the matter of Meg

[4play]

so if scan DPI of my chrome determines output print enlargement quality, what does the "meg" of the scan have to do w/ whatever ??? all the info i see from labs says they scan @ various meg, NOT DPI. if my chrome is scanned @ 20 or 50 or 75 or whatever meg how does that translate to what i understand of the scan DPI & its relation to enlargement quality ? & my understanding is as follows...

[INPUT (film) scan DPI/OUTPUT (print) DPI] times (1.4 by .9) = viable image size.

Ex. – [4000 DPI film scan/300 DPI print] = 13.33…. enlargement.
[13.33] times (1.4) = 18.5, [13.33] times (.9) = 12.
So 4000 DPI input film scan printed @ 300 DPI output image
allows for 13.33… times enlargement which gives an ~ 12 x 18 print.


also, what about the dynamic range & bits of color depth ? should i enquire of a lab as to those values their scanner is capable of ?

enquiring minds want to know...

:)

[4play]

i found out ! the meg labs refer to is...

the final RGB file sizes expressed in mb. The number of pixels measured vertically x the number of pixels measured horizontally will equal the final size in mb. If we scan your slide at 3600x2400 pixels we would end up with a 24.8mb
file. 3600x2400 pixels is a constant that can be expressed in different ways ie: 4x6" @ 600ppi, 9x6 @ 400ppi, 8x12" @ 300ppi, 12x18" @ 200ppi, 36x24" @ 100ppi, 50x33.33" @ 72ppi. These would all be the same 24.8mb file, with the same number of pixels.

so now i know...

[PacAce]

4play wrote:
i found out ! the meg labs refer to is...

the final RGB file sizes expressed in mb. The number of pixels measured vertically x the number of pixels measured horizontally will equal the final size in mb. If we scan your slide at 3600x2400 pixels we would end up with a 24.8mb
file. 3600x2400 pixels is a constant that can be expressed in different ways ie: 4x6" @ 600ppi, 9x6 @ 400ppi, 8x12" @ 300ppi, 12x18" @ 200ppi, 36x24" @ 100ppi, 50x33.33" @ 72ppi. These would all be the same 24.8mb file, with the same number of pixels.

so now i know...



Is there a "reference" file type that goes with this "file size"? I ask because the file size by itself really is meaningless because the same image saved in different file formats and with different file compressions will give you different file sizes.

[4play]

ummmmmm... huh ?

no wait ! i know a little something about this one. i do know different file formats matter. TIFF being the greatest size & detail, JPEG being the economony format. other than that i am not qualififed to give any advice other than do NOT bet on horses ! stupid longshot... the only other info i got from the lab was this -

"The other key factor in determining quality is the quality of the pixels that are in the image. If you scan a slide at 100% at 4000dpi (actually it's ppi - pixels per inch) on a typical desktop scanner and we scan the same slide at 100% at 4000dpi on our scanner - you will see a dramatic difference. While both scans will have the same files size in mb. Our scan will have greater color rendition, highlight and shadow detail. File quality cannot be judged on file size alone."

they also said it was hard to tell my knowledge level from my 1st inquiry & so they kept it simple so as to not possibly overwhelm & confuse me. i do not know what file type they format the scan to. you also mentioned "compression" ? oh great ! another new term to boggle my mind w/ ! thanks a lot .... :)