RAW to TIFF conversion and size

[brian_donaldson1]

I did a search and found some information but not exactly what I was

looking for.

 

I am shooting in RAW. Hard to work with outside of Photoshop CS2. I

save my RAW to CD. But I want to convert to TIFF. When I do, the file

is 23 meg in size.

 

Is there a way to save the RAW to TIFF without making the file 3x to

4x larger than the RAW?

 

Thank you

[lex_jenkins]

It's possible to compress TIFFs but it doesn't reduce file size very much and can cause compatibility problems with other programs.

 

Some photo editing programs can work with PNGs. I don't think they're actually lossless but they're close. And the file sizes tend to be close to the size of the original RAW file, at least with NEFs from my D2H.

[andreas_weber]

In RGB a TIFF *should* be about 3x as large as a RAW file with equal dimensions. The TIFF contains brightness values of three colors for each pixel, the RAW only of one color. Therefore a RAW should be close in size to a greyscale TIFF...

 

Andreas

[mendel_leisk]

The raw file's your best bet for compact, lossless archive, you're on the right track there. So what is your intent with the tiff: to work with in Photoshop? You could do that, and finally convert to jpeg. You still have the raw, if you want to have another go at it.

[steve_dunn2]

<p>As someone else pointed out, RAW images contain one colour per pixel*. Once you've converted your RAW file to some sort of RGB format, you have three colours per pixel. Assuming all else (bit depth, compression method) remains the same, you'd therefore expect a converted file to be 3x larger.</p>

 

<p>Of course, everything else often doesn't remain the same. You don't give any hint as to what sort of camera you're using, so I'll write about mine, the EOS 20D. Its RAW files are 12 bits per pixel, which is not a depth typically found in other file formats, so you normally have to choose between 8- and 16-bit depth. If you decide you want to keep all the information, you'll be using 16 bits, causing the file to grow by about a third (so it's now 4x the size of the RAW file, not 3x). Or you can throw away the lower bits and shrink the file by a third (so it's now about 2x the size of the RAW file).</p>

 

<p>And there's the issue of compression. 20D RAW files are losslessly compressed (which is quite common, but there are also some cameras which do not compress their RAW files). The compression ratio varies, of course, depending on the contents of the image, but this compression typically saves around a third. If you're saving the converted file in an uncompressed format, add another third or so to its size. If you're using lossless compression, chances are it will be somewhat comparable to the RAW file's compression. If you're using lossy compression, such as JPEG compression, you can adjust the file size over a huge range at the expense of loss of image quality.</p>

 

<p>As others said, you can choose compression for TIFF files, but this can cause compatibility problems. TIFF is a format with a great deal of flexibility, but not all TIFF implementations can handle all of its options. If you're saving the files and planning on opening them using the same program at a later date, this isn't a problem; it should be able to read any file it can write. If you're saving the files and planning to give them to someone who may be using a different program, you should probably be conservative in which TIFF options you choose, and that includes not using compression (or perhaps sticking with LZW compression, which is not as good as some of the other options but is more likely to be portable).</p>

 

<p>Personally, I work at 16 bits, but once I'm finished doing my editing, I convert down to 8 bits and save it as a ZIP-compressed TIFF (since I plan on opening it in the future with the same, or a later, version of Photoshop Elements, which can handle that format). A full-resolution image typically comes in around 10-15 MB, compared to the RAW file which is usually 7-9 MB. If I'm giving the file to someone (taking it to the lab to be printed, burning it to CD for a friend, whatever), I'll also save a highest-quality JPEG, which is perfectly good for most uses yet is substantially smaller than either the RAW or TIFF.</p>

 

<p>*: At least, most of them do. Cameras using a Foveon sensor would have three colours per pixel, but there aren't a lot of those cameras around.</p>

[brian_donaldson1]

My goal was to give the .tiff file to the subject so they can look at them without any special software, and still maintain the same file size and quality as the .cr2 file. I failed to mention these are Canon .cr2 files.

 

I guess I am not really 100% happy with jpeg after seeing and working with RAW. My subjects are rock bands. In RAW, I can count the number of sweat beads on the persons face. In jpeg, the beads just are not there. Know what I mean?

[tom_swanson]

What quality settings are you saving those jpegs at?

[mendel_leisk]

"My goal was to give the .tiff file to the subject so they can look at them without any special software"

 

jpeg's the best candidate for presentation to the client: much more portable due to compact size. Tiffs cannot even be viewed properly on some viewer programs, older versions of ACDSee for example. And giving away full res tiffs is akin to selling the cow.

 

"In jpeg, the beads just are not there. Know what I mean?"

 

Starting with the raw file, if you output both a tiff, and then a high quality setting (not maximum) jpeg, with the same sharpening etcetera, I would wager you would have a very difficult time descerning any difference between the sweat beads. Try it: a high quality jpeg *is* a lossy format, but the departure from tiff quality is going to be very very subtle. With both zoomed to 100% and centered on the same detail, toggling between them I doubt you'll be able to tell which is which without looking at the header.

[alexandru_petrescu]

You could save the cr2 into tiff and then reduce the size and resolution of that tiff. That may loose the beards however.

 

I can do that like this: from cr2 to dng with Adove DNG Coverter (free); then vuescan the dng and save as e-mail quality. That transforms the 12mb cr2 into 500kb tiff. If I vuescan the same dng with Quality "archive" instead of "e-mail" I get a tiff of 22Mb. I'm sure the same can be achieved with Photoshop.

 

The size of the resulting tiff depends on how many bits per color, resolution and the eventual tiff compression method, all being tiff parameters.

[ruud_van_gaal]

Only 12 bits per single pixel? That would mean around 4 bits per R/G/B, which is less than JPEG (which has 8 bits per color). Why would RAW be better than JPEG then (which it is)? Surely not interpolation?

I guess my world is overthrown and I have to google a lot more to see what's going on here.