Thursday, June 19, 2008

RAW vs BMP

Many who are new or have transitioned into the digital age of camera technology prefer to backup their precious images, but completely untouched and of the highest quality. With the amount of storage available today there is no need to compress your images unless you plan on distributing them throughout the internet or through storage media with low space. Even though the quality on most compressed images is adequate, when it comes to editing an image it is best to have it in its best quality. There are really two options available to have an image in its “pure” form, RAW or BMP.

First of all the term RAW is not an image format, contrary to the belief of some. An image format has to be standard and supported by different programs. Secondly, there is no RAW standard as different camera manufacturers tend to have their own RAW formats. The beauty of RAW is that there is absolutely no processing involved and instead of an image you get the state of an image according to the cameras’ sensor. If you compare it to a negative used in analog photography it makes more sense. A negative is a state of an image with no defined value. In a digital image every pixel is accounted for and all elements of that image are finite. With a negative (and RAW) the maximum amount of information of the image state is available to you. Get it? Aside from the size, one major downside to RAW is that most of the state information that represents an image is unusable. Things such as color, brightness go beyond what a computer is able to process and therefore what the human eye can portray.

As soon as an image hits the digital domain it has to be represented in the form of binary data. No matter how much binary data is used to represent an image there will always be a loss of data and the exact representation of that image will differ from the original thing. This is why many will not move into the digital domain and prefer to stick with their analog equipment because the images produced are more exact. The good news is most cannot tell the difference between a digital and analog version of an image while the rest just don’t care. The best method to store an image digitally has been in the form of bitmaps, such as what is used in BMP files. In general a bitmap is nothing more than a mapping of the bits of an image in a b-dimensional array, where b is defined by the bit depth. Bit depths range from 1 to 64, with 24 bit being the most commonly used as anything higher really doesn’t result in better image quality. Bit depth can be associated with color depth so it makes sense why higher depths don’t make a difference since the average human cannot perceive billions of colors. Bitmaps are not compressed and represent the image to its fullest. There are a few common bitmap formats, all of which follow the same practice of digital image representation. The Microsoft BMP standard happens to be the most common. There are many benefits to BMP, such as compatibility and quality. One notable downside to BMP would be file size, even though there is a compressed BMP standard which I do not recommend using.

So which format should you use to backup your digital masters? I recommend storing all of your images in BMP format and skipping RAW altogether. The major reason for this which I didn’t mention above is compatibility. I stated BMP was a very common format used by most operating systems, but the opposite is true for RAW. Usually you need to use a proprietary program provided by your camera manufacturer to read the RAW files and you can expect them to be very basic with very little, if any, editing features. If you decide to get a new camera you may find that it uses a different RAW format, so all of your older RAW images will be incompatible. I mentioned that size is fairly large with BMP files, but compared to RAW they are smaller. Some RAW formats are encrypted and cannot be read by Adobe Photoshop. So when you need them they need to be converted with proprietary software or worse yet, transferred back to the camera for conversion.

If you plan on keeping your photos for a long time I recommend shooting them to an uncompressed bitmap format and then compress them. You could do lossless compression with TIFF, but TIFF is not one of the web compliant standards so you will find yourself transferring to a lossy compressed file eventually if you plan on doing web stuff. Bottom line – master and backup with bitmap and publish with JPEG.

2 comments:

Unknown said...

Thank you.

Unknown said...

Superb article!
Got my doubts cleared.
Thank you so much.