j_hallgren
Posts: 1427
Joined: Sun Jun 04, 2000 11:48 am

Is 48-bit Scanner Really Needed?

Tue Feb 19, 2002 1:33 pm

Ok, so I'm not much of a real av-photo person BUT I know that you folks have knowledge of things like this, so I ask....

Question from potential scanner buyer is: Under what conditions will I be able to use the 48-bits?

Since my LCD on laptop is max'd at 24 bits as I understand it...and the Visioneer 8900 specs say it outputs only 24 bit EXCEPT to Photoshop LE which I don't quite follow...

Anybody have any info to clue me in? Thanks!!


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ckw
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RE: Is 48-bit Scanner Really Needed?

Tue Feb 19, 2002 5:54 pm

I think what is meant by the specs is that you need Photoshop to be able to manipulate a 48bit tif - and even then the amount of manipulation you can do is very limited. I think only PS ver. 6 provides true 48bit (16 bit mode) editing.

You are correct in saying you will see no difference on your LCD screen between a 24 bit and 48 bit scan. The difference is the "head room" you gain to make adjustments to the image. The more data the software has to work with, the smoother the tones of the final image.

For example, if you try and brighten a shadow area - in 24 bit images, anything more than a minor adjustment results in "gaps" the tone curve which can appear as less the smooth tonal transitions - working with 48 bit images lets you make larger adjustments and still retain smoother tones in the shadows. Against this, you will be working with a file 2x the size, so memory & processor power become an issue.

Cheers,

Colin
Colin K. Work, Pixstel
 
cfalk
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RE: Is 48-bit Scanner Really Needed?

Tue Feb 19, 2002 6:32 pm

That's interesting Colin. So would that mean that if I have a photo that needs significant touching up, like gamma or brightness, that the results would be better if I scan at 48-bit, make the changes, and as a last step save as 24-bit jpeg?

Charles
The only thing you should feel when shooting a terrorist: Recoil.
 
ckw
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RE: Is 48-bit Scanner Really Needed?

Tue Feb 19, 2002 10:38 pm

Charles - yup, that's basically how it works ... but you have to get the workflow right, as not all tools/filters work on 48 bit images, even in PS6. But when it comes to levels and curves, I think you'll be surprised how much more room you have to manouever.

Though it won't work miracles ... an underexposed pic with no shadow detail will still look like an underexposed pic with no shadow detail  Smile but if the detail is there, just a bit lost, working in 48 bits (16bit mode) seems to help a lot.

Cheers,

Colin
Colin K. Work, Pixstel
 
cfalk
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Joined: Mon Dec 04, 2000 6:38 pm

RE: Is 48-bit Scanner Really Needed?

Wed Feb 20, 2002 1:04 am

Thanks for the tip Colin. I'll try that. That would probably be quite usefull with bad weather shots.

Cheers,

Charles
The only thing you should feel when shooting a terrorist: Recoil.
 
j_hallgren
Posts: 1427
Joined: Sun Jun 04, 2000 11:48 am

RE: Is 48-bit Scanner Really Needed?

Sat Feb 23, 2002 4:44 am

Thanks to Colin (and Charles)for the replies!

Your Q&A helped explain it...found later that the Epson scanner I am trying ALSO states it outputs only 24 bits (in quite small print)...so I guess the other 24 bits end up in the "Bit Bucket" UNLESS you have the higher level software on the receiving end...

I can see how making changes in 48 bit mode would improve the result, even in 24 bits, after reading a "bit" in some PhotoShop books.
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sia jubilee
Posts: 141
Joined: Mon Feb 14, 2000 12:48 am

RE: Is 48-bit Scanner Really Needed?

Sat Feb 23, 2002 11:55 pm

indeed! We definitely need this 48 bit input.
Because of the lost during scanning.
maximum inputting is needed.
That makes sure the output on screen(the file) is in the best quality. More detailed scans.

Alan Tsui
Hong Kong

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