OT: Slide scanning (followup)

No but if you need to crop it severely you may need that initial resolution to get a usable picture out of what's left.

Reply to
John Stumbles
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That's one from my annals of ISP support.

This ios early days. Customer has 128k leased line.

"No emails have arrived in the last 4 hours, is there a problem?"

Inspection of their incoming mail queue revealed 62Mbyte of email entitled 'Video of our New BABY!!!'

When I mentioned the name and the problem he sighed 'I might have guessed..Delete it please'

However some companies regularly transfer images that big or bigger. I helped set up Getty Images IP links to synchronise their libraries either side of the Atlantic..Marketing is probably STILL the biggest user of Internet bandwidth.

Reply to
The Natural Philosopher

Don't be so sensitive.

I simply quoted (accurately) what you wrote.............. just wanted the OP to realize that you 'can' convert JPEG to TIFF ...... although it would just make little sense to do it.

Reply to
Rick Hughes

I'm not sure .. but if you do a search on DiMagic Scan Dual IV it will tell you what it handles .... there are all sorts of carries for slides & negatives.

I'm just using it for 35mm mounted slides and 35mm strip negatives. I bought it as it was highly rated for the job on various digital imagery forums.

I'll be selling it on once job is finished.

Reply to
Rick Hughes

You don't, it takes multiple slides at a time in the carrier .. or full strips

Reply to
Rick Hughes

I'd agree max poss resolution at scan time.

Reply to
Rick Hughes

What model HP scanner are you using? Cheers, Bramblestick

Reply to
Bramblestick

a few thoughts might help you

a 35 mm slide is 24mm x 36mm

typical film resolution is 100 lines per mm, (give or take). Taking that as meaning a single scan line on the film can only resolve 100 pixels (Near enough - though film is an analogue storage medium):

at 1 byte per pixel that means one 35mm slide needs 8.6MB storage

24 bit colour (3 bytes per pixel) needs 25.9MB/slide

and 48 bit colour = 51.8MB.

In practice these large storage requirements are reduced by compression techniques.

Either loss-less or lossy.

Loss-less techniques include storing repeat counts of identical pixels & the like. Often only a limited leeway for storage reduction.

Lossy techniques eg JPEG involve looking for similarities bewteen adjacent pixels & then assuming they are all the same. Not a reversible process. JPEG images are commonly compressed at between

10% and 90% with a consequent permanent loss of quality. Even worse happens when a JPEG image is reprocessed & resaved using a JPEG compression process. 10% of a picture originally saved at 10% is only 1% of the original. Avoid!

You need to be sure your "converted JPG files" were not in compressed form before conversion to TIFF. Otherwise the TIFF files cannot be "full definition" scans.

It could be that in a few years time, with improved equipment, you might want to squeeze a better picture out of the originals. Which could be a major problem if they are no longer available and the scans are at compressed (reduced) definition. However if they have been scanned at max definition now, you will never have a need to return to the originals - AND you WIN!

Computer storage capacity is going up in leaps and bounds & its price is dropping faster than a stone. Thus best, IMHO, to just store (archive) the data regardless of cost. If physical storage volume is a problem someone will be along within 2 years with a method of storing the stuff, without any lost data, in half the space at half the price. Just be patient & above all else don't lose even 1 bit of your data.

NB: these large files need careful resampling to produce a *good* and appropriately reduced working file for printing or editing.

There is an excellent discussion this & a wide range of other scanning issues at

formatting link
Quite readable. Take a look.

Lastly there is one aspect which is almost always overlooked. A fundamental theorem in information theory states that to be able to later fully reconstitute a waveform from sampled data, samples must be taken at twice the highest frequency of the waveform.

Each scan file is actually formed from data sampled off the slide. For "waveform" read "scan line": for "frequency" read "dots (pixels) per inch".

Hence those slides really ought to have been scanned as if they were storing information at 200lines/mm. I'll leave reworking the sums to you. 8-( )

HTH

Reply to
jim
8<

sj4890, I don't think its a current model.

Reply to
dennis

Its not a real problem, my mail server can take 300 Mbyte as it is currently setup.

Reply to
dennis

"The ScanDual IV will not work with any film holder other that the 35 mm strip holder supplied, They crop the top of 126 film as you said above."

Grrr.

Andy

Reply to
Andy Champ

It seems silly doesn't it? But internet advancement/history suggests we'll be doing it within 2-3 years.

Reply to
Steve Walker

I know perfectly well, thank you.

Which bit of "He communicated well and although his default is .JPG files he agreed to *convert* them to my chosen format instead. " (my emphasis) are you struggling with?

MBQ

Reply to
Man at B&Q

My publisher used a website called Big File to send me an 80Mb pdf.

Reply to
Peter Johnson

I really don't know what the theoretical limit is here - but I know if someone sent me a 50MB image and it sat there clogging the connection I'd be pissed off, even more so if it turned out to be something that I couldn't give a crap about, or something that could just as easily be sent as a few hundred KB of JPEG.

(TNP - I can understand there are times when that kind of size is necessary; been there myself sometimes - but only when agreed in advance and the systems involved are set up to handle it. My gripe's with the clueless who have no concept of file sizes, working with images, or how the systems involved can or can't cope - and sadly they seem to far outweigh the ones who *do* have a clue)

cheers

Jules

Reply to
Jules

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