saving with cs2 on a mac

noah

noah

Messages
1,059
Edit My Images
Yes
why when i save my files does the file size come out much larger than the estimate on my mac. it happens when i use save for web and contrain to a size too. say i go for 160kb max most of my files are 200kb. very annoying, didn't used to happen on my pc.

can anyone shed any light?
 
Hmm thats a strange one.
I know on the PC when you use Save As, and it gives an estimation of size (for JPEGs), the file usually ends up around 20k larger, on account of the embedded EXIF detail I think.
 
yeah, i see your point. but using 'save as' mine goes double or triple the file size! means i have to save at quality 4-5 to get them down to upload here!
 
How are you saving - just saving your large file for the web ?.

I always scale down my images to keep the quality, in 4 stages. and then fit image to 800 x 800 and finally save the jpg on quality 10. I found the images don't have any compression artifacting etc. and the quality is very good. (I also use a mac).

My action for "800 JPG" is setup as follows

open image
flatten layers
convert to sRGB colour space
scale image down 20%
scale image down 20%
scale image down 20%
scale image down 20%
fit image 800 x 800
sharpen for web
convert to 8 bit
save as jpg quality 10

building an action is the easyest way as you can switch in or out parts of the action when needed, I sometimes switch out 1 or 2 stages of scale image depending on which camera / file size im using. You can also batch hundreds of pics at once with the action. and even include it into other actions.

Hope this helps

Mark
 
It is not a problem but down to the way files are organized into two parts, a data fork and a resource fork, on the Mac's filing system.

The data fork is essentially the actual file while the resource fork provides additional information about it. The file size displayed in the Save for Web dialogue of Photoshop is the size of the data fork, but when viewed in Finder you will see the combined size of both forks.

To use an analogy with photographic terms, the resource fork is the equivalent of EXIF data being added to a file which helps the system understand it better. Most commonly it will include codes which identify which application was used to create the file so that when you double click on it the appropriate program will load. This is how it knows to load Photoshop for .JPG file you created while loading Preview for images you download, for exmaple.

Different applications may also include other information they think will help them handle the file without needing special file formats. A text file editor may include information about the state of the document when it was saved such as where the scrollbar was positioned, and whether anything was selected, so that it can be restored exactly as you left it. Photoshop usually (though not in Save for Web) will create a thumbnail of the image to use as an icon. These custom icons are stored in the resource fork.

Windows and Unix type filing systems do not support resource forks, and so if you copy a file to another system [*] or to put it online you will only copy the resource fork. So while the file size may be bigger on your hard disk, when you do put it on the web it will only upload the size you originally expected.

In short, it is nothing to worry about, the file will be the size you expected for your intended use, it will just use more space on your local hard disk.

Michael.

[*] Actually to be technically accurate, if you copy a file to a Windows or Unix formatted hard disk via the Finder it will also copy the resource fork but this will be saved in a separate hidden file. Copying via ftp, a web upload, or the normal cp or mv commands will ignore the resource fork though.
 
mho01 said:
My action for "800 JPG" is setup as follows

open image
flatten layers
convert to sRGB colour space
scale image down 20%
scale image down 20%
scale image down 20%
scale image down 20%
fit image 800 x 800
sharpen for web
convert to 8 bit
save as jpg quality 10
Click to expand...

Is there any reason you convert the colour space before resizing? I am just wondering whether I should do that as I would have thought that because the image will be dithered during scaling you would still want the benefit of a larger gamut during this stage.

Michael.
 
mij said:
Is there any reason you convert the colour space before resizing? I am just wondering whether I should do that as I would have thought that because the image will be dithered during scaling you would still want the benefit of a larger gamut during this stage.

Michael.
Click to expand...

Makes no difference as the image will only be 800 pixels along its longest side.

If working on large images any changes are left until the end, depending on where to file is going.
 
yeah i use an action too.

constrain to 500x700 pix for my website max dimensions.
convert to lab
select lightness
sharpen 100% 0.2 diameter x3
convert to rgb
save for web

it's what i've been doing for the last year on my pc and works well for me usually.

mij, i'll upload a couple of files to check, i think i see what you mean.

thanks all for the tips chaps :)
 
right, still having problems.

photoshop estimates 98kb on a 700x495pix photo at 72 dpi. 6/12 quality.
mac calls it 212kb
photobucket calls it 172kb

ggrrrrrrrr, this is just plain confusing.
 
You must log in or register to reply here.
Back
Top