Response to microdol 1:3+ 120 film= superfine grain??

Microdol-X used undiluted gives extra grain reduction at the expense of film speed (about one stop) and to a small degree sharpness. When diluted 1+3 it no longer reduces film speed, grain or sharpness any more than, say, D-76.

Words of wisdom from Richard Knoppow on USENET:

The later Microdol-X is a Metol based developer which relies of sodium chloride (table salt) to provide a fine grain characteristic. Sodium Chloride is both a restrainer and also affects the development kinetics in a way which results in the kind of crystal growth desirable for fine-grain. D-25, a formula with somewhat similar results relies on the sulfite to provide the halide solvent action and is takes advantage of the fact that Metol will develop in a nearly neutral environment, thus causing the least emulsion swelling and attendant "grain clumping". When diluted 1:3 both Microdol-X and D-25 loose much of their fine-grain characteristic. At this dilution the sulfite content is low enough so that there is not so much solvent action. The film speed also goes up to normal. The results diluted are very similar to D-76. Microdol-X at full strength will still deliver finer grain than most other developers, including Xtol. The price is a stop of speed and a lack of edge effects which some find results in "mushy" looking images. This last is important probably only for 35mm users. In fact, Microdol-X delivers about the same film resolution as other developers. Microdol-X is similar to (but not the same) as published formula D-25. It is Metol in a buffered solution of Sodium sulfite and Sodium bisulfite which is nearly neutral in pH. It is the nearly neutral pH which is partly responsible for the lack of grain. Highly alkaline developers (i.e. Rodinal) cause emulsion swelling which allows "clumping" of the silver grains as they grow during development. The visible grain of a negative is actually aglomerations of silver grains. The induvidual grains are microscopic in size. Microdol-X (and D-76) also have a rather strong concentration of sulfite which is a mild solvent of undeveloped silver halide (not metallic silver). This solvent action also changes the way the silver grains grow during development. This high sulfite concentration is also a reason for the seeming lack of "acutance" Sulfite has a rather complicated relationship with the developing agent. Its main purpose is to protect the developing agent from becoming oxidised by the air at the surface of the developer or by air entrained in the developing solution. A develping agent is an absorber of oxygen, that is part of how it works, so it is vulnerable to oxygen in the atmosphere. The sulfite also tends to protect the developing agent from exhaustion by the developing reaction. This is really the important factor. When a film is developed, the developer will become exhausted faster in the more dense regions of the image. This can result in a complex of things at a high contrast edge. The reaction products can result in either a boost or a reduction of devlelping action there. The reaction products move a little, going over the boundary of the image and causing a slightly retarded action on the low density side from the reaction products of the high density side and vise versa. In effect, this exagerates the contrast at the border and makes he acutance higher than it would be otherwise. Diluted developers and low sulfite developers have much more of this effect thus the popularity of dilute Rodinal for those who like this effect of "sharpness" To much of this edge effect actually lowers resolution but resolutin is not what the eye interprets as sharpness, unless it is very low. Measuremtents by Dr. Richard Henry showed that the _resolution_ of film is the same with Microdol-X, full strength, D-76, and Rodinal. The visual effect can be quite different. When used full strength, Microdol-X or D-25 result in about 3/4 stop loss of speed. When diluted 1:3 the speed becomes normal but the grain is then about the same as D-76. I used to use Microdol-X at 1:1 where it seemed still to be very fine grained but didn't have the speed loss. I found it has a nice tonal quality but I finally standardised on D76 1:1 for most film since I found the difference in grain wasn't great and the tonality seemed fine. Microdol-X at 1:3 begins to have noticable edge effects and might be satisfactory to those who want that look. It is still finer grained than Rodinal at that point.

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