which is the best format to shrink images.?

[rookie wizard]

i came to know that shrinking photos for uploading purposes degrades their quality. so what is the way around this problem.? choosing the best format ? jpg,png,tiff,raw, etc or using specific conversion algorithms ?

though technical data is welcome, but answers from personal experience are more appreciated.

thanks a lot.

[teaking]

If you shrink anything you loose something, there isnt a way around loosing data from making an image smaller.

But if your uploading the general rule is 600px wide is a pretty good size to view the image at, and JPEG has the better compression rate over TIFF and im pretty sure PNG. You can also lower the quality setting on JPEG or change the sub sampling which lowers the file size at the risk of colour problems.

But if your uploading a file for someone to download over FTP then stick the original TIFF file on there no quality loss then, as if you put the RAW up well you open your self up to a new world of problems viewing it

[RichardTaylor]

Are you uploading pics:
(1) for others to view on a web browser?
(2) to transfer to other people?
(3) archiving?

If your images have alpha channels (suitable for compositing) then PNG is the way to go.

RAW is not an image format - it is a file format.
It can't be viewed unless you have you have the right image editor.
If you are uploading for archiving as you have your original data intact I would use this method (however I don't archive on line)

If you are uploading pics for others to view, on web browsers, then JPG is probably the best way to go due to browser compatibility and smallish file sizes.

If you are uploading pics for archiving and downloading by clients etc (not web viewing) the I feel TIFF is the way to go as it is a lossless format.

[wulf]

You are looking at two different things.

1. Resizing an image. You inevitably lose some quality but a decent resizing tool should give an acceptable result.

2. Saving an image in a lossy format. To be honest, a JPEG image saved at a low compression level is going to be almost indistinguishable from the original.

The most important factor in both instances is not to keep on repeating the operation. Try not to resize the image more than once and, while saving during editing is a good idea, use a loss-free format (for example the native file format of your editor, such as PSD for Photoshop or XCF for Gimp).

Wulf

[edbayani]

in 1983 when i got my first computer, a powermac 8500, i installed genuine fractals, a resizing software that was lossless. i used it for resizing to billboard sizes. i don't know if it is still available

[digirebelva]

Originally Posted by edbayani

in 1983 when i got my first computer, a powermac 8500, i installed genuine fractals, a resizing software that was lossless. i used it for resizing to billboard sizes. i don't know if it is still available

Yes it is still available..up to version 6 now I believe..

As Wulf said, a once saved jpeg from the original is pretty much indistinguishable from the original, but saving for web viewing is going to reduce the image quality..no way around that.

[BCampbell]

Originally Posted by rookie wizard

i came to know that shrinking photos for uploading purposes degrades their quality. so what is the way around this problem.? choosing the best format ? jpg,png,tiff,raw, etc or using specific conversion algorithms ?

By "uploading purposes" I assume you mean for viewing on the web, which for 99% of applications means you should be using jpg, so we'll start there. Use jpg.

I wouldn't necessarily say shrinking a photo "loses quality". Actually in some cases it can increase apparent quality. When you resize to a smaller size using most decent editing software (Photoshop, GIMP, etc.) the software is pretty smart about which pixels to toss out and which to keep and which to interpolate. Usually a photo will appear sharper and seem to have less noise when you resize.

One thing you will want to do is run a light unsharp mask on your photo after resizing. This will clear up edges and straight lines that tend to become indistinct.

[wulf]

For uploading purposes, a Flickr account (or similar online services) works pretty well. They create multiple sizes from your original, including a bit of sharpening.

Wulf

[rookie wizard]

Originally Posted by RichardTaylor

Are you uploading pics:


If your images have alpha channels (suitable for compositing) then PNG is the way to go.

RAW is not an image format - it is a file format.
It can't be viewed unless you have you have the right image editor.
If you are uploading for archiving as you have your original data intact I would use this method (however I don't archive on line)

1. what are alpha channels,i would like to know all about them, heir use, effect on the image, etc

2.please clarify again when will you use raw format..? i dint get it. by 'uploading for archiving' do you mean storing data with a third party online data storage company ? or such ?

[RichardTaylor]

(1) This will help.
Create a Transparent Image with Alpha Channel - Tutorial

(2) Yes.