Post-Processing: Sharpening

In this article, I wanna show you an easy but essential post-processing technique: Sharpening.

Why do images need to be sharpened? Because of the digital sensor's nature areas with high contrast, like edges, are not recorded properly. This is because every pixel records only the average light that hit it and not the exact pattern. When a pixel in the sensor records an edge it won't record half a pixel black and the other white but will only record a grey pixel. I know this is a very simple explanation but getting into this topic would take a lot of time and all we want to do today is learn how to sharpen images, so how is it done?

Sharpening is something most comeras do automatically after taking a shot. In point and shoots the sharpening is usually enough, allowing the user not to post-process the image at all.
DSLRs though are designed for advanced photographers who want more control over their results. This is why they're configured to do a much softer sharpening in Jpeg and no sharpening at all in RAW files.

This configuration gives the end user the widest range of possibilities, because a sharpened image can not be desharpened, while an unsharpened raw file can be sharpened at will afterwards. Now we're going to take a look at how it's done.

If we're processing a RAW file in Lightroom or Photoshop the process is slightly different but the adjustments required will be the same. In this example I'm going to use photoshop.

Once you're done editing your image (sharpening should be performed the last), go to filters->sharpen->unsharp mask and you'll find something like this:

The first setting is amount. This determines the amount of contrast this filter will add in the borders. The higher the setting the more aggresive the sharpening will be, be careful though because it will come to a point where the image start to look odd.

The second setting is radius. This determines how many pixels around the borders will get the extra contrast treatment, same as before, the higher the setting, the more aggresive the sharpening.

The third setting is threshold. This lets you preserve smoother areas of being sharpened as well as the sharpening of noise. However this setting will affect the general sharpening negatively so i would preserve the smoother areas and the noise more selectively, by copying it to another layer for example. My advice is keep this setting low

As to the other 2 values there is no setting I can recommend you that will work on every image. You'll have to find out yourself which is the best for your shot. To do that start by raising the amount to around 400%. Then tweak the radius until the image is sharpened without visible artifacts, like halos around the sharpened objects. Keep in mind that the higher the resolution of the image, the higher the radius value has to be. Once you find the adecuate radius, lower the amount to a more reasonable value.
You can view the results in the small preview window or on the normal photoshop window. Keep in mind though, that to view the sharpening effect properly the image should be displayed at 100% or 50% zoom to avoid issues with aliasing of the images.

I set amount at 94% and radius at 1.8 and threshold at 4

I selected such a small radius for 2 reasons. First this image was at 6Mp which is not a very high resolution. Secondly there were small subjects with high contrast against the snow like the brown bushes, that would give a strange look if the sharpening radius was bigger than the details themselves, this something you will just realize when you try sharpening an image yourself.

These are my results

Before

Full image:
Before: After:

100% crop

Before: After:

As you can see the sharpened images have clearer details, which gives them a more realistic and "professional" look, while the unsharpened ones have a hazy effect, making them look unrealistic.

Tip: If you've read through this tutorial and found sharpening is way too complicated, you can always set you DSLR to sharpen the images automatically, which is done differently depending on the camera. Doing this, however, will give you much less control over the sharpening and can result in badly sharpened areas. What I recommend, as always, is shooting in Raw and then applying Lightroom's default sharpening settings, if lightroom gets it wrong you can effortlessly change the settings and the photo won't be ruined as would happen with in-camera sharpening.

Summing up I would say that sharpening is an essential post-processing effect, that should be performed on every image. I recommend applying a default sharpening filter in lightroom for your regular workflow and tweaking it when there is a special shot you want to sharpen perfectly or the lightroom's adjustments don't work well.

Shooting silhouettes

In our last post, I mentioned that we could create silhouettes in a very easy way, just by using the central spot metering mode . Now I'm gonna show you how to create this effect that can give such a distintive touch to a photograph.

What is a silhouette? A silhouette is created in the limit between an underexposed and a normally exposed area. This means that to create a silhouette we will need a source of light behind our subject that makes it darker than the rest of the scene, like in the example above.

But having that source of light won't create this effect by itself. If we use matrix metering mode (default mode) the camera will try to expose the whole image properly, spoiling the silhouette effect. What we want is the camera exposing properly for the lighter areas only, leaving the rest underexposed to create the silhouettes. To do that we will use central spot metering mode, you can read infomation in more depth in the last article, but basically you want to center the source of light in the frame and then use the AutoExposure-Lock button to tell the camera to expose properly for that lighter area. The darker zones will automatically be underexposed, creating the silhouette effect.

This technique is not very easy to use and will probably require some practice from you, but once you are used to finding light sources behind your subjects, you will be able to create very nice silhouettes.

TIP: As with many effects in digital photography, this one can we created in Photoshop too, so if you can't get to shoot silhouettes or you just don't get them perfectly, you can tweak them later on the pc. Here's how it's done in Photoshop

• Open your image

• Go to Image->Adjustments->Levels
• Take the lever at the lower end of the brightness range and shift it to the brigther areas, like in this screenshot

• Once the areas you want to silhouette are dark enough, click ok.
• That's it, this is what it will look like now.

Note: This only works if the shot was taken with a light source behind and has already some silhouette effect. If the shot has none of that effect you'll need to select the area you want to silhouette (I recommend using quick mask mode, pressing Q) and then repeat the same procedure.

And that's it for now, I recommend you not to take the easy way and try to take the silhouettes straight in the camera, but if not you can always cheat your way to perfection :D . Experiment and have fun

Understanding Metering modes

In our series of articles about "Mastering the basics" we learned about the different settings to use to get the right exposure, but we never talked about the way we metered available light.

Now, we're going to take a look at the camera's metering modes.

Every modern camera has a sensor that measures how much light is getting through the lens. In most cameras we can chose how we want the camera to do it. There are 3 different metering modes:

Matrix metering: The most used of all modes, the camera measures light from all points in the scene, and attemps to set the exposure in a way that the whole scene is properly lit.
This is a very easy to use and effective metering mode because the largest possible part of the image will be properly exposed. Similarily to the auto mode, though this metering mode has its limitations when we want to have some advanced control over the resulting image.

Center weighted spot metering: This mode comes in very handy when shooting differently lit scenes. Imagine for example, that you're shooting at a concert. The whole scene is dark, except for the performer in who is lit by spotlights. Using the matrix mode, the camera will try to expose the biggest part of the scene, as a result the preeminent darker zones will be properly exposed, while the performer will be overexposed. This will be in many cases far from the ideal result. In these situations we'll use the center weighted metering mode, now the camera will prioritize the area in the middle and expose properly for a portion of approximately 25% of the image around its center.

Photo by sint

Central spot metering: This is the most selective mode, the camera will expose properly for a point situated in the exact center of the image. The rest of the scene will not be taken into consideration. I do not recommend this mode in most of the cases because light can change a lot from one point to another and the readings won't be very useful if we use one point only. It can be a good mode to use if we want to select an exact point for the camera to expose properly though which can be useful for example for creating silhouettes or for complicated light situations.

Now, when you read about the last two metering modes you were probably asking yourself, what about the framing? What if I want the performer in the concert to be properly exposed, without framing him in the middle?

Well, camera designers were aware of this problem and that's what the Auto Exposure Lock button is for. Most DSLRs have this button that allows you to lock the exposure settings once your camera has taken the light readings and adjusted its settings accordingly. This will allow you to take the light readings from the performer by placing him in the center and then, with the AE-Lock button pushed frame the shot as you want to.

Summing up: Center weightered and center spot metering modes, allow you to chose the part of the image you want to be correctly exposed, while matrix metering mode will try to have the whole image exposed properly.

Shooting star trails

In our last article we learned how to shoot all kinds of light trails, now we're going to take a deeper look at how to shoot star trails.

First of all. What are star trails?

When you look at the stars at night, they seem to be stuck, but if you stare for a couple of minutes you'll start to realize that they're moving, only very slowly. This effect is created by the earth's rotation and not by the movement of the stars themselves. Every star in the sky makes a whole turn around the pole star. This particular one is right in the axis of the earth's rotation and this causes it not to move in the sky and always head north, that is why this star has been used by travellers thousands of years ago to guide themselves in the night, yes I like science :D but we're moving away from our main topic.

What is the effect of this motion when we shoot stars at night?



If we shoot stars with a shutter speed long enought to capture this movement, the stars will create trails in the form of circles around the polar star, decorating our shot with a very interesting sky.

How do we set up our camera to achieve these results?

This will be a little more complicated than with standard light trails. First of all you will need a remote control, or any other device that allows you to use the bulb mode of your camera. Setting up the maximum 30 sec exposure configured in your camera won't be enough to capture the star's movement.
To set up bulb mode we'll need to go into manual. Se the ISO to minimum, aperture preferably to a high value and shutter speed to bulb mode. Set the focus to manual and focus on infinity.
I also recommend using a long focal length because stars will appear to move faster when the lens is zoomed in.

And this is it, you can start to experiment with different compositions and shutter speeds, keep in mind however that very long shutter speeds will create too much noise in the image, remember turning the noise reduction function of your camera to minimize this effect. If you want to have longer trails, you can create a series of relatively short exposures and then blend them together in photoshop.



It is important to be able to identify the pole star, since all the stars will turn around it, making it a strong subject of your composition. To find it look north and find a very bright star.

And last but not least, keep in mind that this kind of photography works best at clear skies without luminic contamination, so run away from big cities.

Photographs by Corica, Warner Strauss and me.

Creating Panoramas

When we see panorama pictures we tend to think that these are taken with very specialized equipment. While this might generally be true, there are very easy ways of creating our own high resolution panorama with only a point and shoot camera or even a camera phone.

In this post. We,re going to learn how to use Hugin, an open source program, to create our own panoramas.

First of all we have to take the pictures. You need to take several pictures, as many as you want, that overlap themsleves partially on the sides, like this:



The overlapped area doesn't need to be as big as in the example, it will be enough with overlapping 30% of the image.

This will help the software find similarities between the images in order to stitch them together properly.

Now we will install the program. Download the installer from here. Once the program is installed, launch it and load the images you want to use for your panorama. Click on the load images button. Once you have selected the images, the program will start to align them automatically, if not click on the align button. This process may take some time depending on your computer and the size of your images, once it's finished you'll be presented with an image like this:



You can adjust the margins here so that you've got no black background, but I recommend you fix this in photoshop or any other editing program later. When finished close this window.

Now you only have to click on Create panorama. Select the folder and filename and you're done. Hugin will automatically stitch the images together and blend the margins making it look as a single image. When the process finishes, as before this may take some time, you'll have you image saved in .tif format.

Open it in your favourite editing software, cut off the black areas and you'll get something like this:

As you see this tecnique requires no special equipment and is very easy to learn. You can use any shots you want even those from a camera phone if the quality is enough. This is what I got from a couple of shot taken with an N95.

If you want your image to be of even higher resolution you can take the shots vertically, which will allow you to use more shots to put together the same field of view. This example is made with 5 vertical shots put together.

So, as we've seen it's very easy to create your own panorama shots by just shooting consecutive images and then stitching them together on the pc. Next time you go shoting landscapes, give it a try!

Shooting in RAW

When I was thinking about this post I was considering making it a RAW or Jpeg post, but after giving it some thought I think to me this question has a definite answer.

Shoot in RAW



Ok so why do I have such a firm opinion on the question?

Well, first of all let me introduce you to the topic.

RAW and Jpeg are 2 different image formats implemented on most modern DSLRs. We can configure our camera to store the images in RAW, Jpeg or both.
Now, what are the advantages and disadvantages of both filesystems? We'll start out analyzing how Jpeg works. When your camera captures an image configured in Jpeg it doesn't save what comes straight out of the sensor, instead it applies a series of automatically adjusted "filters" that adjust contrast, saturation, white balance etc. After that the camera compresses the image almost without losing quality and then saves it to the memory card.

The way the camera handles RAW files though is pretty different. When configured in RAW the camera will save the information coming out of the sensor without applying any further adjustments to the image.

Of course this lack of post processing and compressing has some issues. RAW files need specialized programs to be opened, like lightroom or picasa, but if you're a serious photographer you'll want to use one of those programs anyways so that isn't a problem. If you still consider this an issue you can always shoot in RAW+Jpeg so that you have a Jpeg copy of your RAW just in case you want to open it with other programs or in other devices other than a pc. Also shooting in RAW will occupy more space on the memory card, but with today's memory card storing 8gb at very reasonable prices I don't think this could be an issue.

Now back to the question at the beginning. Why do I encourage you to shoot in RAW?

The answer is simple: You're smarter than you're camera. (Ok most of you)

When you shoot in Jpeg your camera will automatically adjust a lot of settings according to its preferences, if you shoot in RAW instead your camera and developing program will only suggest the settings used but you will be able to adjust every one of these yourself. During this process you will be able to see how any of these changes affect the end result allowing you to adjust the processing to your very own taste.
This may sound like it's a feature only image enthusiasts would like to use but, trust me, it comes in very handy at shots where your camera's metering is fooled by special lighting conditions rendering it unable to create a decent image.

So all in all, shooting in RAW doesn't slow down your workflow in any way and it does give you a lot of options to adjust shots to your exact taste or to fix shots the camera didn't get too well.

Have a different opinion? We all can learn from each other, feel free to post a comment about it!

Camera modes

Now that we know the effects that every setting has on our image, we're going to learn how to tweak those settings in our camera's menu. It is possible that your camera has a different menu system but usually all DSLRs have the options I'm going to talk about.

Auto: Not much to say about this mode. It is fast and useful for the times where you just haven't got the time to think about the settings. The camera makes all the decisions about the exposure and even the metering modes, but now that we've learned how to use every of those settings, we want to have control over them, right?

P mode: This one is similar to auto mode, you set the ISO and the camera will automatically set the shutter speed and aperture for the shot. Also P mode allows you to control the metering modes, something we will talk about in future articles

Shutter Speed priority: This is were we start to take control of the settings, this mode will allow us to set the shutter speed and ISO we want and the camera will adjust the aperture to match the available light. Very useful for taking action shots or for playing with motion like we saw in the article about Shutter speed.

Aperture priority: This mode allows us to control aperture, and ISO while the camera will take care of adjusting the shutter speed. This mode is very useful for taking control of the depth of field like we saw in the article about aperture.

Manual: This is the mode, where you control everything. ISO, shutter speed, aperture, metering modes, white balance... .This might sound like it's the ultimate mode to use once you understand every setting, but in my opinion this mode makes it too difficult to get a correctly exposed shot, since it will be you that will have to tweak every setting until you get the correct amount of light. There are moments though where this mode will be the only option, like when you want to use the bulb mode of your camera. This mode allows you to have the shutter open for as long as you want and can be helpful for making very long exposures, like in star trail shots.

So, you will be asking yourself, which mode should I use?

The answer to this question depends on your skills and the situation you're in, as i said before you can use auto mode if you want to take a photograph quick without losing time on adjusting the settings, but the rest of the modes will give you more control over the shot.
I personally find myself shooting usually with P mode that allows me to control the ISO so that the camera doesn't accidentally bump it too high ruining the shot because of the noise. When i want to use some of the exposure settings creatively I just go into aperture or shutter speed priority mode, since they're much easier to use and will give you identical results to the manual mode.
Sometimes you'll just need to use the manual because the camera won't be able to get the shot exposed like you want. Don't be afraid of using it now that you know what every setting does, do keep in mind though that it will probably take some time to get the shot properly exposed. But hey you're doing this just for fun right? Just take your time and enjoy experimenting!

Mastering the Basics: Understanding Aperture

After having learned about shutter speed and ISO settings, now we're going to take a look at the aperture.

The aperture setting is the size of the opening in the lens.

Every lens has a couple of blades, called iris, that are put together to regulate the light that gets through, depending on the aperture setting used.

The aperture is indicated in the camera as the f number. A high f number will represent a small aperture while a small f number will represent a big one. This might sound counterintuitive but is easier to understand if we imagine the f number in the formula 1/f. The higher the f number the smaller the end result.

But enough with the technical details, what is aperture good for?

Tweaking the aperture settings will not only control the light intake, but will also control the size of the depth of field (In short, the depth of field is the part of the image that is in focus). This will allow us to use the depth of field that we find appropiate for our shot. Imagine for example that we are taking a portrait picture. We want everything in the background to be out of focus, so that it doesn't distract from the main subject. In order to achieve that we will use a small f number, that will result in a big aperture, creating a shallow depth of field.
If we were shooting a landscape for example we would do the exact opposite so that all the parts of the image stayed in focus.

The maximum aperture setting will depend from each lens and is an important factor to have in mind when buying new gear, prime lenses, those without zooming possibilities, are the ones which allow higher apertures. It is easy to find cheap prime lenses allowing for f1.8 apertures and more expensive ones even allow for f1.4 or f1.2. Zooming lenses instead have smaller apertures and their maximum aperture varies depending on the focal length used. The 18-55mm kit lens from the D40 for example will allow for a f3.5 aperture at 18mm but only f5.6 at 55mm. Zooming lenses with bigger apertures are only found in the professional level and are used by sport photographers for being able to capture fast shots even in low light.

Summing up, rising the aperture setting will let in more light while making the depth of field smaller and the maximum aperture depends on the type and the quality of the lens.

Mastering the Basics: Understanding shutter speed

In my last article I mentioned how tweaking every setting to get the correct exposure had it's pros and cons. The first setting we're going to take a look at is Shutter speed.

The Shutter speed is the amount of time that the camera's sensor is exposed to light.

This simple setting has a great impact on the end result of the photograph. Using a fast shutter speed will freeze the moment, while a slow one will capture motion in the shot.
Keeping this in mind is very important because we will need to change this setting often depending on the type of photography we're doing. A classic example for this is sports photography. At sports events we're often photographying fast moving subjects, so we will need to set a fast shutter speed to capture the moment.
Sometimes though we will want the photograph to show the movement in the scene. Using a slow shutter speed moving objects will be blurred giving the viewer a sense of speed.

The problem with slow shutter speeds is that it's difficult to hold the camera completely still, so at certain speeds the whole photography will become blurred.

Sometimes we will need to use a slow shutter speed because there isn't enough light available even when rising the ISO and aperture. When this is the case it is very useful to use a tripod that will allow us to have the camera completely still during the exposure of the shot. Using a tripod will also allow us to use very long shutter speed to create interesting effects like light or star trails, which we will talk about in further articles.

Mastering the Basics: The Exposure Triangle

Before we go into more advanced aspects we have to master the basic aspects of photography. The first concept to understand is the exposure triangle.

The exposure triangle is a representation of the 3 settings that will determine how much light reaches the camera sensor.

It consists of three elements.

ISO: The sensor's sensitivity to the light
Shutter Speed: The amount of time the sensor is exposed to light.
Aperture: The size of the opening in the lens that lets light in.

An easy way to understand this is to imagine a hosepipe: The aperture is the width of the pipe, the shutter speed is the time the pipe is open and the ISO setting is the pressure.

As you can imagine from the example above, there are several possible combinations that will let in the same amount of light, like for example increasing the shutter speed and then compensating that by decreasing the ISO setting, something common for night shots.

When we use the auto mode of our camera, it will automatically chose a combination to let the correct amount of light in, but while the amount of light will probably be correct, the combination used may not be the best one to get the results we expected from the shot. This happens because each of the combinations has its advantages and disadvantages that will depend on how and what we're shooting. If we want to be able to chose the combination of settings ourselves we will have to take a look in greater depth to each of the three settings: ISO, shutter speed and aperture, which we will do in the three upcoming articles.