Kansas, that seemed very complicated and arcane.

I actually do like Serps explained. I hope many people read this thread and learn how to save their pictures so that they are 75k of size.

Of course, because dimensions must be less than 550 pixels wide by 600 pixels high, it goes without saying that you have to resize your picture (Image/Image size) before saving, but the dpi makes no difference at all, "Saving for web" automatically saves at 72 dpi.

If you use photoshop and want to save your pic optimal for a given filesize, you should indeed make use of Save for the Web (ctrl-shift-alt-s) as Serps pointed out.
In the save for the web-dialog you can push the little arrow to open up a menu:


There you click optimize for file size, which popups a second dialog-box:



Fill in your maximum filesize and Photoshop wil return the most optimal settings in the save for the web-dialog.



Edit:
Links to my images were broken for a while. So I've put them elsewhere. Thanks to http://imageshack.us/ for hosting.

I'm glad we are tlaking about this. What size do you guys work in? When I drag the phto over to my canvas it ends up being about 3.5 x2 inch picture.

I work in 300 dpi because I read a tut saying not to work in crappy 72 Ddi?

It seems to me that what I'm hearing now that 72 is fine for the web.

I apprecaite this thread, because as you see you don't know what you don't know until you tell the truth about how you are doing it.

I was afraid at first because I didn't want to be the butt of the joke, but my time is valuable and I need the feedback, so I can impliment it and cut down on the steps.

Hopefully, speaking up will help others that don't want to ask.. Thanks everyone...

Kansas, if you have a 600 pixels by 600 pixels picture at 300 dpi, it will PRINT out 2" X 2". If you have the same 600 pixels by 600 pixels picture at 72 dpi and try PRINTING it, it will be 8 1/3" X 8 1/3" and will look crappy.

When you are working on that 600 pixels by 600 pixels picture, whatever dpi setting it is at will make no difference at all. Click "View/Actual pixels" and it will occupy the same space on your monitor. If you want to be more precise in your Photoshop work, double that picture's number of pixels when working on it and half it back when finished.

Voilà!

i always work on pics at the final size (550X600, 72dpi). I think it's the best way to be sure that what you post is what people will see.

serbs this a good explanation! but it's also possible to click the litle arrow direct by the red number 2. then comes a pop up with the choice "optimize to datasize". edit the size e.g. 75kb and PS would do the best for this size.

oh netwel this is what i mean, i was to slowly

I find it useful to double the picture's pixel size in order to work on it when I have fine details to draw with the paintbrush.

For example, when I do a cutout of an animal and I don't want it to look fake, I have to draw some fine furry stuff around it.

I wouldn't be able to achieve the same quality of work if the picture would be in its final size; the lines would be too coarse and it would seem out of place.

Are you creating a new document at 300 dpi and dragging the image onto it? If you take a low res image and bring it into a hi res file, the low res takes on the properties of the hi res in terms of dpi.

If you know this, please do not get offended by this over simplified explanation:

DPI = dots per inch. We deal with web images that are 72 dpi because our screens are generally 72 ppi (pixels per inch). This means that each linear inch of our image is divided into 72, and each of these 72 sections contains information (colour).

In a 300 dpi file, each inch is divided into 300 sections, so, as you can see, contains more information...larger file.

If you take a 72 dpi image and drag it into a 300 dpi file, and because the size of the inch doesn't change, your image will only take up the first 72 sections of the available 300 per inch. In fact, you fit just under 4 of these 72 sections in a 300 dpi inch. This is why your image shrinks.



To avoid shrinkage, instead of creating a new file at 300 dpi, take the original 72 dpi file and go to image-->image size and resample image checked on, change the resolution to 300. Your image size will not change, in terms of width and height, but your resolution will. If you don't check resample image, your image will be 300 dpi, but smaller in terms of width.

Once you are done, do what Michel and others have said about saving to web.

I hope this has not confused you. If it did, let me know. Maybe someone else can word it differently.

i haven't had any real experience when it comes to profesional photoshop work, for example: printing ( magazines, newspaper, ads,etc...) but i've heard a variety of comments about which is the standard or recommended resolution for this type of work, like no less than 300dpi or more than 300dpi is better, and does it have to be in CMYK mode. i wanted to see if anybody could tell me something about profesional printing.

i know this doesn't have anything to do with saving but i just wanted to know.

Sage, you are right, but I would had that what you will achieve here is to increase the number of pixel your image is made out of.

Another way to do that is to simply drag your picture into the other picture you are working with and Control + T (Free Transform) to make the picture fit your needs.

Serious: Printing is different than web. Before you save artwork for print, you have to know what the printer's line screen resolution is.

dpi = dots per inch (scanners, desktop printers)
ppi = pixels per inch (screen)
lpi = lines per inch. (press)

On press, to create images, the printer uses lpi. This is the printer's resolution. In a nut shell, the more lpi there are, the greater your dpi should be. Generally, your dpi should be 2X the lpi.

This is because each printer dot (this is how images are printed. If you look at a newspaper, you can actually see the dots on images) is made up of 4 dots from your image. (2 wide by 2 deep).

For a newspaper, where the paper used "drinks" alot of ink, printers usually use a line screen of 50-55. This means that your image should be about 100-110 dpi. Anymore, and your file is too big for nothing.

High end magazines, which use good paper that doesn't drink alot of ink are usually printed with a line screen of 140-155 (roughly)

this is why the optimal dpi for magazines is around 300 dpi (150 line screen X 2).

Again, this explanation is in laymen's terms. If you are sending a job to the printer's, ask him what lpi is going to be used, multiply this by 2, and set your image's resolution to this.

You shouldn't "bump" up the resolution as I explained above, because the computer will be guessing as to how to interpret the extra pixels. Images should always be scanned at 100% of the size it will be printed, and at the resolution it will be printed.

And, yes, for press, your file has to be in CMYK, because these colours are the primary colours the press uses (known as 4 colour printing)

[quote="Michel"]

True, but if your image doesn't have enough resolution (information) and you stretch it, it will become pixelated. You can reduce the size of a pict without losing quality, but enlarging is different. (Maybe I misunderstood Kansas )

Serious,

Newspaper minimum standard resolution = 200 dpi
Hi end magazine standard resoution = 2500 dpi
Web standards = 72 dpi

Do not confuse print resolution with web resolution. CMYK is print. RGB is web. It's that simple. So...when you download the image from PSC, you don't need to change it 'cause it's going right back up there. Unless you want to create a Hi-res, very clever print ad from one of these silly source images and make booo-kooo bucks doing it...and if that's the case please tell me who's willing to pay you for that!

WHAT???

thanks sage and eve. good things to know!