Preview Save As TIFF Compression Options

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Level 1

79 points

Preview Save As TIFF Compression Options

Preview lets you save an image (e.g., RAW camera image file) as a TIFF file. You can save as No Compression, LZW Compression, JPEG Compression, and Packbits Compression. My expectation was that the compressed TIFF options would save a smaller file than an uncompressed file. I have tried each option, and Uncompressed, LZW, JPEG and Packbits all result in a TIFF file of exactly the same size. What is the purpose of these options if they don't save space? Seems very odd to me. (In my case, I started with a 43MB Sony .ARW file - and (all) the output TIFF files are 337MB in size.)

David

iMac, macOS High Sierra (10.13.6), 27 inch Retina i5 32GB

Posted on Aug 18, 2018 1:07 PM

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Answer 1

Old Toad

Level 10

215,190 points

Aug 18, 2018 3:15 PM in response to DRedfearn

Not sure how you exported the image out of Preview but when I export a 144 KB jpeg file out of Preview as a tiff file this is what I get for the various file sizes:

Checking the resulting files confirms the sizes indicated.

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Answer 2

Old Toad

Level 10

215,190 points

Aug 18, 2018 3:37 PM in response to dialabrain

I did the same with a Nikon NEF file:

Sure got some wild results. I read an article several years ago comparing JPEG with TIFF and the author came to the conclusion that he couldn't see the difference until he went to print mural sized prints. For my work, even printing poster sized prints, JPEG is perfectly adequate, particularly with my eyes. 😟

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Answer 3

dialabrain

Level 10

135,509 points

Aug 18, 2018 3:41 PM in response to Old Toad

Well I know it is possible with some images to end up larger because of compression quirks. I've never seen such a large discrepancy though as I got. The only results I got that resulted in a smaller file than the original RAW file was to save it as a jpg.

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Answer 4

DRedfearn Author

Level 1

79 points

Aug 18, 2018 3:42 PM in response to Old Toad

That is exactly what I did - I just started with a .ARW RAW file from a Sony A7RM3 camera (42Mpix). It may be that the RAW image can't be compressed for some reason. Starting from a JPEG (which already has lossy compression applied) may be different. It's pretty clear that TIFF (compressed or uncompressed) is not an efficient storage format for RAW files. I have photo editing software that can save the edited image in a TIFF file, but the only options they support are 8-bit vs. 16 bit color (16 bit much larger of course).

David

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Answer 5

DRedfearn Author

Level 1

79 points

Aug 20, 2018 1:01 PM in response to DRedfearn

I also asked this question on dpreview and got a good answer. I was starting with a RAW image that uses 16-bit color. It is almost impossible to compress this because of the very subtle color changes in the file. I am told that there is some compression for 8-bit color but not enough to make it worth the time.

David

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Answer 6

dialabrain

Level 10

135,509 points

Aug 20, 2018 1:08 PM in response to DRedfearn

David, I'm not certain how good an answer you were given. It might explain why there was little to no compression but not why it ends up 4 to 6 times larger. When I converted a 52MB RAW Nikon file to a jpg it reduced to approx 8MB. I still think there's something we're missing.

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Answer 7

Kurt Lang

Level 9

68,436 points

Aug 20, 2018 3:18 PM in response to dialabrain

It's normal for camera RAW images to be smaller than a TIFF written from that image. From my Nikon D800, a typical RAW image is about 48 MB. The uncompressed TIFF saved from that is about 105 MB.

If you want to get the size down, use LZW. It's lossless and saves quite a bit of space.

Using JPEG compression is the most pointless option for TIFF images I have ever seen. You are literally saving your image as a JPEG inside a TIFF wrapper. If you really want a JPEG, just save it as one to begin with.

JPEG is lossy, though. Even using the highest quality option, information is tossed. It's a very slight difference compared to an uncompressed image, but it's still a loss. Each time you open and save the file, you compound the loss. LZW can be opened and saved a zillion times, and the last will be the same as the first.

No idea what Packbits is. I've never used it (not even an option in Photoshop). As such, I have no idea of it's lossy or lossless.

That you are getting no size difference between an uncompressed and LZW TIFF out of Preview means Preview is doing something wrong.

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Answer 8

DRedfearn Author

Level 1

79 points

Aug 20, 2018 3:14 PM in response to dialabrain

JPEGs are "lossy" - when you save as a JPEG, you throw away tons of information that was in that RAW image. Set your camera to RAW + JPEG and compare the size of the RAW and JPEG image files from the camera. If you wonder what is lost, then view the two images on a large, high resolution display - and zoom in and pixel peek. You will see the difference. Of course, if you printed the JPEG and the RAW saved as a TIFF, you would very likely not notice any quality difference in the two images. The JPEG compression algorithms have gotten so good that I just use the out-of-camera JPEGs most of the time. I only go to the RAW image - and post-process - when I have screwed up!

The motivation for my question was when I was using the Perfectly Clear processing software which outputs either TIFFs or JPEGs - but didn't apply any compression to the TIFFs. I knew this option to compress a TIFF was present in Preview, so tried it, and got no benefit. That was because I was starting with the RAW image with 16-bit color coding - and compression algorithms try to identify identical pixels which don't need to be saved - with 16-bit coding, there are very few or no identical pixels.

I am hopeful that the HEIF coding standard (that Apple uses now for the iPhone cameras) will become a standard - it is a much more efficient compression algorithm than the JPEG process. Camera companies, however, are pretty conservative about these things - and they like proprietary RAW formats. They even change the format across camera models. (The RAW format for the Sony A7Rm2 and the A7Rm3 are different.)

I am satisfied that this is correct explanation for the compression failure for TIFFs.

David

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Answer 9

DRedfearn Author

Level 1

79 points

Aug 20, 2018 4:04 PM in response to dialabrain

Well, on my A7RM3, Sony offers both compressed and uncompressed RAW formats. The default is the compressed RAW format, but if you want 80MB RAW files you can choose the uncompressed option. You really have to pixel peek to see any difference. I think Nikon and Canon use lossless compression for their RAW. I wish Sony would get with it and do the same.

David

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Answer 10

Kurt Lang

Level 9

68,436 points

Aug 20, 2018 5:43 PM in response to DRedfearn

I’d have to look it up again in the manual, but I think I can save RAW images as uncompressed. I just leave it at the default since the camera and the high speed Compact Flash have no problem keeping up with rapid shooting.

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Answer 11

dialabrain

Level 10

135,509 points

Aug 18, 2018 3:28 PM in response to DRedfearn

FWIW, I tried the same thing using a RAW Nikon file. Trying to save as a TIFF or PNG file results in a file 4 to 6 times larger than the original RAW file. No idea why.

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