Editorial

From the editor Eugene Struthers

Welcome to Glamour-photography Ltd.

Q & A.

Is there any way of knowing what is a safe shutter speed to use in relation to the focal length of the lens? A simple rule of thumb which will give a good indication of the minimum recommended shutter speed is to think of it in terms of a reciprocal of the focal length of the lens you are using; with a 500 mm lens 1/500 sec or the nearest setting, with a 200 mm lens you should not use more than 1/200 sec.

What can I do if the aperture I need for the flash requires a faster shutter speed for the daylight than I am able to use with my focal plane shutter? You should use a higher - powered flash gun or move it nearer to the subject; this will enable you to use a smaller aperture and a slower shutter speed.

How is the flash exposure calculated for daylight shots? In each case you must first establish the correct exposure for the daylight for example:- 1/60 sec at f8. If using a flash to fill in shadows then first establish the correct exposure for the flash and then set the aperture for between one and two stops smaller, whilst adjusting the shutter speed to correspond accordingly to compensate for the day light exposure. If you decide to use the flash to balance a dark foreground with a brighter back ground then the aperture needs to be adjusted a half stop less than the correct exposure for the flash to avoid an unnatural effect. However; if the flash is being used to stimulate sunlight on a dull day then you should reduce the daylight exposure to between one and two stops and set the correct exposure aperture for the flash exposure, maintaining a shadow which will be at an angle compatible with sunlight which will be cast from the flash-gun.

How do I get more depth of field in close up shots? You will find that the depth of field will drastically decrease at a close focusing distance, so to achieve maximum depth of field it is necessary to use the smallest aperture available. In some lenses this will stop down to f32 and smaller. By changing and altering the camera position and setting up your subject in as far as possible on a similar plane.

How do you calculate the extra exposure for very close up pictures? A camera with a TTL metering will make an allowance for the increased extension if a bellow unit or extension tubes are used. If a reading is taken with a separate meter it is necessary to increase the exposure indicated by the factor which is produced by dividing the square of the distance from the lens to the image by the square of the focal length of the lens. This means that a lens of 50mm focal length extended to 80mm would require an exposure increase of 80 (squared) divided by 50 (squared) = 6400 divided 2500 = 2.56; so if the exposure was one second. The adjusted exposure would be approximately 2 1/2 secs.

Are converter lenses worth considering? A good quality converter lens can be an effective way of increasing the focal length of a long focus lens, from 150mm to 300mm, but the results will be less satisfactory with lenses of a shorter focal length. A converter will double the focal length of the prime lens, but will also reduce the maximum aperture by two stops .

Do you get more depth of field when you use a telephoto converter or does the depth of scale stay as it is? Depth of field scale will no longer apply when a converter is fitted. The depth of field will be less than the prime lens alone at the same aperture. The converter will reduce the marked aperture for example:- a X2 converter marked f8 will in fact be f16. The difference however of actual depth of field and that indicated by the scale for the marked setting won't be that great.

Is there more than one way of taking an exposure reading? The incident light method, with the correct meter. This involves aiming the meter from the subjects position towards the light. This is ideal for subjects with an abnormal tonal range such as a black dog in a black room. The conventional method of measuring the light reflected from the whole of the picture area and letting the meter calculate the average reading. The photographer can also use the light from the brightest and darkest areas of a scene and then calculate the average himself. This method is effective with high contrast subjects example:-street scenes at night, when the photographer is unable to take a close up reading from an average tone. The substitute method will be used for subjects with an abnormal tonal range such as high or low key images. This will involve placing a grey card in the same lighting conditions as the subject and taking a reading off this.

Eugene Struthers Esq

Thanks for all your support and comments.

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Have fun see you next month :-)
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