What are color spaces / color profiles and why are they important?
Sometimes you might read advice about using the ProPhoto RGB color space for editing. Or to make sure you convert your image to the sRGB color space before posting an image on the web.
But what's the difference between these color spaces, and why does it matter what color space an image has? How do you change the color space of an image? That's what we'll look at in this article.
First things first, there are 3 aspects involved with displaying color from a digital image. The first is the color model, this is a mathematical model that describes how color can be represented as numbers (data).
There are different color models, such as CMYK (used for printing), LAB (used for converting from one color model or space to another, sometimes used for editing), and RGB. RGB is the most common color model, used for editing images and displaying images.
Although your Lab or printer may print using CMYK, they will normally want your image in an RGB color space as well (then they will convert the image to CMYK upon printing). So, for this article we'll just be looking at the RGB color model.
Within a color model, you then have color spaces. These describe a specific implementation of how the data should be mapped to colors, based on the color model. There are a lot of different color spaces that use the RGB color model, the main ones being sRGB, AdobeRGB, and ProPhoto RGB. We'll look at these in more detail shortly.
Lastly, we have the color profile. In the case of images, the color profile is usually just the color space, embedded within the image. This way, your computer (or any other device) can tell what color space the image was saved with, and how the image data should be represented as colors on screen.
As well as color profiles embedded in images, we also have output profiles for devices, such as your monitor or printer. These describe the way that the colors will be mapped to those can be displayed by the output device. In the case of a printer you may have multiple profiles, based on the different combinations of inks and paper that can be used.
In the case of displaying an image on your screen, your computer reads the color profile of the image, and then maps the data into the LAB color space. From there, it then maps the colors to what your monitor can display, using your monitor's color profile.
RGB Color profiles
When working with your images there are 3 color spaces / profiles you are likely to come across. Each one has it's own uses. The difference between each color space is the number of different colors that can be represented.
sRGB
sRGB is a relatively small color space, i.e. it doesn't allow for a large range of different colors. However, the range of colors it does allow for is roughly equivalent to that which most monitors can display. It is also the standard default color space used by most web browsers.
The image below shows the human color range, represented by the horse-shoe shape. Inside that shape is a triangle, which represents the range of colors covered by sRGB.
Plot of sRGB Color Space compared to human vision by Dicklyon on Wikipedia (licensed CC-BY-SA)
Adobe RGB
Adobe RGB is a very common color space used for storing and editing images. It is sometimes written as Adobe RGB 1998, or can be abbreviated to aRGB. It covers a wider range of colors (has a wider gamut) than sRGB. This is what makes it more suitable for editing, and printing.
Typically most printers can produce a range of colors greater than sRGB, but mostly covered by Adobe RGB.
Plot of Adobe RGB Color Space compared to human vision (licensed CC-BY-SA)
ProPhoto RGB
ProPhoto is a large gamut color space (covers a wide range of colors). This makes it even more suitable for storing all the colors that your camera can capture than Adobe RGB. However, there are a few caveats to ProPhoto RGB, which explains why not all photographers use it.
You really need to be photographing your images in RAW format and then editing them in 16 bit to make the most of ProPhoto RGB. Most image editing software doesn't currently support 16 bit editing. (The full version of Photoshop does but GIMP and Photoshop Elements do not).
Our display devices can only display a much smaller range of colors than ProPhoto RGB allows for. So it could be argued that using such a large color space is pointless. However, having those extra colors available in the image doesn't really cost anything. And in the future, when better displays are developed, then you won't have thrown away color information that could now be displayed.
As you can see in the image below, ProPhoto RGB actually includes colors that are outside of what we can see. The large color gamut covered by ProPhoto RGB could potentially cause issues when these colors are then remapped into a smaller color space. However, this is rarely an issue in real life usage.
Plot of ProPhoto Color Space compared to human vision by Fred the Oyster on Wikipedia
Setting a color space / profile
Most cameras allow you to choose a color space as part of the image quality settings. Often they only have two choices - sRGB and Adobe RGB. These settings don't matter much unless you shoot in JPEG format.
If you shoot in RAW format, then you can choose whatever color space you want to use when converting the RAW file. Where this setting is located depends on your image software, search the help for the software if you don't know where the color Profile setting is.
Displaying images on the web
If your image does not contain a color profile, then most web browsers will display the image using the sRGB color space. Furthermore, many web browsers are not color managed, and display images as if they have an sRGB profile, even if the image has a different color profile.
This can cause problems, because it means the mapping of the colors is then wrong. How wrong it will be is dependent on how large a color space the image is actually in, and the saturation of colors in that image.
An image with an AdobeRGB profile displayed as an sRGB image will typically have more muted colors. An image in the ProPhoto RGB color space displayed using an sRGB profile will have much more muted colors. This is most obvious when you have bright, saturated colors in an image.
Below is an example of an image saved with an Adobe RGB profile. The first image has been converted to sRGB, while the second image has been assigned an sRGB profile. This is what happens when a browser displays an image as sRGB that has a different color profile.
So, it is important to make sure that you convert your images into the sRGB color space before uploading them to the web. Note that some image sharing websites may do this automatically for you, but it is best to check with them to make sure.
If you use a color managed web browser, such as Apple's Safari, then your images should appear correctly whatever color Profile the image has. The browser reads the color profile from the image, and then converts the colors to the correct colors for displaying on screen. But if you want others to be able to see your images correctly, then you should still convert your images to sRGB for web display. Most people don't use a color managed web browser.
Both Photoshop and Photoshop Elements have a handy 'Save for Web' option (File > Save for Web...). This will allow you to convert the image to sRGB, resize it, and set the level of JPEG compression all in one place. Photoshop Elements will automatically convert the image to sRGB when using Save For Web, while Photoshop has a 'convert to sRGB' checkbox option in the Save for Web dialog.
GIMP doesn't have a Save for Web feature like Photoshop does. Instead, you can go to Image > Mode > Convert to Color Profile... and then choose sRGB. After converting to sRGB you can then do a save as to save the file for web use. (Though you should probably resize the image to a small size as well if you haven't already done so).
Photoshop and Photoshop Elements also allow you to convert an image to sRGB without using Save For Web. In Photoshop Elements you can go to Image > Convert Color Profile. In Photoshop CS / CC the option is Edit > Convert to Profile. But for most photographers using Save for Web is more convenient than resizing, converting the profile, and then saving in separate steps.
Of course, an alternative to having to convert an image to sRGB is to just create the image with an sRGB profile in the first place. For some people this may be acceptable. But for most photographers, we want to capture as much 'information' (detail, dynamic range, color range) in our images as possible. Thus, storing images with Adobe RGB or ProPhoto RGB and then converting downwards for the web when necessary is worth the little bit of extra work.
Device calibration
Having a correct color profile for your output device (such as a monitor or printer) is also important. This ensures that the colors you see on your monitor or in your print will match that of the image.
Without accurate profiles, you might print an image and find it comes out with slightly different colors to how it looks on your monitor. Or you might send your image to someone else and the image could have different colors on their monitor. (Actually this can still happen if you have a calibrated monitor and the recipient does not, but differences can be greater if neither of you has a calibrated monitor).
You can generate a correct color profile for your monitor by using a calibration device. You can read more on this here: Why calibrate your monitor? Similarly, you can purchase a device for calibrating your printer. Many printer manufacturers also offer downloadable profiles that you can use.
Note that even with a calibrated monitor and printer, your prints might not exactly match what you see on screen. Although a printer generally covers a wider range of colors than a monitor can, there are some colors that are a monitor can reproduce, but a printer cannot.
Both Photoshop CS / CC and GIMP offer a 'soft proofing' option that allows you to view what the print is likely to look like. You can also activate an 'out of gamut' warning that will highlight all colors that the printer will have to remap to a slightly different color to be able to print.
To sum up:
- A larger color space allows for your image to contain a larger range of colors.
- Most monitors have a small color space, so you won't be able to appreciate the larger range of colors. You will likely be able to see a difference in print though (and possibly on screen in the future as monitor technology develops). Some monitors available today already cover the Adobe RGB color space.
- When displaying an image on the web you should convert the image to the sRGB color space, otherwise your image may display with muted colors.
- Calibrating your monitor (and printer if you print at home), then soft proofing before printing will avoid problems where the color in prints comes out differently to on screen.
- If you get your photos printed at a lab, check if they advise what color space they expect photos to be in. (Then convert your images to that color space if necessary before sending them to be printed).
Lightning Photography Tips
In the previous article I looked at the different ways you can set your camera up to capture a lightning strike. In this article I'll cover some more tips on how to get great lightning photos.
Ka-boom (lightning) by Leszek.Leszczynski on flickr (licensed CC-BY)
Safety First
There's not much point trying to get a great lightning photo if you get fried by a lightning strike in the process. Even if a lightning strike doesn't kill you, it can leave you seriously disabled. So it is very important to think about your safety.
Lightning can strike out up to 10 miles from a storm. As a general rule, if you can hear thunder, then you can be hit by lightning. The closer to the storm you are, the greater the chance of being hit. It is recommended to always keep at least 6 miles away from the storm.
OMGIALMOSTDIED by J.J. Verhoef on flickr (licensed CC-BY)
Because sound travels more slowly than light, you can count from the time of a lightning strike until you hear the thunder to calculate your distance. Each 5 seconds that passes between the lightning and the thunder is 1 mile. If you are 6 miles away, there should be 30 seconds between the lightning and the thunder.
Ideally you should photograph the lightning from a safe place. This can be a building that is grounded (has wiring or plumbing that goes down into the ground). Or it can be a metal topped (and bodied) car.
Wham! by Karsten W. Rohrbach on flickr (licensed CC-BY-ND)
Keep the camera steady
No matter what method you are using to capture a lightning photo, your images may suffer from blurring caused by camera shake if you are hand-holding the camera.
If you're shooting from a car, then you can buy a window clamp. This clamps onto your open window, and has a mount on top that you can attach your camera to. This provides a stable platform for the camera that will prevent the image blurring from camera movement (unless you bounce up down in the car while the photo is being taken).
If you're shooting from a building, or somewhere safe in the open, then use a tripod, wall, or ledge to keep your camera steady. Note that if you're out in the open, a tripod can act as a lightning conductor.
Lightning by veggiefrog on flickr (licensed CC-BY)
Camera settings
Exposure settings are mostly determined by the light levels and whether you are using a long exposure to capture the lightning strikes. So there can't really be any recommended settings, though I will give some suggestions you can use as a starting point.
For a lightning shot you typically want most of the image (particularly the sky) to be quite dark. This ensures that the lightning will stand out and contrast strongly against the rest of the image.
To take control of how the image will look, I would recommend using Manual Exposure mode. Generally you will want to use your camera's base ISO setting (normally ISO 100 or 200). This will reduce image noise and allow for a longer exposure time.
Spring Storm at Buenos Aires by lrargerich on flickr (licensed CC-BY)
An aperture setting of around f/8 - f/11 should give a sharp image. It also reduces the amount of light reaching the camera's sensor, allowing for a longer exposure.
Shutter speed should normally be as long as possible to increase the chance of capturing a strike or multiple strikes in an image. As with the other exposure settings, it depends on the light levels and the look you are going for, but 30s is a good starting point.
Rayo de Zeus / Zeus's Lightning - Tepic, Nayarit, MEXICO by Christian Frausto Bernal on flickr (licensed CC-BY-SA)
For focusing, it is best to switch the camera to manual focus, so that it does not try and refocus each time you take a shot. You can focus the lens first using autofocus, then switch to manual focus to lock the focus in place.
Or you can focus the lens manually. In this case, since the lightning will be several miles away (or even if it's only half a mile away), setting the focus to near infinity will give best results.
Camera power
Most of the methods used for photographing lightning (other than the Lightning Trigger) use a lot of energy. So it is a good idea to make sure you have enough power for your camera.
If you're working indoors, you might consider connecting your camera to the mains power (using the appropriate adapter). But this could be rather risky as a power surge caused by a lightning strike could then fry your camera. Even if you have good surge protection in place, it likely still won't protect against a direct lightning strike on or near your house.
If you're working outdoors, make sure you bring a spare battery. If you're planning on setting a camera up outdoors and then leaving it to photograph the storm while you retreat to safety, then a battery grip would be a good idea.
Battery grips are available for most DSLRs and some other interchangeable lens cameras. They allow the camera to run on two batteries instead of one, so the camera will last twice as long until the battery runs out.
Lens / Focal length choice
Composing your photo can be rather difficult, since you can't know where lightning is next going to strike. A telephoto lens has a small field of view, which will give a nice large image of any lightning strike. But because the field of view is small, there is only a small chance that lightning will strike where you have the camera pointed.
Electrical storm over Brisbane by Richard.Fisher on flickr (licensed CC-BY)
A wide angle lens, on the other hand, has a much larger field of view. This means that any lightning strikes captured will appear smaller in the image. But you also have a much greater chance of capturing any strikes in your image.
Composition
For a good lightning photo, you want to fill the majority of the frame with the sky. This is, after all, where the lightning will happen. However, it is also a good idea to include some foreground interest as well.
Lightning storm over Berlin by Matt Biddulph on flickr (licensed CC-BY-SA)
If you can frame the photo so as to include the point where (or near where) the lightning strikes, this can really show the scale of the lightning.
Capturing multiple strikes
A single long exposure photo may be able to capture multiple lightning strikes in a single image.
Marden lightning by Elsie esq. on flickr (licensed CC-BY)
But if you are taking multiple shorter exposures rather one single long exposure, you can still merge the images to create the same effect.
You will need to have used a tripod or other form of support so that the camera position is exactly the same for all the photos. Load the photos into your image editing software, such as Photoshop or GIMP, and add them all as layers to a single document.
Set the blend mode of each layer (image) except the bottom layer to 'Lighten'. Only the parts of each layer that are brighter than the layers below will show through. Since the only part of each image that should brighter than in the other images will be where a lightning strike was recorded, you end up with a single image combining the lightning strikes from all the images.
How to photograph Lightning
Storms that generate lightning aren't something that you see every day. But when you do get a thunderstorm, the flashes of lightning can make for some spectacular photos.
Eclairs by ComputerHotline on flickr (licensed CC-BY)
There is one obvious difficulty with Lightning Photography. The strike happens so fast that there is no way you can press the shutter button of your camera in time to capture a strike when you see it. Thankfully though, there are a number of different ways you can work round this.
Long exposure lightning photography
The most common method of lightning photography is simply to use a long exposure. Any lightning strikes that occur during the time the camera's shutter is open will be recorded in the image, so you don't have to worry about timing your shot at all.
Ride the Lightning by Owen Zammit on flickr (licensed CC-BY-SA)
The length of the exposure really depends on the light levels. If you're shooting in the evening or at night time, light levels will be pretty low. This should allow you to use a shutter speed of 30s, or use your camera's bulb mode for even longer exposures.
During the daytime
During the daytime it gets quite a bit darker when a thunderstorm hits. But it is not normally dark enough for a long exposure. To get around this you can use a neutral density filter in front of your lens to reduce the amount of light that reaches your camera.
For An Instant by muntoo on flickr (licensed CC-BY)
This will allow you to use a longer exposure time. Bear in mind though that the neutral density filter will also reduce the amount of light from the lightning that will reach your camera. So you may end up with strikes that don't record as brightly as they would with one of the alternative methods below.
Continuous Shooting
Your camera's continuous shooting drive mode allows you to take a continuous stream of photos, one right after the other. So by holding down the shutter button during a thunderstorm, you can take a lot of photos, and you should be able to capture any lightning strikes.
Lightning over Short Hill Mountain by kcdsTM on flickr (licensed CC-BY)
There are a few different problems with this method though. First, you will have to sort through a lot of photos just to find the one or two that contain a lightning strike.
Another problem is that most cameras have a limit on the number of photos that can be taken continuously. If you use RAW format for saving your images, then you may only be able to take a few shots before the camera's buffer fills up. Then it will need a bit of time to move the files to the memory card before you can take any more shots.
This issue can be worked around by using JPEG format for saving the images. Turning down the quality settings and image size settings will also result in smaller files, which means you can shoot more images in a continuous stream without problems.
There is also the possibility that lightning could strike in the short time between the camera finishing one photo and starting the next photo. While this is not very likely, it is a possible disadvantage compared to using a long exposure.
Use an intervalometer
The use of an intervalometer is very similar to (and has the same problems as) using continuous shooting. With an intervalometer you set your camera to take photos continuously with a user specified delay between each shot. This technique is normally used for timelapse photography, but it will work for lightning photography as well.
This is how Belo Horizonte says “hello.” by Marcin Wichary on flickr (licensed CC-BY)
Some camera models have a built-in intervalometer. For other models you need to purchase one as an additional accessory (they plug into the camera's shutter release cable socket).
Lightning Triggers
A lightning trigger consists of an optical sensor that can detect the flash of a lightning strike. As soon as it detects lightning, it triggers the camera to take a photo.
An example of a lightning trigger is the appropriately named Lightning Trigger. The benefit of using a trigger is that it will work with short shutter speeds, allowing you to capture lightning during daytime thunderstorms.
Because it only fires the camera on a lightning strike you will also end up with much less photos of empty skies to sort through. The disadvantage is, of course, the additional cost. If you are a storm chaser or live in an area where thunderstorms are common, the cost may well be worth it though.
Motion detection
Similar to a lightning trigger, some cameras can automatically take a photo when they detect lightning. This ability varies between camera models, so you will need to check whether it is possible for your camera.
Some Canon compact cameras can have the ability added through the use of the CHDK firmware enhancement, which adds the motion detection feature. You can read more about it here: CHDK Wiki: Lighting Photography done automatically with Motion Detection.
Electricity in the Sky by Andreas. on flickr (licensed CC-BY-SA)
Similarly, Canon DSLRs don't have a built-in motion detection feature, but can have it added via the Magic Lantern firmware enhancement. You can read more about this here: Lightning Photography with Magic Lantern.
You may need to experiment a bit with the motion sensitivity settings to get the right amount of sensitivity for capturing a lightning strike. But after that you can leave the camera to take photos automatically whenever there is a strike.
While this method is much cheaper than using a lightning trigger, note that it will use up your camera's battery a lot faster. And for some camera models, a motion detection feature may not be available at all.
In the next article I'll cover some tips on safety when photographing lightning, other camera settings, and what sort of focal lengths work well for lightning photography.
How to use a green screen to put a different background behind your subject
Have you ever wanted to extract a subject from one photo and then place them in another photo? For example, taking a photo of your child in their sports kit, and then making it look like they're playing in a full size stadium.
This process of mixing images together is known as compositing, and is becoming increasingly popular. While it might sound difficult, it can actually be very easy. The trick is taking the photo of your subject against a background that makes it easy to extract the subject from the background.
Private School Girl by "PictureYouth" on flickr (licensed CC-BY)
For this purpose a green screen (also known as chroma key) background is often used. In this article we'll look at how to take a photo using a green screen, and then how to use photo editing software to remove the green screen and composite the image.
Read the rest of this entry »What is Bokeh?
Bokeh is a word used to describe the out of focus areas of a photo. It does not really mean how out of focus an area is, but rather how the out of focus areas are rendered.
A Cup of Bokeh, please? by Shermeee on flickr (licensed CC-BY)
You will find that some people are very particular about bokeh, while others aren't really bothered. Just like one person might love a particular photo, while another person might think it is nothing special, the bokeh characteristics of a photo can be quite subjective.
Camera lens reviews, particularly those in Japan, now often include photos with out of focus areas particularly so that viewers can judge the bokeh.
Read the rest of this entry »Photographing Reflections
Photographing reflections can be a great way to add interest to your images. When you have a shot of both a subject and their reflection, it helps emphasize the subject. In some cases you might want to make the reflection itself a subject. And reflections can also work well for abstract photography.
Dynamic Serenity by papalars on flickr (licensed CC-BY-ND)
Is it possible to post-process photos automatically?
Post processing describes the act of editing a photo. Making adjustments to the color, contrast, sometimes to the crop. In fact the adjustments that can be made are practically limitless. It is known as post processing since it is carried out after (post) the image was captured.
i don't know but today seems kinda odd by spaceabstract on flickr (licensed CC-BY)
Making adjustments to each image you take might seem like it would take a long time (and depending on the adjustments, it can). So you might be wondering if there is some way to apply post processing to your photos automatically. That would cut down on a lot of work for you. So, is this possible?
Read the rest of this entry »What are step up and step down rings?
Many cameras allow you to screw a filter onto the end of the lens to achieve a certain effect. For example, one of the most popular filters is the polarizing filter, used to reduce reflections and glare, and to enhance colors and contrast in landscape photography.
When you purchase a filter, you need to make sure that it comes with the correct size threads to screw onto your camera's lens. Different cameras and lenses have different filter thread sizes, and filters are also available in a wide range of different sizes.
The problem comes when you have a filter in one size, but your lens has a filter thread of a different size. This can easily happen when you upgrade from one camera to another, or if you buy more than one lens. To solve this, you can use stepping rings.
Pile of step up and step down rings
How to take great photos of boring subjects
Most of us don't live in areas surrounded by beautiful vistas. We don't have a list of models (or willing friends / family) that are happy to pose for use whenever we feel like some portrait photography. And you might feel that you don't really have anything interesting around you worth photographing at all.
While a beautiful location or model can make getting a great photo easier, they're certainly not essential. In this article we'll look at taking great photos of boring subjects.
Read the rest of this entry »What would be a good basic lens kit?
What lens should I buy?
is probably one of the most commonly asked photography questions by those with interchangeable lens cameras. Unlike cameras, where differences between different models tend to be fairly minor, the differences between lenses can be quite large.
Lenses can be quite expensive as well, sometimes you may pay more for a new lens than you do for the camera itself. While you may replace your camera body in the future, lenses don't often get outdated, and so should be considered more of a long term investment in your photography. So it is a good idea to think about whether you really need a particular lens before splashing out on it.
Camera and two lens kit
Ultimately, what lens to buy can only be decided by you. A good lens kit depends on the kind of subjects you like photographing, your budget, and even your style of photography. However, there are a number of things you can think about to help you in making a decision that will provide the most Bang for your buck.
Read the rest of this entry »
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