jpg or gif

Len · 14-03-2004, 19:27

Does anyone know what the advantage is of converting a jpg image into gif image? I dont mean an animated gif.
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Owd Bert · 15-03-2004, 09:05

As far as I understand a GIF can only have 256 colours so I don`t think they would be suitable for showing the majority of photos.

Len · 15-03-2004, 22:56

Owd Bert

Thanks for that.
I'm just wondering what sort of applications they are used for. Apart from animation.
I suppose they would be a smaller file compared to a jpg file of the same image.
I shall have to get myself a book and read up on it.

Mick · 16-03-2004, 13:16

just read this in paint Shop Pro 7
GIF use this format to compess line art and images with areas of similar colours.
it supports 8bit(256)colour.

JPEG use this format to compress photographic images.
it supports 24 bit (16.7 million) colours and uses lossless compression

Roy · 16-03-2004, 13:52

on a low colour image a gif file is a lot smaller than a jpeg image. If you look around this website, you'll see that nearly all images are .gif and low colour. It saves a lot of bandwidth.. Just try saving one of the gifs from here (for example the post reply button at bottom left) in jpg format at the same size and have a look at the difference. As well as the file size the jpg image will probably not look as sharp because of the compression that is used.

Hmmmm... I've decided to do the comparison for you!

1st one is gif and is 834 bytes, 2nd one is jpg and is slightly larger and far worse looking at 924 bytes.

I highly recommend Adobe Photoshop 7 or greater for doing images for the web. There is an option to save for the web and you can compare how it looks before and after in different styles, gif (using different amounts of colours), jpg (high,medium,low) etc.etc.. It also tells you the exact file size before and after as well.

Roy · 16-03-2004, 14:01

just for interests sake as well, another example of usage of jpg/gif. The montage on the front page of accyweb is actually several different pictures just put next to each other. Because JPG makes things blurry with the compression the first two images on the left (which contain the solid colour text)are saved in gif, whilst the photo style images are saved in jpg. Now if you actually compare the file sizes of these images you will realise that the gifs are in fact larger!! So the reason for using gif in this example is because it makes text look far sharper than with jpg....

Mick · 16-03-2004, 14:53

if you want photoshop 7 i have it with the manuel

Len · 16-03-2004, 18:43

Thanks Roy.

Very interesting I shall do some experimenting with them. All my images on my web pages are jpg so I may now have to consider changing some of them to gif.

What causes the compressing?

Thanks mick but I have photoshop6 and it has a "save for web" option, which I have been using it also has a optimize option on it and a load of other things one can select from, including gif/jpg.
The thing is, actually knowing what you want to do with the image. i.e. what you are going to use the image for. Now that is the question.

Is there a golden rule about gif/jpg?

Aussie Gobbiner · 17-03-2004, 06:48

Check these out Len,

These are the same photo of the same pelican at Berkeley all saved in gif format... the 3rd one is saved with 256 colours... the second with 16 colours and the 1st with 2 colours.. below I will put the same image as jpg with 3 different compression ratios...

Aussie Gobbiner · 17-03-2004, 06:54

The first image saved with about 50% loss of quality the middle with about 20% loss of quality and the last with about 90% loss of quality... check out the difference between the middle one here and the 256 colour gif above..