Higher and Lower Sensitivity

During a recent visit to the safari park I found myself in a situation where the ISO setting of my camera was to play a big role in how the shoot turned out. Although I have prior experience with adjusting ISO settings, I hadn't previously done so with as wide a range of settings; at this shoot this was from ISO400 to ISO6400.

On arriving at the park, I knew I wanted to make the animals the main subject in the majority of cases, so would need to throw the background out of focus. I also wanted the subjects to fill the frame, so was armed with my Sigma 70-300mm telephoto lens, mostly shooting at the 300mm focal length. I started out using aperture priority at f5.6, and the default setting of ISO100. I realised on the mostly overcast day that I was getting a very slow shutter speed reading, so increased to ISO400. I was perhaps being overly cautious with the ISO setting, considering the capabilities of modern cameras of dealing with noise at higher ISOs. I was now getting a reading of around 1/200s which was still too low for hand-holding at 300mm without vibration reduction, but at least I was able to use my elbow and the frame of the car window as a makeshift tripod (most of these images were taken from the driving seat).

300mm, f/5.6, 1/200, ISO 400

 

300mm, f/5.6, 1/200, ISO 400

A little further on, my shutter speed started suffering again, so I bumped the ISO one more notch to ISO500.

300mm, f/5.6, 1/320, ISO 500

As I ventured further into the park, the light levels falling on my subjects varied considerably, mostly due to shade from foliage or shelters. It was at this point that I realised I would be changing my ISO a lot to preserve a sensible shutter speed, I then remembered my new camera has an auto-ISO setting. I switched to shutter priority, choosing a speed of 1/500s (occasionally switching to 1/640) which I hoped would get sharp images and turned auto-ISO on. This meant the camera would now preserve the shutter speed of 1/500s but automatically adjust the aperture and ISO settings to produce a correct exposure. This meant I could concentrate on the composition and subject of my images and let the camera do the technical spade-work. I've chosen a selection of images from the day that feature a range of different ISOs selected by the camera.

195mm, f/4.8, 1/500, ISO 2500

170mm, f/4.5, 1/500, ISO 3200

300mm, f/5.6, 1/640, ISO 1800

300mm, f/11, 1/640, ISO 800

220mm, f/8, 1/640, ISO 800

170mm, f/4.5, 1/500, ISO 1400

300mm, f/5.6, 1/640, ISO 6400

300mm, f/5.6, 1/640, ISO 5600

100mm, f/4, 1/500, ISO 2200

The above images are all shown after post-production in Adobe Lightroom, and at much smaller than original size. To accurately compare noise, I selected the two extremes of the ISO spectrum used, removed all post-processing from the images, and enlarged them to 100% in Lightroom, before selecting and cropping out a small area of dark and light in the image to compare noise:

ISO6400:

There is definite 'speckling' in both the light and dark areas of this extremely high-ISO image, although to be honest I expected a lot more.

ISO400:

  

It's clear to see the noise is much less evident in these two enlargemements, even though the darker image isn't as dark as the one used for ISO6400.

Conclusion

Higher ISO's clearly introduce noise to an image, however my modern camera (Nikon D610) seems to be excellent at handling even extremely high ISO's. Coupling this with the fact that software like Lightroom and Photoshop have noise reduction filters built into the software, means that noise can be dealt with in post-production, so there's no good reason not to crank up the ISO to get the shots that wouldn't otherwise be possible.

Measuring Exposure, Part Two - Scene Five

Betting Shop - Birmingham New Street Station

Best Exposure

26mm, f/4, 1/50, ISO 800

Exposure Compensation: +0.67

This subject of this image is the bright betting shop sign, with the floods of commuters passing by. The scene is located just outside of Birmingham New Street station, and is partially enclosed (just out of the left of the frame is open, where sunlight can enter). I liked this exposure the best, as the sign isn't washed out, but you can still see details on the pedestrians and the reflections on the ceiling are still nice and bright.

26mm, f/4, 1/80, ISO 800

Exposure Compensation: 0

This image was taken with the light-meter's recommended settings. It's ok actually, but the man in the foreground's face is cast in shadow, and the BETFRED lettering isn't quite as white. I expect this is due to the camera trying to achieve 18% grey.

26mm, f/4, 1/50, ISO 800

Exposure Compensation: +0.33

I can't see any perceptible difference between this image and my 'best exposure' image. I think I chose the other image due to a better arrangement of people within the frame, rather than for exposure reasons.

26mm, f/4, 1/100, ISO 800

Exposure Compensation: -0.67

This is the darkest image of the series, and looks like it could have been taken at night-time. The outlines of the people are now almost silhouette, and the white of the signage is nowhere near as bright. An acceptable image if I wanted to turn this day scene into a night scene, as its not clear from the image itself that natural light is entering from the left of the frame.

26mm, f/4, 1/80, ISO 800

Exposure Compensation: -0.33

This image appears very similar to the default exposure settings image, the main difference being the brightness in the reflections on the shop window.

Overall Response

Similar to the first series of images produced for this part of the project, exposure can be adjusted to give an impression that the time of day is different to what it actually is. Also, the prominent white of the shop sign has to be taken into consideration if you want your whites to be bright.

As a side note, I learnt a new Photoshop technique that I used with this series of images. As mentioned in another post, I had to manually change the exposure compensation to get the five images required, and this meant that the five images weren't exactly lined up. In these betting shop images it was a particularly obvious problem, probably due to the strong diagonal lines running across the image. I found out that Photoshop was capable of perfectly lining up all the images together, which is what I did here. I'll record the procedure and how I found about it under a new section of this blog - 'Photoshop Techniques'.

Measuring Exposure, Part Two - Scene Four

Winter Night Shelter - St. Martin

Best Exposure

18mm, f/3.5, 1/1000, ISO 1600

Exposure Compensation: +0.67

This series of images, as in scene four, where taken inside the church of St.Martin in the Bull Ring. I noticed a row of inflated air-beds with wooden dividers, and signage within the church informed that homeless people were offered a bed for the night over the winter. I thought this was a great concept to photograph, and in my mind I could see the sunlight streaming through the window onto the airbed; a visual embodiment of a potentially life-saving gesture. This exposure, over-compensated by two-thirds bathes the bed in the most light, most accurately representing the scene I imagined.

18mm, f/3.5, 1/2500, ISO 1600

Exposure Compensation: -0.67

This image is underexposed by two-thirds of a stop, and the subject has been almost completely lost in shadow, as such I would consider this particular version unusable.

18mm, f/3.5, 1/1600, ISO 1600

Exposure Compensation: -0.33

This is a little better, but still there is not enough attention being drawn to the main subject.

18mm, f/3.5, 1/1250, ISO 1600

Exposure Compensation: 0

Again incrementally better, but at this recommended setting there is no clear subject, and I think viewer's of the image would be unsure of what they are supposed to be looking at.

18mm, f/3.5, 1/1000, ISO 1600

Exposure Compensation: +0.33

The bed itself now begins to appear more obvious, and I'd select this as the only other acceptable exposure in the series, although the illumination of the bed by the sunlight is enhanced better with two-thirds of a stop compensation.

Overall Response

This is the first series of images that features unusable exposures. Although 'correct' in terms of averaging-out the brightness in the scene, if you have something different in mind you need to be able to override the camera's suggestions. By bracketing my shots I was able to achieve the effect I wanted, and would probably further over-expose on my chosen image in post-production.

Measuring Exposure, Part Two - Scene Three

The church of St Martin in the Bull Ring

Best Exposure

18mm, f/3.5, 1/500, ISO 1600

Exposure Compensation: 0

This is the first scene in this project so far where I have chosen the exposure suggested by the light meter as the best exposure. For this scene I wanted to capture the beautiful, bright stained-glass window while contrasting it with the darker, serene interior. The recommended exposure does this well, capturing the essence of what I had in mind, and also preserving many of the details in the scene.

18mm, f/3.5, 1/160, ISO 1600

Exposure Compensation: +0.33

With a third of a stop of exposure compensation applied, the foreground with the chairs and slabbed flooring is brightened considerably, whereas the change in the window and on the back wall is not so drastic. This effectively cuts the scene into two sections; the brighter bottom third of the image and darker top two thirds of the image. In my mind this creates two subjects in the frame; the window and the seating area. I do like this image, and feel these settings could work great in a slightly different situation, perhaps with people sitting down so attention could be brought to the congregation.

18mm, f/3.5, 1/200, ISO 1600

Exposure Compensation: +0.67

I don't see a huge difference between this image and the previous one, except in the colour of the light streaming through the window, which appears more golden in colour. This does give a feeling of warmth to the scene, which would be good as a general-purpose interior shot of the church, for a newsletter or web article.

18mm, f/3.5, 1/400, ISO 1600

Exposure Compensation: -0.33

This is very similar to the first image with the recommended settings, and as such could be used interchangeably

18mm, f/3.5, 1/500, ISO 1600

Exposure Compensation: -0.67

At this exposure compensation setting the focus is firmly on the stained glass window; ideal if that is the only subject you want to represent, with the chairs just adding contextual value.

Overall Response

This scene provided a series of images where I think each one is perfectly valid and acceptable, depending on context and requirements. This shows that the same image, but with modified exposure values, can  be suitable for a variety of purposes, due to the changes of mood with varying exposures, and which elements of the scene are made more or less conspicuous.

Measuring Exposure, Part Two - Scene Two

Street Artist

Best Exposure

28mm, f/8, 1/100, ISO 200

Exposure Compensation: -0.33

Choosing the 'best' exposure out of a series of five is surely an artistic decision? The image above of a man creating images using chalk a third of a stop lower in value than that recommended by the light meter. I chose this as although the overall scene is dark, the main subject in the image is the depiction of the girl with the pearl earring, and as discovered in the previous part of the course, underexposure really makes colours 'pop'. Thus, the eye of the viewer is drawn to the rich colours and subtle gaze of the girl with the pearl earring, then it is led diagonally through the frame to the other, unfinished, works, and the artist himself.

28mm, f/8, 1/80, ISO 200

Exposure Compensation: 0

This is the exposure suggested by the light meter. It seems well balanced, and a decent representation of the lighting conditions at the time. The reason I didn't choose this image as 'best' exposure is because it is too ordinary; good perhaps for an article on street artists and buskers, but as a piece of art I personally like it a little more dramatic, as per the first image.

28mm, f/8, 1/60, ISO 200

Exposure Compensation: +0.33

Very similar effect to the previous image, but with the colours in the scene beginning to look a little washed-out.

28mm, f/8, 1/50, ISO 200

Exposure Compensation: +0.67

With this much overexposure applied I feel the scene looks a little flat.. that's good if you wanted all three chalk drawings to be observed equally, which may be ideal depending on the situation.

28mm, f/8, 1/125, ISO 200

Exposure Compensation: -0.67

Underexposing by two-thirds of a stop makes the blue colouring even more rich, but the overall scene appears very dark. almost as if the picture was taken at dusk, when it fact it was just after lunch-time.

Overall Response

In this series of images my main concern wasn't particularly the overall balance of the scene, but of bringing attention to a single element, using exposure to enrich colour. Using such a simple technique as exposure compensation I was able to turn an ordinary image into one with a little more 'pop'.

Measuring Exposure, Part Two - Scene One

My camera comes with a bracketing feature, where you choose a bracketing amount, and the camera will take three images in quick succession; one at the recommended exposure value, and one above and below by the amount specified. Unfortunately my model will not do this for five images, nor will it deal with half-stops, instead it will allow third or whole stops. I accomplished almost the same result as required by the brief manually, by choosing increments of a third of a stop, and turning the exposure compensation dial between each shot. This method is more cumbersome, and results in a series of images that aren't exactly lined up in relation to each other, but it does the job.

Council House - Birmingham

Best Exposure

18mm, f/5, 1/640, ISO 200

Exposure Compensation: +0.67

I chose this image as the best exposure as it most accurately portrays the lighting conditions at the time. All of the other exposures feel too dark, when I know the day to be cloudy but bright.

18mm, f/5, 1/800, ISO 200

Exposure Compensation: 0

 This image has the settings suggested by the light meter. The scene looks gloomier than it actually was at the time, and a lot of the fine details of the building are difficult to see clearly.

18mm, f/5, 1/1000, ISO 200

Exposure Compensation: +0.33

This is better than the default settings, but still the scene feels later in the day than it actually was.

18mm, f/5, 1/1250, ISO 200

Exposure Compensation: -0.33

This image is not an accurate representation of the day, in the image the sky has turned dark, and it looks like it's going to rain. Evidently then, underexposing an image can be useful for changing the mood of a scene, in contrast to the actual conditions at the time.

18mm, f/5, 1/2000, ISO 200

Exposure Compensation: -0.67

I don't know about council house, this looks more like haunted house! The whole scene is cast in darkness, you can barely see the figures standing in shadow just past the pillars, and the lack of foot-traffic in this scene enhances the sinister, creepy effect.

Overall Response

In this image I wasn't looking for any kind of special effect; I just wanted a nicely balanced image that was representative of the conditions at the time. Using only the camera's recommended settings I would have been left with an underexposed image that didn't really get across to the viewer that it was a fairly cloudy but bright day.  

Measuring Exposure, Part One

Learning about the use of exposure compensation was one of the things that made a huge difference in the quality of my photography when I was self-teaching prior to starting this course. Its easy to assume that the camera knows best, when in fact it's important to know when to override the camera's decision for artistic or technical reasons.

Lighter Than Average 1

55mm, f/5.6, 1/125, ISO 800

Exposure Compensation: +2

Searching for 'high-key image' on google image search gives results which are overwhelmingly of female models and babies, portraying elegance, delicacy, and purity. Further research gave examples of companies assigning these attributes to their products, such as Apple's marketing materials for the iphone and ipad range. I strove for a similar result with this photograph of Selfridges in Birmingham. I purposely overexposed by two stops above the values recommended by the light meter, in order to give a paler and more clinical feel to the elegant silver shape of the building, the light-coloured pavement and wall, and the overcast sky. The scene, devoid of people or clutter reminded me of those concept images you see of future new developments. I believe the overwhelming 'whiteness' in the image, enhanced by the overexposure, and the modern curves of the building gives an almost sci-fi look.

Lighter Than Average 2

55mm, f/5.6, 1/125, ISO 800

Exposure Compensation: +0.67

A situation where I've needed to overexpose a scene many times in the past is with a back-lit subject. In this image the wide expanse of bright sky caused the light-meter to choose exposure values which threw the details of the church and the people in the foreground into shadow. In order to bring out these details I knew that I'd need to overexpose. To gather comparison images I set the bracket settings on my camera to 0.7. I chose this value as I wanted to retain a natural look to the scene, and not make it appear too washed out, This meant that the camera would, in quick succession, take an image with the settings suggested by the light meter, then one underexposed by 0.7 of a stop, then one overexposed by 0.7 of a stop. Here is the image with the settings suggested by the light meter:

55mm, f/5.6, 1/125, ISO 800

Exposure Compensation: 0

Lighter Than Average 3

19mm, f/3.5, 1/640, ISO 200

Exposure Compensation: +0.67

For this image I was looking for a scene with as much white as possible, in order to demonstrate and deal with a difficult situation for the light meter. The camera assumes that the average image will have some dark areas, and some light areas. With this in mind it averages out the scene, trying to achieve 18% grey. This works well in most situations, but in images dominated by white, such as a snow scene, it causes an underexposure, turning the white into grey. The opposite happens in scenes dominated by black. In the absence of a snow scene, I chose the 'Hall of Memory' in Birmingham. Although not pure white, it's a very light shade, and was also back-lit at the time. The above image is with +0.67 exposure compensation applied. With hindsight, it probably needed another half-stop of compensation added, but this is easily rectified in Photoshop. To compare, the following image is with the settings suggested by the light meter:

19mm, f/3.5, 1/1000, ISO 200

Exposure Compensation: 0

Darker Than Average

45mm, f/5.3, 1/60, ISO 200

Exposure Compensation: -2

Finding somewhere to take an image with gloomy or even sinister connotations was surprisingly difficult in the middle of the day, but I did find this underpass with strong orange lighting, which seemed far removed from the bright, even lighting on that overcast day. I decided to underexpose this image by two stops to dull down the brightness of the lighting and create a darker, more foreboding environment. When I had decided this 'stage' in my mind, I then waited a few minutes for the 'cast' to appear, in this instance a solitary figure in dark clothing walking away from the camera. This gives the impression that this person is being watched or followed. Other aspects of the scene add to this grimy, unsettling feel; the litter on the floor, the old stickers on the back of the traffic sign, and the bland, blocky concrete of the underpass.