Window VI :: Day & Night

Dappled Ambient Daylight

The quality of light varies a lot during the day but the changes to night and artificial light can be even more dramatic. This is even more obvious in any photographs we take. The artificial light normally has a different colour temperature and this may show up as a colour cast. (orange in my example below)

This colour cast can be fixed by a process normally know as White Balance, which is just a name for the task of removing that cast and it will vary depending on where you undertake it. It can be undertaken in digital cameras by the camera as your take the picture, often as little icon in the menu for daylight, sunny, cloudy, artificial light etc).

Jpeg direct from camera showing orange colour cast despite AWB

Most modern Digital cameras have an AWD (Automatic White Balance) setting that the camera best guesses the colour temperature (usually very well). If you are taking a jpeg image this adjustment is applied to the image, if you Capture in RAW the adjustment is applied to the preview but the un-altered data from the sensor is also stored and the white balance is easy to change later.

RAW image post processed with a WB adjustment

Most Photo Processing software also has white balance tools built in, and it is possible to make the same adjustments to removed colour casts in the post-processing step (as I have undertaken in my example above). How the adjustment is carried out varies with each package but most offer a simple approach using a dropper tool (that is pointed at part of the image that should be a neutral colour) through to sliders that adjust the colour temperature in degrees Kelvin (how colour temperature is measured)

Colour Calibration :: Before You Panic II :: Tonal & White Balance

Back in the HSL Luminosity Tint & Shade post, I suggested that luminosity has a big impact on how we judge colour. I also showed how getting a tonal balance in black and white tonal range first, then switching the colour back on can enhance the feeling of colour. There is another important tool to help your colour judgement in a photo and that is White Balance.

The Idea behind white balance is an adjustment to match the colour temperature of your light source, and this is achieve by either warming (usually adding magenta) or cooling (usually adding green) the overall colour rendition. Human vision automatically undertake these changes so we seldom notice the effect of different light sources. However cameras will record these colour cast and that often leads to an unnatural looking image. In the early days of colour film, specific film stocks where developed for different light sources (specifically incandescent and tungsten lights). You needed to use different film under different lights. Digital Photography has enable these adjust to be undereaten in the camera when it prepares the jpeg render of the image. Most DSLR & mirrorless cameras can be White Balance calibrated for given scenes and lighting conditions. RAW formats which record more details of the image and only carry out the white balance (so AWB or Auto White Balance is ok) to render the jpeg thumbnail embedded in the RAW format in camera. However the photographer is able to carry out white balance after the photo is de-mosaiced and re-rendered in postprocessing steps. White Balancing can also be used to remove colour cast created by strong reflections of highly coloured surface.

It is my experience all the software I have used, with a white balance feature, can do a reasonable job removing colour casts providing you pick a neutral grey tone (or White or 18% grey card) in your photo.  As discussed on the video above those packages that let you then copy the white balance adjustment across a number of photos, then let you take a reference image perhaps with a “white balance” card infront or held by your subject. make an adjustment and then copy that across the rest of that set of exposures.

There seems to be quiet a school of thought that you can not perform White Balance on a Jpeg files (including the video above) after it is captured, but my experience is if you have a reference shot of a suitable card (with a white or neutral grey patch) you can improve the reliable rendition of colour. The example below is a jpeg file straight from my Olympus OMD EM10iii camera, which I post processed in Picasa 3 (ie an old bit of software).

.

In the example above I have already adjusted the tone to get the the white on my test strip lighter then I used the white balance eyedropper and pointed to one of the two very light grey patches on my test card and clicked. That’s all that’s required. Note I haven’t had to use an expensive bit of specialist gear or customised colour profile.

It is my observation that it requires both Tonal and White Balance together to “clean up” colour in a photo.

More Observations on Photographing Art

I have previously hinted that photographing art might be superior to using a flatbed scanner (well at least the ones built into most multifunction printers). Well I now have a strong case to confirm this suspicion. I have been working on a series of mixed media painting I’ve called the “Summer People” for my larger Endless Summer Project. Whilst I have left the people blank (they are only temporary visitors to the beach) I decided They need to have coloured clothes, and fluro colours are still popular with the summer people. However when I scanned these I was amazed… The fluro colours were flat and very pale. I’ve been looking for an explanation about the direction of light or quality of the light source but I have none to explain this observation. Taking a Photograph the same painting (images on the right below) in daylight the colours are much truer including the non-fluro ones.
  
The main advantage of a flat bed scanner is it (in theory) avoids dimensional distortion, such as non paralleled edges produced when the camera is tilted. I did make an old fashion copy stand out of an old enlarger mounting and can connect my canon camera to my studio computer in tethered remote live view mode (see below). The image is upside down here because of the way the camera is mounted on the stand and because the painting is facing me. I could fix this by putting the painting upside down on the table top or just as easy fix in while post processing in lightroom, I can also focus and control exposure from the computer and once I have every thing set up just slide the canvases one at a time check focus and exposure and click. Its actually faster than loading a scanner closing the cover and click then waiting for the scan, Looking at the preview screen doing adjustments (like rotation) and loading the next canvas…

I also need to be careful not to use a zoomed in or wide angle lens, which can cause barreling (curved rather than straight edges to the canvas) A focal length between 50 and 70mm on my crop sensor canon avoids distortion so I have to adjust the camera height up of down to best frame the picture. In this case I lifted the copy stand onto an adjacent counter top.


Another issue with using a camera, is there is less control of the light source and a colour cast can be common. I prefer to only photograph art (and in fact only paint) in daylight. Not direct sunlight but a strong diffuse light such as a window. Even so the colour of the room and its contents will affect the light so it is also wise to consider white balance. By taking RAW format this can easily and well adjusted in post processing. I therefore take a calibration photo using just a commercial colour wheel and one of my notan (greyscale) cards.

In this case the test is a little “warm” but may be acceptable. I use lightroom and it has a very decent Auto White Balance, in this case it is colder and more clinical, but better colours and grey scale. You can manually adjust the degree of correction but I’m happy to go with the auto correction. Further lightroom lets to refine the adjustments on one image and then copy that to all others captured at the same time.

I prefer to leave room on the margin to allow for trimming later and to individually crop and rotate each picture (again its easy in lightroom) but if you are copying a lot of items the same you could put masking tape as location makers and then fill the frame and have the cropping automated as well.

I am pleased. Using my DSLR canon camera, mounted on my homemade copy stand and tethered to my studio computer, I can reliably and quickly get superior copies to those achieved with a flat bed scanner. By also taking a calibration shot, and photographing in RAW format and then post processing in lightroom, I can also automated white balance and minor exposure adjustments across a whole series of images. Giving me much better and consistent set of images of my art to post on-line.

The Notan Strip on my Hat

So why would I paint a set of Notan inspired grey shades onto my hat?

I’ve noticed that when I use a polarizing filter in the strong harsh light, The filter is definitely adding a warming effect into the colours and infact acting a little like a 2 or 3 stop neural density, My experience over the last couple of weeks and particularly a sunburnt nose saw me purchase a basic white floppy hat. Not a high fashion item but very useful on a hot sunny day. Then I realised that if a drop the hat to the ground and included it in at least one exposure I had a perfect reference tool to fiddle with the white balance in post processing, Adding a series of Notan reference tones hopefully will mean I don’t have to keep using my reference card, they are there on my hat.

The acrylic paints I used have, as usual darken once the dried so I may have to repaint the tones again a little lighter

PhotoEditingTools :: White Balance, When & Where

Colour correction, usually just called white balance these days, has been an issue since the earliest days of colour film. Some aspects even stretching back further into the martials used in the construction of black and films. Looking around current net explanations the need for colour compensation might be related to a technical limitation of colour film or modern digital sensor, actually the truth is they are pretty good at capturing the true light and they are getting better. The issue is the human eye (and yes a lot of this pre-processing is done at the back of the eye and on the way to the brain) is very good at accepting that a wide range of illumination is actually a “white” light source and reflection of it in the surroundings. This acceptance of what is supposed to be white is general subconscious and takes a very short time. Yet light sources (particularly artificial ones) can vary in strength and their colour profile, which can be measure on the Kelvin Scale (shown on the right), which actually an absolute measure, but it has been adopted in photography as a measure of colour temperature. These measure all very technical and somewhat theoretical but essentially different light sources emit light that corresponds to different hues (colours). A candle or tungsten globe seen in daylight will appear quiet yellow/orangish but in a room just illuminate by that light source our eyes will happily convey the image as if illuminated by a white light. The camera however will “correctly” capture the image a with distinct orangey bias. Objects that our eye saw a white will actually be orange and other colours will have excessive yellow and/or red tints. Thus the photo may look wrong.

Cambridge Colour  website has a great tutorial on the theory of colour compensation (aka white balance) as well as good practical advice, for those that want to investigate this deeper.

The best place to adjust white balance is in your camera, and this is an area you will need to consult your camera manual but most digital cameras, even the less expensive point & shoot ones will have a number of white balance options typically indicated by icons like those on the right. They normally cover a decent range of common lighting sources. What’s more AWB Automatic White Balance techniques have become very dependable in most modern cameras, so it is the obvious default setting. Older Camera phones might be the biggest exception here, particularly in low and/or artificial light. So it is worth looking at you camera settings on your phone. understanding the right setting and changing them as required could make a big difference to your low light photos taken with your phone

When It comes to RAW photos the white balance may not have to be set in your camera (ie just leave it on the default AWB) because there is usually enough information stored in the RAW file to allow the colour adjustment to be undertaken on the RAW image, Most RAW photo editors then allow the recalibration of the image to either a given Kelvin temperature, standard light sources or even a better estimate of the “as shoot” balance.

Having advised that AWB (Auto White Balance) is probably the best default I need to point out that there can still be situation that can confused the camera (ie an scene of dominantly warm or cool colours). Alternatively if you are always reaching for the warming slider trying setting your white balance to cloudy or shade.

#TheDress …as a lesson in white balance?

What a massive amount of the social web and the internet bandwidth has gone into the less than important discussion of whether #TheDress is gold and white or blue and black (or any other colour for that matter)
There is some science at play (ie most folk can see differences but are not so good at absolute colour) BUT I am amazed in the 100 or so tweets I scanned no one have mentioned the Colour Temperature of Light and/or White Balance. The original image looks ok but it has a slight blue tint and the highlights in the background are “blown out” (in photoshop jargon “clipped”). What you see depends on whether you use this clipped background as your reference white our interpret the dress background as white. I have seen the mauve/blue cast in shadows on images where the highlights are blown out many times and I reach for the White Balance (see below) but so many people are used to just looking at their (often tiny) screens in a variety of lights and screen intensities and probably desensitized to what is colour balanced and what is not.
Hopefully most photographers will notice this straight away. And fix the cast before it is published. If you don’t believe me try colour balance for yourself, you can get a copy of the image here. download it and look at it with your normal software (I’m using Picasa here and the white balance correction tool here is call Neutral Colour Picker. You click on the eyedropper and then pick a white or gray part of the image click on that and picasa then removes any colour cast. If I click on the base colour of dress notice it was warmed (added a yellow/brown cast to the background). The photographer took a photo of a white dress with gold strips, I do not doubt this for a moment.

Different software has different ways to do this and for example lightroom has the neutral tool eyedropper but it also an Auto White Balance button which is pretty reliable. A better place to start is in your camera. Get out your camera manual and work through colour temperature and white balance. Try out some of the setting and situations they are recommended. You will probably reach the same conclusion most other photographers have, set your camera to auto white balance and try to ensure the exposure is fine (no blown out highlights) Unless you think you need to do differently (ie you are shooting in a specific lighting condition with specific colour temperatures)

Postcript

Looks like I'm wrong, the whole photo must be overexposed, not just the background. The Dress is Navy & Black!

Photofriday :: Artifical Light

For PhotoFriday‘s topic Artifical Light

Purple Haze, or not so blue moon.

Looking back through some of last month photos, I was puzzled by the purple haze in my photos. i was experimenting with ISO and Aperture in manual mode trying to “just” get crisp detail in the shadows on the moon but leave the sky black. At the time I hadn’t notice the strong colour cast (it was after all dark at the time). My only thought it is a bad decision by the camera on white balance, which I normally leave set to auto (for not particular reason). Luckily there are lots of tools to fix white balance in retrospect and the one-click fix for colour in picasa fine tuning tab did the trick nicely.

PhotoProject :: Photographing your Art Works

I have seen and read a lot about how to photography your art and/or why you shouldn’t. Most of it seems wrong to me, or at least all overly complicated. There is really no reason that your should not be able to get very good results, even with a mobile phone

Keep it Simple but Precise.

It really doesn’t matter weather you will be taking the photo with a very basic point and shoot camera, a smart phone or an expensive DSLR camera. There are a few basics you need to understand to get a clear, well exposed and undistorted image. Firstly you need to make sure that the art work is well lit by even light. inside that means on a wall opposite a decent sized window and out of direct light. If outside it may be better in the shade or waiting for an overcast day. If you want to use artificial lighting make sure you understand the next section. It is important that the artwork is normal (at right angles) to the axis of the camera lens. This gives the photo the best opportunity of everything being sharply in focus and avoids much of the possible distortion. Hanging or taping the work to the wall and setting your camera on a tripod of nearby bench can help you get this right. The camera should be pointing straight at the art work not pointing up or down. I have a nifty little level that plugs into my flash hot-shoe which makes checking the alignments very easy. The autofocus mechanism of most cameras are very reliable these days especially when you are pointing at a single subject in one plane. so I would suggest you go with auto focus, usually that requires half pressing the shutter key. The other important aspect about keeping the image clear is avoiding camera movement as you take the photo. If you have your camera on a tripod or sitting on a form service is is best to use the cameras timer. If you have to hold the camera try using the fastest shutter speed (better than 1/60 seconds). The next step is upload your photos to your computer, but leave the camera and art work set up. Whilst you can preview the photo on the LCD panel on the camera back you will be able to check details better on a larger screen. If something needs to be change everything is still set up.
There is a tendency to get as close as possible to the artwork and use the zoom in to get a wider angle view, However this can distort the edges of your work (they start to look curved) and introduce depth of field issue so that while the centre of the work is in focus the edges are not. Step back a bit use and no zoom or just a little zoom in (rather than out), or better still use the prime (single focal length usually 50mm) lens are this will be the least distorted. If the side of your art work diverge you are probably not alighted with the centre of the artwork and at right angle to it. It the sides diverge out and up you viewing angle is to low. If they diverge out and down you are to high, move the camera down a little Obviously curved edges you will be too close.
Normally it is best to photograph your art without a frame (unlike my example here) and it the art work is framed behind glass you will have to deal with the problem of reflections. The can generally be avoided by angling the light source. If you are using natural light that might mean angle the artwork against the wall, but remember to also tilt the camera so the axis of the lens is at right angle to the art works surface. If you are using artificial light use two but angled at 45degrees to the art work.

Strive for Accurate Colour

Colour is probably the area that most people stumble when photographing art. The auto exposure in cameras is trying to expose everything to an average grey, art work is usually move vivid and vibrant. Colour calibrated screens are not going to help if you have the white balance wrong. White balance is an attempt to make surethat parts of your subject that are white or close to white are also white in the photo. The temperature of light is quiet deep issues, and I will skip the theory here and just comment that different light sources (particularly artificial lights) can introduce significant colour casts into a photo. Most modern cameras do have white balance settings, typically marked sunny, overcast/cloudy, Incandescant, tungsten etc according to the light source some go further and allow you to adjust by the colour temperature (specified in digress Kelvin) of your lights (better brands of flash and strobe lights will give you these temperatures). If you suspect colour matching issues it will be best to do some test shots, such as including a colour wheel in the picture and look at these photos after you have loaded viewed them on your computer screen. Leave your camera set up and if necessary, make an adjustment, take a new photo, upload it and look at it. Once you are happy remove your colour test and take the final Image.
Cameras, computer screen, and projectors and printers are not capable of reproducing the full dynamic range of light our eyes are capable of seeing. Again this a deep topic and I wont cover it here, but adding a tiny amount of contrast and saturation in post processing may help lift the colours, but keep the image looking natural, particularly for smaller thumbnails of the work.
One final bit advice of colours, is for those that want to reproduce their work as a smaller thumbnail on a website for sale. Don’t get to carried away with colour management as it likely to make your photo image look dull when the viewed on typical users screens. When you want to prompt your art on the net have a look at your photo on a variety of screens and devices (for example colour calibrated images can look very dowdy on apples new retina screen which get a lot of their appeal from their rendering of saturated colours). If you are photographing your image to have it reproduced, such as printed on canvas or art paper (or even sold via Red Bubble etc) then of course colour calibration becomes very important.

Do Not Over Post Process

Whilst it is unlikely that you will want to “publish” your photo un-edited it is wise to consider that also keeping the post processing as simple as possible with  also be import. The key steps being crop the image to the edges of your work (that normally means don’t have boarders showing), perhaps some white balance adjustment (its better done in the camera, see above), a light tweaking of contrast (raising the contrast just a little) and possibly a very little lifting of colour saturation. However be retrained, some of the “zany” filters in phone apps and the filters on web album sites can go too far and ruin an otherwise honest photo of your art, moving any of the sliders too far to the right, in photoshop, lightroom, iphoto and picasa can also undo your good work,  If there are blemishes (like dust stops) retouch them out, but do not try and retouch things in the art work. Finally consider the size to export (small thumbnails for a web site or full size, high resolution for a canvas print). You don’t need elaborate software for these steps (for example Picasa, free to download, will do all these steps) or alternatively you can look at on-line apps like Aviary.

“Da Vagues”, pastel sketch on craftboard prepared with gesso and acrylic background paint. 20 by 45cm.

The following video, from YouTube, by does go through most of theses steps is a straightforward easy to follow tutorial by Tyler Stalman, of SatchiOnline.

Removing A Colour Cast

Having been inspired by a couple of pizza recipes on MasterChef, the results were worth a photo but alas under the halogen downlights (2,700–3,300 K) there was a strong orange colour cast. These downlights have a much lower colour temperature (those K numbers) than daylight (5,500–6,000 K). You can of course use the white balance setting in your camera and set it to artificial or tungsten. However I was hungry and just took the photos as they were. Not to worry most photo editing software will have the ability to make an adjustment for such colour bias as a post process. In picasa there is the nifty Neutral Colour Picker tool under the tuning tab. Click on the little eye dropper and them click on something in your images that you want to be white or a neutral grey tone. There is part of a cook book on the left hand side so I use that, and instantly the colour bias is removed although I also used both the fill light and highlight sliders to lighten the image a bit. An appetizing pizza bianca recorded for posterity!

White Balance

White balance is one of those items well down in the setup menu and in an even more obscure corner of the manual. Few digital photographers have probably even given the setting a second thought.

In simple terms white balance is an adjustment to the colour of an image so that white objects appear white. In older cameras there where a few setting option

• Shade, when subject mainly in shade , it reduces bluish tones of the photo
• Cloudy, for cloudy days
• Fluorescent Light
• Artificial Light, (Tungsten light)

More recently cameras will have -

• Flash, when using the built in flash
• Daylight, for taking photos in strong direct daylight
• AWB (Auto White balance), the camera tries to automatically adjust the white balance. This is the softest default setting to leave your camera on

Higher end cameras may even have setting like -

• Manual
• Fine Tuning, the basic settings like shade
• K (colour temperature)

But don’t panic about always getting the perfect setting. The colour temperature of your photo can always be adjusted as a post process. The Tuning tab in Picasa has a neutral Colour picker, which lets you select a neutral gray or white part of your photo to remove any colour cast. Alternatively the little light blub beside this is a one click  fix for colour. Most advanced packages will have a similar tool.