Tiffs or files over 200k

[hayden]

I can't post a file over 200k, which I understand because you ask people to limit them to that size.

But why can't I post a Tiff? I've got a scanned image of a catalog and as a tiff it's only 40k or so, but as a gif it's 300k and as a jpeg it's 800k. I guess tiff compression works well on B&W scans. Anyhow, do browsers have trouble with tiffs or is there another reason to not allow them?

Thanks,

Peter

 

[Harv]

Peter -

The safest, most universal image file formats for browsers are GIF and JPEG. All browsers that I know of have the built-in ability to read both of those.

TIFF is a widely used format, especially in the hard-copy publishing arena. Most profesional applications know how to interpret this format, and it does offer (as an option) lossless compression, although it generally doesn't reduce the file size as much as JPEG can.

Most browsers (at least the ones I am familiar with) can interpret TIFF files only with the proper helper application (something you set up in your browser preferences). There are also byte-ordering issues with this format. i.e. the byte order for a Mac TIFF file is the reverse of that for an IBM PC file, although most software can handle either.

I don't understand the file sizes you mention, since JPEG has the best compression algorithms of the three. GIF works pretty well on images with few colors and sharp transitions, but for a TIFF to be the smallest of all baffles me.

Offhand, I would suggest you may be scanning at way too high a resolution for posting on the web, so you might want to review your settings. If you stay within Muhammad's recommended maximum width of 720 pixels, a black and white image should not produce a very large file.

I'm sorry -- what was the question? /w3tcompact/icons/crazy.gif

 

[BobT]

Peter,

Harv is right about the problems many users will have reading the TIFF format.

Besides keeping the image width to a maximum of 720 pixels, go into your image application and change the setting for "resolution" to 72 pixels per inch. Many scanning programs will use defaults of 200 or more, and it makes for huge file sizes. Besides, 72 pixels per inch is the highest amount of information a browser can use anyway, so anything higher than that is a waste of space.

If you follow these two suggestions given, you should wind up with a JPEG file of moderate size (20-50K).

Hope this helps.


BobT.
A Indiana Boy

 

[Muhammad]

Peter,

We don't allow TIFF files since any TIFF in JPG or GIF format will be much smaller in file size, and more suitable for the web (because of the smaller file size). I'm really not sure how the TIFF could be smaller than the other two. if the image is black and white, you can reduce the number of colors in the GIF to reduce file size, without reducing quality much. JPG quality can also be reduced from 100% down to 50-60% usually (sometimes 25-30% on a photo) and still retain "good" quality.

 

[Harv]

Bob -

A little techno-chat here -- I have studied this stuff so much that I am more confused than when I started. /w3tcompact/icons/crazy.gif

I have always known 72 dpi to be the standard "screen resolution", yet as I test my own web-based stuff on both Macs and PC's, I recently discovered that PC's claim a 96 dpi standard. I think that only affects the way that font sizes are interpreted. Many web pages include text set to, say, 8pt or smaller, which when rendered on a true 72 dpi machine like a Mac is too small to be legible (ie - there just ain't enough pixels to describe the characters).

As for scanning resolution, you're right that if it's intended to be viewed in a browser you should scan at 72 dpi for a 100% reproduction. However, at the scanning end of things, the resolution you choose also determines how much detail you're going to pick up. If the original is very small, you may want to use 200 dpi, which will pick up finer detail and of course give you a magnified final image.

Browsers actually ignore the resolution information in the pict file and just present all the pixels regardless. In other words, if the final image is 720 pixels wide, it doesn't matter if it was scanned at 72 or 800 dpi. It will show up the same size on the screen.

See how I confuse myself? Am I making sense to you?

I gotta hand it to Muhammad -- he answered the original question here in a fraction of the words and was much clearer about it. I guess that's why he's the master and I'm just a $1,000 a month member. /w3tcompact/icons/wink.gif

 

[BobT]

Hi Harv,

I meant to say to "save" the image at 72 dpi, not scan it at that. You are right, too much detail would ordinarily be lost if scanned at that low resolution.

BobT.
A Indiana Boy

 

[hayden]

OK, I'll just scan at a lower resolution. My images are gigantic when viewed with the browser anyway.

The tiff file has to be compressed to get the size I'm seeing, and with a B&W text scan there's lots of compression opportunity, arguably more than witha tiff scan line compression that a Jpeg image block compression, so I kind of understand the size difference, but it sure isn't intuitive.