In sharpness and tonality, it is recognizably a Delta film. If you make an 8x10 inch print from a 6x7cm Delta 3200 negative (at EI 3200), and an 8x10 inch print from a 35mm Delta 100 negative (at EI 100), the grain in the two pictures looks surprisingly similar. Of course, one is only about a 4x enlargement, and the other is around 7x, but the family resemblance is clear.
Push the film further, to EI 6400, and you can see the difference in the grain, but magically the tonality doesn't change, and the sharpness doesn't suffer. At photokina, I found out why. There are no fewer than four different emulsions in Delta 3200. This allows Ilford to control the highlights, mid-tones and shadows separately. The curve gets steeper, but it retains the classic flattened S-shape of a pictorial emulsion, without going up in a steep, straight line like most ultra-pushed films.
You can push it even further, out to EI 12,500. The first time we tried rating it that fast (I say "we" because my husband Roger Hicks and I were working together), we shot some cars in the car park at Dover docks. Although the choice of subject may seem a bit eccentric, it is useful because you can get an excellent indication of sharpness and resolution from number plates (English for license plates -- if you're being really pedantic, "registration marks"). When we got the negatives on the light box, we found we could actually read the number plate on one of the cars. On the negative these numbers are less than 1/32 of an inch high.