Scanner Question 24bit/48 bit vs. resolution

[Eve Giddion]

Truely I don't understand image technology.
When I scan a picture and I want it in a JPG should I use plain JPG
or progressive?

When I talk about an image and I say it is a big picture how do I
differentiate that I'm talking about file size v/s the physical
measurements of the picture?

And, when I scan a picture, but it is too large (in megs) and I want
to make it smaller, should I decrease the scan from 48 bit color to 24
bit or should I lower the resolution?
I know what r esolution is as defined as being able discern between
two points, but I'm not sure how it works in a scanner.

I'm scanning family photos. Most are DIY photos, but some are
professional. I want to archive the pics, but I don't want to lose
any picture quality. Most of the pics will not be manipulated in PS
or a anything like that. Some might. But I don't want to scan
something now at the wrong settings and regret it later.

Some are scans of Polaroids and I know they can be scanned at low
setting.

I'm using 24 bit and 1200 bit resolution, sometimes 2400 sometimes as
low as 300.

Can someone please help me out?
Or give me an address to a Scanner FAQ.

Eve G.

 

[JAD]

Truely I don't understand image technology.
When I scan a picture and I want it in a JPG should I use plain JPG
or progressive?

that has to do with web publishing ( how the pic appears when the page
loads)

When I talk about an image and I say it is a big picture how do I
differentiate that I'm talking about file size v/s the physical
measurements of the picture?

Size(dimentions) in pixels or inches
file sizes in megabytes

And, when I scan a picture, but it is too large (in megs) and I want
to make it smaller, should I decrease the scan from 48 bit color to 24
bit or should I lower the resolution?
I know what r esolution is as defined as being able discern between
two points, but I'm not sure how it works in a scanner.

No loss of quality? then don't change the color depth.
This is software related. Generally you would scan at the highest the
scanner will produce.
Changing the 'inches/pixels' dimentions would be the first way to decrease
'megabytes' in relation to file size.
The average home printer will shoot out 300DPI resolution pictures. Higher
end 'photo' home printers 1200. Archiving at 8x10 inches 1200 dpi would
be a good size IMO.

I'm scanning family photos. Most are DIY photos, but some are
professional. I want to archive the pics, but I don't want to lose
any picture quality. Most of the pics will not be manipulated in PS
or a anything like that. Some might. But I don't want to scan
something now at the wrong settings and regret it later.

All your photos , once scanned should be 'manipulated' in PS (or similar) to
make them archiving sizes.

Some are scans of Polaroids and I know they can be scanned at low
setting.

yes and no...that becomes a individual setting for each poloroid ( IMO)

I'm using 24 bit and 1200 bit resolution, sometimes 2400 sometimes as
low as 300.

pretty much what you should be doing, according to the output device you
would use to hardcopy/print them.

 

[Bob Fallona]

This site is probably number #1 for scanner info. Doesn't seem to have any
axe to grind and offers simple and straight forward advice and tips:

http://www.scantips.com/

 

[John Weiss]

You cannot scan a photo and retain photo quality. Film such as Kodachrome
and lower-speed Kodacolor have a resolution equivalent to something around
10,000 dpi. To get such resolution on a scanner is not possible with a
home-grade scanner.

Also, JPG is NOT the format to use to retain resolution. JPEG compression
is a "lossy" compression, so you will lose resolution any time you try to
compress the file. "Progressive" scanning merely allows the entire picture
to be displayed faster (usually, via web download), with progressive
resolution increases as the download is completed. It makes less difference
when viewing from a local hard drive.

To retain as much resolution as possible, use the highest resolution and
color depth available, and output the original scan in TIFF or other
uncompressed format. The downside is processing time and file size, but you
have to make a choice here. GIF is not suitable for the "professional"
photos, because it uses only 256 colors max, even though it uses lossless
compression. GIF (or compressed JPEG) may be suitable for the Polaroids,
B&W, and "Instamatic" photos, though.

Finally, what do you intend to do with the pictures? Anything more than 300
dpi (some would say 150 dpi) is wasted for web display. If you have 5x7 or
8x10 enlargements that you might want to reprint in the same size, or
standard 3x5 or 4x6 prints that you might want to enlarge, go with max
resolution and color depth, and live with the file size; archive to DVD
and/or external hard drive. The Polaroids and Instamatics will not require
any more than 600 dpi and 24 bit (or less) color, because the camera
lens/film combination will likely not give any better effective resolution.

Scan a few at various settings, then print and or process them in Photoshop
to get an idea of what's possible and suitable for your uses.

 

[Eve Giddion]

Thanks for taking the time to reply to my inqury.

Mainly what I am doing is backing up pictures I've taken and had
developed.
A few special pictures were taken by a photo gallery and I wanted scan
these in high quality. I really don't have any plans for these
"special pictures" at the moment, but I thought if years down the road
I wanted to do something, I would hate to have messed up scanning
them.

I didni't realize the 10 K dpi fact. Just out of curiosity, any idea
what the DPI on a 5 meg pixle camera would be?

Also, when you say the heck with the size, scan at max.....
well I shouldn't be concerned with a 500 meg picture?
10 to 20 pictures per DVD wouldn't label me a nut?

Again, thank you for your time and advice.
I'm still waiting for the flames I usually get.

Eve