Re: filmscanners: Re: Scanning problems

[Richard <soho@eircom.net>]

> I've just had my 6x7 trannies scanned by a lab specialising in digital. I
> paid for a 50MB scan and got a 7MB jpeg back. I took the CD back to the
> manger, who told me that it was a 50MB scan, compressed to 7MB and that all
> the information would be there when I opened it up!!! I think by this he
> means that when you go to Image Size in Photoshop it does say 55MB (4800
> pixels x 3900 at 300dpi), although the file is 7MB. Is this the file size if
> saved to psd format? I've lent my Real World Photoshop book out.

Every jpeg file will be different depending on the content. Solid colour
compress more than gradients etc. A 50Mb solid white file compresses to
1.8Mb, whereas a 50Mb gradient compresses to 3Mb. The more colours and
greater complexity of the image the less compression.

> I explained that jpeg was a lossy compression, that information had been
> lost when converting to jpeg and it was no good to me. He looked at me as if
> I was mad and said that he uses jpeg for all his customers to get more
> images on the CD. I argued that jpeg does loss information and drops the
> colours that the eye cannot see. He told me that I had to specify tiff
> otherwise he saves as jpeg, then reluctantly said 'so you want me to do the
> whole job again'.
> 
> This lab specialises in digital, how can people accept jpegs? So much
> information has been lost for manipulating  (levels and curves) in
> Photoshop. I won't be going back there again...

I wouldn't be so dismissive about jpegs. Open a file in PS and save it as
jpeg maximum quality. Now open the jpeg and copy and paste the image onto
the PS file. Zoom in and turn the layer on and off to see the difference.

I suppose you could have requested a 16bit file, this would have restricted
the format and compression type supplied to you.


Regards

Richard

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