Photoshop Question: File>Save for Web & Devices

[gendarmee]

Hello there
Accidentally found that converting the picture with this option (File>Save for Web & Devices) on photoshop helps retain the colors whilst uploading pictures to Facebook.

My question is, what exactly happens when one optimizes a picture for web using that option?

what is sRGB, DPI & PPI What exactly happens if one reduces the PPI to 72 while resizing?

 

[battletone]

Hello there
Accidentally found that converting the picture with this option (File>Save for Web & Devices) on photoshop helps retain the colors whilst uploading pictures to Facebook.

My question is, what exactly happens when one optimizes a picture for web using that option?

what is sRGB, DPI & PPI What exactly happens if one reduces the PPI to 72 while resizing?

Are you shooting in AdobeRGB? Save for Web does a very good job of converting to sRGB. There are other methods to change the color accurately if you need for less compressed files.
72ppi isn't the issue, its the overall resolution you should be concerned with.

 

[KmH]

Hello there
Accidentally found that converting the picture with this option (File>Save for Web & Devices) on photoshop helps retain the colors whilst uploading pictures to Facebook.

My question is, what exactly happens when one optimizes a picture for web using that option?




what is sRGB, DPI & PPI What exactly happens if one reduces the PPI to 72 while resizing?

• sRGB is a color space. Most online printers and web sites require images be in the sRGB color space. a couple other commonly used color spaces are AdobeRGB and ProPhotoRGB. Color space - Wikipedia, the free encyclopedia
• DPI = dots per inch and does not apply to digital images because pixels are either square or rectangular. It is a term from the pre-press industry that still applies to pre-press processes. http://en.wikipedia.org/wiki/Dots_per_inch
• PPI = pixels per inch. http://en.wikipedia.org/wiki/Pixels_per_inch

Ppi (or the often misued dpi) do not apply until an image is going to be printed. At that point it tells the printing system how many pixel to print in each inch.

If you have 3000 pixel by 2000 pixel image and have it printed at 100 ppi (pixels per inch) the print will be 30 inches by 20 inches. (3000\100=30.00 ...2000/100=20.00.

If you have the same 3000x2000 pixel image printed at 72 ppi it will be 3000/72=41.67 inches by 2000/72=27.77 inches.

Some online print labs will not print images at less than 100 ppi because squares can start to be visible in the print, though those are usually cause dby the fact that the JPEG image format converts images to 8 pixel by 8 pixel squares when it reduces file size form the original image capture.

 

[Garbz]

sRGB is the key to everything here. It is the standard colour space. Colour spaces define how red a red is, how green a green is etc. sRGB is standard colour space that is assumed by every application that isn't colour aware. This includes the internet.

This basically means you want a very good reason for not using sRGB. A very good reason would be that you actually take you images and print them on a good printer (we're talking 8 colour inkjets or professional labs). This is the only time you get any kind of different result. Even then you usually need to know what you're doing to get the benefit and not screw your colours.

I would suggest to you if you shoot JPEG, then set your camera to sRGB to avoid the headache. If you shoot RAW, then set Adobe CameraRAW to sRGB on the bottom of the ACR window. If you process RAWs in Lightroom, then go into the options and change the profiles to sRGB.

Colour management is a hassle, and causes a lot of headaches. If you're one of the very very very few people who take their image to print giving it the kind of attention and money that would benefit from a wide colour space, then learn how to use it, but even then it's usually a hassle and worth sticking with sRGB.