question on scanner resolution specification


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looteer

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#1
i m thinking of buying the epson 2450, but not too sure about the resolution specified....

as stated on the specification for the 2450,
the optical resolution is "2400 x 4800 dpi with microstep drive....."

see http://www.epson.com.sg/html/perf2400_-_epson_perfection_24.html

my question is how many megapixel is that as compared to a digital camera megapixel

IF it is stated as 2400 x 4800 PIXEL (instead of dpi), then i can multiply and get 11.52MP, but i don't understand why they use the term DPI here.....

any scanner experts??:)
 

kurtlim

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it is measure by pixel, the dot was taken from printer. btw, always take the lower figure to judge a scanner. the higher figure as you said, is achieve by microstep motor. we should use the optical resolution which is 2400ppi. that turns out to be (2400x~1.42")x(2400x0.94")=~7.7MP if scanning a 35mm slide/negative.
 

looteer

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oh! i see you point.... :)

so if i scan in an A4 size 8.3" x 11.7" i will get like (8.3" x 2400dpi)x (11.7 x 2400dpi) = 559,353,600 pixels or 559MP!!:eek:

but this seems so exaggerated, can this be true........

or is it 2400dpi for 3 channels RGB so 800dpi per channel?? :dunno:

ultimately, i would like to know if i scan in a full A4 size photo, can i reprint to A3 size without seeing jaggies??
 

Zerstorer

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Don't bother too much about the numbers, the output file size or pixel dimensions can be anything you desire. According to reviews flatbed scanners perform only up to 1900-2000dpi(even if rated at 2400 or 3200 optical dpi) at best because of design limitations compared to film scanners which perform close to their rated specs.

Flatbeds are not resolving enough for 35mm film, they are fine for medium or large format though.
 

looteer

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Zerstorer,

does it mean that i can forget about spending another S$140 for the "EPSON Perfection 3200 Photo" instead of the "EPSON Perfection 2450 Photo".....

coz i was thinking might as well get the best since its only S$140 extra....

what do you think??:)
 

Zerstorer

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Originally posted by looteer
Zerstorer,

does it mean that i can forget about spending another S$140 for the "EPSON Perfection 3200 Photo" instead of the "EPSON Perfection 2450 Photo".....

coz i was thinking might as well get the best since its only S$140 extra....

what do you think??:)
There are several reviews from users who upgraded from the 2450 to the 3200 on the web. Most stated only a very marginal increase in quality, but most appreciated the faster speed and the additional film holders.

However, if your interest is only 35mm film, you might be better off with a 35mm film scanner.

Those Epson 3200/2450 owners are predominently medium/large format users.
 

binbeto

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#7
Get the best you can afford.. else if u buy 2450 now.. and upgrade to say 3450 later..

U might be "tempted" to rescan all your slide/pic.. Frightening, is it?
 

mpenza

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#9
Originally posted by looteer
so if i scan in an A4 size 8.3" x 11.7" i will get like (8.3" x 2400dpi)x (11.7 x 2400dpi) = 559,353,600 pixels or 559MP!!:eek:
....
Do note the resulting amount of details captured by scanning depends on input. e.g. a 35mm negative contains much more information than a 4R and scanning at a high resolution helps. For printed pics, magazines, etc, generally scanning at 600dpi (which is about twice the rated print resolution of 300DPI) is enough. Scanning more would just result in a much bigger file size with no extra details captured.

There's actual theory behind all these numbers and the reason why CD quality music/sound is captured at 44kHz (sampling "resolution" in the audio world > double the human audible range) instead of much higher which just take up additional storage with no increase in quality.
 

gavinjung

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don't forget... the megapixel count from scanning film and from a digital camera are not directly comparable. given a choice between an X megapixel scan or an X megapix image from a modern digital camera, i'd take the one from the digcam. everything else equal, the results from scanning film produces more grain than a digital cam. at small print sizes, the two would give similar results, but as you reach their size limits, the scanned image will be limited by grain (or noise) before detail (mp count). the problem is partly because film has inherent grain that scanners can't completely smooth out (even if you use vuescan) and partly because you're essentially taking a picture of a picture. at any rate... a lot of film scanners can do upwards of 20+ megapixels... even mid range ones can do 12, both of which can outdo any 6megapixel camera evenif you factor in grain. :D just don't think that because you have a 7.7mp scanner,t hat you've got the equivalent of a 7.7mp digital cam.

GJ
 

tert

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#11
like looter, i am considering purchasing a scanner.

my main use for the scanner would be to archive some of my photos, which i hope to do so through scanning my negs, and also for web posting...

since i dun think i would be doin any photo printing, would i really need the features of a dedicated film scanner? would the epson 1260/1660 be sufficient?

thanks a lot! :)
 

ChObiTs

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#12
Originally posted by looteer
oh! i see you point.... :)

so if i scan in an A4 size 8.3" x 11.7" i will get like (8.3" x 2400dpi)x (11.7 x 2400dpi) = 559,353,600 pixels or 559MP!!:eek:

but this seems so exaggerated, can this be true........

or is it 2400dpi for 3 channels RGB so 800dpi per channel?? :dunno:

ultimately, i would like to know if i scan in a full A4 size photo, can i reprint to A3 size without seeing jaggies??
Nope it is not kua zhang i tried a 4R photo at 9600 ,.... hmmm it took up 15 gb ..... : )
 

mpenza

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#13
Originally posted by ChObiTs
Nope it is not kua zhang i tried a 4R photo at 9600 ,.... hmmm it took up 15 gb ..... : )
This took up lots of space and will contain as much info as a 600DPI scans....
 

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