Photography Travelogues – Finding the right balance

June 28, 2012 by 5 Comments

Young Street Merchants in Hosap, Eastern Turkey

Our bus stopped at the top of the hill at the entrance to the Hosap castle, so it didn’t take the residents in the town below too long to work out that potential customers were about! However, to sell to us, we also had a price: they had to pose for a photograph!

Does the colour look approximately correct in the photograph above?

We can see it is late in the day with yellow sunlight kissing the tops of the background hills, leaving the shadows cooler and almost blue. It’s an emotive response to colour, but is it accurate? And should it be accurate?

Often, the colours we use in our photographs are technically incorrect (depending on the colour model we’re using as a reference), but they still look pretty good!

For instance, your camera uses its white balance system to set a ‘correct’ colour balance, but since the camera doesn’t know what the light is like, it can only adjust the white balance to a theoretical ‘zero’ or ‘correct’ position.

Speaking non-technically, white balance is the term used for getting the colour cast correct at the point of capture, or when processing the raw file. It uses a temperature (yellow/blue) and tint (magenta/green) colour model to make colour adjustments. Colour balance is when we change the colour cast, usually during editing the file. The colour balance dialog uses the three red/cyan, green/magenta and blue/yellow channels. Both approaches to controlling the colour cast in a photograph can achieve similar results and  are sometimes referred to interchangeably.

This is the image with the white balance suggested by the camera. The camera has seen the warmth in the light and neutralised it, but perhaps cooling the colour a little bit too much.

If you’re not  happy with the colour balance, you can use the white balance tool in Capture One to change it. Using the white balance picker, click on objects that are white or neutral in colour, or that  should be or could be neutral.

In this image, I have clicked the white balance picker on the girl’s white handkerchief, but I think it has too many optical brighteners in it because the result is much too blue.

In this third example, I have clicked on the grey roadway on the right of the image. Whether the road should be neutral grey or not isn’t really the point, because the rest of the image looks just right. I find using the white balance picker on various areas in the image while processing in Capture One is a useful way for determining the best colour balance, even if the white balance setting isn’t ‘accurate’ or ‘correct’!

You also have to be aware of how your viewers feel about certain colours. For instance, technically speaking, snow at high altitudes in the shadows is blue, but if it looks too blue in a photograph, it can look unnatural to many people. For this reason, snow photos can benefit from a slightly warmer colour balance, even though this may be technically incorrect.

So, if a technically correct colour balance isn’t necessarily the best, why do our cameras try to set it?

Whether we end up using a technically correct colour balance in our final edit is one matter; starting our photographic editing with a technically correct colour balance within our image file is another.

Many photographers find it very useful to start with a correctly colour balanced file. It helps ground their creative process and it also gives them a place to return if colours go awry.

So, unless you are sure about the colour balance you want in the final image, good camera practice dictates that we aim to produce image files which can produce a neutral or natural white balance. This is one of the reasons shooting raw files is so important because you can always reset the white balance within a raw file, something that can be much more difficult (if not impossible) to do with a JPEG file.

In the hero image at the top of the page, I have used two white balance settings. The girls in the foreground have a warm white balance setting, while the background has a cooler, bluer setting. Providing this subtle colour contrast also helps bring the subjects forward, emphasising them against the cooler background.

I hope you like it!

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Photography Travelogues – The Great Barrier Reef 1/2

November 2, 2011 by 8 Comments

They say that daylight has a colour temperature of around 5500 K, but out to sea under a blue sky, this isn’t always the case. It’s funny how our habits as photographers change – or should I say, how my habits have changed. When shooting film, I’d usually have an ultraviolet (UV) filter on my lens ‘to take the blue out’.

While invisible to the human eye, ultraviolet radiation generally records as blue on colour film and as haze on all films. It has a similar effect on digital sensors as well, but of course, many of us don’t believe in using filters anymore.

There is an argument that states, why would you want to degrade the quality of your lenses by placing another piece of glass (or, heaven forbid, plastic) in front. If the lens designers thought a filter was a good idea, surely they would have included it as part of the design. This argument fails in several places, of course, but even so, given digital photography allows us to adjust our image files so easily, many ‘essential’ filters are no longer used. And in any event, the majority of UV filters were sold for ‘protection’ of the front lens element, and you could clean them with a dirty sock if you had to because, if scratched, they were not as expensive to replace as the front lens element.

Not that I ever cleaned my lenses with a dirty sock. Ever.

Here’s the original exposure with the white balance in Capture One Pro 6 set to ‘Shot’ mode. In other words, this is the white balance setting suggested as a starting point by my camera. Of course, capturing raw files means I can change the white balance to any setting I like when converting the file. According to Capture One Pro 6, the Kelvin is 7943 K and the Tint is set to 3.0.

Note, there are no adjustments made to this file at all – it is effectively straight out of the camera. However, you can see quite clearly that it is ‘daylight’ over Australia’s Great Barrier Reef, so what happens if I set the white balance in Capture One Pro 6 to ‘daylight’ (or if I had set the white balance to daylight on my camera)?

At a 5500 K daylight setting, the photo is considerably bluer. And this isn’t what I remember seeing, either. The human eye when coupled to the brain is an incredible imaging device, not only adjusting the ‘exposure’ but also filtering out colours. I remember very clearly how strong and vibrant the colours over the shallow reef were compared to the darker blues of the deep water outside. This colour contrast is lost due to the overpowering blue colour cast.

I’ve taken a dozen helicopter rides over the Great Barrier Reef and every time it is different. In August, I was on Hamilton Island, giving a workshop with David Oliver and Bruce Pottinger. We do this every year and one of the highlights is the helicopter ride over Whitsunday Island and then out to the reef.

On this day, there was a strong southerly wind and the air was very hazy, which means that the images are lacking in contrast. The greater the distance, the more haze you look through and we’re at around 1500 feet (from memory). So, while I didn’t have an ultraviolet filter with me, I could use Capture One Pro 6 to tweak the colour temperature (just a little warmer) and increase the contrast. I also added an adjustment layer to darken down the sky at the top.

If you’re interested in the photography workshops we present on Hamilton Island, or you just want an excuse to visit Australia’s tropical north, please visit http://hamiltonisland.com.au for more details, or visit my site at http://betterphotography.com. It’s a great excuse for a week on Hamilton Island

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Custom White Balance

October 28, 2010 by Leave a comment

Custom White Balance

Create a custom White Balance for your camera

For landscape photography this works much better than relying on the cameras Auto White Balance (AWB) or factory made fixed Daylight settings.

AWB and factory fixed WB settings are typically not calibrated for your camera but for an average camera.

A custom White Balance created in direct sunlight at midday will work throughout the day giving your images the natural look and feel of the light. Images shot at sun rise or sun set will maintain the warm color temperature of the low sun. Shooting in shadows at midday will give the images a slightly cooler look, as you would expect.

Create a custom White Balance with Capture One

Custom WB with Capture One

Create your own Custom White Balance setting in Capture One. When using a ColorChecker use the second brightest neutral patch. This patch is the most neutral patch on the target.

 

In Capture One you can easily create a Custom White Balance preset for you camera

• I always use the GretagMacbeth ColorChecker as my White Balance target but other specially made White Balance card can be used. At midday with clear blue sky take a picture of the White Balance target placed in direct sunlight.

• In Capture One use the White Balance picker from the White Balance Tool to pick on the White Balance card.

• In the White Balance Tools Action Menu use the add preset to save the just made White Balance pick.

• This Custom White Balance preset can now easily be applied to the real photos.

People living in areas where there are big variations in the midday Color Temperature throughout the year can refine their presets by having a Custom White Balances made for each of the mayor seasons, e.g. summer, fall, winter and spring.

An alternative method, which I prefer is to create a custom White Balance presets in the camera. Most cameras have this option. This way your images will look right already from when you load them into Capture One.

Filed under Capture One Tips & Tricks Tagged with

RAW Conversion Explained In-depth

September 4, 2010 by 2 Comments

Joe Cornish - Paddy's Hole Teeside

Joe Cornish - Paddy's Hole Teeside

RAW Converters vs. In-camera JPEG Files

Most high-end cameras have the option of saving either JPEG or RAW files. This article will dig into how a JPEG file gets created in a digital camera and how it is limited compared to working with RAW files thus giving you a better background for selecting the right format for you.

A RAW file contains all the information which is measured by an image sensor during the exposure of a picture. Later in the process this will provide total freedom when you want to decide how the scene should be rendered using a RAW converter.  The in-camera JPEG is just one interpretation of the scene. When you set your camera to output JPEG files it actually starts with the same data that is contained in the RAW file and the camera computer acts like a built in RAW Converter. All the processing steps needed for converting the RAW data to a JPEG file will be calculated by predefined settings. Once the shot is converted to the JPEG file it cannot be reprocessed from the original RAW data.  This is the real disadvantage of using the JPEG conversion in the camera.  Naturally, you may tweak the JPEG file in an image-editing program afterwards, but at this point a wide range of decisions have been made on how to process the file. Those decisions cannot be undone without a severe loss of quality.  Working with RAW files means that you still have complete freedom to work with the initial captured information and process the image exactly as you like it. And yet still achieve the highest possible image quality.  To get a better understanding of this we will take a look at the different processing steps needed to convert at RAW file to a JPEG file:

  • Bayer Interpolation
  • White Balance and Color Correction
  • Tone Curve
  • Noise Correction
  • Sharpness
  • JPEG compression

Bayer Interpolation

As the first step an image file with color information for each pixel needs to be created. Please note that in camera science, a pixel is denoted as one photosite of one color. This differs from e.g. a computer monitor where a pixel contains all three colors. In the sensor 2 out of 4 pixels are Green, 1 out of 4 is Blue and 1 out of 4 is Red.  This means that the RAW file does not see the true color information for each pixel. In this process the task for each pixel in the RAW file is to “guess” the values of the 2 missing colors.

This process is called Bayer Interpolation or “de-mosaicing”.  The name Bayer refers to the original pattern of how to arrange the Red, Green and Blue pixels in the sensor. This pattern was patented by Bruce E. Bayer back in 1976 but it is still today by far the most common pattern for color pixels in color image sensor.  The Bayer interpolation process calculates the missing color information from the values of the surrounding color pixels in order to create a normal R, G, B color file.  This is not an exact science – each camera manufacturer or RAW conversion software vendor have their own custom algorithms for the process. There is a huge difference in the quality of these algorithms, which provide the basis of the ability to see fine details in true colors. Later processing steps can still alter the result but if for instance some details are not established in this step it is not possible to re-establish them later.  Some of the finest Bayer interpolation algorithms can be found in RAW Converter software like Capture One and Leaf Capture. Dedicated RAW converter software contains very advanced and complex algorithms. Only very few camera manufacturers have managed to build high quality algorithms into their camera’s “computer” and even some of the largest DSLR camera manufacturers have only managed to implement simple algorithms for this step.

Bayer Interpolation Pattern

Bayer Interpolation Pattern

Bayer interpolation.  The first figure shows the RAW file with the color pixel arranged in the Bayer Pattern. The second figure shows the RAW file after the Bayer interpolation process. Color information for the 2 missing Colors for each pixel has been calculated.


White Balance and Color Correction

When it comes to colors the most important parameter to get right is the white balance (WB).  This process simply determines the “color” of neutral colors.  Getting the WB right is the basis of getting accurate color and it is the fundamental starting point for all further color corrections. All cameras have options for setting the WB and all have some sort of auto WB.  This might offer a reasonable starting point but often these algorithms are not optimized for the individual camera and will lead to some color cast in the images as well as wrong color interpretation. Occasionally, these auto WB algorithms will produce a completely wrong result and will select a really poor WB. Using in camera JPEG files with wrong or slightly wrong WB might lead to color cast and wrong colors in the final image. This kind of color problem can be extremely difficult to fix afterwards in an image editing software. By using a RAW file and a RAW Converter you will have full control over the WB and it can be adjusted to exactly the right WB for the camera and the scenario.

Tone Curve

Like in the days of film there is a tone curve involved when making an image from a digital camera. Back then you were able to choose films with different tone responses (contrast / base characteristics) and in the development process there were still some tweaks that could be done. The tone curve determines how to render all the different levels of light from deep shadow to highlights. The human eye has the ability to see both very bright details and very dark details at the same time.  This is also the case for today’s digital cameras. However, when an image needs to be displayed or printed it is only possible to use a quite limited range of tones. Therefore it is necessary to make a decision on how much of the shadows, the mid tones and the highlights that should be seen. This is what the tone curve takes care of.

If the camera has been set to save  JPEG files then the tone curve is applied in the camera computer. The different camera manufacturers have different perceptions of what they consider being the ideal tone curve.  Some manufacturers prefer a tone curve with high contrast (giving punch to the images but lacking the ability to maintain shadow details) and others like less contrast (which provide better results in portrait scenarios). Some prefer the ability to maintain many highlight details while others hardly keep any.

When an in-camera JPEG file is saved, then it is converted into only 3×8 bit per color pixels – or 256 levels of grey per color channel. This means that if you did not like the tone curve applied by the camera, your ability to tweak it afterwards is quite limited. If deep shadow details are missing, it may not be possible to get them back at all.  By using RAW files and a RAW converter you maintain all bits available from the RAW file and you will be able to apply exactly the tone curve you prefer.  Some RAW converters like Capture One even gives you the ability to select different default tone curves (Film Curves) or the possibility to work with a totally linear curve. This provides you with complete freedom to create your own look.

Noise Correction

Today, we see cameras with previously unreachable ISO levels.  This has been a result of improvements on many fronts. In particular the quality and design of sensors and the refining and complexity of the noise reduction algorithms. Without high quality noise reduction methods, images shot at high ISO levels would not be useful at all. How useful some of these extreme high ISO options are, is very much dependent on how the images are intended to be used. However, without doubt you can reach a quality level at high ISO today that has never been achievable before. For in-camera JPEG files large amounts of noise reduction is applied even at quite low ISO levels.

Noise reduction is an “art” in the field of image processing.  The challenge is to determine what is useful and valid information in the file and what is just noise and then deal with the noise.  There are many different algorithms in this field and the results vary. Some of the cheapest algorithms just blur out information with high loss of details, where other algorithms use very sophisticated methods to clean up the file with a minimum loss of details and color accuracy. Again the benefit of working with RAW is huge compared to using the in-camera noise reduction. If the JPEG files blur all the details which should have been included in the file there is no way to get it back. If you work with a high quality RAW converter like Capture One you have full control over the differentiation between noise and details while still getting a good default compromise – most images don’t need tweaking.

Sharpness

How much sharpness should be applied to my images and what should the camera settings be? This is a big topic and I will explain some of the things that need to be taken into account.  Let us start with the camera you are using.  Most cameras use an anti-aliasing filter in front of the image sensor. The purpose of this to minimize the potential moiré that can occur because of the way the sensor sees colors via the Bayer Color Pixel Pattern.  This anti-aliasing filter blurs the image just a little bit but how much depends on the camera manufacturer and the camera model.  The pixel size of the sensor in your camera also has an influence. Likewise, the lens you are using and the aperture will also highly influence how sharp an image will look.  This means that even in situations where you are using the same camera you will need to compensate for the different levels of sharpness you get from using different lenses and apertures. Finally, it is necessary to determine how much Photoshop work you plan to add afterwards and what size and purpose you prepare the image for?

It will be difficult to apply the right amount of sharpness for a JPEG file in the camera. If you do need to shoot JPEG make sure that sharpness is not set too high as this cannot be fixed afterwards. The only right solution here is to use RAW files and a RAW converter and then depending on the use and origin of the individual image adjust the sharpness.  In the best RAW converters like Capture One you have the possibility to save sharpness presets that may afterwards easily be applied to groups of similar images which will speed up this process considerably.

JPEG compression

The whole idea of using JPEG files in a camera is that it makes it possible to compress the image file to a much smaller size. Thus you are able to store large quantities of files onto the memory card and you are able to save the files faster. If you need to shoot long burst of images this might be the only option that gives you a long enough burst period. JPEG is a standard for how to compress an image file but there are many options within the standard that greatly influences the quality and size of the image.

Typically you will have options for different JPEG qualities on your camera.  A simple parameter is the size of the image. This is straight forward but you may also have a couple of options for how high compression you can expect to get.  If you need to shoot JPEG it is important that you test the JPEG quality settings or simply go for the best quality.  It may not be in the details that you see the loss of quality, however, if you e.g. have a sky with a smooth color transition the JPEG compression may break up this transition. The final thing that happens in a camera when shooting JPEG is that the bit depth of the image gets reduced to 8 bit per color channel. After this process, the image then gets compressed by the JPEG compression engine and you end up with a file that is much smaller than the original.

It might be that too high compression settings lead to image files with low quality. However, it is still an amazing technology and it is possible to make JPEG files which are about 8 times smaller than the original which still look almost identically to the original image – this is of course as long as you do not try to tweak it!  If you find that you generally like the results of the camera JPEG image files this might lead you to think that it is not necessary for you to use RAW.  However, I urge you to see the difference with your own eyes and use RAW files for your own images combined with a quality RAW converter. You will soon realize that your images hold more than you have ever expected!

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