This Blog Has Moved

MY PERSONAL BLOG is now hosted by BlogSpot at http://tedpugh.blogspot.com.

2010 in review

The stats helper monkeys at WordPress.com mulled over how this blog did in 2010, and here’s a high level summary of its overall blog health:

Healthy blog!

The Blog-Health-o-Meter™ reads This blog is doing awesome!.

Crunchy numbers

Featured image

A Boeing 747-400 passenger jet can hold 416 passengers. This blog was viewed about 1,400 times in 2010. That’s about 3 full 747s.

In 2010, there were 17 new posts, growing the total archive of this blog to 32 posts. There were 13 pictures uploaded, taking up a total of 11mb. That’s about a picture per month.

The busiest day of the year was April 8th with 31 views. The most popular post that day was OK! I Hold My Hands Up.

Where did they come from?

The top referring sites in 2010 were canveybeat.wordpress.com, canveybeat.blogspot.com, employmentfor.com, en.wordpress.com, and hoiantoday.info.

Some visitors came searching, mostly for ted pugh, mid tone grey, harry borden blog, midtone grey, and “ted pugh”.

Attractions in 2010

These are the posts and pages that got the most views in 2010.

1

OK! I Hold My Hands Up April 2010

2

How Grey Is Mid-Tone Grey? September 2010
2 comments

3

The Fat Lady Still Hasn’t Sung September 2009
3 comments

4

Let’s Not Spoil Dinner This Year… December 2009

5

About December 2008

An HDR Image To Illustrate That Tonal Range Thing

Moonlight on water - single shotWHILST ON HOLIDAY, it occurred to me that my posts regarding photographic tonal ranges and realistic images had been poorly illustrated. Graphs are one thing; but a simple photograph, as they say, is worth a thousand words.

I was musing on the problem last Saturday night, which just happened to coincide with a bright full moon, in a dark blue sky, which many photographers attempt to capture. Moreover, my room’s balcony looked onto the sea and I found myself with a perfect vantage point for capturing the moonlight shed upon the water.

Such a scene is not easy to accurately capture. It is impossible using conventional photographic techniques (without resorting to darkroom tricks); but the new digital medium provides a means of coming close to revealing nature’s beauty by allowing High Dynamic Range (HDR) images to be produced.

You might think that taking a night-time photograph would require a high ISO setting; but the fact is that nature’s moonlight can be far more powerful than any studio lamp. That was the case, on Saturday, when averaging the scene’s highlight and shadow spot readings indicated 1/1000th second at f16 using 200 ISO.

The result (inset above) is fairly pleasing; but it is not an accurate representation of the original scene. The moonlight, because of its power, has bled across the clouds, masking their definition and diluting the blue of the sky. Moreover, the tonal range from the 200 ISO setting has been unable to capture the foreground’s shadowy detail – and that elusive ripple in the middle portion of the moonlight’s reflection upon the water is almost blown.

Moonlight on water - HDR bracketed shotThe image inset here is a much more accurate rendition. It was produced by combining the first image with a sequence of six more shots, made by bracketing the original exposure and taken in quick succession. By combining all the different tones captured by the camera’s sensor into a 16 bit colour space, capable of representing each value individually, we can finally achieve the missing foreground detail and reproduce the scene’s original colours and surreal mood (produced by the moonlight playing on top of the low-lying clouds) accurately.

In this case, the seven different photographs were combined using Photoshop; but HDR images are supported by all good digital image processing software.

When undertaking HDR processing, it is important to ensure that you balance your photographic sequence around the average exposure indicated by your highlight and shadow readings to obtain an accurate image (just as you would normally place the mid-tone in the centre of the ISO slope). However, just as you can arrange to place the mid-tone differently for artistic effect, you can also weight your bracketing towards under or over exposure to introduce specific moods or effects in your final HDR image.

A Considerable Understatement

WHEN I FIRST MOVED the Canvey Beat from its old WordPress host to Blogger, it was knowing that the latter did not provide integrated visitor statistics. But against that I weighed the freedom of being able to host commercial advertising and post video and sound files if required.

I did miss the integrated statistic features in WordPress; but I located the free StatCounter that Blogger allowed me to incorporate in my Blog’s code and provide much more information on my guests; so I was a happy bunny – until Blogger recently got around to incorporate server-side statistics for my use.

Google’s Adsense program provides hosts with the number of impressions that have been served; how many clicks have been obtained; and how much has been earned in a period. But I did not consider comparing the impression count (which obviously compares to page-loads) to what StatCounter was recording. That is, until the gap between StatCounter’s accumulative page-loads and the Adsense impression count (which began much later) rapidly became much smaller.

It was then I noticed that the new Google statistics agreed with the Adsense figures – and that StatCounter was hopelessly out. It was only recording around a third of the page-loads being pulled from the Canvey Beat site.

Well, I knew that the StatCounter code had an inherent problem (because its code is client-side and contained in JavaScript). In an effort to overcome the problem (when clients have JavaScript disabled) StatCounter pulls a small image file from its main server and records that request instead. Unfortunately, both methods fail if the JavaScript fails to load or the small image is not downloaded. And that appeared to be happening frequently on the Canvey Beat site.

I do not believe this is a hosting problem. BlogSpot offers up to one-hundred simultaneous connections, which should be more than adequate for my needs. The Canvey Beat’s host stats indicate that a peak of 58 simultaneous connections was achieved by the Blog on Sunday; but I have not been monitoring previous situations to know if there have been instances much in excess of that. However, one thing is for certain, when there are a number of simultaneous connections to a page heavy in JavaScript (Adsense uses it too) load time suffers and impatient browsers will simply time-out.

I had my girlfriend conduct a test of the Blog during one of its evening peak periods (at around 7:30pm) to see what was happening to the StatCounter at the bottom of the page (I cannot influence it from my computer). To my consternation she reported that, of a dozen page-load requests, seven resulted in the StatCounter code timing-out. She was just left with a browser generated image place holder – and no idea of how many hits the site had had.

Needless to say, I have now removed the counter’s display from the Blog; but I am loathe to do away with the code completely because, although highly inaccurate, I still find it interesting to know where those recorded visitors come from – and who they are.

If you are already using StatCounter, or considering using it, on your site – I still recommend it as a statistical tool. However, I would advise against using it to display accumulative page-loads to your visitors. The chances are you will be understating your case considerably.

By the way, the new BlogSpot statistics (and Google’s Webmaster tools) are great…

Is Camera Calibration Worth The Trouble?

I THOUGHT I had finally dealt with the subject of camera calibration in my last post; but, as the rain drives against my bedroom window, discouraging me from going out, I find myself reading Mac’s last comments – and agreeing with him in many respects.

I cannot say that I actually enjoy the prospect of calibrating new equipment and, like Mac, I would rather be using a new camera straight out-of-the-box to capture new images – than spending an hour blue-tacking a grey card to the wall; lighting it; photographing it; and analysing the results. (Pre digital, with the need to shoot each film stock  and develop and dry the negatives, you could easily ‘waste’ half a day).

Mac is perfectly right. It is no fun messing around with all those ISOs, clipping points, EVs, and colour spaces. And, if I add that my new Nikon’s calibration only indicated an error of 1/3 EV in five of its seven main ISO settings: many of you will be wondering why I bothered. After all, apart from another photographer, who is going to notice that the exposure is off by a tiny third?

Well, the answer is that I will – and so will those with the power to decide to publish or reject my work. Glossy magazines set extremely high standards for photographic images – and so do most photo stock agencies. In the highly competitive freelance industry, it is often the quality of the photographic coverage provided with a speculative feature article that can clinch the sale.

In these days of reduced disposable income; higher prices; government cuts and looming redundancies, many are looking to turn their hobby into an additional income stream and there are now numerous photo stock agencies on the Web offering amateur and professional photographers alike the ability to market stock photos at the world-wide magazine and Website market. Individual rewards are low; but the market is large – and, these days, any additional income is useful. But it is easy to have images rejected; because the professional eye of a photo editor is much more discerning than that of the average photographer.

I once wrote an article on the then new web photo stock industry – when it was in its infancy and there were only a few sites around. As a test of the quality required I submitted two different photographs to Fotolia and sat back to await the results.

Neither image was well composed or particularly striking; but what they shared was that the exposure was spot-on. In photo A, the ‘wrong’ lens had been used, which distorted the lid of the trinkets box and, in photo B, the composition was, frankly, quite awful.

Photo A, with the ‘wrong’ lens, had been contrived to produce a white knockout (which many amateurs cannot produce). Apart from the lens and the weird composition it is a technically perfect shot.

Photo B’s only claim is that it is a faithful reproduction of the original scene (with an ill considered focal point).

When I wrote the article, Fotolia had one of the highest rejection rates. Each photograph that was submitted went before a panel of editors to decide whether it would be included in their library or not.

What I was trying to discover was whether a poor (but perfectly exposed) image would be accepted by the Fotolia panel – and therefore establish that using the ‘correct’ exposure gave the photographer an edge. After all, no one could say that the subject matter or composition in these images had produced a saleable photograph in either case.

Photo B was accepted by Fotolia (and, much to my surprise, achieved a sale some six-months later). Photo A was rejected; but, given the site’s high rejection rate, I think the case was nonetheless proved that using the ‘correct’ exposure influenced Fotolia’s panel. Even a tiny third EV over-exposure, in these shots, would have significantly degraded their tonal range and, in particular, their accurate colours.

So, while I sympathise with the view that camera calibration is a pain, I would be lying if I said I thought it was not necessary. Could I have produced those technically perfect images without calibrating the camera? Well, I could have fiddled around with various settings until I achieved the right image; but why go to all that trial and error each time you need to render an accurate scene? Better to spend an hour calibrating your equipment and then be sure that every subsequent photo you take will be ‘perfect.’

The two images here were set-up, taken, and transferred to Bridge in under five minutes. No messing around – and just the two exposures were taken (based only upon a spot reading of the white background and racking it up by three stops).

Like many, I too prefer taking photographs – and that includes not having to waste my time in Photoshop trying to rescue a poor exposure.

You do not need expensive equipment in order to earn money from your photography; but, as my research discovered, producing that ‘perfect’ exposure will set your work apart from the competition and make it more likely that it will be accepted.

How Grey Is Mid-Tone Grey?

I HAD NOT EXPECTED to create such a furore among readers from just mentioning camera calibration. It seems that I have inadvertently begun a topic that many of you want me to continue with.

Janet says: ‘Please talk us through the graph,’ and Martin asks: ‘What the hell is mid-tone grey anyway?’

Well, mid-tone grey is the term given to the colour of the industry standard 18% Grey Card, first produced by Kodak, to which all light meters are generally calibrated. Whatever you point your light meter at, the read-out you obtain will be expressed in terms of the amount of exposure required to reproduce the object measured as a mid-tone grey.

The 18% description of the grey card is misleading, because it describes reflectance – so photographers now tend to refer to 50% luminance instead.

In the RGB colour space, mid-tone grey has a value of 118, 119, 121 – a fact which enterprising readers can use to print their own grey card (if they are prepared to put-up with the small inaccuracies introduced by different types and grades of paper).

It is important for the photographic and print industry to have a standard by which everything can be measured and, as a photographer, mid-tone grey is the most important standard you are likely to run across because it defines what is the ‘correct’ exposure for any scene. Once mid-tone grey has been defined, all the other shades, from pure black to pure white, can be described in terms of it – and we can arrange to speak in terms of EVs (Exposure Values).

Few scenes, which you are likely to photograph, consist of a single tone. Individual objects absorb different amounts of light and reflect what they do not use back to the light meter – and it is those different levels of light that your camera’s film or sensor records to produce an accurate image of the scene.

Different levels of light in a scene can be described as different EV levels – with EV0 being given to the scene’s middle tone; positive EV numbers given to brighter levels; and negative values given to darker areas. EV1 is twice as bright as EV0; EV0 is twice as bright as EV-1 – and so on. The distance between one EV number and the next represents a doubling (or halving) of light strength (and is equivalent to the doubling or halving of exposure by changing a camera’s aperture by one full stop).

In a daylight scene, such as a landscape, there can be many hundreds of different light values that can be distinguished by the human eye; but no film or camera sensor can capture that full range (in a single shot). In digital photography, accurate scene representation is limited by the RGB colour space, which only has a range of 10EV (values: 0, 1, 2, 4, 8, 16, 32, 64, 128 and 255). That, however, is not the main problem facing photographers; because electronic sensors can only accurately record a much more limited range of around 8EV. (Cheap sensors may only be able to reproduce much less).

If you look at the inset graph, produced from calibrating a Nikon D40, you can see that the horizontal EV scale runs from –7EV to +7EV; but the only exposures that result in a sensor image lie between –5EV and +3EV.

If you examine the graph further, you should see that those elongated Ss (which each represent a grey scale image) become increasingly horizontal the lower they appear on the main curve. The more negative the EV (under-exposure) the fewer tones that can be captured by the sensor. You can measure the tones recorded by any S using the vertical Level scale which records the (single) RGB value.

(Although misrepresented on this graph – more later – the same ‘drop-off’ and compression is exhibited as exposure is increased).

Taking the green curve (representing the results at ISO 3200) we can see that the straight part of the slope at –1EV records grey values of between around 90 and 110; but at 0EV its range is extended by 50% to between about 135 and 165.

But the main point to note is that all the exposures, in this graph, are ‘wrong.’ The only mid-tone greys that have been captured lie on the 1600 ISO and 800 ISO curves at EV0 – and they are both located on their S’s shoulder, where any additional exposure will quickly degenerate the mid-tone into a much lighter shade.

It should be pointed-out that we are not calibrating the Nikon’s internal meter here. Rather, we are calibrating the Nikon’s exposure to a Sekonic incident light reading – so there is bound to be some discrepancy. (The difference here is around .5 EV in the Nikon’s ISO sensor ratings which are, relatively speaking, over-rated – if you accept that the Sekonic is correct).

The anomaly serves to illustrate the importance, for all serious photographers, to properly calibrate all new equipment before attempting that unrepeatable shot.

So what does this graph generally tell us? Well, first of all, that image tones are only accurately recorded by the film or sensor on the straight portion of the ISO slope. Furthermore, that getting the exposure ‘wrong’ moves the mid-tone to a new ‘mini slope’ in which fewer tones can be represented. It is the latter characteristic, emphasized when considering a single ISO slope, that is replicated between different ISO settings.

For professional photographers reading this: I now admit that the graph I am using is a bit of a con. (You don’t normally calibrate a camera with an integral light meter to a handheld without first calibrating both meters to ensure they produce the same mid-tone reading. That is why there is an apparent inability of the Nikon to reproduce an EV0 mid-tone here.) But I have chosen to use this graph for a purpose: not only does it illustrate that each ISO has a different tonal range (each ISO’s S would be adjacent to similar EVs and not offset from each other if that were not the case) – it also illustrates that different manufacturers appear to use slightly different benchmarks when calibrating their meters. The reason why TTL metering is nearly always off to a handheld meter is that the camera’s sensor is only reading what level of light is reaching it through the lens. (And all lenses absorb light to a greater or lesser degree).

If you use a professional camera (and a professional handheld meter) you will find that both provide a facility for calibrating one to the other. The standard adjustment range is 1EV in tenth steps, which is more than sufficient for any good equipment.

There is no need to take photographs when calibrating meters: just use both to take readings from an evenly lit standard grey card and adjust the one you know to be ‘incorrect’.

The other facility that most good camera manufacturers provide is an exposure compensation dial, which normally provides the ability to adjust metered exposure between –5EV and +5EV. It is not a coincidence that this range is the same as the range used to calibrate a camera’s actual exposure; because using it provides photographers with the ability to easily calibrate their camera’s automatic programs as well as its manual settings.

Camera calibration allows you to arrive at suitable adjustments, if necessary, to be applied to the TTL meter’s reading for each ISO sensitivity (and accurately place the mid-tone at 50% luminance). Keep a durable record of the adjustments required and dial those into your camera’s settings, as necessary, when using different ISOs.

In my reply to Mac’s last comment, I said that selecting the correct ISO was also all about mood – and, if you take a look at the different results of taking a sequence of calibration grey card shots, you can better see what I mean. Low ISOs tend to produce a light and airy mood; high ISOs dark and sombre depression.

Often, mood can be important – as beautifully expressed in Harry Borden’s portrait photography. Harry can make a baby appear positively angelic by exposing for the highlights – and make a politician appear positively menacing by concentrating on the shadows.

And that brings us nicely on to the subject of clipping-points…

Clipping points are those EVs in which the last vestige of any detail is still represented – before all is lost in pure black or white. They are located where the ISO slope begins to heel and to shoulder.

So how do you produce an ‘angelic’ baby portrait? The answer is to meter the brightest white in the scene and accurately place it on the ISO’s shoulder – allowing the shadows to take care of themselves. In other words, if the ISO’s shoulder clipping-point is at +2.7EV, use your TTL metering to set the brightest white at mid-tone grey – and then rack the exposure up by 2 2/3 stops.

To produce that menacing portrait, or gloomy scene, perform the same exercise for the darkest shadow and place its mid-tone reading on the clipping-point you have established on the ISO’s heel by under-exposing. (Let the highlights take care of themselves).

And no, you cannot reproduce those precise effects in Photoshop from a standard exposure; because you cannot reproduce the subtle logarithmic tone compression that occurs towards both clipping-points.

Would you ever place a mid-tone reading past the clipping-point? Yes. When producing knockouts (when a commercial product shot requires a pitch black or pure white background).

But then you need to know what ISO to use – to ensure all the tones (and colours) in the product are reproduced accurately. Manufacturers tend to invest a great deal of money in patenting the colours used in their logos; and, if you don’t reproduce them accurately, you will be unlikely to get paid or offered any more work.

And here endeth the lesson on photographic exposure and camera calibration. I am supposed to be on holiday 🙂.

The Borden Effect

JUDGING by my mailbox, Harry Borden’s appearance on Channel 5’s How To Take Stunning Pictures (Tuesdays, 7.30pm) has led to a number of readers hunting through drawers to retrieve their forgotten digital camera and revive their photographic interest. But, it seems, many of you were stumped by Harry apparently saying: ‘Expose for the light,’ – and my last post has simply added to your confusion.

Now I do not personally know Harry; but I think I can say, with some certainty, that he does not set his camera’s exposure using its TTL meter. You only have to take a look at his work to see the rich tonal ranges that can only be achieved by selecting the correct ISO setting and taking an incident light reading of the sitter’s skin tones to position the mid-tone correctly. However, Harry’s advice is pertinent if you are metering your subject through a camera’s standard centre-weighted or averaging system.

The thing to remember is that: whatever you point your meter at will be rendered mid-tone grey. Standard light-meters are not colour sensitive – they only see in black and white – or, more accurately, they only measure the light reflected from the subject. (An incident reading is taken with a calibrated white dome over the sensor to measure the light reaching it).

If you point your camera’s meter at the scene’s shadows, you will pull the blacks up the ISO slope to its mid-tone – and push all the whites in the scene over the graph’s shoulder where they can only be represented as pure whites. A classic case of over-exposure that has no highlight detail.

On the other hand, if you fill your meter with the brightest white in the scene: you will pull the whites down the slope and push all the shadow detail past the graph’s heel where only pitch black can be represented. Serious under-exposure.

I did not see the programme; but, if you point an averaging meter at a typical portrait subject, slightly more weight will be given to the subject’s clothing and the darker background (which is pretty standard to contrast with the sitter’s skin-tone). So, generally speaking, the result will be slight over-exposure leading to blown highlights that can ruin the image.

Harry’s advice is consistent with fooling the averaging meter into thinking there is a little more light than there actually is – thus moving the mid-tone slightly back down the slope to ensure that as much detail as possible is retained in the highlights.

If you look closely at Harry’s work, you will see that it is not the sitter that he takes pictures of – it is the light that illuminates his subjects. Capturing that is his main objective. Being able to record the moment as well is what lifts his work from the excellent to the spectacular…