When sizing an image I hear we should go more by "pixels"?? But then there are those that go by inches?? What general "rule" is there in regards to sizing of an images?? We cannot add pixels if we wish to imcrease the size, but an image can "lose" pixels when reduced?? So, if I make an image smaller what is the difference between using pixel sizing and obvious others?? Does it lose MORE quality if reduced by pixels or by inches?? ~3D ;-)

3DSprite: The short answer is "Depends on what your target medium is". Use pixels if you're targeting the Web (or just monitor display) and use inches or centimeters if you (or someone else) is going to print it. You can "add" pixels through a process called interpolation. PhotoShop uses bicubic interpolation as it's default and I have found it to be excellent. However (you knew that was coming, right?), interpolation will not add detail that wasn't there previously! It will only increase pixel density, enabling you to raise the resolution for larger output. If you uncheck the two boxes at the bottom of the image size dialog box and then chage the image size or dpi size, you will be able to see the way these factors interact. For instance, when you render in Poser 4 no matter what dpi you specify in the render settings, it always comes out 72dpi but the size, in inches, can get rather large. If you import the finished picture into PhotoShop and invoke the Image Size dialog, then uncheck the 2 boxes I just mentioned, and change the image size to 1/4 of it's current size, you will notice that the DPI number increases dramatically. PhotoShop is just squeezing the pixels into a smaller space. Nothing else changes, not even the file size! This is about as far as I want to go with this from memory. They say that as you get past 50, two things start to go. The first is your memory, and I can't remember the second thing :o) -Jim

But there are three ways to reinforce your memory... 1. By association 2. By repetition 3. ...??? Darn! I forget! Pictures for uploading are best in 72 or 75 dpi for viewing or file size... But I like to do finish work in 150 dpi and a maximum of "Thousands of Colors-RPG" (not enough computer memory to do more)... At higher resolution, edge "Jaggies" disappear, detail is retained in "Scale", and "Sharpen" is far more effective... And then, I reconvert back to 72-75 dpi for "Upload" Walt

Gee 3D- One of the first thing I tell my Photoshop classes is that there are no inches in PhotoShop, just pixels! Some file formats support an inch "tag" that determins how big something will print, but in Photoshop you only work on pixels. I've seen things like "my web page pictures were saved at 300 dpi so they are high quality", the dpi setting is meaningless for anything while on the computer, especially for web pages. When you scan or prepare an image always think how many pixels are required for the end application (and it gets complicated with the 2 X lpi = dpi rule, which I will not go into right now), but always think in terms of pixels, inches (and dpi) is just a figure of speach!

I think in pixels. I do work for print, and then I have to convert my measurements, but I convert the inches in print size to pixels. Honestly, I don't think I could get the accuracy if I had to work in inches. I just automatically think pixels and 72 pixels per inch and go from there

You should only give consideration to inches if you will output to a printer or other offline format, as others have said. If this consoderation must be made, it is the FIRST consideration to make. If you spend all your time and work on a 300x300 pixel image, and you want to print to an 8 inch square, you're screwed. Interpolate all you want, the printed output will not look good. In general, if you're planning to print on a home-quality color inkjet printer, 150dpi is sufficient... so do the math and figure out how many pixels you need for your desired output size. If you'll print on a laser or dye-sub printer, you'll want 300 - 600 dpi output, or, two to four times both the horizontal and vertical pixel resolution of the above (four to eight times the area resolution). I believe the Photoshop manual devotes several pages to resolution and dpi. -sk

The "old school" of thought is 2 x lpi of the printer, real halftone printing on an offset press will use a lpi of about 80 to about 175, so you need about 160 dpi for newpaper quality printing, 350 dpi for the best quality printing (like in the brochures you get in a new car showroom). Lasers and inkjets don't really have an lpi, they have a "assumed" lpi, ranging ing from about 52 for 300 dpi lasers to about 120 for 720 dpi inkjets, so a dpi of about 105 is correct for a 300 dpi laser, 210 for a 600 dpi laser or inkjet, 240 for a 720 dpi inkjet. You should never go higher than that, the above will do the best output the printer can do, the "reformed" school of dpi uses a dpi of about 75% of the above numbers.