Assignment 1: Tutor's comments

Overall Comments

Thank you for your assignment.

You have submitted 12 colour images of Penshaw monument. The images themselves are generally well constructed and have a strong theme running through them. You have also submitted a comprehensive blog and description of your ideas and images.

Your images and blog indicate that you have a good grasp of the basic ideas behind workflow.

Assessment potential

You may want to get credit for your hard work and achievements with the OCA by formally submitting your work for assessment at the end of the module. More and more people are taking the idea of lifelong learning seriously by submitting their work for assessment but it is entirely up to you. We are just as keen to support you whether you study for pleasure or to gain qualifications. Please consider whether you want to put your work forward for assessment and let me know your decision when you submit Assignment 2. I can then give you feedback on how well your work meets the assessment requirements."

Feedback on assignment Demonstration of technical and Visual Skills, Quality of Outcome, Demonstration of Creativity

Having a good and efficient workflow pattern is an important aspect of digital photography, enabling you to achieve your creative potential.

Once you have established an efficient way of working then it gives you the chance to concentrate more on your concepts and techniques.

Good to see the research you have done on Gary Winogrand. He was a highly influential photographer who has influenced generations of other practitioners and his way of working is well worth consideration. One of the strengths of your submission has been your attention to editing. However there are a few other points worth mentioning.

Planning

It would also be worth mentioning at this stage how you are pre-visualising your images. You have obviously considered what your subject is going to be and at this stage it can help to do a rough sketch of your ideas (this is often more applicable in situations such as some commercial assignments where you are working with an art director).

Other preparation could include cleaning your sensor and lenses, making sure that all batteries are fully charged and making a tick list so that you know that you have all the necessary equipment. It is also at this stage that you might consider trying to pre-empt any problems that might occur.

In addition you should use a card that has been formatted. This erases all previous images on the card (make sure you do back-ups), recreates the file system including new directories and improves the overall performance of the card). Try to avoid deleting single images from your card.

Image capture

Your exposures generally look fine but you do not mention your methods for getting correct exposure readings. I am presuming that you are reading the histogram data on the camera. This is important as it allows you to catch the full range of tones available with no visible edge clipping.

I can see that you are enjoying using Lightroom to edit and work on your images, which is great. Lightroom is used extensively in professional practice along with Capture One Pro and sometimes Adobe Bridge.

It’s good to see that you take time away from your pictures before a final edit, as it can give you the space to see your images again in a fresh light. This is not always possible when working professionally when speed is sometimes more important when turning a job around, but when possible is always worth it. Although you may not have found it useful in this instance, it is worth doing and you will find with time that it can make a difference.

You do not state whether you are shooting in a RAW format (I am presuming that you are). This is important to obtain the maximum amount of information and to increase your post production possibilities in Photoshop and Lightroom.

In your blog you do not mention how you are backing up your images.

This is another important aspect of workflow.

Several professionals that I know back up their images on 3 separate hard drives, one of which is kept at a different location (I have had many students who have lost work after not backing up information).

For further image security it may be worth looking at RAID drives where the information is stored over several drives. These are often used by professionals as it is offers further security.

Your images are well composed with an attention to detail and a keen sense of composition and framing.

The strength of the project is enhanced by the clarity with which you have tackled your subject. The constant presence of the monument within the frame give the work continuity and a conceptual strength which I would encourage you to build on in your subsequent assignments.

 

Learning Logs or Blogs/Critical essays Context

Your blog is detailed, comprehensive and easy to navigate.

Suggested reading/viewing Context

I have attached a sheet detailing professional workflow practice.

You may find the following of some use:

Langford, M ‘Basic Photography’ p. Focal Press 2007

Assignment 1: Workflow

Brief:

The purpose of this assignment is to explore the subject of workflow through a shooting assignment of my own choosing. Before completing the first two exercises for the course I felt I  had an established workflow which worked well for me, completing the exercises made me question this however - was my workflow too rigid? Was it preventing me from exploring alternative methods of processing? If my workflow was so good why did I have so many unprocessed images on my hard drive? With these points in mind I wanted to explore the subject of my workflow in an analytical way, carefully considering each aspect and spending time thinking about my choices and ways of working. I tried to put aside all of my preconceptions and at the end of the assignment I hoped to be able to use what I had learned to make practical adjustments to my ways of working that would be of benefit in the future.

Choosing a Subject:

I wanted to choose a subject that would provide many different types of image, would be of interest and would be accessible. I arrived at my choice of Penshaw Monument near Sunderland by chance - I took a number of photographs from the top of the monument on a family day out and felt this could be a subject worth exploring further.

Penshaw Monument is a symbol to the people of wearside (as important as say the Tyne Bridge or Angel of the North would be to the people of Tyneside) it dominates the local landscape and can be seen for miles around and is featured on Sunderland football clubs badge. It is a Doric style structure based on the Temple of Hephaestus in Athens built in memoriam of John George Lambton, the Earl of Durham, in 1844. The monument was given to the National Trust by the 5th Earl of Durham in 1939.

One of my areas of interest in photography is how the familiar can be transformed for example through viewpoint. Recognisable monuments are mainly represented through a 'chocolate box' aesthetic which is not a style I am attracted to - by choosing Penshaw Monument as my subject I wanted to explore this kind of 'tourist' view while also making pictures that are less typical of the kind regularly seen.

Preparation:

I began by brainstorming a number of possible approaches so when I arrived at the monument I would have some ideas of what kind of shots to take. I also began thinking of different times I would want to take the photographs:

• The 'tourist' view
• People included

• Abstract/details

• Night time

• Sunrise/sunset
• Context e.g. Local houses
• 'Chocolate box' view

• Light and shadow

Plan for shooting the images:

One of the factors that led me to choose Penshaw monument as a subject was that I pass it every day on the way to and from work. Not only that but the structure is so prominent that I can see it in the distance for most of my journey. I wanted my chosen subject to be reasonably accessible and felt that I could stop off at the monument often to and from work and would be able to take pictures in a variety of different times of day and weather conditions.

Usually if I am pursuing a long term project I review and edit my images after each shoot. I find that this can influence me in subsequent shoots - for example I might not take a particular image because I feel I have already taken something similar. As part of my research I was inspired by an article about Garry Winogrand which detailed his ways of working.

Winogrand was a prolific photographer, when he died he left around 2500 rolls of undeveloped film and is estimated to have shot around 5 million images in his lifetime. Winogrand believed that emotional attachment to an image led to poor editing choices and would take the extreme solution of waiting up to 2 years before even processing a roll of film. By doing this he believed he separated the act of taking the image from his selection process; by having virtually no memory of taking the picture he was able to make decisions based purely on the content of the frame and not influenced by emotion.

When I shoot I always download my images regularly and review them straight away - as mentioned this can influence what I shoot after this, I may choose not to take a certain image because I think I have already captured it. For this assignment I took the decision to shoot over a number of weeks (months as it turned out) and to only view the images and begin making my selections when I had taken them all.

Taking the pictures:

One of the main reasons I chose Penshaw Monument as my subject is that I thought I would be able to stop off regularly to and from work and take pictures in a variety of conditions. In reality things turned out very different: stopping off going to work never happened because the weather conditions often meant I would be a mess before I got to work or because I was worried I would end up spending to much time taking pictures and be late. It was also difficult to stop off on the way home, I work quite long hours and was often not in the mood to stop off or needed to get home for family reasons so it was not practical. In my head I thought I would be able to stop for 10 minutes or so and take some pictures, in reality I spent 1-2 hours each time I stopped.

A benefit of choosing Penshaw however was that I spent a great deal of time looking at the structure on my journeys and would think a lot about different images I might take. A downside however was looking at the structure when conditions were interesting and knowing that I either didn't have time to stop off or have my camera with me.

When to stop became an issue as well - I initially intended to spend around 2 months on this assignment but it has actually taken me around a year! Even at this point I had to force myself to start bringing the assignment to a conclusion - my main reason for this was fearing I had not taken enough pictures and had not explored all of the possibilities I had thought of. With hindsight I should have set myself a strict deadline, something I will try to do for future assignments.

Selecting the images:

I used Lightroom 4 to catalogue and process all of my images: I had taken 832 images over 8 shoots. Firstly I applied the keyword 'Penshaw Monument' to each of the images and created a collection (Penshaw DPP Ass 1) for the images so they were easily accessible from the rest of my image library.

Next I viewed each image in turn and flagged any I wanted to consider further while rejecting any with obvious technical problems. For this initial select I ended up with 284 flagged images and 3 deselects. I then processed each image in turn which gave me the opportunity to view each picture in more detail. If I found I no longer wanted to consider the image for selection I removed the flag, at the end of this process I had a rough edit of 214 pictures including two I had processed alternatively.

I am conflicted about whether this part of my workflow is the right way for me to select images - on one hand this was a very time consuming process which has not resulted in me removing many sections, I felt an element of frustration that I could not be more decisive. On the other hand I think this part of the process could be the most important part of my workflow as it gives me the chance to spend an extended amount of time getting to know the images and aids my decision making process going forward. The unfortunate reality however is that the process takes time and that is something that is a luxury for me. On first indication taking Garry Winogrand's advice and leaving some time before reviewing my images has made little difference - I imagine that I would have made similar if not identical selections if I had edited the pictures straight after shooting

In the past I have always found having pictures to look at greatly aids my decision making process so decided to have 6x4 prints made of my selects. One of the principles of this project is that I wanted to present a group of different images of Penshaw. With this in mind my first action when I received the prints was to sort them into separate categories - I ended up with 18. Next I reviewed the pictures in their category selections by placing them onto a large table top and looking at them side by side. I then sorted them into three selection criteria - pick, maybe and reject. At the end of this process I had 120 selects, 24 maybe and 70 rejects. I was now feeling quite restless with the selection process and was coming to realise that I was been much too protracted in my approach. I viewed the pictures again with a more critical eye - if there was anything in the image that led me to think 'maybe' I discarded it as I now realised this meant the picture would not make the cut. Despite this I still ended up with a selection of 54 prints!

Final selection:

At this point I was keen to try an approach that I have read many photographers find useful - I decided to display the prints on my wall and leave them for a couple of weeks before making my final selection. I was still faced with something of an impasse however as to which of the pictures to choose. In the end I forced myself into being decisive and began deselecting images by taking them down from the wall - often my selection process was governed by a gut instinct rather than by analysis, in fact I made a conscious effort not to overthink at this point as I was beginning to recognise this was the main driver of my procrastination.

I was surprised at how quickly I managed to pair down the selection to 12 images (although I did have 10 pictures that nearly made it and which can be found here) was this because of the time I had spent 'living' with the pictures - had this aided my decision making? Perhaps I knew from the beginning which images were my favourites and I had been putting off the inevitable?

The final 12:

ISO 1250, 24-70mm f2.8 lens @ 56mm, 1/125 sec @ f5.6

The fields around Penshaw are used for grazing cattle (although the cattle are not always present.) On this particular occasion I took the opportunity to feature this cow as foreground interest. I have chosen to open the set of images with this because I can imagine something similar being used by the National Trust to advertise Penshaw - to me it offers a 'tourists view.' People are excluded and there is a sense of wildness about the monuments setting, the cow and monument have a sense of balance because of their relative size and positioning in the frame and the orange/ginger cow contrasts with the surrounding grass.

ISO 200, 24-70mm f2.8 lens @ 70mm, 1/90 sec @ f11

As I have mentioned, Penshaw monument dominates the local landscape so I was keen to show this in a number of images. Although the monument is quite small in the frame it is clearly the point of interest, the pattern of the corn and its positioning draw the eye. Some of the shots I discarded that were similar to this had tractor tracks in the corn as leading lines but I prefer the low viewpoint here that does not include them. The inclusion of the electricity pylon also acts as a reminder that of how modern technology transforms the landscape and seems to anchor the monument in the distance.

ISO 250, 24-70mm f2.8 lens @ 70mm, 1/350 sec @ f11

This was from the first shoot I did at the monument which gave me the inspiration to pursue it as a subject. I like the disorder in this image which contrasts with the horizontal and vertical alignment of the pillars and shadows. The high contrast tones add a graphic dimension, also, images of people taking photographs is a subject I am interested in pursuing as a long term project. The way the adults in the group are trying to create pictures while the children play has an interesting narrative quality about family days out.

ISO 400, 24-70mm f2.8 lens @ 48mm, 1/250 sec @ f9.5

This picture is all about the atmosphere created by the fog, I like the way the monument is just visible and the muted tones.

ISO 400, 24-70mm f2.8 lens @ 24mm, 1/2000 sec @ f9.5

I took many images of the monument in silhouette but kept coming back to this one. I think the tones work well here the sun just visible behind a pillar gives a strong sense of mood. I am not sure this would be placed as being north east England without prior knowledge of what it is.

ISO 1000, 24-70mm f2.8 lens @ 70mm, 1/350 sec @ f11

The composition attracted me to this image, through my research I cannot recall seeing a picture of Penshaw from this angle. The height of the structure is emphasised by shooting from the side and the tones pick out the brickwork which gives an indication of the monuments age.

ISO 1000, 70-300mm f4.5-5.6 lens @ 122mm, 1/1000 sec @ f6.7

This image was shot from about 10 miles from the monument. Unlike the corn image Penshaw is not the obvious subject here, the picture is about the way the layers of mist add depth and is evocative of early morning. This is also emphasised by the 'letter box' crop.

ISO 200, 24-70mm f2.8 lens @ 24mm, 1/125 sec @ f8

I imagine this image being featured in promotional advertising, the jaunty angle gives a modern feel. Although the composition is unconventional I think it is easy to read what the picture is of and the angle of view adds interest as the eye moves around different aspects of the monument. The early morning warm sunlight hitting the stonework complements the blue sky.

ISO 400, 24-70mm f2.8 lens @ 60mm, 1/180 sec @ f11

I chose this image because of the sense of wilderness in the scene. I also like the way the sunlight hits the top of the grass where the monument meets the horizon. The viewpoint isolates Penshaw from any sign of the modern world and the floodlights that surround it are also excluded.

ISO 400, 70-300mm f4.5-5.6 lens @ 125mm, 1/750 sec @ f5.6

This image is opposite to the previous one because it gives an indication about the environment around the monument. I have an interest in allotments and am attracted to the way their owners often build interesting structures. A lot of the other allotments I photographed in the foreground were more ordered than this but I chose this image because I like the way the slightly ramshackle shed contrasts with the order of the monument in the background.

ISO 2000, 24-70mm f2.8 lens @ 31mm, 1/250 sec @ f5.6

This abstract image of the monument has many similarities to the one chosen earlier but in the end is quite different. The orientation is portrait rather than landscape which emphasises height and the almost monochrome palate gives a cold and foreboding feel unlike the warmth from the early morning sun provided in the initial image.

ISO 800, 24-70mm f2.8 lens @ 24mm, 1/60 sec @ f9.5

I took many pictures using the steps to the monument as leading lines but chose this because of the strong way they lead the eye to the structure. This was taken at dusk and the floodlights have just come on, the darkness of the tones however give a sense of creepiness rather than warmth and the picture contrasts with the reassuring view that opens the set.

Conclusion:

I have found this assignment invaluable in understanding my own personal workflow. Before beginning I was quite dismissive about the learning's I would take from the exercise, however, it has highlighted both weaknesses in my approach that I was probably not confronting while making me realise that I very far from having an established workflow of my own. Firstly, I understand now better than ever before that I need to shoot more, however, I need to come up with a strategy to aid this as self doubt seems to be my main issue. I have plans for a number of long term projects and this is what I plan to concentrate on to drive me forward as well as forcing myself to pick up my camera more often - whether I feel in the mood or not.

For the purposes of this assignment I have taken a protracted approach to selecting my images. At the time I thought this was for the better good of the assignment and my development but really I was just putting off progressing. I have understood for a while that procrastination is a major issue for me and have thought I had this under control, clearly however it is not. If I am truthful I could have predicted most of the images I have chosen for my final selection at the initial stages. Again self doubt is the enemy here and I believe that the more I 'practice' the more my confidence will grow and the more willing I will be to trust my instincts.

In the end my understanding of workflow has gone full circle. Initially I thought this was one of my strengths, now however I understand that although I am confident in using the software I have a long way to go in being confident in my own selection and decision making. Everything I now read that comments on workflow now takes on a new resonance and meaning and informs my ways of working. Yes this assignment has been much more difficult to complete than I foresaw anticipated and yes I have spent much longer on it than I first wanted to. However, that could all be for the long term good as long as I put the lessons learned here into practice.

Exercise 8: Your Camera's Dynamic Range

This exercise is one that I put off attempting for quite a while because of how complex it is and due to the fact that I saw little benefit in completing it. I produced a set up similar to the one described in the text, set the exposure compensation to +0.5, the point at which the camera's highlight warning began to show. I then took spot meter readings from the highlight area (represented by the white A3 drawing pad in the centre of the frame) and shadow area (the area inside the house.) The readings I got were 1/1000 @ f16 for the highlight area and 1/125@f5.6 for the shadows. Using a dynamic range calculator I found through an internet search.

I arrived at a difference of 6 stops between the shadow and highlight area - about half the dynamic range I had been led to believe my camera was capable of through various tests I had read! A quick examination of the image in Lightroom however showed that I should have taken a meter reading for the shadows from the area underneath the children's sand table at the front left of the image. This shows the inherent flaw in this exercise - it is an attempt to be quite scientific in analysing dynamic range and yet provides too many variables to give accurate data. My understanding of dynamic range comes purely from using my camera in different situations and gaining an idea of how it will behave. At the same time I need to decide which elements are most important in the frame and whether my cameras metering will be fooled into under or over exposing - I have learned that the eyes can often fool you into how light or dark a scene is and to use the histogram to judge whether a full range of tones will be recorded. Completing this exercise has done nothing to further my knowledge in this area, maybe this is because I am already familiar with the way my camera operates. I doubt whether I would attempt a repeat of this exercise with a new camera - I would probably experiment with how the it behaves in real situations to understand its strengths and limitations.

Exercise 7: Your Tolerance For Noise

For this exercise I fixed my camera on a tripod in front of my bookcase and took a series of photographs increasing the ISO setting with each shot. The subject I chose featured both light, dark, detailed and plain areas. I then examined each image at 100% to note the difference that the increased ISO setting had on each image.

ISO 200 - no noticeable noise

ISO 400 - no noticeable noise

ISO 800 - small amount of noise in shadow and coloured areas, particularly purple of Parr book and black areas.

ISO 1600 - noise starting to take on an artificial look, definition of writing on the books seems less sharp.

ISO 3200 - noise now obvious across whole of the image and now noticeable in lighter areas.

ISO 6400 - noise has a more speckled appearance and looks less natural.

ISO 12800 - noise very prominent and visible evident without viewing at closer magnification.

ISO 25600 - image appears very degraded throughout and decrease in saturation is evident.

Generally I would say my camera handles increased ISO well - I would have no issues using settings up to 1600 and 3200 does not represent significant degradation of image quality either. Often the ISO speed chosen is entirely dependent on circumstances when an image is taken - given bright enough conditions I would always choose the lowest setting possible as this gives the best quality and most versatile output for the final image. Recently I have began to shoot in automatic ISO mode in situations where the light is changing rapidly and a fast shutter speed is required - experience has taught me that increased noise in an image is a necessary compromise to achieving image sharpness.

Exercise 6: Highlight Clipping

For this exercise I chose to photograph my bathroom window during the day - the textured window pain distorted the outside detail making the image abstract while a large range of tones from dark to highlight were represented.

I fixed the camera on a tripod changing the exposure compensation +/- 4 EV (in the second row of images I have taken screenshots from Lightroom with the highlight and shadow clipping warnings selected - highlight shown in red, shadow in blue):

The default exposure setting the camera has chosen has generally exposed well for this scene with only slight overexposure in the extreme highlight area at the top left of the frame. At -1EV this is almost gone and at -2EV the highlight area is exposed correctly although there is a small amount of shadow clipping in the bottom left of the frame. As the exposure is decreased the blue/orange/yellow tones become more saturated in the picture, conversely the higher the exposure setting the more muted and washed out the tones appear. Examining each image at close magnified detail I found that the texture of the window is lost until -2EV, although this is not very noticeable at -1EV.

In the +EV range saturation decreases along with increased exposure compensation. The screenshots showing highlight clipping show clearly where detail is lost on the textured window.

For the next part of this exercise I experimented with the raw files adjusting the highlight and white sliders in Lightroom. At 0EV I found that most detail could be shown in the highlight areas but could not be completely returned. At -1EV full detail could be achieved although the resulting image was appeared much 'flatter' than the -2EV shot, the histograms were significantly different as well with the altered -1EV shot being compressed towards the left while the -2 EV shot contained a full range of tones from highlights to shadows. Using the exposure slider instead resulted in much more similar looking images without any obvious negative factors such as noise. There was a slight difference in colour saturation however with the -2EV picture appearing more natural. The 'best' result I achieved was decreasing the exposure in the -1EV image by one stop and then decreasing the highlight slider by -48.

Deciding which image has the 'correct' exposure is difficult - to my eye each of the shots has a different quality which appeals to my eye. In theory the -2EV image is the most correctly exposed as it has a full range of tones with neither shadow or highlights being clipped. This makes the picture very dark however with the histogram heavily weighted toward the left. The shot does have an appealing low key feel however and the colour saturation is pleasant. Although a small amount of detail is lost in the -1EV image this is my favourite as it has the best balance between highlight and shadow while having a good amount of contrast - for this image the loss of detail in the window texture does not really matter.

In manipulating the raw files of these images I could not really see any negative elements being introduced into the image such as noise. Despite this being a high contrast scene my camera has exposed the scene well, maintaining detail in both the highlights and shadows which leads me to think I should trust the cameras metering system because I will have a great deal of freedom to alter images in post production. This view does not take into account photographic intent however, and relies on the photographer making decisions about an images' use when at the computer. This concept is problematic for me - on the one hand received wisdom suggests notions like 'the decisive moment' and the idea that 'true' photographers only ever press the shutter when the picture is perfectly framed and exposed in the camera. While this is unrealistic, the opposite end of the spectrum is the photographer that snaps away at everything and then tries to make something of value out of this using software. This exercise has made me think a little more about where I sit on this spectrum. The truth is I fluctuate day to day. Currently I am trying not to get too hung up on overthinking and trying to follow my instincts more, pressing the shutter when I previously may not have.

A new year wake up call….

I am not someone that really does new years resolutions, but a couple of weeks into 2013 I find myself in reflective mood about my photographic studies. A catalyst for this was an email from the OCA concerned that I had not yet submitted my first assignment - I am approaching a year studying DPP and this was something I promised I would not repeat after TAOP which took me 3 years to finish mainly because of self doubt and procrastination. I have given myself similar wake up calls in the past which clearly have not had the desired effect of me progressing quicker so I needed a different approach. Before I could do this however I realised I needed to be completely honest with myself about where I am and what I need to do going forward.

Firstly I took stock of where I am - in truth I have been working on assignment one since the beginning of the course and have quite a bit of material already. Maybe I should just use what I have now and get the assignment finished? After all the assignment is not even part of the assessment.

Secondly I looked at my blog - 8 posts in nearly a year is not a great record. I did not keep an online blog for TAOP and one of the things I struggled with in that course was working through the exercises successfully (I jumped around the course work quite a lot and in truth did not even attempt a number of projects.) Also, I struggled to show the extra reading (and thinking) I do about photography. Having an online blog was meant to remedy this as I thought the publishing aspect would push me to complete more - I would not want to be embarrassed with showing my tutor I had achieved very little. Objectively though this idea was now proving a hindrance as I am in that very position. In truth I have lots of material collected on my computer partially written up, over the last few months I have been telling myself that as soon as I get on top of this I can start progressing. Truthfully these 'extras' are nice to do but not the core of the course - I need to focus myself on working through the exercises and assignments as a first priority and add these other items as and when time allows.

Finally there is the thorny issue of time management. I have a busy life with a demanding job and family life, however, the truth is  I do not make the best use of the time I do have available. Being busy is merely the excuse I use - after analysing the time I do have available I found that I have at least an hour each evening, probably more, which I could be using for reading, writing up exercises and research or even (shock horror!) taking pictures! Along with that I have 6 hours free on my day off while my children are at school - I just need to find a way that any errands I need to complete are out of the way so I can make best use of this time as this is the absolute key to me being able to make real progress. Combined with this I do not have a plan for timescales to complete exercises and assignments. I have spent some time mapping this out on a calendar - the targets are quite broad but I think achievable. Each week I will spend 5 minutes understanding whether I am on target or not. If manage to achieve these goals then I will be sending DPP for assessment in November.

I know from the last 6 months of TAOP during which time I completed most of the work that I have the drive to be able to complete the course within the parameters I have given myself. The key to success for me is gaining momentum - once I begin with my plan I am sure the work will begin to flow.

Exercise 5: Sensor Linear capture

I must admit to feeling an element of 'interesting, but so what?' When I read through the notes for this exercise. Sensor linear capture refers to the way a digital camera's sensor records an image - basically in camera processing adjusts the tone curve of the image, if it did not do this the image would appear too dark. The exercise requires manipulation of an image's tone curve to simulate this and then the application of the opposite effect on the manipulated image before comparing the results.

Before beginning I decided to do some research in the hope that this might shed some light on why this exercise is important. Martin Evening in "The Adobe Photoshop Lightroom 3 Book" (2010 Adobe Press) provides a good explanation. He asserts that all digital images contain data that is a linear representation of light hitting the sensor:

 "As the light intensity doubles, a sensor records a brightness level that is two times higher...human vision perceives things quite differently from the way a sensor sees and records light...our eyes compensate for increasing levels of brightness in a non linear fashion...Our human vision system is able to adapt to widely changing light levels by constantly compensating for such extremes."1

The way a sensor records light and represents image data looks very dark - even though it may be perfectly exposed. Therefore, in order for a digital capture to look right to our eyes the linear data must at some point be gamma corrected, that is effectively lightened at the mid point.

For further reading on linear capture Evening provides a link to an essay by Bruce Fraser on the Adobe.com website:"Raw capture, linear gamma and exposure."

The first paragraph provides an indication of why linear capture is important, Fraser states that by ignoring the way a digital camera captures an image you run the danger of "failing to exploit the camera's dynamic range, and creating exposures whose shadows are noisier than they need to be." He goes on to explain how levels are distributed in an image using the example of a 12 bit image with 4096 levels and 6 stops of dynamic range:

"If a camera captures six stops of dynamic range, half of the 4,096 levels are devoted to the brightest stop, half of the remainder (1,024 levels) are devoted to the next stop, half of the remainder (512 levels) are devoted to the next stop, and so on. The darkest stop, the extreme shadows, is represented by only 64 levels."

When the cameras processing is applied these levels are redistributed evenly across the image, hence if a photograph is underexposed to maintain the highlight detail the resulting raw conversion will have to open up the shadows and spread the darkest 64 levels over a wider tonal range which runs the risk of exaggerated noise and posterization. He suggests that the best exposure to achieve is one where the highlights are as close as possible to blowing out without actually doing so.

For the exercise I chose an close up image of a lego figure that had a full range of evenly distributed tones  in the histogram:

No adjustments

Linear image - curve adjusted

For this image I opened the photograph in Photoshop, converted to 16bit, made a curves adjustment with a steep but smooth downward curve which resulted in an under exposed image which simulates sensor linear capture.

'Restored' image - curve adjusted

For this image, I opened the saved version of the simulated linear capture image again converted to 16bit and made a curve adjustment opposite to that applied in the previous image, that is pushed up to increase brightness in a smooth curve.

I compared this image with the original until I achieved an equivalent result with a similar histogram.

No adjustment detail

Restored curve detail

Finally I examined the original and restored images at high magnification on screen. I found that there was evidence of increased noise and posterization in the shadow areas of the restored image. (The detail shots above show this a little although the effect is not pronounced.) I concluded that by performing these extreme adjustments on this image I was simulating trying to increase exposure on an underexposed image. I have always held the view, picked up from where I do not know, that it is important in digital photography to preserve highlight detail above all else as that cannot be recovered in post processing. I always believed that an underexposed image was preferable to an overexposed picture as underexposure is easier to compensate for in software. I guess this remains true, however, I am surprised at how few tones in an image are allocated to the dark and midtones. Correct exposure it seems is more of a minefield than I first thought the key to which I believe is understanding the image you want to create at the time of capture, understanding which tonal values are most important to the pictures success and using knowledge and experience to achieve this. In truth I rarely worry about exposure, my camera usually does a pretty good job and I always shoot raw so can alter the exposure in post processing if need be. This exercise is beginning to make me understand how little I actually consider exposure at the time of pressing the shutter and that I need to learn more about how my camera behaves if I want to produce optimum results.

At the end of this exercise I feel I understand more of how a digital camera's sensor captures an image. The true importance of this however is something I am guessing will become more significant as I explore the next few exercises which are concerned with highlight clipping, noise and dynamic range.

1 p.629 The Adobe Photoshop Lightroom 3 Book: The Complete Guide for Photographers by Martin Evening (2010 Adobe Press)