Vuescan file size for B&W

[Author]

I am using Vuescan ver 7.5.53 with a Scanwit 2720 scanner.
I am obtaining raw scan files of b&w negatives. The raw file size
is 17.6MB

I rescan the raw file as transparency and save as jpeg.
The status bar tells me the file is 2.5MB. If I check the
jpeg black/white option on the files tab display, the file size
is reduced futher to 0.88MB

However the file size after scanning is 5.33MB. Why doesn't the
actual file size agree with what is reported on the status bar?

Thanks fo any information
George

 

[Jim]

I rescan the raw file as transparency and save as jpeg. Jpeg compresses the image

However the file size after scanning is 5.33MB. Why doesn't the
actual file size agree with what is reported on the status bar?

Jpeg compression at work. What you see in the status bar is the amount of
memory that the image needs after decompression.
Jim

 

[Bart van der Wolf]

SNIP

Why doesn't the actual file size agree with what is reported
on the status bar?

It is only an estimate. The true size would require a full compression run,
because the compression depends on image content, and differs with each
image.

Bart