Belfry Bulletin Number 069

Belfry Vol. 7 No.69

Bulletin May 1953

Colour Photography in Caves by R.M. (Pongo) Wallis.

Some time ago an article appeared in ‘B.B.’ on the subject of cave photography. This was intended mainly for the beginner, and so dealt with ordinary black and white photography. Colour photography is very much more difficult and it would be foolish to experiment with it until one can more or less guarantee a good result in black and white, but it is, to my mind, very much more worth while. A good monochrome picture can be very good but a colour one is in a different street.

Unfortunately, is more expensive and it does not do to bang off a picture on the least provocation, which is probably a good thing. There are quite a number of colour films on the market these days but none are cheap. The least expensive size is of course the 35mm. Kodachrome and Ilford Colour processes are available for these’ miniature workers at 24/1 and 18/6 for 20 exposures respectively. These are processed by the makers without extra charge directly into transparencies which can be viewed directly or projected. In the same size there is also ‘Agfacolor’ and ‘Pakolor’ at about the same price, but these are processed (at an extra charge) to a colour negative from which a colour print can be made. These are gain expensive and these two processes are not for those with shallow purses. In larger sizes ‘Agfacolor’ and ‘Pakolor’ are again available and also ‘Kultichrome’ and ‘Dufaycolor’ which give transparencies, but not ‘Kodachrome’ or ‘Ilford Colour’ which are only available in the 35mm. size. The most suitable film in the larger sizes is probably’ Ektachrome’ (which again gives transparencies) but is normally only available as a cut film. I have used Dufacolor (though without much success) but my main experience has been with Kodachrome and Ilford Colour. The former is available in a version suitable for artificial light, while the latter, at present, is not, and a correcting filter must be used with it which makes is very slow indeed. My own experience indicates that Kodachrome is worth the extra money and in any case if all the 20 exposures are taken underground its extra speed will certainly save the 6/1 by using less flash.

The general principles involved as to viewpoints, etc., are just the same as in monochrome. General views do not seem to be very effective and frequently appear to be lacking in colour. Closer shots of formations etc. at distances from 3 to 20 feet usually result in a much more effective picture. It is not necessary to look for colour and even scenes in which there seem very little the photograph often shows that there is in fact, a good deal.

The main trouble likely to be encountered is in estimating the exposure which needs to be very accurate to get the best results. A variation of half a stop completely alters the result and a greater variation than this will give a worthless picture. (In monochrome a variation of a whole stop either way will be barely detectable). Guessing the exposure will very seldom be sufficiently good and even with the most experienced worker is sure to result in some wasted frames. A set of exposure tables or a simple calculator must be considered essential. These are simple to make once one knows some accurate figures to start from.

The figures that follow have been proved accurate by practical experience and ca be relied on. If followed implicitly they will give exposures within the plus or minus half-stop range. They cannot do better than this as the photographer’s judgement must still play a certain part. Kodachrome 351 (for ARTIFICIAL LIGHT) AT 2 ALTHOUGH A RATING OF 3 OR 4 IS BETTER. The exposures given are for Kodachrome; for Ilford Colour they should be increased 3 or 4 times. In an average cave location with the subject at 12 feet from the flash, use an aperture of f5.6 with a flash of 40 grains of Johnson’s No. 2 powder. In dark chambers use one stop larger and in very light ones, one stop smaller. When the distance is doubled or halved use TWO stops larger or smaller.

BB69/2 From these figures a complete calculator or set of tables can be made covering any distance, size of flash etc. the only matter left to the photographer’s judgement is whether the situation is light, dark or average.

This is admittedly not always easy, but if in doubt say ‘average’ and you will be not far wrong. One should, in fact, think twice before using ‘light’ as except in close-ups or very small well formationed chambers this seldom applies. Similarly, ‘dark’ should be reserved for very large chamber and places where the walls are mainly unreflecting mud.

Colour film is ‘balanced’ for the type of lighting for which it is to be used. Artificial light film is intended for ‘photoflood’ lamps by flashpowder gives very good results and the difference in colour rendering due to the flash is not usually noticeable. Magnesium ribbon should not be used, however, as it usually imparts a blue tinge to everything. Ordinary flash-bulbs are satisfactory though expensive, but for the best results the ‘yellow-dipped’ variety should be used. I have not tried using uncorrected Day-light type film, but as the artificial light variety gives good results the former is unlikely to do so.

The fact that colour fill requires accurate exposure means that it will not handle satisfactorily subject with a wide range of lighting contrast. Accordingly the flash should normally be placed as near the camera as possible in order to avoid shadows. In places where this is not possible and particularly where the subject matter is at a wide range of distances from the camera, extra flashes should be used to ‘fill in’ the less brightly lit areas. This technique requires a fair amount of experience to be completely successful but at its best it will give far better pictures of complicated subjects than can be obtained with a single flash. Note that all the flashes need not be fired simultaneously, but it is best not to include a figure in the picture as the person may find difficulty in staying quite still during the period between the firing of the flashes. Back-lit subjects can be taken and sometimes are extremely effective but a small fill-in flash is almost always needed as well if a good picture is to result. As a general rule, this type of lighting requires one stop larger than with plain frontal lighting. Obviously, the actual flash itself must be hidden from the camera behind a rock or other suitable obstruction.

With regard to the type of camera to use, a box or other cheap one is definitely unsuitable as the lens is not intended for colour work. The majority of present day cameras however, have colour corrected lenses and are an advantage, as the same result can be achieved with a reasonable quantity of flash. 100 grains need not be considered excessive in colour work and with this limit an f6.3 lens will cope with most subjects up to say 15 or 20 feet. A much larger lens than this is really needed for the big chambers and a miniature explosion would be needed to get an exposure in the gloom. There are plenty of cameras, however, between about £15 and $25 with lenses of about f3.5 which will be entirely satisfactory.

I do hope that you will have a shot at what I think is the most interesting part of caving. If you do you will also become a member of what is a very exclusive band as there are very few who take underground pictures in colour. If you feel that it is too expensive, bear in mind that once you have bought the film your only further expense is, normally, only the processing charge, and with Kodachrome and Ilford Colour this is included. In the 35mm size at least the cost is about 1/- per exposure. With black and white the pictures in the same size the negative is about 1½d. and the smallest enlargement, even if you make it yourself is 2d., while with larger ones or those made professionally the cost is much more, so that if you are often give prints to your friends you may even find that it is cheaper to turn to colour!

R.M.W. ********************************************** ARCHAEOLOGICAL NOTICE. It has recently been suggested that a number of club trips be devoted to sites of great Archaeological interest such as Avebury (Wilts), Maiden Castle (Dorset) etc. Will anyone interested please contact Keith.

Gardner, 22 Wesley Hill, Kingswood, Bristol. The Maiden Castle trip would be run in conjunction with a coach party from Clevedon Archaeological Society and seat will be reserved for those wishing to travel this way.

Also if anyone is interested in spending part of their holidays excavating, or if they would merely like to visit sites in their holiday area, the Mason-Gardner Archaeological Bureau will be glad to assist.

BB69/3 I hope that this will help to satisfy Archeaocurious but would add that if less noms-de-plume were used, we might get to know who really is interested in getting things going.

R.S.G. ************************************** MENDIP RESCUE ORGANISATION The Annual Meeting of the Mendip Rescue Organisation was held at Bristol University on Sunday March 15th. At this meeting concern was expressed about the availability of information re, digs in progress or new discoveries. It was stressed that however efficient the organisation was, the difficulties of effecting a speedy rescue could be considerable due to possible lack of cooperation by cavers themselves. All Clubs were asked to stress to members that it is essential that someone must know the whereabouts of persons underground, especially those engaged on ‘New’ work. In the ordinary way, the usual message left at the Belfry or other HQ, or with those at home is of course sufficient, but work on a new series in a known cave or a dig ‘somewhere on Mendip’ would leave the Rescue Wardens with little or no information to work on.

It was suggested that members could co-operate by following one of the courses of action set out below, always remembering to those to whom it is divulged. a. Have someone that knows intimately the dig etc., on the surface so that in the event of trouble the Warden and his team could be led direct to the incident. b. Inform the Hon. Sec., of what is happening do that he can describe your probable whereabouts to the Warden. c. Deposit a sealed envelope (if you don’t trust your Sec.!) with your Hon. Sec., to be opened in an emergency, and. TELL someone that you have done so. d. Report to a Warden of your choice when you go underground and also when you return.

T.H. Stanbury Warden, M.R.O. ******************************************* In case any member is unfamiliar with the procedure to be followed to call out the M.R.O. it is set out below.

T.H.S. 1. The person having knowledge of the accident will go to the nearest telephone and ring the Police (Wells Police Tel. is Wells 2197).

2. The Police will require the following information:a. Name and address of caller. b. Number and situation of telephone. c. Nature of accident. d. Name of cave. e. Position of accident in cave. (if known). f. Number of persons in party. g. Whether experienced cavers.

3. The informant will remain at the telephone for further instructions. ************************************************** There are a number of back numbers of the BB available at a cost of 1½. Each from Caxton at 55 Broadfield Road. ************************************************** Apology I regret that owing to an oversight on my part, I did not include the Hon. Librarian on the list of official in BB67. ‘Hon. Librarian’ of course, should have been placed after John Ifold’s name on page 4.

BB69/4 I have been told that a certain hole hear the Belfry is about to ‘go’.

Again!!!!!

Hawkeye. ************************************************** The second circular relating to the International Congress in Paris has been received. The first part on the Convention will take place in Paris from 7th to 11th Sept. From 13th to 19th Sept. there is a tour to the Limestone areas of the Causses: from 20th to 26th Sept. there is a tour a. of the Pyrenees or b. of the French Alps.

Costs.

The figures below are of course only provisional and are based on those given in the circular.

Return fare to Paris……………………………………………………………………………..£10/ - /Accommodation, etc. in Paris…………………………………………………………………..£ 8/10/Membership fee…………………………………………………………………………………£ 5/ 5/Causses Excursion…………………………………………£22 to …………………………….£27/ -/Alpine or Pyrenean ditto…………………………………...£16 to ……………………………£22/ -/Total cost therefore will be between £59/ -/ - and £70/ -/ Would all those interested please get in touch with the Hon. Sec. Permits for the extra Cash over and above the recently increased basic allowance should be made to the appropriate authority well in advance of Conference time.

K.C.D/T.H.S. **************************************************** T.H. Stanbury Hon. Editor, 48, Novers Park Road, Bristol. 4.