08.03.2012

TAOP

PART FOUR: LIGHT.

Exercise: Higher and Lower Sensitivity.

Equipment: Canon G12 on Av.  ISO settings 100 and 800.

For this exercise I took pairs of exposures in each location, one at ISO 100 and a second at ISO 800.

The first was at a round-a-bout and included a town scape and slow moving traffic.  

ISO 100.  f5.6 @ 1/320.  No obvious camera shake.  Good depth of field.  No motion blur on the vehicle.  At 300% pixilation was clearly visible but fine detail was still seen. No serious noise.

ISO 800.  f5.6 @ 1/1,250. No sign of camera shake.  Good depth of field.  No motion blur on the vehicle. Even at 66% noise was becoming evident in the shadow and dark areas. At 100% it was intrusive.  At 300% pixelation was clearly visible and fine detail was being lost.    

I produce the two pictures as taken and two details from them.  What may not be obvious is the loss of colour saturation at the higher sensitivity.

Conclusion.  No advantage in using higher sensitivity on this occasion.  

The second pair was at Sainbury’s shop exit and involved people walking across  my line of vision.

ISO 100.  f5.6 @ 1/125.  No camera shake.  Good depth of field.  Slight sign of motion blur particularly on the legs.  Pixelation similar to the first pair.  The black interior of the open boot is totally free of noise.

ISO 800.  f5.6 @ 1/1250.  No sign of camera shake.   Good depth of field.  No sign of motion blur even on the small pram wheels.  The darkest area I could find was the rear wheel of a car.  This was very noisy.  The loss of colour saturation is more pronounced in this second pair, due possibly to the lower shutter speed of the ISO 100 image.  The loss of detail is well demonstrated by the steps detail that I reproduce.

Conclusion.  The controlling of motion blur was not worth the loss of picture quality on this occasion.

The third pair was taken at waist level with me walking towards my target.

ISO 100.  f5.6 @ 1/30.  Camera shake is very evident giving the whole image has an out of focus look.  There was no noise in the black of a door.  The other criteria are not worth commenting on because of this blurring.

ISO 800.  f5.6 @ 1/400.  Little sign of camera shake.  Good depth of field.  Small amount of motion blur but not sufficient to spoil the image.  There is some noise in the black areas of the image.  This image suffers from the same pixelation and saturation problems as the other examples but this time the drop in quality is more that compensated by the fact that the shot was only possible by using a fast shutter speed and high sensitivity.

Conclusion.  Well worth the loss of image quality to obtain the shot.

Back in the time of black and white film the limitations of the various products was paramount.  A change of speed meant wasting the end of a roll.  Pushing and pulling film was a regular procedure that required a whole arsenal of rapidly deteriorating chemicals.  Are Ilford Pan F, FP4 and HP5 still made?  Pixels and noise may have taken the place of grain but tools are now available to smooth out these problems, at least to some extent.  Noise reduction and filter programmes can counter these problems but as usual there is a cost, and that cost is sharpness. 

Noise does not have to remain a problem if saturated colours are more important than sharpness as noise reduction programs used either within the camera or in post production can limit its effect.