dpi question?

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Lunaray

I have a Nikon IV ED film scanner up for auction on eBay and I received a
question from an interested bidder concerning dpi. He was wondering how big
of a print he could produce at 2900dpi, I wasn't sure how to answer, but I
told him that he would be hard-pressed to find a printer that could match
the 2900dpi capability of the scanner, was this somewhat correct? He was
concerned about 2900dpi of the IV ED scanner vs. 4000dpi of some other more
expensive film scanner, would he notice a difference?

Thanks all!

Ray
 
Lunaray said:
I have a Nikon IV ED film scanner up for auction on eBay and I received a
question from an interested bidder concerning dpi. He was wondering how big
of a print he could produce at 2900dpi, I wasn't sure how to answer, but I
told him that he would be hard-pressed to find a printer that could match
the 2900dpi capability of the scanner, was this somewhat correct? He was
concerned about 2900dpi of the IV ED scanner vs. 4000dpi of some other more
expensive film scanner, would he notice a difference?
Click to expand...

That last bit is wrong, any printer can print whatever fits on it...

It's a question of scaling:

The simple answer is to divide the size of the image by the dpi of the printer.

A scan of a 35 mm frame is 36mm on its long side, there are 25.4 mm in an inch:

36/25.4 * 2900 = 4100 pixels. (24/25.4 * 2900 for the width)

Then how is it printed? Printer s/w allows you to selct the resolution of the
printing:

At 300 dpi: 4100 / 300 = 13.6 inches
133 dpi: 4100 / 133 = 30.8 inches

Easy as that.

Cheers,
Alan
 
I have a Nikon IV ED film scanner up for auction on eBay and I received a
question from an interested bidder concerning dpi. He was wondering how big
of a print he could produce at 2900dpi, I wasn't sure how to answer, but I
told him that he would be hard-pressed to find a printer that could match
the 2900dpi capability of the scanner, was this somewhat correct? He was
concerned about 2900dpi of the IV ED scanner vs. 4000dpi of some other more
expensive film scanner, would he notice a difference?
Click to expand...

No, the printer dpi rating is NOT a factor regarding image size.

A 35 mm film frame size is 36x24 mm, or 1.417x0.945 inch. However, alignment
wont really allow us to scan that much of it, so call it 1.4x0.92 inches
(you may desire to crop it even smaller, for artistic reasons).

Digital image size is dimensioned in pixels.

(1.4 inches x 2900 dpi) x (0.92 inches x 2900 dpi) = 4060x2668 pixels.

Then when you print, you might scale to print at 300 dpi, or at 200 dpi, as
the situation allows, depending on how large a print you need.
The ratio of (scanning res / printing res) is the enlargement factor.

2900/300 = 9.7x enlargement 2900/200 = 14.5x enlargement.
4000/300 = 13.3x enlargement. 4000/200 = 20x enlargement.

There are many possibilities, but printing at 2900 dpi simply is not one of
them. We print more like at 300 dpi, and this pixel-spacing difference from
2900 dpi is what causes/allows the enlargement of the small film size.

Specfiically, if you print 4060x2668 pixels at 300 dpi, and computing 4060/300
and 2668/300, this printed size is 13.5x8.9 inches.

But you could also print these 4060x2668 pixels at 307 dpi or 291 dpi, or 200
dpi, or any other value, to get other printed image sizes.
 
You've both given me more information than my little pea brain can can
process, maybe I can put it simpler! Is there an appreciable difference in
quality between a scanner that can scan at 4000 dpi as opposed to one that
has a maximum scan rate of 2900 dpi?

Thanks for your help!
 
Lunaray said:
You've both given me more information than my little pea brain can can
process, maybe I can put it simpler! Is there an appreciable difference in
quality between a scanner that can scan at 4000 dpi as opposed to one that
has a maximum scan rate of 2900 dpi?

Thanks for your help!
Click to expand...
Yes because the 4000 dpi scan will allow satisfactory printing to a larger
size. However, up to the maximum size permitted by 2900 dpi, there will be
little if any perceptible difference.
Jim
 
You've both given me more information than my little pea brain can can
process, maybe I can put it simpler! Is there an appreciable difference in
quality between a scanner that can scan at 4000 dpi as opposed to one that
has a maximum scan rate of 2900 dpi?
Click to expand...

Seems an odd question from someone seeking to sell a 2900 dpi scanner <g>

Difference in quality when doing what?

Basically, the 4000 dpi scanner can create a larger image (dimensioned in
pixels) which would allow printing larger prints (inches on paper), with
that capability being in the size ratio of 4000/2900, or 138%. Excluding
cases of extreme cropping, then 2900 dpi is enough to print 8x10 inches very
well, and somewhat larger perhaps a little less well, but the 4000 dpi
scanner would be more capable for even larger images. This is not much issue
for goals of small images, for example video screen size or 6x4 inch prints.
That answer is "often no, depending on the goal".

Another factor, even for smaller images, is that the 4000 scanning resolution
could also minimize aliasing (false film grain effects) more than the lower
capability. That answer is "perhaps yes", but hard to quantify.
 
Lunaray said:
You've both given me more information than my little pea brain can can
process, maybe I can put it simpler! Is there an appreciable difference in
quality between a scanner that can scan at 4000 dpi as opposed to one that
has a maximum scan rate of 2900 dpi?

Thanks for your help!
Click to expand...

2900 dpi will produce excellent prints at A4 (10x8 or 12x8) size as the dpi
to the printer is over 300. It would be extremely difficult to pick the
difference. Other factors such as the quality of the optics and focussing
would be more important.

I haven't tried A3 prints but there seems to be an assumption that you need
4000dpi. However 2900 dpi still gives you over 200dpi at the printer so they
should be OK. Some experiments might be useful.
 
Another factor, even for smaller images, is that the 4000 scanning resolution
could also minimize aliasing (false film grain effects) more than the lower
capability. That answer is "perhaps yes", but hard to quantify.
Click to expand...

Higher resolution is generally better as rule of thumb (one can always
step down to lower resolution when required).

However, when I moved from 2700 to 4000 (LS-30 to LS-50) I discovered
something unexpected: pepper spots! They were too small to register on
the 2700 scanner but are clearly visible on the 4000 scanner.

So, while 4000 did improve not only aliasing but pretty much
everything else (OK, it was also a step up from 10-bits to 14) this
improvement was not totally free.

Nevertheless, I personally would always chose the higher resolution.
Unlike flatbed scanners where the source (the photograph) only yields
up to 600 (some say only 300) we are not quite there with film
scanners due to the pesky nature of grain clouds.

Don.
 
To put it simple, 2700-2900dpi scans can produce 8x12" 300dpi (Fuji
Frontier) or 320dpi (Noritsu) prints without resampling. The prints will be
very high quality. If you want to go bigger size with the same quality (say,
12x18" 300/320dpi) without resampling, 4000+dpi is recommended.
 
Wayne Fulton said:
Seems an odd question from someone seeking to sell a 2900 dpi scanner <g>

Difference in quality when doing what?

Basically, the 4000 dpi scanner can create a larger image (dimensioned in
pixels) which would allow printing larger prints (inches on paper), with
that capability being in the size ratio of 4000/2900, or 138%. Excluding
cases of extreme cropping, then 2900 dpi is enough to print 8x10 inches very
well, and somewhat larger perhaps a little less well, but the 4000 dpi
scanner would be more capable for even larger images. This is not much issue
for goals of small images, for example video screen size or 6x4 inch prints.
That answer is "often no, depending on the goal".

Another factor, even for smaller images, is that the 4000 scanning resolution
could also minimize aliasing (false film grain effects) more than the lower
capability. That answer is "perhaps yes", but hard to quantify.
Click to expand...

Have you heard about the new £169 Plustek OpticFilm 7200? Its a true
optical resolution 7200dpi so can print A1 prints (@300dpi) from full
35mm or can use a quarter of the area of a 35mm film and still get A3
prints (@300dpi). Reviews in UK press seem to confirm this:
http://www.datamind.co.uk/Merchant/plustek_opticfilm_uk_press.htm

But is 7200dpi really better than 4000/5400dpi?
Chris Street
 
Higher resolution is generally better as rule of thumb (one can always
step down to lower resolution when required).

However, when I moved from 2700 to 4000 (LS-30 to LS-50) I discovered
something unexpected: pepper spots! They were too small to register on
the 2700 scanner but are clearly visible on the 4000 scanner.
Click to expand...
Ah, you use Fuji film :)
 
LOL! Very good!

Actually, it's much worse... 1980s Kodachromes... fx: Growl!
Click to expand...

<g>

Yes, I have Kodachromes too, though not that old. I like KC a lot, but
I've changed to Velvia simply because of ease of scanning.
 
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