image size reduction

[EOS_JD]

a pixel is just a sample point. put many of them together and you get a picture. Yes it is that ambiguous. The use of the word is highly context sensitive.....

I agree with this.

 

[pxl8]

a pixel is just a sample point. put many of them together and you get a picture. Yes it is that ambiguous. The use of the word is highly context sensitive.....

I agree with this.

So a pixel is a sample point. OED defines point as:

a very small dot or mark on a surface

So a pixel is a point which is a very small dot.

Pixel = dot

Ok, I'm being a bit silly here but I think the point (groan) is clear. Pixels are just another word for dots, points, squares, triangle, circles, etc. The phrase was introduced in technical papers as a way to reference a "thing" - it's not exclusive to digital images or any particular type of data although it often associated with bitmap images.

PPI can describe image resolution & DPI describes device resolution. The PPI value in the image defines the desired real world size whereas the DPI of the device describes it's output resolution. DPI/PPI tells you how many dots the output device will use per image pixel to render the image at the target size but that's not something you often need to know or care about, unless you're coding a device driver

Or to put it another way - an image is made from pixels and pixels are rendered from (device) dots that might be smaller, larger or the same size as the pixels.

edit to add - of course it could be argued that the dots that make up the pixels have become the pixels (picture elements) of the rendered image, if we keep going we'll end up with quantum pixels

 

[EOS_JD]

So a pixel is a sample point. OED defines point as:



So a pixel is a point which is a very small dot.

Pixel = dot

Ok, I'm being a bit silly here but I think the point (groan) is clear. Pixels are just another word for dots, points, squares, triangle, circles, etc. The phrase was introduced in technical papers as a way to reference a "thing" - it's not exclusive to digital images or any particular type of data although it often associated with bitmap images.

PPI can describe image resolution & DPI describes device resolution. The PPI value in the image defines the desired real world size whereas the DPI of the device describes it's output resolution. DPI/PPI tells you how many dots the output device will use per image pixel to render the image at the target size but that's not something you often need to know or care about, unless you're coding a device driver

Or to put it another way - an image is made from pixels and pixels are rendered from (device) dots that might be smaller, larger or the same size as the pixels.

edit to add - of course it could be argued that the dots that make up the pixels have become the pixels (picture elements) of the rendered image, if we keep going we'll end up with quantum pixels

We both know where each other is coming from and we know each other is right to a certain degree The symantecs of what we think could be and have been argued both ways. Lets argree to stop here

 

[shooting_stars]

This thread has made for a very goodread - however I have a question: Is there a golden resolution for hosting pics on the web?

At the moment I am not resizing my pics and upload them as is to Flickr, but want to change this to make efficient use of it.

 

[EOS_JD]

The way I understood it is this.

Think of your monitor resolution. Mine is 1680pixels x 1050pixels.

If I have an image that is say 2000 x 1200 pixels, clearly at 100% I cannot see all of the image. A web image should be viewable at 100% but not so big that someone can copy and print it!

Size your image to 600 pixels on the longest edge and you will be able to view the image at a reasonable size your monitor.

If your screen res is lower, say 1024px x 768px, clearly the image will look bigger but will not actually be any different.

The rule is keep images small - they are quick to load, small enough that stealing is less likely to happen.

A 600px image (on the longest edge) will be small but ok to view. If you are using flikr, maybe a 700 or 800 pixel may suit you better.

Resolution doesn't matter for showing on the web.

A 600 x 400 pixel image saved at 300ppi is EXAXTLY the same image as a 600 x 400 image saved at 72ppi.

The difference would only be noticeable when printed as the 300ppi image would be smaller. (see above)

 

[shooting_stars]

Many thanks!