Why are tif files larger than psds?

QP
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Q_Photo
Mar 3, 2004
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Why are tif files larger than psds? Files are Adobe RGB. Flattened, no alpha channels. 12” x 18”. 300ppi. 5400 pixels x 3600 pixels. Copies of art from a calendar. These are resulting file sizes: psd = 48.8 mb. tif = 55.6 mb. tif (compressed) = 64.4 mb. Anyone know why?

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SF
Scott_Falkner
Mar 3, 2004
I suspect Photoshop files, being proprietary, can support higher levels of compression natively than can TIFF files. One possibility is that the channels are compressed seperately. Try it with a grayscale iamge and you will likely find less difference in file sizes.
JS
John_Slate
Mar 3, 2004
PSD uses RLE compression.

What type of tiff compression created a bigger file?
HK
Harron_K._Appleman
Mar 3, 2004
John,

The LZW algorithms used for TIFF compression can produce just such strange results when working with 16-bit files. See…

Chris Cox "LHZ TIFF compression not working ?" 2/5/03 7:12pm </cgi-bin/webx?14/1>

=-= Harron =-=
JS
John_Slate
Mar 3, 2004
The file sizes above would be from 8 bit 5400×3600 RGB
QP
Q_Photo
Mar 3, 2004
They were 8 bit and LZW. I save nearly all completed work in tif (not compressed) and never had this occur before these files. The few times I have used LZW it would reult in a file about three quarters the size of normal tif or psd.
MM
Mick_Murphy
Mar 3, 2004
On my machine flattened PSD and TIFF versions of the same file with no alpha channels are identical in size down to last kb. Do you perhaps have ‘Save Image Pyramid’ selected in the compression dialog? This bumps up the file size a bit.
QP
Q_Photo
Mar 3, 2004
They were 8 bit and LZW. I save nearly all completed work in tif (not compressed) and never had this occur before these files. The few times I have used LZW it would result in a file about three quarters the size of normal tif or psd.
SJ
Sandy_J
Mar 3, 2004
LZW compresses by essentially grouping same pixel colors which is why grayscale images or those with solid bkgds compress smaller than complex images. RLE is a different method.
RW
Rene_Walling
Mar 3, 2004
It is possible for certain images to "confuse" the LZW algorythm into producing a large file than the uncompressed image.

This may be what you are seeing.
QP
Q_Photo
Mar 3, 2004
Sorry about double post. Yes Mick, I also always got same size files for tif & psd. “Save Image Pyramid: NOT checked.
JS
John_Slate
Mar 3, 2004
On my machine flattened PSD and TIFF versions of the same file with no alpha channels are identical in size down to last kb

Well that does not seem right either.

Perhaps maximize compatiblity makes an otherwise smaller PSD the same size as an uncompressed tiff.
MM
Mick_Murphy
Mar 3, 2004
I’ve got max compatibility to never. Using it doubles the PSD size. Out of interest I just rechecked by saving some files and flattened TIFFs and PSDs are identical in size. PSCS.
JS
John_Slate
Mar 3, 2004
OK now I’m confused.

Doesn’t a flattened PSD file have RLE compression applied to it?

If it does, how could it be the same size as an uncompressed tiff?
DJ
dennis_johnson
Mar 4, 2004
If I save out an identical image as PSD and as uncompressed TIF, depending on the image the TIF is around 25-30% larger file size than the PSD. This is indicative that the PSD format has native compression built into it. I do not know what type of encoding PSD uses for compression. If someone is achieving identical file sizes saving to both PSD and TIF, then they must have enabled a compressed TIF format.
QP
Q_Photo
Mar 4, 2004
No Dennis. Both Mick and I have stated that we can save an UNCOMPRESSED tif and a psd (same file) and they are the same exact size. I can’t speak for Mick, but I’ve been saving to uncompressed tiffs for years. I never encountered this behavior before these scans. I repeat: ((psd=48.8 mb. tif=55.6 mb. tif (LZW)=64.4 mb.)) Files are Adobe RGB, 8 bit. Flattened, no alpha channels. 12” x 18”. 300 ppi. 5400 pixels x 3600 pixels. Copies of art from a calendar.
JS
John_Slate
Mar 4, 2004
I never encountered this behavior before these scans.

That’s odd since I believe smaller PSDs to the the norm.

I would truly like to know how you get the same file size.
MM
Mac_McDougald
Mar 4, 2004
I have *never* gotten same file size with TIFF/PSD, from versions 3-7. The PSD is almost always smaller, sometimes by just a few K, sometimes a few MB, depending on rez and composition of image.

I’ve also *never* gotten a larger TIFF file using LZW than without it, assuming 8 bit, no layers, RGB or grayscale.

Mac
MM
Mick_Murphy
Mar 4, 2004
Well I never even thought about this before but I just checked and the results may be of interest although I have no real idea what the significance is.

Started with a flat PSD, no channels, created originally in CS from scan. Open and resave as PSD in PS6, then resave as TIFF. Identical file sizes. Same file, same process in CS also gives identical file sizes. However, the PS6 files are marginally smaller than the PSCS (19,824 kb versus 19,833).

Do the same with older file originally created in PS6. This time, the TIFFs are larger than the PSDs and all four files are different sizes.

PS6 PSD – 48,525 kb
PS6 TIFF – 49.341 kb
PSCS PSD – 48,534 kb
PSCS TIFF – 49,349 kb

Explanations on a postcard please.
RW
Rene_Walling
Mar 4, 2004
Those minor differences in size can be explained by differences in the headers of each file.
JS
John_Slate
Mar 5, 2004
PS5 PSD: 31,666kb
PS5 TIFF: 46,892kb

hardly minor.

yeah I know 5 is old. I use it at home.
MM
Mac_McDougald
Mar 5, 2004
Depending on image, PSD can be quite a bit smaller, as it obviously has some sort of proprietary compression built in.
So does a .psp file in PaintShopPro, a Corel PhotoPaint file, a PowerPoint file, etc.

Mac
JS
John_Slate
Mar 5, 2004
OK so how is Mick getting the types of file sizes he is getting???

Mick:

Try this if you don’t mind:

Open a new RGB file, 5" x 5" 300ppi.

Set the gradient tool to NOT dither and use the shift key to draw a gradation from default black at the top of the file to default white at the bottom.

Save as uncompressed TIFF, then as PSD.

For me:

Tiff- 6,597 kb
Psd- 119 kb!!(this type of image compresses very well)
MM
Mac_McDougald
Mar 5, 2004
Just for yuks, I did this (using white background for the new image, no tranparent layer)…

Photoshop Elements 2:
Tiff: 6600k
PSD: 123k

Photoshop 7:
Tiff: 2205k
PSD: 46k

this as per your example.

Mac
MM
Mick_Murphy
Mar 5, 2004
John

I did that in CS. Results almost identical to yours. Tiff is 6602kb and PSD is 125kb. Don’t know how Mac is getting such different numbers in PS7.

The images I used above were all photos so presumably that is at the heart of it. TIFF compression is also much higher for line art than photos. The same image with LZW is 37kb.

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