CousinMadness wrote in post #2401655
Hi Dimitri,
For the most part our digital images are viewed right here on the screen you are staring at. Few end up in print form, even fewer enjoy life as a huge print that you could see from the side of the Motorway. To this end and for the purposes of my reply, we'll take the stance that the majority of us are concerned with optimising images for the web.
What this means is that your snazzy 10.2 megapixel SLR with the $1000 lens and RAW capability is serious overkill. Well yikes... you've probably never heard your camera being described as overkill... but it is. We allow ourselves to become brow beaten by retail hysteria that we really need more megapixels. Don't be a Lemming - stop and think for a minute. The latest Canon creates a RAW image containing 10,000,000 of those pesky little microns. This is reduced generally by average online photo gallery standards to around 200,000 - 300,000. For this forum the maximum is 100,000. OK... so where has the other 9 million 900 thousand gone to? Down the toilet that 's where... along with your hard earned money.
I've wandered... back to Dimitri's question. Why is the "save for web" feature safer?
The Adobe algorithm for jpeg compression was procured by Thomas Knoll in the early 90's. Many have tried to emulate it's amazing capabilities... but the fact is it is an ingenius piece of code. The "Save for web" algorithm calculates "how busy" parts of the image are and gives precedence to those areas. Open skies and large similarly coloured areas are "attacked" more vigorously by the compression code.
The program figures out which areas of the image you are least likely to notice the data it has thrown out. You can also virtually dial in the end kB that you want right down to +/- 5kB. Using "Save As" is not unlike taking a machete to cut off that loose thread on your shirt collar. It chops the kB drastically with little control and does so across the luminance and chrominance spectrum. Chunks of coloured areas will really suffer and you can say goodbye to fine details and hello "jaggies".
"Save for web" is safer because it eliminates the guess work as to which parts of the image really won't miss a few hundred kB's. It's bad enough that we are throwing out 99% of the original 10 megapixel image... at least this way we will have thrown out the least important ones so our picture can wow the POTN members that little bit more.
Sorry for the hijack Elizabeth... and I hope this gives you a better understanding Dimitri of how it all works when you drag that slider bar in Adobe to get the numbers down for web posting.
Cheers, and thanks for asking. Ol Cousin here has a load of useless information stored in his heid. It's only handy when someone asks.
Cuz....
who else can ramble like this anyway? ,noone,i assure you.
Anyway,now,i hear you,of cours i hear you,i`ve always saved as....save as...though and never had any of the problems you mentioned above,not to my knowledge anyway.
Mind you,i don`t compress them very hard,i like them around 1100 wide and around # 10 on the slidding bar,which gives me around 400 kbits (or whatever they are called.
but of cours,a big thanks for all the info you just gave us,very valueable indeed.
