High Acutance Develper
In his book "Photographic Processing Chemistry" (1974 Focal Press), L.F.A. Mason lists a typical High Acutance Developer.
This may possibly be the formula for Hyfin, which was Ilford's High Acutance developer, available from 1961 until the early 1970's. Mason calls it a typical formula:
High Acutance Developer
Sodium Sulphite (anhyd) 5g
Sodium Carbonate (anhyd) 5g
Water to 1 litre
Development times 15-25 minutes
Requires a minimum of 600ml of chemistry per 35mm or 120 film.
Mason notes that additions to the formula have been proposed, either 0.1g/litre Potassium Bromide or 5ml of 0.0001% Potassium Iodide solution. (He may be referring to other similar formulae like FX-1 etc)
Hyfin was sold in packets containing 5 sachets of developer each one making up 600ml of solution. I have two packets of Hyfin & will weigh the contents of a scchet next time I'm in the UK.
Hyfin instructions were:
Pan F & FP3 - 18 minutes @ 20°C
Continuous agitation for the first 10 seconds then 5 seconds every minute.
Gives 1 stop more effective film speed
In the early 60's there were 3 High Definition devopers availabe in the UK, lford's Hyfin, Kodak's High-Definition Developer & Johnson's Definol.
It's no co-incidence that Hyfin & HDD are very similar to Beutler's High Definition developer, sold as Neofin Blue, and another similar developer is Crawley's FX-1 formula.
The major differences are that Beutler has 1g Metol/litre & Crawley's FX-1 only 2.5g Carbonate + 15ml 0.0001% KI, compared to the formula above. The decrease in the Metol level compared to Beutler is likely to increase the edge effects & acutance further.
The addition of Potassium Iodide is likely to have little or no effect now as most modern films contain far higher levels in their emulsions, particularly Tmax & Delta films. It may have been more important with certain films Crawley speculates that it was needed in HDD for Pan-X
Mason would have known Crawley and his work, Ilford began manufacturing his chemistry for Paterson around 1963.
Last edited by Ian Grant; 08-02-2009 at 06:32 AM. Click to view previous post history.
Someone asked what the makers of Acutol showed that I said was impossible. In one of their blurbs, they showed what purported to be two characteristic curve shapes. The one depicting Acutol had a curve with its maximum slope at zero exposure, the slope decreasing as exposure increased until it became flat. It was a better approximation to the usual curve of CI vs log(exposure). Whoever did the blurb shouldn't have. The curve Acutol was supposed to be better than had a nice toe, a long straight line, and no shoulder.