The first images for this exercise were taken in Sneaton forest, where I wanted use a minimum aperture setting for the increased depth of field, with low light conditions, to be able to ‘freeze’ the movement of fast flowing water.
At ISO 200, f/29, the exposure needed to be 4 sec, so movement of the water is shown as a blur (I must admit to preferring this type of image for water flow)
Still at f/29, but ISO 640, a shutter speed of 1/25 sec is required. Movement in the water still causes some blurring.
At ISO 3200 the shutter speed of 1/125 sec is enough to stop any significant blurring in the moving water.
For the next set of images we move back to the beach. The object of this exercise was to freeze the waves while still maintaining a reasonably sharp focus in the background. This involved using the minimum aperture while altering the ISO to allow faster shutter speed.
The camera was in aperture priority and tripod mounted.
At ISO 200, 2/22, a shutter speed of 1/80 sec was required for this image. The waves still have a significant amount of blurring, so that they tend to run into each other and look less powerful.
At ISO 400, 1/160 sec, the waves are not running together so much, but they’re still not ‘crisp’
With ISO 800, the shutter speed is reduced to 1/250 sec. Now we can see the curl of the waves and the force as they break. At this speed there’s more of a feeling of power.
This effect has really surprised me. I was expecting to see the difference in clarity in the waves but I wasn’t prepared for the difference on the impact of the image.
In the shopping centre I wanted to stop the escalator while keeping the shops in focus, so a similar setup was used. The main difference was that the camera was hand held. I had to do this to avoid the attention of the security staff – that’s also why the images were taken from the top of the escalator (the security chappies were downstairs). I’d much rather have had the shoppers’ faces.
Starting at ISO 200, I had to use 1/8 sec at f/22. The vibration reduction in the lens helped, but close inspection shows some significant blurring due to camera shake as well as the moving people.
ISO 500 allowed a shutter speed of 1/20 sec but this was still not good enough for a hand held camera and with moving subjects.
At ISO 1600 a speed of 1/60 sec was enough to stop the movement. Close investigation of this image shows an increase in noise – particularly in the dark areas.
The next three images demonstrate another advantage of varying the ISO. I was using the D200 with a 500 mm lens, without a tripod and trying to photograph gulls in flight. This involved panning with the camera in continuous focus – not easy with a lens of this size! It was also quite windy. The D200 doesn’t have the same level of noise reduction as the D300s.
At ISO 100 the fastest shutter speed I could attain was 1/320 sec. With the speed of the bird, awkward shooting angle and wind I couldn’t manage a sharper image than this.
ISO 400 allowed a shutter speed of 1/640 sec with a resultant sharper image.
At ISO 1000 a shutter speed of 1/800 sec enabled a much sharper image. Out of focus areas due to movement of the bird and / or the camera were greatly reduced. I think the increased noise in the image is more than compensated by the clarity of the image.
Noise can be the down side of using high ISO settings. Software is available to remove some of this noise (e.g. Topaz Labs De-noise), but the image has then been digitally manipulated which is not always acceptable. It’s also possible that the increased noise may be beneficial to an image – particularly if using monochrome. The Nikon D300s operates very well at high ISO settings and can automatically reduce noise if programmed, so it’s not too much of a problem for me.
Demonstrating the effect of increased sensitivity has been a useful exercise. Not only as a means to take images in low light without additional lighting, or to keep good sharpness throughout an image without using slow shutter speeds, but also to enable hand held shots where a tripod would be difficult.
No comments:
Post a Comment