Keeping file sizes under control

[Julian Thompson]

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I'm getting 20 megapixel scans of my negatives which I have as DNG's - straight from Vuescan these are around 150mb or so per frame. Then I open them in ACR and do some developing to knock them into shape and when I save ACR shrinks them (somehow!?!) to around 80mb per file. I am happy with this file size.

 

But then, I try to import them into Aperture 3 and it won't display the images. I've tried all the options in ACR and searched the web but I can't find a solution.

 

So, if I can't do a DNG then I shall do a TIFF but then the file size is back up at about 150mb again which is really too big for me.

 

Can anyone help?

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[andybarton]

Aperture probably won't import Vuescan DNGs.

 

And 150 MB is too large a file for most mere mortals anyway.

 

I scanned a 6x6 on my V700 last week. When it was opened in PS, it was over 1 gig in size. Completely un-necessary and un-workable.

[stunsworth]

The flatbed scanners I've used have been very optimistic with their maximum scan resolutions. Bigger files without increased resolution is my conclusion. Scan at half the claimed resolution and see if you like the results.

[andybarton]

Indeed... but 1 gig+ is still too big...

 

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[Julian Thompson]

Yes I have a V750 which I am using at 4000dpi. This gives me an approx 20 megapixel file. I can see that if I go higher than this (to the claimed 6400 optical resolution) then indeed it's a waste of time but I'm convinced that its ok at 4000.

 

So -Andy - remember, I'm actually saving the Vuescan DNG as an Adobe DNG through ACR. So I can't see why aperture is struggling with them. Lightroom reads them fine.

[jbl]

I've been wondering about this too. I have a Coolscan 5000 and I have a DNG produced by VueScan that's around 135mb. If I run Adobe DNG Convertor on it, the DNG shrinks to around 66mb. Does anyone know what causes/allows this? Does the VueScan DNG raw have other stuff in it?

 

-jbl

[adan]

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"Then I open them in ACR and do some developing to knock them into shape and when I save ACR shrinks them (somehow!?!) to around 80mb per file."

 

"If I run Adobe DNG Convertor on it, the DNG shrinks to around 66mb. Does anyone know what causes/allows this? Does the VueScan DNG raw have other stuff in it?"

 

Aperture probably won't import Vuescan DNGs.

 

Actually, what is probably fouling up Aperture is the ACR compression (and that is what is making the files smaller, just a lossless compression scheme). It has been noted on the Digital Processing forum several times that .dngs, modified by opening and saving from either Adobe program, Lightroom or ACR, especially compressed, are often no longer readable by other RAW developing programs.

 

Apparently Adobe modifies and/or compresses .dngs according to the book (which Adobe wrote) - but Apple and other software writers don't always comply fully with Adobe's .dng specs - which then comes back to bite users who try to move .dngs among different, supposedly dng-compliant programs.

 

Same for running a .dng through DNG Converter (another Adobe product). I note that the DNG Converter preferences allow one to embed "the original RAW" in the .dng - but I don't know what happens if one embeds a .dng within a .dng (and besides, Adobe says embedding the original makes the new file larger, so one may just end up back where one started - at 150 Mbytes).

 

Andy B. may be right, though, that Aperture won't read Vuescan files anyway - only way to test that is to bypass the ACR step and try opening a fresh, untouched Vuescan .dng directly into Aperture.

___________________________________

 

As to file size, there are, of course, two ways to reduce that without compression: lower the bit depth or lower the resolution.

 

Bit-depth is pretty simple - 16 bit files will always be twice as big as 8-bit files (or 48 vs. 24 for color). If you can get the tones and colors pretty close to correct in the scanning process (which I know is tricky in Vuescan's interface, sometimes) - so that the image won't need much manipulation after scanning - then 8-bit is probably adequate for a lot of work. That's a judgement call the photographer has to make.

 

There are two ways to look at image resolution: Input (how much can you really capture?) and output (how much do you really need?)

 

How much can you capture?

 

Kodak and Fuji data sheets put the average-contrast resolution of their slowest color films at around 60-80 lppm for K64 and 70-90 for Ektar 100 and Velvia. So for those films, 4000 ppi (= 160 pp mm) is about right - two pixels for every line of resolution (to avoid aliasing). TMax 100 falls in the same range - the magical ISO 20 microfilms could use more.

 

Tri-X is about 50-70 lppm under average contrast and lab conditions, and Tmax 3200 is down to 40-60, which means that scanning above 3200 or 2700 ppi is just making photomicrographs of grain. (Obviously we can play with developers and get some variation there).

 

In any case, 4000 ppi scanning requires an 80 lppm scanning lens to actually use the full resolution available.

 

How much do you need?

 

Erwin Puts promotes the idea that 10 lppm in the final print is all the best eye can resolve. That works out to 254 lines per inch (which is just about exactly what photo-grade inkjet printers can pull off).

 

So for a 20" x 30" print, one needs 5080 x 7620 pixels. Ooops - that's more than a 4000-ppi scanner and 35mm film can provide. But that is for a "flawless" image with detail right to the limit of vision 6" from the print - not something anyone expects from 35mm (4x5, yes. 6x6, probably - not 35mm).

 

A National Geographic Kodachrome spread is 10" x 14", or one quarter the area and half the dimensions of a 20 x 30 print. To print at 254 ppi, that requires a scan 2540 x 3810 pixels (cropped to 2540 x 3556 for the format difference). To print at the higher standard of 300 ppi, it requires a 3000 x 4500 scan, or probably 3200 ppi if there is cropping for the slide mount.

 

So even the old 2700-ppi scanners were adequate to reproduce a Kodachrome in Nat. Geo., and 3000 ppi is a reasonable round number.

 

3000 ppi is what I scanned at with my 5000ED. That got me files in the 40-80Mbyte range (8-16 bit). I had very few images that actually showed any more detail using the native 4000 ppi.

 

But roll the dice, do the math, and figure out what works for you.

[jbl]

I emailed Ed Hamrick about this and he said that the VueScan format has a full RGB per pixel whereas the file produced by DNG convertor would have a Bayer pattern applied so each pixel is only one color.

 

I think I'll be sticking with the VueScan files :-).

 

-jbl

[Julian Thompson]

That's very interesting indeed - but the question I guess is whether you can SEE any difference I suppose!

[plasticman]

That's very interesting indeed - but the question I guess is whether you can SEE any difference I suppose!

 

I think that one consideration is whether you're archiving your scans. While not directly a chore, I find the actual scanning to be rather time-consuming, so my intention is to scan just once at the best possible quality and burn that to disk.

How one treats the 'print' from that negative is entirely open - but the 16bit, 4000dpi negative can always be retrieved at a later date, if needed.

[pop]

... the 16bit, 4000dpi negative can always be retrieved at a later date, if needed.

 

What time frame are you thinking of when you mention a "later date"? Months, years, decades or "long"?

[plasticman]

What time frame are you thinking of when you mention a "later date"? Months, years, decades or "long"?

 

That's a good question - but the 'real' negatives will be there for a while too, and if I ever think it's worthwhile, there's the option of drumscans for really important images, or investing at some stage in an Imacon Flextight scanner.

 

For me part of the beauty is the flexibility of film, in this respect. Then it's a case of which lasts the longest - the scanned or the 'real' negs.

[andym911]

Personally I never archive scans...I archive my Neg's.

 

Scan at 2000 and work with files at about 20mb...no more.

prints are stunning...no need for more IMO

 

Just try and test..find your own flow.

 

best

andy

[Julian Thompson]

The other thing I've found about archiving the digital scans is that it only takes one improvement in your scanning workflow and your archived negs are out of date. Also, in my case, I am likely to buy a better scanner soon, so my V750 scans will benefit from re-doing on the new scanner, again putting the archives out of date.

 

But, then again, with a 1TB disk costing fifty quid nowadays maybe the question should be why on earth you would NOT archive the raw scans!

[NZDavid]

Did anyone mention RAM? 8GB is about tops these days and probably worth it; I make do with 2GB.

 

My newspaper prints at 200dpi, magazines are 300dpi -- about 250dpi will yield a good print.

 

I have scans done at 18MB and these are good for tabloid covers (37cm by 28cm approx.) at 200dpi and fullpage magazine prints at 300dpi.

 

I had some landscapes done at a whopping 349MB and each one took just 20 secs to open.

 

30-50MB is probably a happy medium.

[StS]

Well, an external 1,5TB disk is below 80 Euros now. This is not much incentive to save space....

 

Stefan

[plasticman]

I'm beginning to wonder what I'm gonna do when I get the Hasselblad. I think then the scans will have to be rather more modestly dimensioned, as my 35mm 'negatives' are about 120megs each...

[andybarton]

My Hasselblad scans from the V700 run to around 200 - 300MB as 16 bit grey scale

 

As I said above, if I used the highest scan setting, I produced a file over 1 gig in size, which I decided was a bit excessive...

 

I am looking forward to seeing what the scanner can do with some E6.

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[plasticman]

As I said above, if I used the highest scan setting, I produced a file over 1 gig in size, which I decided was a bit excessive...

 

Ah sorry Andy - I'd read that post before but then forgotten about it. One-gigabyte images do seem a bit on the big side...

Still, I guess this does offer the chance to print a couple meters wide, or so...

[stunsworth]

Every flatbed scanner I've used has been hopelessly optimistic regarding the maximum scan size. They scanning at half the maximum DPI. I'd guess you'll have just as much detail, and the files will be a quarter the size.