file sizes (Full Version)

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viv -> file sizes (8/23/2006 4:22:13)

I cant work out why when I save a artwork in PS it says the size is one thing, but when I look at the file size in my documents in has increased, sometimes quite lot, Im sure there is a easy answer to this but I just cant find it, cause obviously when you lower the file size in PS you lose so much quality of the pic..once again Im consfused

come back to edit and to ask this...the original pic I wanted to use as my avatar is 150 x 150 at 6.58kb, but when I downsize it in PS to 80 x 80 the file size is 10.2kb..how can this be[:@]



jaybee -> RE: file sizes (8/23/2006 5:45:52)

Depends what you're resizing it to, the quality etc. Different file types are more suitable for different graphics and you need to play around with them to find the best one. Sometimes a png8 is smaller than a jpg at medium or a gif.

As you have Photoshop the easiest way is to use Save for Web. Top right you can specify the file type via a dropdown and see the impact in the right hand image pane. Bottom right you can change the image size and also see the impact on the file size.



Donkey -> RE: file sizes (8/23/2006 7:29:33)

In corel photopaint (which I use) there is a distinction between re-sizing which does nothing to the file size and re-sampling where you can change the resolution, and the file size changes if the image or resolution is made smaller.

Your original image is 150 x 150 pixels so it should resample at 96dpi down to the maximum avatar size of 115 x115 with little loss of quality. If the file size is too big you can increase the compression when you export the file as a jpg or png. This will give you a slight loss in quality, but it should not be necessary as your original file size is only 6.58 kb.



dankos -> RE: file sizes (8/23/2006 23:12:42)

quote:

ORIGINAL: viv

I cant work out why when I save a artwork in PS it says the size is one thing, but when I look at the file size in my documents in [it?] has increased, sometimes quite lot,

What kind of image format (JPEG, PSD, TIFF)? Where are you getting the size (from Win browser, Image>Size)?
quote:

Im sure there is a easy answer to this but I just cant find it, cause obviously when you lower the file size in PS you lose so much quality of the pic..once again Im consfused

come back to edit and to ask this...the original pic I wanted to use as my avatar is 150 x 150 at 6.58kb, but when I downsize it in PS to 80 x 80 the file size is 10.2kb..how can this be[:@]
You may be changing the quality, or, more likely, you've saved with EXIF information. Doing a save for Web saves without the EXIF info, making for a much smaller JPEG file.



viv -> RE: file sizes (8/24/2006 3:20:26)

Im saving the images as JPEG, I make the art then click SAVE AS and if it is just too big, as in they take too long to load onto my site, and as I have so much up there, I try to keep the file sizes reasonably small, but of course want to keep the quality of the art at the same time.f I make a fanart and save it in PS the size might be 140kb but when I look at it in my documents it says its 150kb or something like that, and of course if I decrease the size when I save in PS the quality goes down and then when I put up on my site they dont look as good when you go to view the large image.

So I should be saving as Web saves which I didnt know you could do and this will make the file size smaller but keep the quality which is what I want, and then I can just treat them the same way as I always have.

This probably sounds confusing to you, it sure does to me, but I sort of understand what you are getting at, so will try it with next art I make and see what happens.

Thanks for the help.



dankos -> RE: file sizes (8/24/2006 11:38:34)

quote:

ORIGINAL: viv

Im saving the images as JPEG, I make the art then click SAVE AS and if it is just too big, as in they take too long to load onto my site, and as I have so much up there, I try to keep the file sizes reasonably small, but of course want to keep the quality of the art at the same time.f I make a fanart and save it in PS the size might be 140kb but when I look at it in my documents it says its 150kb or something like that, and of course if I decrease the size when I save in PS the quality goes down and then when I put up on my site they dont look as good when you go to view the large image.

So I should be saving as Web saves which I didnt know you could do and this will make the file size smaller but keep the quality which is what I want, and then I can just treat them the same way as I always have.

This probably sounds confusing to you, it sure does to me, but I sort of understand what you are getting at, so will try it with next art I make and see what happens.

Thanks for the help.

What quality are you specifying and pixels/inch? Quality 4 or 5 and ppi at 96 should be fine.
Take a look at the following JPEG images made in Photoshop CS from a 55 mb scan of a 35mm slide:
[img]http://www.dkosaka.com/images/lilypadsFV5.jpg[/img]
Quality 5, formed by save as, 36 kb
[img]http://www.dkosaka.com/images/lilypadsFV8.jpg[/img]
Quality 8, formed by save as, 45 kb
[img]http://www.dkosaka.com/images/lilypadsWMed.jpg[/img]
Quality 5, formed by save to Web, 18 kb

Setting for a high res monitor, (96 dpi) I set the size to a 4 inch width.
You can see the difference in quality between 5 and 8 is not obvious, yet there is a big file size difference. The lesson is that for such small images you should stick to medium quality. The first and second images retain the JPEG EXIF header which adds overhead and is useless on the Web. The third image was formed by File>Web. Its size is dramatically smaller because it doesn't retain the EXIF data. In practice, any image you form with about the same dimensions should be about the same size, 18 kb. Of course, keep your source images in a lossless form such as PSD or TIFF.



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