how to reduce the file size of an image

Hello all,

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

Ty in advance.

In article ,
(didi) wrote:

Hello all,

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

Do you mean you want a 62kb image that is still 320x240? Or do you mean you want to retain the same aspect-ratio?

From: (didi)

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

File > Save for Web and try a jpeg compression setting of about 30-50 or so. Click '2-up' to see the compressed version side by side with the original to make sure you're not losing much quality. The estimated image size should be visible in the bottom left corner of the image window. Change the "quality" setting to increase/decrease file size and image quality until you get what you need, then save the file with a new name so you still have the original.

Or you can do the same thing in ImageReady ... I can often get 650 x 480 jpegs down to 40-50 KB with good quality, so 320 x 240 in 62 KB should be pretty easy, you may be able to go with a setting of 70-80 or so.

This will require some loss of data during jpeg compression, but you knew that, right?

Bill

In article ,
(Bill Hilton) wrote:

From: (didi)

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

File > Save for Web and try a jpeg compression setting of about 30-50 or so. Click '2-up' to see the compressed version side by side with the original to make sure you're not losing much quality. [...]

Or Save for Web and use "Optimize to Filesize" (little arrow on the right of the window.) If you give it a crazy low value, it will bottom out at JPEG format with zero quality at the lowest possible size, not always your target.

Is it a photo? If not then you might try saving it as a gif and reducing the number of colors in the image.

didi wrote:

Hello all,

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

Ty in advance.

The files size dictates the resolution/dimension ratio of an image. Reduce the file size and either the dimensions or the resolution have to be reduced. Below 72 dpi a picture will not 'look' normal on a PC screen. You figure out the rest, eh?
Doug

"Rowley" wrote in message

Is it a photo? If not then you might try saving it as a gif and reducing the number of colors in the image.

didi wrote:

Hello all,

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

Ty in advance.

"Techno Aussie" wrote in message

The files size dictates the resolution/dimension ratio of an image.

Reduce

the file size and either the dimensions or the resolution have to be reduced. Below 72 dpi a picture will not 'look' normal on a PC screen. You figure out the rest, eh?

The file size (on disc) is determined by the number of pixels in the image and, in the case of a compressed format such as JPEG, the degree of compression applied. The resolution setting (pixels per inch or PPI) has no effect whatever when the image is displayed in a web browser. The monitor display resolution setting will determine the image size. An image editing program can of course display the image at whatever size it chooses. The resolution setting in the image file will be used by print programs to determine the default print size of the image. The PPI setting of the image does not relate to the DPI setting of the printer.

John

(jjs) wrote in message news:...

In article ,
(Bill Hilton) wrote:

From: (didi)

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

File > Save for Web and try a jpeg compression setting of about 30-50 or so. Click '2-up' to see the compressed version side by side with the original to make sure you're not losing much quality. [...]

Or Save for Web and use "Optimize to Filesize" (little arrow on the right of the window.) If you give it a crazy low value, it will bottom out at JPEG format with zero quality at the lowest possible size, not always your target.

Thank you for the answers. I think I got confused. In photoshop when I was in "Image size" it was showing 255K. However in Windows explorer, when I was looking at the file size it was saying 14KB! So my file is already small enough in KB. But I still don't understand what the 255K refers to...

"didi" wrote in message

Thank you for the answers. I think I got confused. In photoshop when I was in "Image size" it was showing 255K. However in Windows explorer, when I was looking at the file size it was saying 14KB! So my file is already small enough in KB. But I still don't understand what the 255K refers to...

The basic file size = no. of pixels x 3
(i.e. one byte per channel per pixel).

John

Thank you for the answers. I think I got confused. In photoshop when I was in "Image size" it was showing 255K. However in Windows explorer, when I was looking at the file size it was saying 14KB! So my file is already small enough in KB. But I still don't understand what the 255K refers to...

255K is the size of the image when it is UNCOMPRESSED. 14KB is the size of the image when it is COMPRESSED.

GIF and JPEG files are compressed in order to make the file smaller on disk. In the case of JPEG, the file is made smaller by a process that degrades its quality. When you save an image as a JPEG, the image is small on disk, but its quality is degraded.

When you open an image in Photoshop (or anything else), the image must be uncompressed in order to be shown on the screen. Photoshop shows you the uncompressed size of the image.

--
Rude T-shirts for a rude age: http://www.villaintees.com Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

The files size dictates the resolution/dimension ratio of an image.

That is incorrect. Many image formats, including GIF, JPEG, PSD, and some varieties of TIFF, are compressed on disk. The size of the file is NOT determined strictly by the size of the image in pixels.

Below 72 dpi a picture will not 'look' normal on a PC screen.

Incorrect. When an image is shown on the screen, the resolution is unimportant and the information about resolution is discarded. The computer displays the image at one image pixel per screen pixel. A 320x200-pixel image at 4 dpi will look *identical* to the same 320x240-pixel image at 1,000,000 dpi.

--
Rude T-shirts for a rude age: http://www.villaintees.com Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

There was a time when I thought you actually had a clue, Tacit... Time for a re-think on that area. You contridict yourself here. You say it's "incorrect" that the pixel count of an image dictates the size/resolution of the picture yet go on to say exactly that in different words. Sure you're not just testing your keyboard/mindset to see if what you say can be said any differently?

Doug
-----------------------
"Tacit" wrote in message

The files size dictates the resolution/dimension ratio of an image.

That is incorrect. Many image formats, including GIF, JPEG, PSD, and some varieties of TIFF, are compressed on disk. The size of the file is NOT determined strictly by the size of the image in pixels.

Below 72 dpi a picture will not 'look' normal on a PC screen.

Incorrect. When an image is shown on the screen, the resolution is

unimportant

and the information about resolution is discarded. The computer displays

the

image at one image pixel per screen pixel. A 320x200-pixel image at 4 dpi

will

look *identical* to the same 320x240-pixel image at 1,000,000 dpi.
--
Rude T-shirts for a rude age: http://www.villaintees.com Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

"Techno Aussie" wrote:

There was a time when I thought you actually had a clue, Tacit... Time for a re-think on that area. You contridict yourself here. You say it's "incorrect" that the pixel count of an image dictates the size/resolution of the picture yet go on to say exactly that in different words. Sure you're not just testing your keyboard/mindset to see if what you say can be said any differently?

Sounds like you've become clue-deficient yourself. "dpi" is a completely arbitrary measurement that only takes on meaning when it is used to map the image to a physical substrate (i.e., paper) with a fixed dimension. You can assign any dpi you like to any digital image, from 1 dpi to 10,000,000 dpi, and it does not change the fixed pixel-count height and width. The 72 dpi or 96 dpi figures used for screen display are rough approximations of the physical mapping of pixels to screen inches. And that's almost exactly what Taccy said.

So what's [the | your] problem here?

--
| James Gifford * FIX SPAMTRAP TO REPLY |
| So... your philosophy fits in a sig, does it? |
| Heinlein stuff at: www.nitrosyncretic.com/rah |

From: "Techno Aussie"

There was a time when I thought you actually had a clue, Tacit..

Personally I think Tacit usually gives the best answers of anyone on the entire newsgroup, except maybe for some of the inkjet RGB color management-type questions.

You say it's
"incorrect" that the pixel count of an image dictates the size/resolution of the picture yet go on to say exactly that in different words.

No, he said that "When an image is shown on the screen, the resolution is unimportant" ... resolution doesn't really matter until you're ready to print. He's not talking about the actual pixel dimensions, he's talking about the resolution, which is different.

Bill

There was a time when I thought you actually had a clue, Tacit... Time for a re-think on that area. You contridict yourself here. You say it's "incorrect" that the pixel count of an image dictates the size/resolution of the picture yet go on to say exactly that in different words.

No; "resolution" and "pixel dimension" mean two different things.

Resolution, measured in pixels per inch or dots per inch, is a measurement of how many pixels occupy one inch of output; pixel dimention is a measure of the total number of pixels in an image.

So: Pixel dimension means how many pixels there are; resolution measures how big each pixel is.

It's easy to confuse the two. Think of a raster image as a tile mosaic. Resolution is how big each tile is; pixel dimension is how many tiles there are.

Resolution, pixel dimension, and uncompressed file size are all related. If you take the number of pixels wide the image is, and multiply that by the number of pixels per inch, you'll have how many inches wide the image is...

....when it's printed. That's the confusing part. When an image is displayed on the screen, the resolution is unimportant, and is discarded. Only the pixel dimension matters.

--
Rude T-shirts for a rude age: http://www.villaintees.com Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

"Techno Aussie" wrote in message

There was a time when I thought you actually had a clue, Tacit... Time for

a

re-think on that area. You contridict yourself here. You say it's "incorrect" that the pixel count of an image dictates the size/resolution

of

the picture yet go on to say exactly that in different words.

"Size" can mean (not an exhaustive list):
1) the number of bytes in a file
2) the number of pixels in an image
3) the amount of paper occupied by an image

"Resolution" can mean:
1) the number of pixels per linear unit of paper
2) the number of rows and/or columns of pixels in an image
3) the number of distinguishable lines per linear unit of film
4) the number of distinguishable lines per image

If you are clear about which meaning you intend, you are less likely to be misunderstood.

On 20 Dec 2003 12:44:33 -0800, (didi) wrote:

Hello all,

Here is the deal. I have a pic that's 320x240 with a file size of 255KB. I need it to be smaller than 62KB but with the same dimensions. How can I do that in Photoshop??

For a file that small in pixels, 255 KB seems to be an uncompressed format (320*240*3=225KB) plus unnecessary information.

Any JPG-compression should reduce it to less than a third, I'd start at minimum compression - and in Photoshop you should "save for web" to avoid any additional stuff in the file.

Michael

Ty in advance.

Seemingly you too, fail to realise that the pixel count controls the image's size/resolution. You can't "asign" dots that don't exist anymore than you can pixels that don't exist. If an image is 1024 pixels by 768 pixels in size, it's at 72 dpi to display on a computer screen. Double the dpi count to get a basic quality print, and you halve the actual image size. Unless you are talking about interpolation or other methods of altering the pixel count.
Doug

"James Gifford" wrote in message

Sounds like you've become clue-deficient yourself. "dpi" is a completely arbitrary measurement that only takes on meaning when it is used to map

the

image to a physical substrate (i.e., paper) with a fixed dimension. You

can

assign any dpi you like to any digital image, from 1 dpi to 10,000,000

dpi,

and it does not change the fixed pixel-count height and width. The 72 dpi or 96 dpi figures used for screen display are rough approximations of the physical mapping of pixels to screen inches. And that's almost exactly

what

Taccy said.

So what's [the | your] problem here?

--
| James Gifford * FIX SPAMTRAP TO REPLY |
| So... your philosophy fits in a sig, does it? |
| Heinlein stuff at: www.nitrosyncretic.com/rah |

Seemingly you too, fail to realise that the pixel count controls the image's size/resolution.

No. Pixel count controls size, but not resolution.

Consider two images: one 320x240 at 72 pixels per inch, one 320x240 at 300 pixels per inch. Same pixel count, different resolution. You are using "pixel count" and "resolution" as if they mean the same thing. They don't.

--
Rude T-shirts for a rude age: http://www.villaintees.com Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

Tacit wrote:

Seemingly you too, fail to realise that the pixel count controls the image's size/resolution.

No. Pixel count controls size, but not resolution.

Consider two images: one 320x240 at 72 pixels per inch, one 320x240 at 300 pixels per inch. Same pixel count, different resolution. You are using "pixel count" and "resolution" as if they mean the same thing. They don't.

Unfortunately, they can be. The term 'resolution' is also commonly used for the pixel count of digital cameras. I don't like it either, but that's the way it is.

--
Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/

On Tue, 23 Dec 2003 22:02:08 +0100, (Johan W.
Elzenga) wrote:

Tacit wrote:

Seemingly you too, fail to realise that the pixel count controls the image's size/resolution.

No. Pixel count controls size, but not resolution.

Consider two images: one 320x240 at 72 pixels per inch, one 320x240 at 300 pixels per inch. Same pixel count, different resolution. You are using "pixel count" and "resolution" as if they mean the same thing. They don't.

Unfortunately, they can be. The term 'resolution' is also commonly used for the pixel count of digital cameras. I don't like it either, but that's the way it is.

No. Words are used in multiple ways sometimes - but if you do so it is neccessary to add some more words to specify what you are talking about.

So pixel resolution = number of pixels = size of the image given it its basic elements.
And print resolution is print elements (dots or lines) per real world measuring unit (inches, centimetres) for the printing process. Sometimes people still want do differentiate, then they specify whether they are talking aboult single color print resolution (dots per inch, DPI) or full color print resolution (pixels per inch, PPI), but details on this would lead too far.

Now for an image with a pixel resolution of 320x240 you could specify one of many different print resolutions, 300ppi for a stamp size high quality image or 100ppi for a low quality 3.2 inch wide image. On screen the width of the image in 100% size may vary because of different monitor sizes (followers of the 72dpi myth make good katholics who believe even if reality proves to be different).

For the filesize: Either you use a compressing file format (JPG?) or you reduce the number of pixels.

Michael

--
Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/

Techno Aussie wrote:

There was a time when I thought you actually had a clue, Tacit...

Class, listen to Tacit!

I find that if I think I disagree with Tacit, it's time to thing once and twice again before posting to the contrary - not that I haven't done this on occasion :-)

--

Mike Russell
www.curvemeister.com
www.geigy.2y.net