Re: filmscanners: RE: filmscanners: Re: Hello, thanks, and more.

[Ken Durling <kdurling@earthlink.net>]

On Mon, 22 Oct 2001 14:44:50 +1000, you wrote:

>The only way you can change the "dimensions" of an image without changing
>the number of pixels is to change the dpi.  For example, a 300x300 pixel
>image at 300 dpi will print 1" x 1" on paper.  If you change the dpi to
>150 dpi, it will print 2" x 2".  No change in the number of pixels!  If
>you're resizing an image from 3000 pixels in the width to 750 pixels, you're
>throwing away 75% of the data!


Aha, okay, see my other reply.  I'm slowly coming out of the fog here.
So what's the most "lossless" way to get my 30MB TIFF file to the size
I can post on a website with say a 300K limit per image?

To my present understanding, the only points in the workflow that you
have actual choice of dpi is at the initial scan, and at the final
print.  When saving as a JPEG, different programs seem to have all
kinds of different specifications.  For example, Photo House offers a
choice of "Interchange Format (JPEG/JFIF)"  ;  Standard (4:4:4),
Option 1 (4:1:1) and Option 2 (4:2:2); and a quality factor slider
with a range of 2-255 high to low quality.  PhotoDeluxe just offer
1-10 low to high quality JPEG, with three baseline options, IIRC,
standard, optimized, and progressive.  The last choice offers
different numbers of scans. 

I can see I'm going to have to learn what these numbers mean - but for
now, I guess I nedd to figure out what the relationship is between
file size and image size in regards to JPEGs.  Obviously I want to do
the least anount of changing at the last stage of making the jpeg, but
I'm not clear where in the workflow the most effective balance of size
vs quality occurs.   Not even sure if I'm making myself clear here!  


Ken