PHOTOGRAPHY -25

 

PHOTOGRAPHY -25

FLASH-SHUTTER SYNCHRONY ISSUES IN SLR DESIGNS.

Density of an image owes itself to balanced lighting with all typical light-shadow distribution. So, light has to reach diferent parts of a frame in appropriate intensities . This feature depends on light –orientation, sharp focus and quick registering of the scene. Much of it depends on how the shutter permits light distribution over the sensitive surface of the film. It is this aspect that widely differs between TLR and SLR systems.

 Shutter working in TLR EQUIPMENT

As presented earlier, TLR lenses have ‘in-built’ shutter /Diaphragm blades in ‘one after the other’ sequence with Diaphragm placed behind the shutter assembly. Invariably, shutter is released as the final operation for registering an image; it means –all preceding stages like choice of aperture, shutter speed and critical focus of key objects on the scene are ciompleted. To recall, the functional diaphragm is set for right exposure by assessing flash out put  through GN –assisted information. The diaphragm stays ‘set in a state of right opening’ and when the shutter is released the shutter blades travel from centre to peiphery and again returns to centre. So, the exposure in a TLR BEGINS AT THE CENTRE and again completes at the centre,making right image on the film.

Shutter working in SLR EQUIPMENT

SLR Lenses have only the Diaphragm assembly within.The shutter is incorporated at the interior of the camera just in front of film and is thus named FOCAL PLANE SHUTTER. [FPS]. The FPS has a horizontal run left to right or right to left as per the design. A few FPS have vertical run generally BOTTOM –UP.Thus FPS register image from one endto the other –Horizontal or Vertical. Through this time, the  flash should light up the object. The ‘light stay’ and SHUTTER in open state’  should match ; otherwise only partial images are recorded.

Because a 35 mm film has a frame measuring 24 X 36 mm , exposure has to cover along 24 mm height or 36 mm width. This is the real limiting factor in making an exposure end to end. That is why the prescribed speed for flash photography is marked in colour by camera manufacturers. At other speeds synchrony between Flash and Shutter may fail resulting in partial exposure of frames.

With flash as the light source, extra care may be needed to ensure appropriate image density. So, a blind attempt of using a flash without right safeguards for  exposure can end up in frustration . So, please study the literature for Camera and Flash gun to grasp how they can be co-ordinated .  Always –better equipment deserve and demand proper aligning of control parameters to ensure success.     

Make it a practice to read/ study any pamphlet for its message .Often some fine details of handling the materials is presented as graph or as bar diagrams to suggest the   relationship between parameters in working of controls. Only by such official presentations one can get to have authentic information on performance characteristics.                             More to follow          K.Raman