PMA 2009: Sigma lenses, DP2 and SD15

The Secrets of Differential Focus

Shallow depth of field can be used effectively to isolate subjects and make your visual statement clear.

It has commercial uses wherever something needs to be lifted out of a literal context, such as food shot for a magazine or menu. You don't need to know exactly what the plate or the tablecloth are like, or even the entire dish; it's enough to home in on a small area which looks just right, and let the rest dissolve into blur.

Anyone laying text or inset photographs over a background image will appreciate shots with very limited zones of sharp focus and large areas of diffused detail. This is not a consideration for the amateur, or has not been in the past, but the availability of electronically printed albums (photo books) with layout software on your own PC means you can now think like a magazine designer when putting together an album. Family, events, holidays, parties and hobbies are all popular subjects for photo-book production.

Silk poppy: you can experiment with odd optics for effect. This soft result with muted colour and contrast comes from mounting a vintage Super Takumer 105mm lens on the Sigma SD10 and using it wide open. 1/500th at f/2.8, aperture priority auto with -0.7 compensation.

Of course, you can use a tool such as Focal Point, from OnOne Software (distributed by Colour Confidence in the UK). This is a powerful Photoshop plugin which lets you define the parts of your image you want in sharp focus, and without using layer masks or other advanced Photoshop editing, create realistic lens-quality blur.

However, nothing quite beats the results from a real lens used wide open. Sigma has one or two outstanding tools for differential focus or deliberate blur. My favourite is the 150mm f/2.8 Macro, becauseit combines long focal length with a very wide aperture and ultra-close focus. In the studio, this lens can earn its keep just by shooting small objects in a stylish sharp-soft mode. The 50-150mm f/2.8 is a close second, and the shorter macro lenses (both being f/2.8) an accessible choice for many existing owners.

Euro note: the Sigma 150mm f/2.8 EX DG Macro is a great lens for smooth bokeh and extremes of differential focus. Here, it was used on a Fuji FinexPix S3 with illumination from the tungsten modelling lamps of studio flash. Tripod, 1/45th at f/2.8.

One thing you need to be aware of is that SLR viewfinders do not show differential focus very accurately. Sigma's are relatively good, using a more traditional ground glass simulation than some ultra-bright screens designed to cope with low magnification, low efficiency mirror prisms. Just be aware that what you see through the finder at f/2 or f/2.8 really looks like the depth of field you get at f/5.6. You can check this by making some exposures and viewing them on the rear screen.

There's a good explanation of this phenomenon as seen on high-end Canon kit at dPhotoexpert.com - http://www.dphotoexpert.com/2007/09/21/live-view-versus-the-cheating-dslr-viewfinder/ - this article has become a standard reference for explaining the issue to those not familiar with it yet. Once you are aware, you will not rely as much on your viewfinder to judge depth of field, and you'll make more use of reviewing the image on-screen when setting up shots.

One effect you will see with Bayer pattern sensors is 'colour bokeh' error. It's not a noticeable problem with the Foveon X3 sensor, and is absent in the SD9 which has no microlenses. The lens - however well colour corrected - may show defocused neutral gradations as slightly magenta in the foreground, slightly green behind the subject. This effect was never visible on film. It's caused by the shift in relative colour corrections out of the plane of focus, and depends on whether the rays are diverging or converging when they strike the sensor. You need to be aware of it and perhaps desaturate unfocused zones which have a visible hue shift.

Lemur: the full aperture defocused image of the Sigma 80-400mm f/4.5-5.6 EX DG OS image stabilised tele zoom is very smooth. Shot at 400mm, 1/250th at f/5.6, with the Fuji FinePix S3 Pro set to ISO 800.

The defocused image quality depends on the lens design, the shape and position of the iris (aperture) being critical. Since other aspects of performance are more important, 'good bokeh' or a pleasant out of focus transition is not something which goes with cost or optical performance. Some lenses have it, others don't; it is harder to find in complex, long range zooms than in simple designs. A sure way to get good bokeh is to work wide open, which means a perfectly circular aperture. At least, that's the theory, but many zooms will still show oddly enhanced circles of confusion. Again, you need to try different lenses to find which work best for differential focus.

If the light is too bright, consider using a neutral density filter (a polariser can be pressed into service, but may have other unwanted effects). Most photographers are familiar with using an ND filter to get long exposures for waterfalls or waves, well stopped down. Its other use is to allow wife-open working in bright conditions.

Very sharp grain - or well rendered digital noise - can be effective with shallow depth of field. So can desaturated pastel colours. If anything, vivid colours are to be avoided unless you use them deliberately. They can dominate defocused areas, as any fashion photographer who has shot a street scene at f/2.8 and accidentally included a lit traffic light will confirm. Lights, street decorations, and reflections all take in their own life when thrown out of focus.

Detail of an Apple Mac screen: with a bellows and an old enlarging lens, the SD10 captures a tiny zone of sharp focus from an angled computer monitor screen. Mounted on a mini tripod, manual exposure by trial and error, 1/13th at f/4.

Above all, experiment. Try removing the lens entirely from your camera and holding it with your hand like an extension tube. You don't need a special flexible lens at £200 for creative angled-optic effects - a couple of Sigma close-up lenses screwed together and held in your hand will work quite well! Actually, a magnifying glass can do the job, or that loupe you once used to examine slides. Try macro bellows, or reverse mounted lenses.

The most effective differential focus comes from medium focal length and wide apertures, rather than long teles at moderate apertures. Lenses to experiment with range from the 30mm f/1.4 to the 70-200mm f/2.8. What if you don't have a wide aperture lens? You can get very effective results using something like the 55-200mm DC zoom wide open, or an 18-200mm the same way. It may only be f/5.6 or f/6.3, but if your subject is a close-up, the isolation and foreground/background blur will be enough.

Noodles and stir-fry: food is often best shown using very restricted focus zones. Sigma SD10, 50mm f/2.8 EX DG macro, ISO 100, 1/6th and f/2.8 hand-held by natural light.

In the professional studio, high power flash used to limit choices. In the 1980s, the standard colour negative stock was Vericolor Type S at ISO 160, and most monobloc or pack flash systems didn't turn down below 1/4 power. Even at portrait distances and with large light shapers, you could end up needing to use f/11 at minimum power. When digital SLRs began to take over, the flash makers had to rethink and offer 1/16th or 1/32nd power - the first DSLRs sometimes had ISO 400 or 320 as their lowest option. Habits had already begun to change, with scanning digital backs and continuous light, persuading pro shooters to explore differential focus more.

The result is seen all over today, from Marks & Spencer 'not just food' advertisements downwards, in TV and film as well as stills. We are all now visually trained to accept and appreciate images which have only tiny areas of critical sharpness. The days of stopping down to f/32 and using camera movements to get a plate of food sharp from front to back are long behind us (though restaurant displays around the Mediterranean still depict the exact contents of what you can order, pin sharp, down to the number of prawns!).

So, have a go - start using unfocused detail creatively, and enjoy exploring the qualities of the lenses you own.

Living with the SD14, a Professional View

Let’s start as I mean to continue, cards on the table.This account is written for other photographers – people who take photographs rather than computer geeks or mobile phone nerds: I assume that, unlike them you’ll have a life and you’ll want to be out there chasing images. After all, that is what the SD14 is for.

Through the long evolution of my photography, first with film and then with digital, I have sought pin-sharp detail and colour fidelity, whether I am dealing with landscapes, buildings or the scales on a butterfly wing. That is my kind of photography and I make no apologies.

My cameras have to earn a living; they are not taken out, set on a pedestal, drooled over and put back again. Thus, just two days after taking the SD14 from its box on 2nd May 2007, it was with me on a flower-filled Sicilian hillside recording an orchid I had waited two decades to see. Every day since then I have used it in un-compromising fashion for my professional work. The ultimate trust was to use it to photograph my daughter’s wedding –one false move and the wrath would have been galactic. It worked superbly.

Crab Spider

I began putting down some thoughts after feeding in the words “Sigma SD14 reviews” to a search engine and then being astonished by the widely-differing opinions for Sigma digital SLRs seemingly have the ability to activate love-hate wars like no other. I think it has something to do with the temerity of a small company posing any sort of challenge to the great Gods Canon and Nikon whose acolytes then leap unbidden into a vocal and, often hysterical, defence of their choices.

Worryingly, those people who loudly voice opinions in the photographic press also seem unable to come to grips with basic terminology (the word pixel for instance), have no idea of the difference between sharpness and resolution and are oblivious to the fact that pixel count is not a substitute term for either. Sorry, but I have a perennial detestation of sloppiness (put it down to a physics background). But I have to note that the SD14 seems to gets the ‘thumbs up’ from people who take photography seriously: the thumbs down often comes from those who are either not practising photographers in a sense that you or I would understand or those who feel free to comment without using the camera…

So, the conclusion first…if you want exceptionally fine-detailed, beautiful coloured images that seem to jump off the computer screen and produce superb prints up to A2 (see later) then this is a camera I can unreservedly recommend because that is what I use it for. It is a refreshingly uncluttered machine and free of extraneous gimmicks (exposure modes, bells and whistles) so, if that is not what you wish to hear then I’ve saved you reading further.

In the field

First let me tell you the kind of tasks I set a camera so that you can better assess the viability of the SD14 as your choice of machine.

One major passion is for wildlife subjects -often in close-up. This includes plants and insects in particular and any camera I use has to be equally at home in the field with macro lens and macroflash and also in the studio where it can be coupled to an array of gadgets I have built or modified. Yes, I would love to make a living from close-up, but the reality is that any camera I own has to work much harder than that on a gamut of freelance and editorial work from flowers in the landscape, buildings, trees, sunsets to people ….all obvious draws here in central Italy where I now live and work. I embraced the whole digital business six years ago and love the element of control I get from start to finish: there is now no one else to blame.

I can certainly see that the SD14 is not the camera for everyone (in fact that camera does not exist). If your living depends on speedily-grabbed pictures, bursts of shots and brilliant low-light performance then I think that the physical limits of the Foveon sensor would make the SD14 the wrong choice. The burst rate is low and even at ISO 400 noise is beginning to reveal itself. But then those are not drawbacks for me or for a legion of photographers who can and do take time...

Praying Mantis

Working with the SD14 – the routine part.

For all aspects of my work of this the SD14 has proved itself day after day and I have grown to love using it – in fact, thanks to a life change where I seem to spend much of my time covered in cement or sawdust, the arrival of this camera injected a much needed dose of enthusiasm. Serendipitously its arrival coincided with the appearance of lots of butterflies, fields brimming with poppies and all sorts of photogenic things just metres from home….On a day to day basis, there is no difficulty producing quality images with the SD14 – it is easy to use, as quick as most will need it to be and it feels comfortable in the hand. Furthermore, detail is captured with colour fidelity at a level that makes it possible to get those 50MB files that agencies demand (even for use where 5MB and less would be more than adequate, clients all now demand giant files…).

My ‘workflow’ with this camera has been determined by the time that I needed to spend in front of the computer when I would rather be out and about taking pictures. So, first thing – I use a Lexar card reader that downloads images in a fraction of the time. I have only just started using Adobe Lightbox on the Mac so cannot comment honestly on its worth as a RAW converter.

Currently, I use Photopro to produce a set of ‘Same Sized Tiffs’ from the pictures I choose to keep or that are deemed worthy of printing or sending to agencies. The RAW files will be archived on a hard drive and DVD. I am pretty consistent with exposure so I find any tweaking in RAW is never too onerous to carry out – in this respect the Photopro controls for shadow, highlight, fill-light are excellent. But please Sigma why does it run so painfully slowly and why have you abandoned Mac users and not produced version 3 for them. If you are serious about getting pros to use the SD14 then wake up to the fact that many pros use Macs…

I wrote a short routine in Photoshop to convert these Tiffs to Genuine Fractals Format and then upscale via this programme to produce tiffs of 50MB and more. Long-winded yes but I run it over night if needed. The time factor makes me a bit more selective…

So why this rather than the file-doubling facility in Photopro. Well, Careful visual comparison of prints and of files on screen (at near individual pixel level) shows that when it comes to A3 sizes and larger the Genuine Fractals approach works more effectively than either file-doubling with Photopro or up-scaling with the various options in CS2. Lines and edges are visibly sharper producing an overall sensation of increased sharpness.

The reason is, I think, the following. Many of my pictures of natural subjects at close quarters contain small hairs, veins on leaves and insect wings and other details that are essentially lines or recognisable geometric shapes: same thing with details of buildings (brickwork, stones and so on…). Genuine Fractals functions by recognising patterns that depend on “fractals’ – shapes of snowflakes, veins on a leaf and so on are natural examples of these. These patterns can be ‘scaled’ to preserve relationships in shapes (the angles and curves etc) and thus, with large prints the tiny details I relish are reproduced rather than broken up by random addition of extra pixels. Those hairs on a bee’s knees are the kind of stuff this method renders superbly.

Some Snippets

People are beginning to discover things with the SD14 that are not in the manual:

1. Infra-red sensitivity.

The glass that protects the sensor from dust has a coating that also acts as an Infra-red filter. Without it the SD14 becomes (as claimed by a number of people) “the best infra-red camera on the market” with a lot of room for experimentation.

2. Shooting to the right

Dr Andrew Stevens writes in his Review of the SD14 the BJP (02 May 2007) of over-exposing by 2 f-stops in RAW mode at ISO 100 equivalent and then “pulling back” in Photopro by 2EV to give an effective ISO 25: Kodachrome25 lives in digital form with wonderful colours tones and detail…

For those shooting in RAW mode exposure advice runs counter to what one was used to from film – remember underexposing slightly to increase transparency detail? With RAW exposure the nearer you can push to over-exposure without blasting out highlights the better.

The term ‘shooting to the right’ has been coined for is easier to look at the histogram and adjust exposure until it moves towards the right but stops short of ‘clipping’ where detail is lost.

Many DSLRs have a dynamic range of about six stops to encompass tones from bright whites to darkest blacks. They encode capture using 12 bits of data which means 4096 discrete tonal levels: half (2048) reside in the brightest level, quarter (1024) in the next then 512.256 and 64 for each stop down in the tonal scale. This means that in the lightest areas you can get the greatest subtlety since that is where there are most tonal levels. And it also tends to reduce noise in the shadows.

In practice with RAW it is better to darken an image for this adds levels in shadow areas. In most cameras, the idea of exposing for the middle gray is a hangover from film days – this is what produces the most pleasing JPEGS.

With RAW it is better to expose for the highlights…its never as easy as you want it to be.

Which Macro Lens?

Sigma has a great reputation for their Macro lenses and produces one of the most comprehensive line-ups there is. They start with the 50mm f/2.8 EX DG and go through the focal lengths of 70mm, 105mm 150mm right up to the 180mm. Every one of them can produce 1:1 images on all of the popular, 35mm derived SLR cameras produced today. There is even one designed to work on the newer 4/3rds system.

We are talking here about true Macro lenses, not the marketing hype Macros that are really only a close focussing lens. True Macro photography does not start until you reach the reproduction ratio of 1:1. That means that the image on the film/sensor is the same size as the object the image relates to.Macro photography continues to be called just that until you reach reproduction ratios of around 10:1, after which it becomes Microphotography.

So, why so many focal lengths to do the same job? Well there are a number of reasons, including angle of view, working distance and depth of field.

For example, at the two extremes, the 50mm f/2.8 EX DG Macro lens gives an angle of view of 46.8° and a minimum focussing distance of 18.9cm whereas the 180mm f/3.5 EX DG HSM Macro lens gives an angle of view of 13.7° and a closest focus distance of 46cm, but both give a magnification ratio of 1:1.

The Natural History Museum in London has a couple of Sigma 50mm EX DG lenses in its photographic Department

Now imagine you need to photograph small items repeatedly over a long period of time. The easiest way to achieve this would be with a suitable set-up as seen here where the camera is fixed on a stand and the objects are placed on a table beneath it. Now to use the 180mm lens in this situation would mean a stand with a post over a metre long, not a sensible proposition, whereas a 50mm lens fits the bill perfectly.

Other disciplines require longer working distances, as with shooting insects, butterflies and some smaller reptiles where it is not so wise or desirable to approach too closely. Here, the longer focal lengths come into their own. In between these two extremes are the others that have various advantages and disadvantages.

Traditionally, the 105mm f/2.8 EX DG has been the most popular, not only as a compromise between the extremes, but doubling up as an excellent short telephoto suitable for portrait work. The 70mm f/2.8 EX DG, as the newest of the bunch, has been introduced to fit in the same area on APS-C sized sensors but, sensibly, retains the ability to be used on full frame and 35mm film cameras too.

The 150mm f/2.8 EX DG HSM occupies the large gap between the 105mm and the 180mm and inherits the internal focussing of the longer lens along with the sonic motor. This does make things like bug hunting a little easier, as the autofocus is somewhat quicker. However, fast autofocus is not the prime domain of True Macro lenses because of the need for extreme accuracy in the focussing. Because of this, Macro lenses tend to have finer pitched focussing threads that need more turning to achieve focus.

Sigma's latest Macro lens, the award winning 70mm

Depth of field is a subject in its own right but suffice to say that it is measured in millimetres in Macro photography. DOF also decreases, as focal length gets longer, introducing another reason for having multiple choices. Apparent DOF also changes with sensor size, smaller sensors giving apparently greater depth and introducing another variable.

Another point that should be remembered here is that quoted closest focussing distances are measured from the film/sensor plane. This means that most of the camera body, along with all of the lens, is included in the distance given. This introduces another problem in some disciplines, that of getting light onto the subject without shadows being cast by the camera/lens combo. Over the next few articles we will look at these variable areas in more depth.

20 Beginners Tips For Digital Photography

Many beginners find digital photography rather challenging and rightly so. Today, more and more digital cameras are being created and it seems like the more digital cameras they make, the more difficult they become to use.

You may not want or even need a camera with tons of features. It really depends on the type of pictures you plan on taking.

Regardless of the camera you own or are planning to own, you should have a well-rounded knowledge of digital photography. Hopefully the following 20 tips for capturing digital images will prove to be useful in your quest for taking better photographs.

1. Know your camera. One of the biggest mistakes you can make is not taking time to learn about the features of your camera; some models will have useful functions within the menus. Know your lenses too; find out where they offer the best clarity by experimenting.

2 - When shooting sunny outdoor shots, try adjusting your white balance setting from auto to cloudy. The auto setting will make your shots appear too cold. When you change it to cloudy, it will increase the warmth of your pictures.

3 - If you are looking for superior image quality, the ability to use a large variety of lenses and print large high quality photos, then look towards DSLRs with larger photosites for a given sensor area - more megapixels is not necessarily going to deliver higher quality.

4 - Use your flash outdoors. Sometimes, even on a sunny day outdoors, there is still a need for a flash. If the sun is directly overhead or behind your subject, this can cause dark shadows to appear on the face. The flash will help lighten the subjects face.

5 - Sometimes simply turning your camera and taking vertical shots can make a world of difference. Experiment more with vertical picture taking.

6 - Do not put your subjects directly in the centre of your shot. Move your subject off centre to inject more life into your photos.

7 - Learn how to hold your digital camera. One of the most common problems beginners face is the shaking of the camera because they are not holding it properly. Of course, the best way to avoid shaking the camera is to use a tripod. If you don't have a tripod, then you should be holding your camera with two hands. Put one hand on the right hand side of your camera where you actually snap the photo and the other hand will support the weight of your camera. Depending on the camera, your left hand will either be positioned on the bottom or around your lens.

8 - Learn about the "Rule of Thirds". This is a well-known principle of photographic composition that every beginner should become familiar with. Do a search online and you will find many tutorials on this subject.

9 - Look at other photographers work. Just spending time studying the work of other photographers can provide loads of inspiration.

10 - Join online photography communities. Get active and ask questions, enter competitions and submit your images for critique.

11 - Do not compare your images with other people's, only your last shot.

12 - Do not copy the work of other photographers. Try and develop your own unique style.

13 - Do not leave your batteries in your camera if you don't plan on using your camera for long periods of time. Many cameras will drain the battery whilst it is sitting, and then you'll find yourself unable to use it when you need to. Invest in spare batteries and chargers if your camera is mission critical.

14 - Subscribe to a good photography magazine or online forum. Read books on photography.

15 - Find experienced photographers to go out on shoots with.

16 - Post your photographs in online forums. Learn to accept criticism.

17 - Learn how to use RAW and JPEG formats depending on your camera's capability and your intended use for the image. If you're shooting for eBay or websites, use JPEG as your workflow will be faster; if you're shooting for print or stock, shoot in the highest-quality RAW files and make sure you have an unsharpened, unretouched version saved as a starting point. If you want to use the files on other platforms look at exporting 16-bit TIFF or DNG files.

18 - Don't buy the most expensive photography equipment right away. Practice and learn about photography using cheaper equipment first. After you have been taking pictures for a while, you will then know what kind of equipment you will need. However, do try higher end lenses if you're unhappy with the technical quality of your results.

19 - Invest in a tripod. Some of us have very shaky hands. If you can't stop the shakes, then get a tripod. It will make a world of difference. Choosing your tripod can make a lot of difference to how prepared you are to use it - if you have a quick-release base and a lightweight tripod, you'll find yourself bringing it along on the offchance you might need it. Models like Gitzo's "Traveller" range will be unobtrusive.

20 - If you are not able to carry your equipment with you everywhere, make sure you have a note pad handy. This way if you find a nice shot, you can write it down and visit that location at a later date. When shooting, if you make geographical notes or use the camera's voice memo functions, you can make your stock shots more marketable by adding accurate tags and dates; some models of camera now offer GPS data as well.

HD Tiffany & YuRi (SNSD)

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