Differences between digital photo formats

August 7, 2004 5:34 AM

[Digiphotography] Is there a difference between a digital photo taken in an lossless file format such as uncompressed TIFF vs. RAW Format?
posted by Fupped Duck to technology (6 comments total)

Not really. More software can read the TIFF format than raw CCD format, but since a TIFF will contain all the data in the RAW file, there is no significant difference.

A tutorial on RAW files may help.
posted by majick at 6:43 AM on August 7, 2004

Raw will be a little more flexible.

A tiff is assembled out of the Bayer matrix of R, G, and B pixels.

A raw file is the original R, G, and B pixels as delivered from the CCD, with no processing. This allows a little bit more processing after the photo is taken; exposure compensation and such.
posted by ROU_Xenophobe at 6:43 AM on August 7, 2004

One of my employees recently attended this seminar, given by Photoshop co-creator Thomas Knoll, in which he stressed the capabilities (as ROU_Xenophobe described) of RAW over TIFF in a big way... the attendees came back quite fired up about it. Granted, he is obviously king of the digital image geeks, but I think you can take his enthusiasm for RAW as conclusive evidence of a legitimate functional advantage... even if you might not be able to tell the difference in most situations.
posted by ulotrichous at 7:11 AM on August 7, 2004

It goes beyond simple losslessness--with a good RAW converter (one comes bundled with Photoshop CS), most RAW files allow for 12-bits of color information (as opposed to 8-bits compared to JPEG, and probably 8-bits for the TIFF as well depending on camera model), easy adjustment of white balance, control over the sharpening applied to images, and so on. The camera must apply a series of algorithms to produce a TIFF file (often irreversible--for example, colors may be clipped, sharpening can't be undone, etc), whereas none are applied to RAW files (save hardware-related ones such as mapping out bad pixels, etc).

TIFF is better than JPG when it comes to eliminating compression artifacts, but RAW is still much more flexible. TIFFs are needlessly huge as well--some manufacturers use lossless compression on their RAW files to make them even smaller (though they're still considerably bigger than JPEG's, of course). Some of the higher-end cameras offer TIFF (Nikon D2H does, but not the D70 nor the Canon DSLR's), but all of them offer RAW without fail, and for good reason too.

TIFF a bit of a "poor man's RAW" on cameras that don't offer RAW, but RAW is the real deal. Some people will happily use JPEG over RAW to save space if they can consistently nail their exposure/WB and are happy with their camera's JPEG algorithm, but I've never seen anyone make a case for using TIFF over RAW. TIFF isn't a factor in the JPEG vs RAW debates.
posted by DaShiv at 7:24 AM on August 7, 2004

What DaShiv said, basically. TIFF is largely pointless if you have the option of raw.

Also, you'll find that because the raw file contains sensor data slightly outside the gamut of most colour-spaces, you'll have up to 2 stops of exposure correction in your raw-conversion software - which always yields better results than a simple levels/curves adjustment in photoshop.

The best way to shoot raw is to 'expose to the right' and do as much tweaking as possible in the conversion software, before the image even becomes a jpeg/tiff/psd/whatever.

Much more detail about raw here
posted by cell at 8:17 AM on August 7, 2004

RAW captures the sensor data before any processing is applied to it. It has no inherent white balance correction, sharpening, noise reduction, or any other processing. It's not even demosaiced. It is, almost literally, the "digital negative." It also has, on most cameras, a wider dynamic range and more bits of luminance resolution than a final processed image.

TIFF has all the processing done to it already. Its only advantage is that it is guaranteed entirely free of JPEG artifacts.

Not surprisingly, software running on a desktop computer offers a lot more flexibility than a camera's firmware when it comes to converting sensor data to other image formats. For one thing, you hardly ever get superstars like Thomas Knoll writing digital camera firmware, but he does work on the Adobe Camera RAW plug-in. Also, of course, the algorithms that are practical on a 2+ GHz processor tend to yield much better results than those that are practical on an embedded processor like those in most digicams.

One of the nice things about RAW format is that it does give you some exposure latitude. Shots that are as much as a full stop over or underexposed can often be recovered from RAW, and it is also possible to "bracket" images generated from a single RAW file to increase the dynamic range represented by the final, converted image.

As a bonus, RAW files are typically much smaller than TIFF. RAW files only need to store data for one primary color (red, green, or blue) at each pixel. In a TIFF file, each pixel must have red, green, and blue values. Even if a camera stores more than 8 bits of data per pixel in RAW files, that's still a good bit less data than is in a TIFF. (12 bits per pixel RAW is half the size of a 24-bit TIFF.) This means you get more of them on a card and, more importantly, the camera flushes them out of its internal buffer more quickly, so you can shoot faster.
posted by kindall at 8:24 AM on August 7, 2004