Digital-One_Week-6[1] by arlene salisi

Week 6 Intro to Photography

File Compression

As you know, one of the cool things about a digital camera is that it will allow you to make photos of different qualities and sizes.

Most digital cameras record images in two main file formats:

You can make image files that will be suited for:

with Denni Russel

DIGITAL PHOTO I

email or web uploading

.jpeg (Joint Photographic Experts Group)

for printing without requiring much editing file compression colour space histogram metadata

or, for important shots, high quality prints that will need editing but deliver the best results

File Compression

JPEG

raw examples: .DNG, .CR2, .NES

JPEG It basically works like this:

What the heck is a JPEG?

Point and shoot cameras usually only record in the .jpeg format, although a few new cameras do have raw capture.

A group of "experts" got together and came up with a way to compress the information in a digital image that could be used by anyone on any type of computer. So, a jpeg is a way to compress a photograph into a more manageable size than if it wasn't compressed at all.

When saving a file, the computer writes code for each of those pixels so that it can recreate this scene the next time that file is opened.

JPEG sometimes writen like this: .jpeg this because it is the file type, or an extension... milk-weeds.jpeg

When saving a jpeg file the computer compresses that pixel information by taking a short cut.

JPEG

The upper right corner of this photo has hundreds of brown pixels in a row.

If you know, for instance, that you will only want to use an image you are about to make in an email, or on a website, you can tell your camera to record the image with extra compression and few pixels.

Instead of taking up lots of space writing brown, brown, brown, hundreds of times over (once for each brown pixel), it saves space by writing brown X 342.

Shooting in jpeg mode lets you choose to record images of different sizes in two ways. Firstly, by changing the amount of compression. Secondly, by the number of actual pixel the camera will use.

It has 'compressed' the image information.

It changes the compression by being more or less specific with the pixel information. Instead of writing:

When a computer opens that file it will generate 342 brown pixels in the corrdinates dictated to it.

What are your options?

JPEG 8 megapixel camera: JPEG: (1) Large/Fine: Approx. 3.3 MB (3456 x 2304) (2) Large/Normal: Approx. 1.7 MB (3456 x 2304) (3) Medium/Fine: Approx. 2.0 MB (2496 x 1664) (4) Medium/Normal Approx. 1.0 MB (2496 x 1664) (5) Small/Fine: Approx. 1.2 MB (1728 x 1152) (6) Small/Normal: Approx. 0.6 MB (1728 x 1152)

Don't worry about the RAW format yet. We'll get there...

JPEG Well, there are a few reasons. Firstly, the way information is compressed in a JPEG means that it sometimes doesn't handle subtle variations in colour very well.

JPEG As a general guideline: jpeg low or medium is good for fun shots for emailing (but NOTHING IMPORTANT!!!). Jpeg high for prints of fun shots or for those who don't want to spend time in front of the computer.

This can make the difference between a great photo and an okay photo. Secondly, lower resolution images can only be made into small prints.

If your camera has an 8 megapixel chip and you are shooting in the lowest resolution mode you might only be using 1 megapixels!

brown x3 light brown x2, etc... it might write 'brown x5'. This makes for a smaller file size, and less image subtly.

RAW: Approx. 8.3 MB (3456 x 2304)

So why don't we use .jpeg all the time?

JPEG Low resolution jpegs also use fewer of the actual pixels when recording.

File Compression Find your file compression option in your menu

Photographs are made up of millions of pixels, each with their own colour.

If you're serious about your images not using JPEG at all might be a better choice...

JPEG When you shoot with .jpeg the in-camera computer creates a processed, ready to be printed, image. The White Balance is set. The brightness and contrast levels are set. The sharpness is set. None of this can be altered later in a home computer without reducing the quality of the photo. This means that a photo is ready to be emailed or printed right away.

RAW That's where raw comes into play... A RAW file records all of the information about the scene it has captured and it doesn't process the photo in the camera. If there are 8 million subtle variations of brown in a photo the file will record each and every one - no compression! A RAW file is like a DIGITAL NEGATIVE. It allows for the highest quality images.

RAW

RAW We now know that the freedom to alter the white balance when editing photos is a HUGE benefit of shooting with .raw.

A raw file retains so much information that you can actually change your white balance settings in an editing program without reducing image quality.

RAW

But there are other benefits as well. A .jpeg file can see up too 256 different levels of brightness each for the red, blue, green channels (the camera sees these three colours). That doesn't allow for much subtly. It's easy to loose shadow detail in a .jpeg.

This means that you can capture scenes with high levels of contrast better than you can with .jpegs. Examples of high contrast scenes include: A bright white shirt in front of a dark background A silhouette

A raw file can capture up to 65,536 levels of brightness! This allows far more subtle variations in image detail.

A sandy beach with a blue sky and blue/green water

Downsides of RAW

So, why don't we shoot with RAW all the time?

Secondly, there's the burst rate.

Firstly, there's the size factor. It requires a lot more memory to capture the same amount of images as when shooting in a jpeg mode.

The burst rate is the number of photos you can take in quick succession before the camera has to stop to save them to your memory card.

Of course with the price of memory cards are relatively inexpensive these days, so it's often easy to simply buy more cards.

Downsides of RAW

RAW

Downsides of RAW

When shooting in .jpeg mode this number is significantly higher than when shooting in .raw. You'll have to check your manual to see what the burst rate is for your particular camera.

RAW Programs

In order to print a RAW file your software program has to create another file from your original. Typically this new file will be either a jpeg, a TIFF or a PSD file (we'll discuss those formats soon). Thirdly, and most importantly, EVERY RAW IMAGE REQUIRES EDITING WITH SPECIAL SOFTWARE.

Before it can create the new file, however, you have to tell the computer how you want it to look. You can edit the white balance, sharpness, brightness, contrast, colour space, etc...

You can't take a raw photo and print or email it directly from your camera. You have to edit and convert the file using a program like the one that comes with your camera, or something like Adobe Camera Raw that comes with the latest version of Photoshop, or better still, Adobe Lightroom or Apple's Aperture.

The actual RAW file is never touched. With every change you make to the image your computer writes that information down in a special 'SIDE CAR' file (a file attached to your image file). The computer then reads that special file when generating a new version without every damaging your original RAW file. Basically, shooting in RAW can be a lot of work (but well worth it!).

RAW + JPEG

TIFF and PSD

When you open a file on your computer I would suggest that you not resaving it as a jpeg. TIFF - tagged image file format Remember, every time you re-save a jpeg you lose image quality. Many cameras will allow you to shoot both RAW and JPEG simultaneously.

PSD - Photoshop Document In your editing program you will have a "SAVE AS" option. are two ways to save your files that don't compress the image. With no compression there is no loss of quality.

I'm not a fan of this option as it takes up more space on your memory card without really giving you anything all that useful.

This option will provide you with a drop down list of a number of different ways to save your file.

Colour Space

You have similar options with your digital camera.

While others only allow you to move a slider back and forth along a scale to adjust the saturation level of your image.

In the world of film you have the choice of different films that capture colours differently. Some represent vivid colours (Fuji Velvia) Others are more muted and better for skin tones (Kodak Portra)

Many cameras have specific presets to handle different colour situations: Portrait Saturation Adobe RGB sRGD

These are functions you are going to have to play with to decide what you like best. There's no right or wrong answer here. Colour is subjective! Find your colour control options...

The Histogram

The histogram is a chart that you can view after making a photograph. It looks something like this: The histogram is a very misunderstood, but exceptionally powerful tool in examining your exposures. Even though it is such a handy tool, many photographers, even the pros, don't pay very much attention to their histogram.

Most histograms deal with the brightness levels of the photo. Your camera doesn't have the ability to capture every single intensity of brightness in one shot. Most digital cameras will allow you to capture a range of 5 stops. Does anyone know what that means?

You can access your histogram by cycling through your preview options.

The Histogram The histogram lets us analyze a shot we've just made allowing us to see how the light in a scene is distributed. It helps us to see whether we've captured image detail in the highlights and shadows.

The Histogram

The histogram is designed so that the dark parts of an image appear on the left hand side, while the light parts appear on the right.

This is the photo the previous histogram represented:

The darker the image the taller the spike will be on the left. The brighter the image the taller it will be on the right. This histogram shows that the photo it represents has more mid tones than highlights.

It does this by showing us a graph. This graph shows us how many bright, mid tone and dark pixels there are in a particular photograph.

The Histogram

The Histogram Any information that touches the sides is actually beyond your camera's ability to record. Anything touching on the left will be recorded as pure black. Anything touching the right will be recorded as pure white.

The Histogram

Metadata

EXIF

There is no such thing as a good or a bad histogram.

Metadata is like your own automated notebook that keeps track of all of the choices you made for each and every photograph.

Exchangeable Image File (It was written by the Japan Electronic Industry Development Association - JEIDA)

Sometimes you might want to go to extremes... The idea is to get used to examining the histogram because it will tell you what kind of information you will have to work with.

You can add to your metadata after a shoot and you can analyze the metadata from each shot to see exactly what you did to create it.

This information includes the technical details of the shot. For example:

Metadata is made up of a few different types of information. If you make a landscape photo and the graph appears too biased towards the left, you might want to make another photograph overexposed by at least one stop. This might help you capture more shadow detail!

You have the EXIF data, the IPTC core, the File properties and Keywords to name a few.

ISO setting Shutter speed Aperture value, etc.

EXIF

Most photo editing programs let you this information.

Adobe Bridge

Study your exif data and analyze every minute detail. It will help you improve much more quickly than if you don't...

Photoshop Elements

Keywords If you plan on shooting and keeping a lot of digital photos then at some point you really should KEYWORD each and every image. A Keyword is a descriptive word you attach to a photo that allows you to categorize your images for easier image searching. For example, if you've taken a number of sunset photos over the years and each one resides in a different folder in your computer it can be difficult to find them all. If you had 'keyworded' each image finding them would be as simpl as typing 'sunset' into a keyword search box in your photo editing program.

Keywords