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Author Topic: Why are PSD files so big?  (Read 761 times)

PeterAit

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Why are PSD files so big?
« on: December 01, 2019, 11:03:17 am »

I was rooting around my photo storage disk looking for large files I could delete to free up disk space. I came upon a PSD file that was 938MB and I wondered why. When I multiply the number of pixels (~40 million) by 2 bytes per color (it's in 16 bit mode) by 3 colors per pixel I get 238MB. There's only one layer. Why the discrepancy?
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Peter
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digitaldog

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Re: Why are PSD files so big?
« Reply #1 on: December 01, 2019, 11:48:36 am »

A lot depends on what's on that layer.
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Andrew Rodney
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Frans Waterlander

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Re: Why are PSD files so big?
« Reply #2 on: December 01, 2019, 06:39:43 pm »

A lot depends on what's on that layer.

Like what?
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digitaldog

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Re: Why are PSD files so big?
« Reply #3 on: December 01, 2019, 06:41:33 pm »

Like what?
Like data.
Don't ask questions when the correct answers will be ignored and misunderstood. Your agenda here is quite transparent. Maybe start a new post as a newbie asking about layers in Photoshop, a product I don't know you even own.
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Andrew Rodney
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Frans Waterlander

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Re: Why are PSD files so big?
« Reply #4 on: December 01, 2019, 06:46:46 pm »

Like data.
Don't ask questions when the correct answers will be ignored and misunderstood. Your agenda here is quite transparent. Maybe start a new post as a newbie asking about layers in Photoshop, a product I don't know you even own.

Yes, I own Photoshop; the PSE variety, you know, the one that can store editing information in a data file or in sidecars.

Now back to my question: like Peter, I would like to understand why his file is so big, plain and simple.
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digitaldog

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Re: Why are PSD files so big?
« Reply #5 on: December 01, 2019, 06:54:47 pm »

Yes, I own Photoshop; the PSE variety, you know, the one that can store editing information in a data file or in sidecars.
You own Elements. And you don't understand how Layers work with data; that much is clear. Use the Google Machine; you can talk back at the facts it provides till the cows come home. I'll not get trapped into your troll posting agenda by explaining how layers and the data on them play a role in the final size of the saved image. The OP can ask and I'll be happy to oblige him.
IF you want to understand something, you have to believe the facts presented to you by those who actually know (and those here who in a few months will celebrate 30 years of use, long before the product had Layers). You're on your own bud.  :P 
Maybe some fool on PhotoNet will answer your questions.  ;)
« Last Edit: December 01, 2019, 06:58:59 pm by digitaldog »
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Andrew Rodney
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Frans Waterlander

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Re: Why are PSD files so big?
« Reply #6 on: December 01, 2019, 07:03:38 pm »

The OP can ask and I'll be happy to oblige him.

I'll ignore your insults, again. The OP did ask and I doubt your answer was of much help to him. It certainly didn't help me understand what's going on.
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digitaldog

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Re: Why are PSD files so big?
« Reply #7 on: December 01, 2019, 07:06:57 pm »

I'll ignore your insults, again. The OP did ask and I doubt your answer was of much help to him. It certainly didn't help me understand what's going on.
Ignore them; go away. Doubt; thats what you do best in your posting agenda here and on Photo net. I'm not interested in helping you with your misunderstandings. Or helping you; lost cause!
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Andrew Rodney
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digitaldog

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Re: Why are PSD files so big?
« Reply #8 on: December 01, 2019, 07:26:39 pm »

Peter, if you really want to discuss layers and the data on them with respect to size of saved image, PM me. I'm simply not going to let this thread become locked or go into the septic tank due to Frans again, he's got a huge paper trail of trolling, some outlined below as proof of concept. I'd suggest you lock the thread as you can do as the OP and we can go over this without any pollution from Frans.


Proof of trolling:
He is a Glutton for Punishment but apparently the punishment is worthwhile in order to get attention. And that's the posting agenda that can be seen here and in other photo forums, the list is sadly long but so consistent: Ask a question of the group, then immediately dismiss and push back on anything said that doesn't sync with the predetermined desired answer (notice the question marks!):

Flicker, eyestrain or headache when using a monitor with LED backlighting?

AND:
How do you like your 23" NEC P232W-BK-SV with LED backlighting?

AND:
Three different color calculators can't be wrong, can they?

Do SoLux bulbs meet color temp specs?
And (push back) again:

NEC SpectraView update doesn't work


NEC PA242W with SpectraView problems

NEC P242W with SpectraView weird flicker

Epson R2880 suddenly prints with reddish color cast

We can now add to that long list, nonsense about sensors overheating and being an issue in 10 pages of back and forth that resulted in it all getting deleted here on LuLa but contained on poor PhotoNet:
https://www.photo.net/discuss/threads/are-dslrs-doomed-tony-northrup-says-no.5515216/


I really do not recommend reading them all, rather painful. But I do believe it illustrates a pattern: post about a 'problem', ask for consensus of others to agree the problem exists (rarely if ever does consensus let alone any agreement occur), complain when what he's told doesn't match what he wants to hear, go away for X number of months and start all over again.
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Andrew Rodney
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kers

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Re: Why are PSD files so big?
« Reply #9 on: December 01, 2019, 08:36:07 pm »

I was rooting around my photo storage disk looking for large files I could delete to free up disk space. I came upon a PSD file that was 938MB and I wondered why. When I multiply the number of pixels (~40 million) by 2 bytes per color (it's in 16 bit mode) by 3 colors per pixel I get 238MB. There's only one layer. Why the discrepancy?

my first question would be  :

You state it is one layer; then
is it a layer 0 or a background layer?
if it is a layer0 then flatten it to a background layer and save it again...
see it that changed anything

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digitaldog

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Re: Why are PSD files so big?
« Reply #10 on: December 01, 2019, 08:45:47 pm »

my first question would be  :

You state it is one layer; then
is it a layer 0 or a background layer?
if it is a layer0 then flatten it to a background layer and save it again...
see it that changed anything
Good question as my assumption was one layer in addition to the bkgnd layer.
But another question to clarify would be, where is this 'size' being reported; in Photoshop or in 'the Finder'? I assume again, the latter but it's important to point out, Photoshop's prediction of the open file size optionally shown below each document (if so set) can be wildly inaccurate.
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Andrew Rodney
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Redcrown

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Re: Why are PSD files so big?
« Reply #11 on: December 02, 2019, 01:29:39 am »

Using Windows 10 and Photoshop 21.0 I created a document 6,325 pixels square. That's 40 million pixels.

I set the File Handling preferences for PSD to disable compression and maximize compatibility. I double clicked the background layer to make it "Layer 0". I filled the image with neutral gray and added fine noise to make any compression minimal. These steps should make the PSD as large as possible.

I saved this PSD in 16 bit and got a size on disk of 229.55 MB. I re-loaded it into Photoshop and read the Document size inside Photoshop as 114.5M.

When I set PSD prefs back to compression with no compatibility and flatten to have a true 1 layer background, I get a size on disk of 114.48 MB (smallest possible).

So, I have no idea how or why you got a 938MB file out of a 40 million pixel image, regardless of where you are reading those numbers. One place to look is in the Channels Pallet. Extra channels (masks) can increase files size a lot. But it would take a lot of channels to get to 938MB. 

PSD file sizes are affected by the File/Preferences/File Handling options in Photoshop. Compression makes smaller files. Compatibility makes files larger. Compatibility just sticks a flattened jpeg version inside the PSD file so non-Adobe programs can show the contents. It can almost double file sizes.

Hope this helps, and sorry you got caught in the never ending grade school fight between two of our most famous bullies.
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kers

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Re: Why are PSD files so big?
« Reply #12 on: December 02, 2019, 03:52:42 am »

My second question would be: - are there any extra channels for selections/ masks apart from RGB?

( is it RGB or is it CMYK)
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Martin Kristiansen

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Re: Why are PSD files so big?
« Reply #13 on: December 02, 2019, 04:35:56 am »

Well of course you have Lab channels as well although I have only ever really found the L channel useful. And if you are wanting more variety with channels, for whatever reason, you can use apply image or calculations found under the Image menu. I haven’t used those things in years but I assume they are still there.
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digitaldog

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Re: Why are PSD files so big?
« Reply #14 on: December 02, 2019, 10:50:08 am »


Franz isn't a bully, he's an internet troll. I'm absolutely known by some as a bully dog; usually an accusation placed by those who get annoyed after technical misinformation they provided is corrected.  ;D
"What annoys us about others may say more about ourselves than about them."-C.J. Jung
« Last Edit: December 02, 2019, 11:19:09 am by digitaldog »
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Andrew Rodney
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digitaldog

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Re: Why are PSD files so big?
« Reply #15 on: December 02, 2019, 11:20:57 am »

Well of course you have Lab channels as well although I have only ever really found the L channel useful. And if you are wanting more variety with channels, for whatever reason, you can use apply image or calculations found under the Image menu. I haven’t used those things in years but I assume they are still there.
Lab and RGB doc's are nearly identical in size on this end but Alpha Channels do make the document larger. I saved one flattened PSD and it was 30.2mb on disk but with two Alpha Channels it ended up at 50mb.
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Andrew Rodney
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PeterAit

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Re: Why are PSD files so big?
« Reply #16 on: December 02, 2019, 11:50:16 am »

my first question would be  :

You state it is one layer; then
is it a layer 0 or a background layer?
if it is a layer0 then flatten it to a background layer and save it again...
see it that changed anything

The change made a huge difference! The file shrank by almost 75%, to close to my calculated size. Why is layer 0 so different from the background layer?
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Peter
"Science does not care what you believe" - unknown

digitaldog

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Re: Why are PSD files so big?
« Reply #17 on: December 02, 2019, 11:53:48 am »

The change made a huge difference! The file shrank by almost 75%, to close to my calculated size. Why is layer 0 so different from the background layer?
Because the data (or lack) of a layer plays a huge role. If the layer has mostly transparency, it's far, far smaller than a layer filled with pixels. So as a test, make a new layer that's 'empty' and save. Examine the size. Open the PSD and make half the layer a fill (any color will do). Save and examine the size. Now open and make the entire layer filled with pixels (again, simply do a Fill), save and examine the size.
As I said earlier (before the thread highjack): A lot depends on what's on that layer.
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Andrew Rodney
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Frans Waterlander

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Re: Why are PSD files so big?
« Reply #18 on: December 02, 2019, 06:27:10 pm »

I'm absolutely known by some as a bully dog.

Amen to that.

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digitaldog

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Re: Why are PSD files so big?
« Reply #19 on: December 02, 2019, 06:30:37 pm »

Amen to that.
As an atheist I can simply reply:God spelled backwards is dog.
And your arms are too short to box with the dog. 8)
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Andrew Rodney
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