TIFF FIles

Have been using the Pentax Photo Lab to convert RAW to TIFF ( as recommended ). However the saved TIFF files are massive...25 meg for 8 bit and 50 meg for the 16bit..I'm a little or totally confused as I thought TIFF would retain details but the files would be somewhat less than the RAW size of 10 meg....Once converting RAW do I need to then compress the TIFF file? Appreciate any guidance here...

cheers
Robbie

That size TIFF file is perfectly normal.

Confused of Malvern
'The greatest fool can ask more than the wisest man can answer'

robbiereynen said:

Have been using the Pentax Photo Lab to convert RAW to TIFF ( as
recommended ). However the saved TIFF files are massive...25 meg for
8 bit and 50 meg for the 16bit..I'm a little or totally confused as I
thought TIFF would retain details but the files would be somewhat
less than the RAW size of 10 meg....Once converting RAW do I need to
then compress the TIFF file? Appreciate any guidance here...

Click to expand...

RAW files contain n bits per sensor photo-site whereas the TIFF output file from a RAW convertor contains 8 or 16 bits per colour channel (one of R, G and B per pixel).

TIFF files can support various compression methods (options when saving) however it would be wise to determine if other applications that are intend to use the TIFF files with support the selected compression method.

--
Rob

RAW captures 15 Mpixels of data, but each pixel captures only one color (red, green or blue). Both TIFFs and JPEGs are created from that data by looking at adjacent pixels and inferring the RBG mixture for that pixel. Hence, the TIFF has three times as much data per pixel as the RAW version.

It's true 50 MB is a large file size, but with external drives selling for as little as US$100 per terrabyte, that works out to 20,000 pictures for $100, or half a penny per picture.

I was just looking at a Fry's ad for a 2TB FW/USB drive for $200 and remembering how my Radio Shack Model II's floppy disk drives cost about two or three thousand dollars for about 2 MB total -- or maybe it was 3 MB, but you get the point. Memory is cheap and getting cheaper all the time.

Martin
--
http://www-ee.stanford.edu/~hellman/
http://nuclearrisk.org

As commented elsewhere in this thread, each single 12-bit photosite value is processed to yield 3 separate values, one each for Red Greeen and Blue. Each of these will be 16 bit each. (This is the demosaicing process.) You can save to tiff as 8 bit or 16 bit, so If you do some math, you can see how the 25 or 50 megabyte files result.

The main reason for converting from raw to one of these formats is that the data is not compressed. Or, if it is compressed, it uses a lossless compression (like zip) which retains all the data.

On the other hand, when you convert to jpeg, part of the compression results from permanently throwing away data. The discarded data is not recoverable.

It seems sensible to do your image processing and manipulation using all the image data, and then you can convert to jpeg at the final stage, as needed for web display, sharing by email, etc.

Paul

It's for that reason that most people probably don't convert to TIFF as a general rule. If you're using the Pentax software or other software that forces you to convert to another format in order to use your images, converting to JPEG usually makes more practical sense. The difference in quality is minimal to non-existent for most purposes, and of course, you can always use TIFF those images that you really need to. No need to decide that right away either - convert to JPEG if you don't have a need for TIFF right now, and then if later you develop a need for TIFF, go backl to your RAW and convert it again.

With more modern RAW software, you don't have to convert at all - you can just leave your files RAW. I process most of my files in the sense of tweaking the exposure & color an so forth, but I don't bother to convert them to another format - the mage isn't altered, but software automatically remembers the settings I used. After processing my images, I generate only medium resolution, medium quality JPEGs of the "keepers" for web use, which takes very little room.

--
Marc Sabatella
http://www.marcsabatella.com/
Blog: http://marcsabatella.blogspot.com/
Flickr: http://www.flickr.com/photos/marcsabatella/

Martin Hellman said:

RAW captures 15 Mpixels of data, but each pixel captures only one
color (red, green or blue). Both TIFFs and JPEGs are created from
that data by looking at adjacent pixels and inferring the RBG mixture
for that pixel. Hence, the TIFF has three times as much data per
pixel as the RAW version.

It's true 50 MB is a large file size, but with external drives
selling for as little as US$100 per terrabyte, that works out to
20,000 pictures for $100, or half a penny per picture.

I was just looking at a Fry's ad for a 2TB FW/USB drive for $200 and
remembering how my Radio Shack Model II's floppy disk drives cost
about two or three thousand dollars for about 2 MB total -- or maybe
it was 3 MB, but you get the point. Memory is cheap and getting
cheaper all the time.

Click to expand...

Yeah, I paid $320 for a 32MB drive about 20 years ago. A year or two, maybe three, later my SIL's company paid $10,000, IIRC, for a 1GB drive.

Yesterday, I saw a 1TB drive on sale for $89.00, shipped free. Within 18 months, the 2TB drives will be just a bit higher, and, possibly, 4-5TB drives will be shipping.

--
Charlie Self
http://www.charlieselfonline.com

I only convert to 16 bit tiff if I think the picture is really good (not often then in my case) and work on that in PP if the jpeg looks ropey and then convert the Tiff to Jpeg for web stuff etc.

I think the process RAW - TIFF - Jpeg gives better results (IQ) than RAW - Jpeg.

--
http://www.pentaxphotogallery.com/stevestanley
http://picasaweb.google.co.uk/steve63636

Thanks all for your advice.....

Cheerio!

Martin Hellman said:

I was just looking at a Fry's ad for a 2TB FW/USB drive for $200 and
remembering how my Radio Shack Model II's floppy disk drives cost
about two or three thousand dollars for about 2 MB total -- or maybe
it was 3 MB, but you get the point. Memory is cheap and getting
cheaper all the time.

Click to expand...

They wouldn't have been anywhere near that large. According to Wikipedia, they held 160 KB (for Radio Shack's own 35 track drives) or 180KB (for some third-party 40 track drives) per disk.

Apple II drives stored 140 KB per disk, for what it's worth.
--
--DrewE

DrewE wrote:

"They wouldn't have been anywhere near that large. According to Wikipedia, they held 160 KB (for Radio Shack's own 35 track drives) or 180KB (for some third-party 40 track drives) per disk."

The PC itself had one built in drive and the expansion bay (which cost about $2k) had three more. All were 8" floppies and I'm pretty sure they were DSDD and held either 500 kB or 800 kB each. Remember, these were giant 8" floppies, not the pip squeak 5.25" ones you are referring to.

Martin

It was written: "The main reason for converting from raw to one of these formats is that the data is not compressed. Or, if it is compressed, it uses a lossless compression (like zip) which retains all the data."

I believe that converting from RAW to TIFF is lossy. First because the bit depth is often reduced from 12 to 8 but, even more fundamentally, because each pixel's color is inferred from adjacent pixels. For the conversion to be lossless, it would have to be possible to go backward from the TIFF to RAW and, even forgetting about the bit depth, I don't think that is doable. It's interesting that an expansionary conversion is lossy, but that seems to be the case. Usually, as with JPEG, the reason for incurring the loss of information is to compress the file.

I believe the reason for storing TIFF rather than RAW is because RAW converters are not available in many photo processing programs.

Martin

Martin Hellman said:

It was written: "The main reason for converting from raw to one of
these formats is that the data is not compressed. Or, if it is
compressed, it uses a lossless compression (like zip) which retains
all the data."

I believe that converting from RAW to TIFF is lossy. First because
the bit depth is often reduced from 12 to 8 but, even more
fundamentally, because each pixel's color is inferred from adjacent
pixels. For the conversion to be lossless, it would have to be
possible to go backward from the TIFF to RAW and, even forgetting
about the bit depth, I don't think that is doable. It's interesting
that an expansionary conversion is lossy, but that seems to be the
case. Usually, as with JPEG, the reason for incurring the loss of
information is to compress the file.

I believe the reason for storing TIFF rather than RAW is because RAW
converters are not available in many photo processing programs.

Martin

Click to expand...

Exactly. Tiff files only make sense as intermediate format for post processing. Archive your raw files and produce jpeg images to print and distribute your best.

--
Tom - http://www.pentaxphotogallery.com/tomvijlbrief

Many many thanks. Your information helps me immensely.

cheers
Robbie

Martin,

TIFF is a lossless image format, because it throws away no data in an attempt to make the storage file smaller. (TIFF can be compressed using a lossless compression algorithm.)

Whatever happens in the demosaicing process is unrelated to how that data is consequently used or stored. As far as I am aware, demosaicing is always done in 16-bit precision. The data may, of course, be subsequently down-sampled, but this is not part of the demosaicing, per se.

If you're interested, have a look at the dcraw source code: http://www.cybercom.net/~dcoffin/dcraw/

At it's most basic, dcraw is used to demosaic raw image data, and to save useable image data in a variety of formats. It is used directly or indirectly in a host of software. Easy to compile, particularly under Linux.

Paul