Photoshop file size

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BennyR
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p.1 #1 · Photoshop file size

This is something I have never heard a good answer for. I'm sure there is one somewhere.

When saving a file in Photoshop you can save at 12, 11, or what ever. I noticed when working on a recent large panorama if I saved it at 12 (.jpg) it was 110MB's or so. If I saved it at 11 it went down to 58 MB's or so yet there is no noticeable difference that I can see.

What actually happens? Does it remove pixels that aren't needed. I want to print at 24x36 so I want the best file possible but yet 100MB's is a limit for sending by email (without paying a monthly fee).

Thanks

Aug 05, 2008 at 11:15 PM

Peter Figen
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p.1 #2 · Photoshop file size

You're saving in a lossy (throwing pixels away) format called jpeg. That's a format you should only use for a final file that needs to be compressed for display on the internet or to facilitate faster digital transmission. Just by saving your file as a jpeg you have thrown away data even if you can't see it. Every time you change at least one pixel in the image OR change the jpeg compression scheme when resaving you will further degrade your image. At some point it may become a problem. Most people will recommend that you save yourself a "master" file in a lossless format, either tiff or the native Photoshop format and then save a copy to send or post.

I would not attempt to send any file close to 100 megs via email. While your email provider might allow it, not many on the receiving end are going to be very happy with that big of an attachment. You should use FTP to transmit your large files. Your lab that is making the large prints should have an ftp folder set up just for that purpose and be able to instruct you how to access and use it.

Aug 06, 2008 at 12:55 AM

paulhodson
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p.1 #3 · Photoshop file size

I doubt if you will see a difference even at quality 10. Try having a print made of a cropped part of the image at different quality values.

Aug 06, 2008 at 06:30 AM

SoundHound
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p.1 #4 · Photoshop file size

If you want "The best file possible" you will have to stop using JPEGs because you lose information every time you save to a JPEG. Best to save to non-destructive files such as: TIFFs, PSDs, PDFs, etc. Use the JPEGs only for emails, etc

Aug 06, 2008 at 08:32 PM

BennyR
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p.1 #5 · Photoshop file size

But my question is can you really see a difference. I realize about these lossy formats and stuff but if you can't see a difference......

Some of these would be very large (24x36) so perhaps there could be a noticeable difference.

I don't really understand this throwing pixels away thing very well either. If I have a file that is 6000 x 4000 pixels that is 50 MB's in file size when saved at 12 in PS and I save a copy at 11 which reduces the file size to 35 MB's say. It is still 6000 pixels by 4000 pixels. So what is actually getting thrown away? Maybe the question is at what point will there be a noticeable decrease in quality.

Edited on Aug 06, 2008 at 08:57 PM

Aug 06, 2008 at 08:45 PM

jerryrock
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p.1 #6 · Photoshop file size

Why save as a jpeg when you know it is compressing your files, gradually destroying your image quality?
Every time you edit and save a jpeg it destroys pixels, like metal rusting. Why save the Xerox copy and throw away the original?

You have other file choices that will save your image without the destructive compression as others have mentioned (TIFF, PSD, PDF etc).

Aug 06, 2008 at 09:11 PM

BennyR
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p.1 #7 · Photoshop file size

It started out as intent to email the files to a printer. I think that might not happen now so if I don't I will use .tif's most likely. Still, there's that thing where I can't see a difference.

Every time I see your pic I see Jack Nicholson.

Thanks

Edited on Aug 06, 2008 at 09:26 PM

Aug 06, 2008 at 09:25 PM

mhayes5254
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p.1 #8 · Photoshop file size

Posted the following on another thread several days ago:

You can do a quick experiment to see the effects of compression. Open an image and save it under different names with different quality levels (1, 5, 8, 12). As you change the quality level the compressed file size will change dramatically. Low quality=small file). Level 1 is virtually useless, values above 8 are very good. Try it to see what happens

Although there is always a loss, you will not see a visible change if the quality levels are high (>8 or 10). If you were to edit the file 50 times the changes would accumulate. I normally save at the highest quality just so I do not have to think about it. For images that will be edited you want high quality, however a more important issue is often to save in a 16 bit format like TIFF, PSD, etc to preserve the dynamic range for editing. When the image is finished, many will save it in JPEG.

JPEG is commonly used to send files to print services and will not result in a measurable quality loss.

Aug 06, 2008 at 10:03 PM

BennyR
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p.1 #9 · Photoshop file size

Actually I just did this and thought it was interesting. Didn't really notice a degradation till level 5 or so.

Thanks.

Aug 06, 2008 at 10:08 PM

jerryrock
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p.1 #10 · Photoshop file size

mhayes5254 wrote:
JPEG is commonly used to send files to print services and will not result in a measurable quality loss.

Professional printers require TIFF or PDF files for images used in publications.

Jpeg files are fine for web use or small format printing. Personally, I never use jpeg for printing.

Aug 06, 2008 at 10:36 PM


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