you have picked out the prints that have appropriately-rendered light cloth and dark cloth (I will just call them "the light print" and "the dark print" from here on out), there are three possibilities for analyzing your development:
1. If the light print is the same print as the dark print, your development time is fine as you did it.
2. If the light print is from a negative that received more exposure than the negative used for the dark exposure, you need to increase your develoment time by about as many 1/3s or 1/2s as the two prints are from each other to get to a decent developing time. For instance, if you got EI 80 on the back of the dark print, and the light print is marked EI 50, you need to add enough development to raise the tone of the light cloth 2/3 of a step on a greyscale.
3. If the light print is from a negative that received less exposure than the negative used for the dark exposure, you need to decrease your development time, etc. (see above). For example, if you got EI 80 on the back of the dark print, and the light print is marked EI 125, you need to take away enough development to lower the tone of the light cloth by 2/3 of a step on a greyscale.
All right. You have a working EI, and a rough idea of how to tweak development. Now go back and test again using your working EI. Take notes so you know how the white and dark cloths "should" be rendered compared to the grey card. Make a handful of identical exposures. Process one, using an estimate as to what you need to do with development time based on the results of the last test. Print it just like you printed the prints from the last test. Analyze. If not right, do the same thing with the remaining sheets until it is.
Then you have a working EI and a normal develoment time. With that, you can pretty well guess how to handle any situation that requires either a reduction or incease in contrast.
Since you took a comparative reading between your camera meter and your inceident meter (which should both theoretically give you the same EV), you can also use your incident meter, after compensating the EI to which you set it to match results from the reflected meter. For instance, if the incident meter read 1/3 EV less light than the reflected meter off of the grey card (meaning that it recommended giving 1/3 stop more exposure), you set it to 1/3 EI higher than the one you found in the test.
Good, luck, and don't forget that this is all about YOUR judgement in YOUR aesthetic pursuits. You are not aiming for tightly defined values, but simply for the ability to get what you want from your shot.
