Camera Craft a Feature for Amateur Photographers

Otago Witness, Issue 3854, 24 January 1928, Page 60

Camera Craft a Feature for Amateur Photographers

B X

View Finder.

[ Readers -of the Olaga Witness are invited to submit specimens of their work, and, if they -desire it,' to seek advice from “ Vietd Finder. u Questions will be answered only in these columns and loritten replies cannot be scut.]

THE PHOTOGRAPHY OF FLOWERS,

At this time of the year the gardens are full of blooms, and the recording of choice examples is work which can easily be undertaken by the amateur photographer. It must be remembered that such, photographs lack the charm of colour, but the texture of the petals and leaves can be reproduced, and this in itself is beautiful. Any class of camera rqay be used, but a camera with a fqcussing screen is a distinct advantage. In selecting the blooms it will be found better 'to choose those having no vivid contrasts of 'colours, and such blooms should be as perfect as possible. Simplicity in arrangement should be aimed at. Flowers which liang downwards when growing should be taken in that position, whilst those flowers which are erect .should be taken upright. In between these two extremes we have many flowers which when growing have a slight (troop, and such flowers may be tqken in various positions and yet look quite natural' in the finished photograph. . .

.The choice ol a vase is one of the main items. Here again simplicity is demanded, and perhaps the finest vase is a plain glass one; in any case a vase with an elaborate pattern is useless, for it tends to conflict with the'flowers. An excellent arrangement can lie constructed quite simply foi the photography of some blooms, and especially so in the case of roses. Arrange a piece of black cloth on a'table ,'in a well-lit part of the room. . a piece of plate glass on the cloth and on top of this place the blooms. The picture should 'be taken slightly above the table, with the camera pointing dqwnwards. By this means a certaif amount of subdued " reflection of the flpwers is obtained, and the result will be found to be very pleasing. Good lighting can be. obtained close to a window,, and cafe should be taken to avoid any shaking, and therefore,, during exposure, it will be found advisable not to walk about the room. In order to obtain'a perfectly sharp picture, stopping down to at least f/lfi will be necessary. Thedarriount of exposure to be given depends entirely on the quantity of light falling on tjie subject. For judging the exposure required an exposure-meter should be jised,.. but as a rough guide an exposure of at least twice an ordinary indoor portrait will be required. If the flowers are taken, in an upright position the background should he simple in design, and'a pic.ce of strawboard or brown paper, will be quite a good choice. There is no doubt that the photography of flowers calls for the use of orthochromatic plates or films, or, better still, panchromatic. The use of such material is an excellent illustration of their suitability when compared alongside a photograph taken with an ordinary plate. Maximum- . colour correction can be obtained with orthochromatic film or plates, using a K 3 filter.

The flowers tc be photographed should be cut and placed in water a couple of hours before they are wanted. If placed into water imt before being photographed they are likely to change their position ai they stick tip water. The change of position mar be only a gradual one, biit as , long imc exposures have often tq he given the change may be sufficient to blur the image. The exposure should be on the full side and.the development light. Use a weak developer, and ■' aim, at. slight underdevelopment. If using a camera which does; not permit focussing, the use of a portrait attachment will be an advantage. By tn? use of such an “ attachment of ‘he flowers will be possible. Finally, rem nnher that the resulting pictures will he more pleasing if only a few choice' blooms be taken.' A lar<»e disnlav of ilowo'-s.. when reproduced looks very disapponit ing,

STAINS O»; NEGATIVES.

Their cause. prevention and , , CURE. . ' . :

i By CAI'T. H. T. IJKM? (Tientsin)

A stain which takes the form of a white powdery deposit may ba due to hypo, or, if a fixing hath containing alum has been used, to an aluminium salt. In the former case, tlie cause is obviously insufficient washing, and the prevention is also obvious. If a second washing is not successful, the stain is probably due to one pl several aluminium salts which may be present..: Z >J • . . .. . v ,

<T[ie ajum generally used, is a, double sulphate rif aluminium with the sulphate of potassium. The'fixing bath also may contain an 1 acid, ; but if *tins becomes' neutral- ' ised by an atkaji. such as sodium carbon-' fete carried over'from' the developer, alu-

minium salts will be precipitated. Now aluminium salts, especially those with sulphur, are usually soluble, of, rather, reducible, in sodium or potassium carbonate. The stain- will therefore in all probability yield to a bath of about 5 per cent, sodium carbonate and water. It will also probably yield to a weak acid bath, citric, acetic or tartaric acids being suitable. Thorough washing should follow in any case.

■ To prevent the formation of the stain, it is advisable to rinse the negative before immersion in the fixing bath ; or an acid stop bath may be used, before rinsing, as an excess of acid carried over to the fixing bath may cause another kind of stain. It is not at all necessary to use an acid stop bath if the fixing bath is not allowed '.o become exhausted.

■ These' stains or deposits should not be confused with deposits of magnesium, calcium, or other salts from hard water or from sea -water. These are easily removed, by wiping gently with a small pad of cot-ton-wool before drying. In cases where sea water is used, the negatives must always be rinsed in fresh water finally. A silvery white stain is due to rinsing the negative in alcohol or methylated spirit, and finishing the drying by heat; or it may occasionally occrft- when’ drying at ordinary temperatures. It can be removed by simply re-washing in cold water and drying at ordinary temperature. —Deposited Sulphur.—

A similar stain with 'a faint yellow tinge, even if not readily distinguished from the last by its slightly' different colour, will soon be found to be of a diffe ent nature, as any attempt to renlove it by washing will not succeed. Neither can it be removed by the same method as the aluminium stain already described. It appears to be due to a deposit of sulphur, precipitated fjom the sodium thiosulphate (hypo], by. an acid. When, however, an qcid is added to the fixing bath, it is usual to add sodium sulphite, when sulphur is not precipitated. Therefore, the cause is an excess of acid, or, .what is practically the same thing, insufficient or impure sulphite of soda

As already stated, since sulphur is soluble in sodium sulphite, all that is necesssary is to dissolve it out in a 10 per cent, to 15 per cent, solution of that salt. It mav be found necessary to heat the bath to aoout 100 degrees F., if the stain proves to be very obstinate, but in this case, it will be necessary previously to. harden the film in a formalin bath.

—Oxidised Developer’ Stains.—

Yellow stain caused by oxidised developer is perhaps the comnionest stain met with, but as a local stain it is easily avoided. The developer may become oxidised either by (a) exposure to the air, or (b) exhaustion. In the ordinary process of development, the. developer is' oxidised gradually in reducing the silver bromide from the film. Any stain thus caused is generally regularly distributed, however; or, to be more exact, the image is stained. The stain is, however, often due to a part of the negative being e~"osed to the air, whilst wet with developer. This is frequently the case with films which' are allowed to curl after being flooded with developer, or. in the case of plates, it is due to insufficient developer, which readily becomes oxidised. This stain can be removed by bleaching and re-developing. —lnsufficient Fixing.—

A yellow stain may be caused by the presence of silver compounds in the film. This and the last-mentioned one are not easily distinguished from ehch other by inspection, but the operator will usually have some idea as to which stain (if not both). is present, by the condition of his solutions.

If it is not clear whether it is due to oxidation or silver stain, we may cut off a strip of film from the edge, and experiment with it. If it is silver stain, a n.-r--munganate bleaching bath will probablv change it to a black stain of metallic silver, and the last state will be worse than the first, as there is no way of getting rid of it without getting rid- of the image at the same time, unless.it is so light as to be removable by an ordinary reducer before the image; is appreciably reduced. This stain is caused by incomplete fixeither through a weak or exhausted fixing bith. containing an excess of silver, some of which may remain in the film lifter . washing, or it may be caused also' by incomplete- immersion., in the. same way as the previous stain mentioned, i It is also, caused .if we neglect the instruction always given to leave the negative or print; in tlie fixing bath for double [be time which is reotiired for the. whole of the milky.silver salt to disappear. ; While the negative is in.the fixing bath, the silver; compounds that are being dissolved. out are first converted to. a comino’.’nd of silver and sulphur that is not easily soluble, and as. this compound is invisible, the negative aopears fixed' when it is reallv not so.'? Further•? immersion converts this almost insoluble salt to a dif-’ ferenf and soluble one, and when this is completed, the negative is fixed. If the

negative has been removed from the bath before fixing is complete, the stain will be almost certain to manifest itself sooner or later.

—Stains on Non-Curling Films.—

It should also be noted that films which have a coating of gelatine on the back (r.s most have to prevent curling) can also become stained if the hypo is not washed out of the back of the film. This sometimes occurs if the film is allowed to rest at the bottom of the dish whilst washing, and water allowed to run over the top. only. It is difficult to detect whether the stain in on the back or front of the film.

Perhaps the best way to deal with this, dr any yellow stain, if the apparatus is Available, is to make a positive on a panchromatic plate by projection through a deep yellow filter, and from this make a negative by contact. At any rate, there can never be any harm in trying, as in any case the result is sure to be an im provement, if it is not completely successful ; and the negative is still available for further experiments. ■ From what has been said, it will be obvious that the greatest care should be taken not to allow this stain to occur on valuable negatives. —Brown Stains.— I have only experienced these stains once, but I imagine from their cause that they might frequently occur with tank users, and their cause be not a little mystifying, i traced them to flakes of rust entrapped in a. coll, film from the the rusty “interior of a mjetal camera. The flakes would probably dropped off in handling had the films bev’i developed in q dish, and caused no damage. They are Removable in the permanganate bleaching bath.

The presence of iron can be readily detected by means of nitric acid and potassium sulphocyanide. If a valueless negative containing the stain is available, or if the stain is near the edge of the negative, we may put a little dilute nitric acid on the stain, and then touch it with a drop of potassium sulphocyanide. A deep red colouration of ferric sulphocyanide will at once :esult if iron is present.

—Green Stains, or “Dichroic Fog.”— Green stain, or yellowish green stain, is often the result of the presence of metallic silver, or molecular silver, in a very finely divided state. On holding the negative between the eye and a source of light the stain appears pinkish in colour. This may be compared with the appearance of very thin gold leaf, which appears to be the ordinary colour of gold by reflected light, but by transmitted light appears greenish. The stain also frequently presents a distinctly metallic appearance not easily described.

The stain is formed when the fixing bath is considerably diluted with developer. 1 have never experienced this stain on films, though I know of no reason why it should not appear on them also. It is more liable to occur when silver is present in a large proportion in the fixing bath, e.g., in an exhausted one. It will also be found if insufficiently fixed negatives are covered by other negatives while they are in the fixing bath in such a way that the liquid actually in contact with the negative is rapidly exhausted, and no more of the hypo solution is able to gain access. The stain is rare, and seems less likely to occur if the negative is rinsed before putting it into the hypo. Since the stain consists of metallic silver, any suitable silver solvent will remove it, and will nearly always do so before perceptibly attacking the image, as molecular silver is very soluble. Amongst the suitable silver solvents that may be used are potassium cyanide, and ferricy anide and hypo reducer. A permanganate bleacher may also be used, but this necessitates re-development. (Note. —Potassium cyanide is very poisonous.) These solvents also attack the image, so that ths negatives should be removed as soon as any signs of reduction appear.

—A Mere Matter of Arithmetic.—

One lesson that should be learnt by anyone- who has read this article is that the cause of practically all stains is stale and exhausted solutions: and it does not need much knowledge of arithmetic to calculate that the cost of one spoilt plate would purchase quite a lot of fresh chemicals. It is, therefore, false economy to try to save on chemicals. Proportion the pmount of chemicals you buy at a me, and the amount of stock solutions you make up to the amount of work you are likely to carry out. If you use fresh and unexhausted solutions, and use them intelligently, you will not be troubled much with stains.

—The Amateur Photographer.