Category Archives: a – The intensity of light (natural light)

Higher and lower sensitivity

I’ve done a similar exercise in terms of assessing noise in the DPP course see:-

https://richardbrown56dpp.wordpress.com/2015/06/17/your-tolerance-for-noise/

But in this case it’s a demonstration of how boosting up the ISO is a valuable option.  With modern cameras the range of ISO is staggering (particularly when, in days gone by, I thought pushing Ilford 400 was fast.) My camera’s ISO ranges from 50 to 25600 and is useable in my experience up to 6400.  Compare this to my first digital 1.3 megapixel camera which had three ISO settings – 160, 320, 640.  This increase in useable ISO is particularly relevant when shutter speed and/or aperture cannot be altered for creative or circumstantial reasons.  You may for example wish to record a shot with a large depth of field  and with a fast shutter speed.   At conventional ISO speeds, say 100-400, this may not be feasible but by boosting ISO the desired shot may be available.

As an example these shots show again the bird feeder outside my window and the first three shoots are taken at ISO 100; F8 and 1/15.  Because of the rapid movement of the birds at that aperture the movement will be blurred.  Increase the ISO to 6400 however and there is a better chance of getting a useable shot as the shutter speed is now much higher at 1/800.

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Blurred Sparrow

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Another blurred bird

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A bit more detail in this shot but only because the subject stayed still for a while.

 

 

 

 

 

 

 

 

The second series of three is at ISO 6400

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Similar scene to the above shot but note how the detail is better (due to the faster shutter speed enabled by the higher ISO)

 

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Blue tit feeding. These are very wary birds and rarely stay still but the increased ISO has enabled the shot to be frozen

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Likewise the otherwise rapid head movements have been frozen here.

Of course the big compromise with increasing the ISO is the amount of noise usually in the shadow areas.

For comparison I show below the same area the edge of the UVPC widow frame and the shadowed hedge behind it, at 1:1:-

 

noise 100 ISO

Detail from 1000 ISO shot

Noise 800 ISO

Detail from 6400 ISO shot

As can be seen at this level of viewing there is a significant increase in the noise.  Of course whether this is an issue depends on the use the shot is put to and how big it will be viewed at.  As an A4 print the ISO 6400 shots would probably still be acceptable (aesthetic considerations notwithstanding) but any larger and it may be an issue.  There is the further point that noise can sometimes, with its graininess and edginess, be an artistic or compositional choice – for instance in concert shots.  It should also be noted that I have not applied any noise reduction control in either of the above shots, but this would, under Lightroom as far as my experience goes, reduce the issue somewhat, but not entirely.

 

 

 

 

Measuring exposure

The brief for this exercise is to produce four to six images deliberately under or over exposed and give the reasons for doing so.  To a degree the effect of under or overexposure is affected by the metering mode you are using.  My camera has multi segment; centre weighted and spot metering modes.

As an example here are three shots at the same aperture but with different metering modes.

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F2.8 @ 1/125 ISO 200 Multi segment metering

 

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F2.8 @ 1/160 ISO 200 Centre weighted metering

 

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F2.8 @ 1/250 ISO 200 Spot metering

As can be seen there are small differences in shutter speed.  To further illustrate the point I used the same shutter speed and aperture but just altered the metering.

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F2.8 @1/125 ISO200 Spot metering

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F2.8 @1/125 ISO 200 Centre weighted metering.

 

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F2.8 @1/125 ISO 200 Multi segment metering.

Again the difference is only small but there are variations in the white of the door frame.

I probably use centre weighted more than the others but do use spot metering a lot as well.

The exercise asks you to produce four photos either under or over exposed and I was not sure whether “produce” means take new shots or find existing shots – so I did the former.  These then are ones I have shot previously unconnected with the coursework:-

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Overexposed by one stop to compensate for the rather poor lighting.

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Underexposed by 2 stops to compensate for bright light on water.

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Under exposed by just under 5 stops on a very sunny day to get the tower in silhouette.

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Overexposed by a stop to bring out the figure at the bus stop.

 

 

 

 

 

 

 

This is a shot I did specifically for the exercise:-

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I’m not a great fan of ornaments and I particularly dislike this one. But I wanted to highlight the light play on the surface, so massively overexposed by 5 stops to subdue its environment.

This is the first subject of five ranged photos.  Its an old wax seal belonging to (or acquired by) my grandfather.  I decided to use spot metering on the face of the seal.

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Measured exposure

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Measured exposure -1/2 stop

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Measured exposure + 1/2 stop

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Measured exposure – 1 stop

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Measured exposure + 1 Stop

Of these I think the plus one stop photo works best as it brings out the detail of the carving in the seal.

The second set is of a hanging bird chime and light.  Again not one of my favourite objects, but I thought it would be a useful subject for the exercise.  I used my tilt shift lens for this as I just wanted the right hand side with the chime in focus.   I underexposed by one stop (and used that as the “base” shot) to see if I could get a bit more detail in the clouds and also I wanted to see if any alteration to the exposure affected the bracketing.   It did not appear to, with the camera taking the minus one stop as the point from which the other bracketing adjustments were made.

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Measured exposure (set at minus one stop)

 

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Measured exposure minus half a stop.

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Measured exposure plus half a stop.

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Measured exposure minus one stop

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Measured exposure plus one stop

Of these shots I think the minus half a stop (or minus one and a half stops taking into account the existing adjustment) is the one I prefer as it gives a bit more cloud detail but does not completely subdue the red of the chime.

The next scene was the interior of a garage.  I thought it would give a good indication of the effects on bracketing on the shadows.

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Measured exposure – no adjustment.

 

 

 

 

 

 

 

 

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Measured exposure minus half a stop

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Measured exposure plus half a stop

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Measured exposure minus one stop

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Measured exposure plus one stop

In this case I’m torn between two images.  I like the plus one stop version as it brings out most of the objects in the garage, but possibly at the expense of an y atmosphere – it is a more “clinical” shot.  I also like the minus half a stop shot as this creates the atmosphere – you know stuff is there but you are not sure what it is.

The last subject I chose was a school roof, with a development site in the background, viewable from our landing window.  The site is about a mile away so atmospherics play a part in the quality of the image.

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Measured exposure no adjustment.

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Measured exposure minus half a stop

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Measured exposure plus half a stop

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Measured exposure minus one stop

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Measured exposure plus one stop

The minus half a stop shot gives, I think, more substance to the roof and still provides plenty of detail, the plus one stop gives a more washed out look and the overexposure takes away any dynamism, such as there was, from the scene.   Overall I think I prefer the measured exposure without any adjustment as it provides sufficient foreground and background information.  What the exercise demonstrates is that relatively small adjustments to exposure can have significant impact on the aesthetics of a shot.  I’m lucky in that the camera I use can easily be set to adjust exposure (and also bracket exposures) but also give a pretty clear indication by means of the liveview viewfinder what effect such an adjustment will have.  My main use of bracketing is for scenes with both heavy shadows and highlights so I can merge exposures to cater for this.