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09/15/2007 05:04:47 PM · #1 |
On my old Coolpix 990 one of the output options was TIFF. A lossless format which preserved the data exactly as it was shot. I started wondering why support for TIFF output has been dropped from cameras, and I think I know why; it was replaced by 'RAW'
TIFF and RAW have many things in common, they're both lossless (which means the graphics data doesn't get compressed as it does in JPG), they both support up to 16-bits of data per rgb pixel (most cameras can only output 12 or 14 bits per rgb pixel anyway, so the other bits get ignored). So what's the difference with RAW? - Well, it stores additional data in the header, such as white balance settings and exposure settings, and it's proprietary; each camera manufacturer has their own RAW file format, and their own RAW editing software.
RAW enthusiasts often mention how they're able to get the detail out of the shadows when they're editing a RAW file over a JPG one. Well, what that really means is that they're working with 16 bits of data per pixel (RAW) instead of 8 bits (JPG) so they have all these extra bits of 'shadow' data to work with. But if you take a RAW file and convert it directly to 16-bit TIFF format there is nothing you shouldn't be able to achieve editing that file in Photoshop that you could do with the RAW file using RAW editing software (which is essentially a piece of software that lets you read the proprietary RAW image format, and then edit it in 16-bits)
TIFF was a robust file format, capable of handling 12/14 bits per pixel of data uncompressed, and with an EXIF type header added to the format could also have stored the camera shot data. The camera manufacturers have created an air of mystery around RAW using phrases like 'The Digital Negative' - whereas in fact it's simply a proprietary TIFF replacement.
Wouldn't life have been so much easier if they'd forgotten the whole RAW deal and just extended the TIFF file format? |
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09/15/2007 05:16:30 PM · #2 |
RAW and TIFF do share the 16-bit-per-pixel attribute, but they are quite different. RAW files are not really image files as such; they have not been demosaiced. A TIFF file is like a RAW file that has gone through a demosaicing algorithm to convert it to a 16-bit/channel image file.
The reason RAW files exist is that the camera needs to do very little processing before saving them off. Since the camera has limited processing power, that's a big advantage. It's also an advantage to the end user to be able to do demosaicing using more sophisticated algorithms that require the greater computing power available on the computer.
It is true that any adjustments to exposure, color balance, etc. that you can do in RAW conversion, you can do on a TIFF file. You are just working with a file that's already been converted to an RGB image file. |
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09/15/2007 05:18:20 PM · #3 |
TIFF you're working with an image file.
RAW you're manipulating the data to make an image file to work with.
Message edited by author 2007-09-15 17:19:56.
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09/15/2007 05:40:28 PM · #4 |
Originally posted by kirbic:
The reason RAW files exist is that the camera needs to do very little processing before saving them off. Since the camera has limited processing power, that's a big advantage. It's also an advantage to the end user to be able to do demosaicing using more sophisticated algorithms that require the greater computing power available on the computer.
It is true that any adjustments to exposure, color balance, etc. that you can do in RAW conversion, you can do on a TIFF file. You are just working with a file that's already been converted to an RGB image file. |
And yet a software industry appears to have sprung up around the 'RAW' file format, when in essence all we really needed was a simple 'demosaicing' app which would read the RAW data and output the file as a 16-bit TIFF format? - I suppose that's where the PS RAW converter plug-ins came from. But suddenly we've got Lightroom, Capture NX and many others which are essentially duplicating the functionality that already exists (or could exist) in apps like Photoshop, for no reason.
There seems to be a general misunderstanding over what RAW actually is. It only occurred to me in the past couple of days that once I've got that RAW file into Capture NX, what I'm basically doing is editing a 16-bit image. There's no mystery about it! |
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09/15/2007 05:40:34 PM · #5 |
Originally posted by soup:
TIFF you're working with an image file.
RAW you're manipulating the data to make an image file to work with. |
No, in RAW editing software you are also working with a 16-bit image file. At the point the image file reaches your screen it's already been demosaiced (as kirbic pointed out)
Even if you *could* edit the pure RAW data, you wouldn't really want to! What the pure RAW file mainly consists of is a stream of data containing the 12/14-bit value of each rgb photosite on the sensor. Since the photosites are arranged in weird patterns it has to re-construct this data back into some order, i.e. into an image file for us to understand. So the RAW data gets re-assembled... into a 16-bit image file.
There is nothing you can do to that 16-bit image file in your RAW editing software that you can't achieve with a 16-bit TIFF conversion in Photoshop. |
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09/15/2007 05:51:18 PM · #6 |
The Coolpix 5400 could do both TIFF and RAW. There is no comparison. TIFF took for freakin' ever to write to the memory card. It totally killed the spontaneity of shooting. RAW was still a bit long with regards to write time, but nowhere near as long as a TIFF, and took up considerably less room, too.
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09/15/2007 05:52:56 PM · #7 |
One more difference... Sharpening has NOT yet been applied to the raw data. In tiff format, it probably has... so it's too late to change your mind about how much sharpening to do (so if it were me, I'd just turn the in-camera sharpening down or off if shooting in tiff mode).
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09/15/2007 07:43:18 PM · #8 |
Think I'm happy with 12 meg raw files on my CF cards rather than their 50 odd meg equivalents in TIFF. To me that's one large difference between the formats.
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