AREA NEWS

FILL-IN FLASH G. Sparkes (Area 22).
It certainly improves that shot where a back lit subject`s face is in shadow. I think most people without the latest hi-tech flash guns are put off by the calculations required for the optimum result. Perhaps the best answer is to take one shot without flash and a second exposure with auto-flash, using simple rule of thumb to obtain a quarter and one-eighth flash. Flash outdoors is already reduced by about a half, so using one quarter power or two stops less flash makes it around one eighth flash. If the flash gun can be set for quarter power there`s no problem but many guns can achieve the same reduction by flash mode and camera stop setting. The shutter speed generally needs to be 1/125th second for flash so if the general exposure for 100 asa is F5.6 or F8, leaving the camera stop at F11 should produce the desired result.

STOCK SOLUTIONS NICK WILLIAMS (Area 20).
Weighing out very small quantities of some chemicals can be awkward fiddly and possibly a source of inaccuracy. An alternative is to weigh out a larger quantity of the substance and dissolve this in a known quantity of water to make a stock solution. An appropriate volume of this stock solution can be added to your processing solution.

To get the right weight of the chemical into the brew you need to know the strength of the stock solution in terms weight of chemical per volume of water. The thing to remember is that 1ml (or 1CC) of water weighs 1KG.

Suppose that you wish to make up 100ml of 10% stock solution of Potassium Bromide. The required amount of Pot. Bromide to go into 100ml of solution is 10% of 100gms or 10 grams. The simplest way to do this is to add 10gms of Pot. Bromide to 100mls of water. But this is not strictly correct because there is a small volume increase when some substances dissolve. It is better to dissolve the 100grams in say 75mls of water and then add water to make up the full 100ml. This way you can be sure that 100mls contains 10grams of Pot. Bromide, or that each ml contains 0.1 gram for mixing.

Stock solutions can be made up to any strength but usually 10% is found to be the most useful. Too strong a solution and the substance might not dissolve in the volume of water. Too weak a solution may mean that you will need to add too large a volume of the solution, possibly more than the total volume of the developer required. A 10% solution is convenient in that the numbers are simple to use and there is little danger of a 10% solution failing to dissolve.

An exception to this rule is Potassium Iodide which is always required in such tiny quantities that a 0.1 solution is specified. This means that only 1 gram is required per litre to make the stock solution.

Avoid making solutions of developing agents as these become activated when dissolved in water and will quickly go off.

HOW GREEN ARE MY CAST.. AWAYS? PETER GUY (Area 20).
How are we as responsible photographers and processors when it comes to disposing of our used chemicals? Are they just poured down the sink or are they carefully disposed of? I hope that it is the latter, in order to protect not only our drainage systems. but also our rivers, seas & wild life.

Our waste chemicals can be divided, basically into four groups:

INORGANIC SALTS
are essentially inert and have no significant effect on the sewage treatment process or the environment.

ORGANIC COMPOUNDS,
are toxic to many forms of aquatic life. They are mostly bio-degradable but require oxygen and could put living organisms, which are needed for the breakdown cycle, below a safe level.

SULPHUR COMPOUNDS,
like organic compounds, could be toxic to some aquatic life. They do not require microbial (small life) activity to break them down, but decompose by simple aeration.

METALS
are the real villains and, mainly for their Silver content are highly toxic to aquatic life. Silver nitrate and Silver Chloride are the worst. But all is not lost. The Gods are with us as processors. When the silver is removed from the emulsion by the Hypo action it forms a stable soluble and relatively non toxic silver thiosulphate complex compounds. These are converted into very stable silver sulphide and do not interfere with biological waste treatment systems nor do they cause any ill-effects when the waste sludge is used for soil enrichment.

Well, what about DISPOSAL? Print workers will know that Cibachrome recommend that their chemicals are mixed together for neutralisation. This also holds good form our film processing chemicals and, if possible, reclaim the silver from the hypo/bleach if as machine is available. When the chemicals are mixed together, try to get a pH reading of 7, if you have a pH meter. If you do not have one, mixing the chemicals in equal parts should do.

Controlling the oxygen is more complex. Oxygen tied up by the chemical breakdown process could exceed the limits by 50 to 250 times. So it is best to discard the mixed bucket of chemicals a little at a time. Mix with plenty of water and spread the disposal over a long period of time, if possible, of days or weeks.

CHEMICAL DISPOSAL METHOD