Proof, TIFF, RAW, Negatives

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D90-Sniper

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Snipes
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Ive been reading alot on here lately about different type of images, mainly in the pro/freelance sections.
When people refer to Proof images, RAW images, TIFF images and digital negatives, what do they each actually mean?
 
These words represent the way the file is built and the way the data in the file is stored.

In a 'JPEG' file such as this, the data is compressed in a way that saves space but loses some of the data. This is great for general purpose internet application as they're quick to load, and we don't always need an immense amount of detail when we're browsing something like facebook.

RAW, TIFF and DNG (digital negative) files are types of files that do not simplify the image to save space. They are the full image, pixel by pixel, and are normally large files for this reason. All data that was captured on the sensor is still there, unlike Jpegs.

You can normally tell which file is which based on it's extension, shown at the end of the file name. So 'Flower.JPG' is compressed and convenient, where as 'Flower.TIF' is uncompressed, highly detailed and a large filesize.
 
Ah great, thanks, I may start shooting in RAW and get a bigger SD!!

What does Proof image mean? Is this when you send a client watermarked images to choose from??
 
A proof image is normally a small/thumbnail or unfinished version of an image. I suppose in it's simplest form they're used to show clients a full set from which you'll pick what you like. I'm sure there's many other interpretations and uses though.

With regards to using raw/JPEG...

When you have your camera set to produce JPEG images, this is what it does:
Sensor>Image Date>Sharpen/Contrast/Saturation/White balance etc>Compression>Final file.JPG

When you use raw, it does this:
Sensor>Final file.RAW

What this means is that you do have to put in the contrast, colour and saturation yourself at a level that you want when you get them back to a computer Sometimes this can be a PITA, for example shooting a family BBQ where you just want the pictures straight out to put up on facebook.
If you're shooting something more demanding, you may want to use raw files as you can take them home and tweak them to a much higher level than JPEGs.
 
A proof is any rough, unfinished image. Usually with no afterwork, not even cropping, often with a watermark or something, used for selection purposes.

Almost invariably, the final finished image used for output viewing, by whatever means, is a JPEG. It is compressed, but a high quality JPEGs loses no visible data. They are indistinguishable from a TIFF, which in simplest terms is just a visible version of the Raw - you can't actually see a Raw file, it's just a load of digital data.

Compression works by taking common apsects of an image and reducing the sheer volume of data mathematically. For example, if you have an area of absolutely plain tone that occupies say 1m pixels, then in a Raw/TIFF that would be (very simplistically) 1010101010101010101010101010... and so on and on written one million times. The JPEG would just reduce that down to 10x1m, and it would look exactly the same.

The different JPEG quality standards take a different view of exactly what those 'common aspects' are. Taking an area of graduated tone from light to dark, a high level JPEG might reduce that down to 100 different tones, and a low grade JPEG might reduce it down to just 10.

Some images compress more readily that others. For example, if you have a seascape with just plain blue sea, sky and sand of broadly similar tone levels, then a huge file can get knocked down massively even in a high quality JPEG. But if there is lots of detail in a scene, and lots of tones from light to dark, then that image can't be compressed to anything like the same extent.
 
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