I had just started experimenting with these devs in 5x4 when Barry sadly died, preventing me following initial experiments up, but my impressions are as follows:
Dixactol Ultra single bath: Very sharp, but not the best choice for enlargements with tradiotional 400 films such as HP5 plus. High general stain and grain was quite large. Tremendous holding of hot highlights, almost too good with average scenes with my soft colour head. Longer development to increase neg density increases grain...BUT...I tried this with Fuji Acros Quickloads and it is amazing. The scenes were of bright scenes in rural Spain, with plenty of hot highlights which were well held. Sharpness is incredible. I dev'd identical negs in HC110 (1 pt DilB + 1 pt water - due to very short dev times with Dil B) and compared them. The Dixactol has produced infinitely better sharpness still with completely invisible grain at 20x16. The sharpness was so much better, I printed the HC110 neg several times to make sure I had not made a focusing error! Leaves looked like they had ben cut out with a scalpel. The DixactolAcros negs showed a clear base and very little non image stain. nice pale brown to the image area.
Exactol Lux: Very much finer grain than Dixactol, otherwise similar points apply. I have used this with TMax 100, HP5 Plus, FP4 in 5x4, acros in 120. Reasonably fine but exceptionally sharp with HP5, but for some reason which I cannot understand, strange grain with TMax 100 5x4. The grain is visible as a speckle in a 16x12 (which I certainly had not expected) and not in a pleasant way. It is not obtrusive at 20x16, in fact still very fine, but not pleasant to the eye...cannot put my finger on it. It is perhaps speckly in an irregular way..? Very nice with FP4 Plus, Very, very sharp. I compared this to ID11 1+1 with FP4 and It is clearly much sharper and slightly finer grained. Miles sharper than perceptol 1+2.
Follow the times recommended as a starting point and you will not be far out. DO USE DEIONISED WATER!!!! I used to use tap water, which was fine, then for some reason, it changed and completely wrecked 12 good negs with bizarre streaking (expletives omitted). I must have hit upon something with Forte Fortezo G3 and Acros in Dixactol, because it is lovely , especially after a slight selenium tone. I found that these negs do print about a grade softer on VC paper.
As for film speed, it is fairly good. I had no problems with Tmax 100 in Exatol at ISO 100, having done a fim speed test showing 100 to be the true speed in this dev). Acros in Dixactol- I jumped in at ISO 64 after a brief trial in 120 in Exactol (ages ago) showing that it was very slow indeed (ISO 50). Strangely this time, ISO 64 appeared conservative in Dixactol. 80 would be about right (for me).
Overall, very encouraging, but would not recomment them for flat scenes (certainly not Dixactol) as increased development causes grain and general stain probs. Exposing to hold Z3 shadows with highlight hot spots (sunlit white wall) falling on Z12, my dixactol negs required only short burns in these areas. Not bad eh? I have not tried 2 bath as there has been no need yet. I have tried the partial stand option (agitation every 2 mins) and it does increase compensation.
I will try pyrocat HD if I find a way of getting round the expense of accurate chemical scales and compare them. Has anyone out there done a comparison?