Before this course, I generally tried to keep a shutter speed of 1/100th second or thereabouts for hand-held photos, increasing the Iso to achieve this. This guide was suggested by an instructor on a photography course that I went on in 2008. This sometimes means increasing Iso up to the 3200 limit of my camera. I know that grain can be a problem at high Iso and often in the past, I have excluded photos I have taken for this reason. Iso level has been one of the settings that I generally check before taking a photo, although I forget this occasionally.
Image 1: The queue for the next performance at the Edinburgh Fringe
Nikon 18-70mm at 18mm: Iso 200 f8 for 1/8th second
It had just started raining and people had put their umbrella's up. I sensed the slow shutter speed when pressing the shutter button. I quickly took another photo at a higher Iso and wider aperture.
Version 2 at higher shutter speed
Nikon 18-70mm at 18mm: Iso 640 f6.3 for 1/60th second
The first version is slightly soft when viewed on screen at 1:1 magnification. The second version is noticeably sharper but it has more prominent grain.
Version 1 enlarged
Version 2 enlarged
Image 2: Wild mushrooms
Nikon 18-70mm at 22mm: Iso 200 f7.1 for 1/40th second
There were many fungi alongside the Hadrian's Wall Path in August. I liked this grouping of three clumps as they looked fresh and were relatively undamaged.
I realized that the shutter speed was too low for hand-holding. When I recomposed the photograph onto a portrait format to include more of the tree in the background, I also increased the Iso to 400, equivalent to 1 stop.
Version 2 at a higher shutter speed
Nikon 18-70mm at 22mm: Iso 400 f7.1 for 1/60th second
The first photograph is indeed slightly soft at 1:1 magnification. The second version is sharper and there is no sign of graininess. Indeed the contrast has improved slightly in the second version. (I have noticed before that photographs that are blurred often have lower contrast.)
Version 1 enlarged
Version 2 enlarged
Image 3: Juggler (final version)
Nikon 18-70mm at 40mm: Iso 320 at f14 for 1/2oth second
This juggler was standing on his own in a rather dark and narrow back street in overcast weather. I hoped that the flaming torches spinning in the air might have an interesting visual effect. I was walking with my wife between shows and I did not have a lot of time. I took a sequence of 6 photographs in 40 seconds, and this was the best of the six, after some post processing adjustments of darks and lights.
My camera was set at Iso 100 and f20 when I snapped off the first shot resulting in a shutter speed of 1/8th second. Viewed on the LCD screen, the juggler and background are heavily blurred and dark. The torch flames created a trail of light, but it was not readily possible to tell that he was juggling flaming torches.
First version
Nikon 18-70mm at 40mm: Iso 100 f20 for 1/8th second
I quickly increased the Iso to 320 and opened up the lens to f14. I was aiming for a slowish shutter speed of about 1/15th second in this case to capture some movement of the torches.
With these settings, I took another five photographs. The shutter speed and tone of the photo however seemed to be changing erratically. Three of the photographs were 1/20th (including the final version above) whereas the other two were at 1/4th and 1/8th seconds. I now realize that I had inadvertently knocked the exposure meter switch from matrix to spot metering. No wonder with the burning torches in the central area of the picture that the exposures were going up and down.
With more time, I think it might have been an idea to switch to manual exposure settings to have more control. The picture was unfortunately not as interesting as I had imagined, but it was still potentially a useful situation to learn from.
Image 4: Drochil Castle - another view of ruined vault
Nikon 18-70mm at 18mm: Iso 3200 f8 at 1/30th
Even though it was a bright morning outside, the light was dim inside this corridor of the ruined castle. For the first photograph (not shown), even at Iso 800, the shutter speed was only 1/6th of a second. There was fortunately a nook in the wall where I could place the camera on a solid base to cope with the slow shutter speed. I thought I would take the same subject at Iso 1600 and 3200 to see to what extent graininess degraded the photograph.
In fact, there was little to distinguish the three photographs when viewed on screen. Only at 1:1magnification were there noticeable differences in noise. For the purposes of this blog, I have therefore included only the highest Iso image.
The difference in grain is visible in enlargements of the dark doorway on the left hand side of the corridor, but the impact on the photograph as a whole is relatively minor. One possible explanation for this muted effect could be that I have set my camera to apply noise reduction for high iso photos (800 and above). However, at other times high Iso photographs have been quite badly affected by grain.
The notes mention that grain can typically be found in smooth areas and dark areas of a photograph. It is accordingly possible that the relatively rough surfaces of the castle interior might cover up the visual impact of noise.
Image 5: Edinburgh skyline at twilight (exposure adjustment plus 1 stop)
Nikon 18-70mm at 18mm: Is0 400 f6.3 for 1/30th second
I observed that the level of noise in photographs can increase significantly as light levels reduce. This was particularly noticeable in a sequence of three photographs that I took in Edinburgh for the "Exposure measurement" exercise. In the above photograph, the sky has a smooth texture with virtually no grain. Even though the Iso levels were the same, the level of noise is progressively higher as the available light was reduced. This was most signifiant where the exposure adjustment was minus 1 stop. The latter photograph is shown below.
Image 5: with exposure adjustment minus 1 stop
Nikon 18-70mm at 18mm: Iso 400 f6.3 at 1/160th
Image 6: Butterfly on lavender one of first series
Nikon 70-210mm at 210mm: Iso 400 f16 for 1/125th second
This is an example of a scene where Iso was increased in order to gain a little extra depth of field. I was trying to photograph butterflies that were feeding on lavender. The butterflies rested only momentarily and I was unsuccessful using a tripod.
In order to reduce the risk of camera shake, I found that I needed to use Iso 400 in order to achieve a shutter speed over 1/100th second at f16. I have found by experience that depth of field is quite shallow at apertures wider than f16 when the lens is at its maximum extension. My objective was to obtain sharpness from front to back of the butterflies even though their wings were open at an angle rather than flat.
When I looked closely at the first sequence of images like this one, only a part of the butterfly was in focus and there was also some general softness. I therefore increased the Iso to 640 which allowed a smaller aperture as well as a little extra speed:-
Image 6: Butterfly on lavender one of second series
Nikon 70-210 mm at 210mm: Iso 640 Iso 20 for 1/180th second
This was the best of the photographs that I took. The wings are reasonably sharp but there is still some softness around the head and antennae.
Conclusion
I am reasonably aware of Iso sensitivity settings and use the adjustment frequently to deal with marginal lighting conditions. It has nevertheless been useful to practice this technique in various situations.
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