Update: negative scanning bits, resolution and jpgs

  • Thread starter Thread starter Louise
  • Start date Start date
L

Louise

After having read, and greatly appreciated all the responses I received
and lots of education, I decided to start scanning my 35mm negatives on
my Epson 2400 using the negative holder.

I chose to scan at 48 bits and 2400 resolution and saved as a tiff file.

Opened file in Photoshop, cropped, increased contrast and saved it as a
tiff. All was fine.

Then I decided to email the photo to the person who was with me when it
was taken. In Photoshop I changed the image size and brought the
resolution down to 300. My plan was to save it as a jpg, thus further
reducing the size of the file.

Photoshop will not save any files scanned at 48 bits into jpg format.
If the negative was scanned at 48 bits, it only offers to re-save in
tiff, psd and raw. If the same negative is scanned at 25 bits and saved
as a tiff. Photoshop will re-save it as a jpg.

So, it looks like scanning at 48 bits prevents creating a jpg?

Funny thing is that I opened the 48 bit scanned tiff in ACDSee and that
program was able to save the file as jpg.

Have I missed something? Is there a trick? Or....perhaps I'd better
never scan above 24 bits?

TIA

Louise
 
Have I missed something? Is there a trick? Or....perhaps I'd better
never scan above 24 bits?
Click to expand...


JPG is just 24 bits, in any program. I feel sure ACDsee is only a 24
program too, without any 16 bit mode or tools. See page 187 of its
manual, about file formats it can write - it's all 24 bits. Its manual
doesnt mention having a 16 bit mode. So it surely changed your file to 24
bits when it opened it (so no point to scan more in that case). Several
programs do that (open 48 bits as 24 bits), because not very many programs
can handle 48 bits (16 bit mode). Photoshop and Elements 3 and Corel
PhotoPaint and Picture Window is about all that comes to mind.
 
Louise said:
After having read, and greatly appreciated all the responses I received
and lots of education, I decided to start scanning my 35mm negatives on
my Epson 2400 using the negative holder.

I chose to scan at 48 bits and 2400 resolution and saved as a tiff file.

Opened file in Photoshop, cropped, increased contrast and saved it as a
tiff. All was fine.

Then I decided to email the photo to the person who was with me when it
was taken. In Photoshop I changed the image size and brought the
resolution down to 300. My plan was to save it as a jpg, thus further
reducing the size of the file.

Photoshop will not save any files scanned at 48 bits into jpg format.
If the negative was scanned at 48 bits, it only offers to re-save in
tiff, psd and raw. If the same negative is scanned at 25 bits and saved
as a tiff. Photoshop will re-save it as a jpg.

So, it looks like scanning at 48 bits prevents creating a jpg?

Funny thing is that I opened the 48 bit scanned tiff in ACDSee and that
program was able to save the file as jpg.

Have I missed something? Is there a trick? Or....perhaps I'd better
never scan above 24 bits?
Click to expand...
No, you haven't missed anything and have learned that jpg is only a
24-bit file format. In fact, even if you have 15 or 16-bit data (eg.
65536 colours) you have to *increase* the colour depth to be able to
save it in jpg format.

The main reason for scanning in 48-bits is to give yourself sufficient
headroom to perform edits before finally saving the image. For example,
you mentioned above that you increased the contrast of the image before
saving it. Depending on how much you increased the contrast by, you may
possibly have introduced visual posterisation if the original had been
in 24-bit colour, rather than 48-bit. The more post processing you
apply to the scan, the more likely you are to introduce defects that
will be more apparent when you start with less bits.

Once you have the image in your final form and want to save it as a jpg,
reduce it to 8-bits/channel in Photoshop using the Image/Mode menu item.

Having said that, it really would be fairly extreme processing that
would be required to produce an objectionable difference.
 
Louise said:
After having read, and greatly appreciated all the responses I received
and lots of education, I decided to start scanning my 35mm negatives on
my Epson 2400 using the negative holder.

I chose to scan at 48 bits and 2400 resolution and saved as a tiff file.

Opened file in Photoshop, cropped, increased contrast and saved it as a
tiff. All was fine.

Then I decided to email the photo to the person who was with me when it
was taken. In Photoshop I changed the image size and brought the
resolution down to 300. My plan was to save it as a jpg, thus further
reducing the size of the file.

Photoshop will not save any files scanned at 48 bits into jpg format.
If the negative was scanned at 48 bits, it only offers to re-save in
tiff, psd and raw. If the same negative is scanned at 25 bits and saved
as a tiff. Photoshop will re-save it as a jpg.

So, it looks like scanning at 48 bits prevents creating a jpg?

Funny thing is that I opened the 48 bit scanned tiff in ACDSee and that
program was able to save the file as jpg.

Have I missed something? Is there a trick? Or....perhaps I'd better
never scan above 24 bits?

TIA

Louise
Click to expand...

Hi...

Seems no one else answered, so I'll take a chance :)

Just before trying to save it as a jpg, reduce it
to 24 bits.

(Image, mode, then click 8bits/channel)

Then jpeg will appear as a viable save as option.

The file will be much smaller in 24 bit as well, and
your friend will never ever know the difference.

Ken
 
Hi...

Seems no one else answered, so I'll take a chance :)

Just before trying to save it as a jpg, reduce it
to 24 bits.

(Image, mode, then click 8bits/channel)

Then jpeg will appear as a viable save as option.

The file will be much smaller in 24 bit as well, and
your friend will never ever know the difference.

Ken
Click to expand...
Yes - that worked. Thanks again.

Louise
 
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