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11-20-2012, 06:27 AM   #1
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getting scans printed?? resolution and file size?

hey guys so ive been shooting mostly film for the last year now. pretty much dont touch my dslr unless im on vacation and i want to be 100% that i get a few keepers. i usually dont make prints. i just get my film developed and scanned by the local photo shop. i guess they do a good job but i never really looked at the file size or resolution of the scans too much. i went to get some medium format prints made today (i wanted them to be nice big prints) but the guy told me (i live in korea and my korean is not too great) that the file size was too small to make a big print. he told me to make an 8x10 the file size should be at least 2000kb. the scans i have been getting are nowhere near that size. what can i do???

i plan on buying a scanner when i finally make it home. but for now do i have to suffer from low quality prints? could i just ask the print shop to re-scan the negatives at a higher resolution? is there anyway to boost the file size without ruining the image after it has already been scanned??? i didnt even know i needed to think about this shit before! someone please give me some advice!

thanks!

11-20-2012, 07:12 AM   #2
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What is considered 'photo quality' is 300dpi print. So divide your image dimensions by 300 and you get what the 'natural' photo quality size is.

That's for the purist. In real life, you can get away with less dpi, and you can safely resize your image within reason. I have made several 13x19 and 11x17 prints from drug store scans that were approx 1200pix wide, and they look fine.
11-20-2012, 08:18 AM   #3
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So 300 dpi on 8 by 10 inch needs 3000 dots across

I think WeHaveNo is using 6 by 9 camera.
The purist would need:
90 mm across so the scan file needs 3000 pixels across or more

that is about 33 pixels per millimetre or about 16 line pairs per millimetre

And the lens/focus would be nice at about double that, 32 line pairs per millimetre

So the practical person would get a good print with about half of all the above

Am I on the right track here?
11-20-2012, 09:11 AM   #4
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QuoteOriginally posted by wehavenowaves! Quote
hey guys so ive been shooting mostly film for the last year now. pretty much dont touch my dslr unless im on vacation and i want to be 100% that i get a few keepers. i usually dont make prints. i just get my film developed and scanned by the local photo shop. i guess they do a good job but i never really looked at the file size or resolution of the scans too much. i went to get some medium format prints made today (i wanted them to be nice big prints) but the guy told me (i live in korea and my korean is not too great) that the file size was too small to make a big print. he told me to make an 8x10 the file size should be at least 2000kb. the scans i have been getting are nowhere near that size. what can i do???

i plan on buying a scanner when i finally make it home. but for now do i have to suffer from low quality prints? could i just ask the print shop to re-scan the negatives at a higher resolution? is there anyway to boost the file size without ruining the image after it has already been scanned??? i didnt even know i needed to think about this shit before! someone please give me some advice!

thanks!
The labs here in Vancouver will want the original negative or positive when they do enlargement prints. You tell them the size of the print and they will do the appropriate scan, which of course you get charged extra for.

I would not recommend taking in a digital image of a negative or positive done at the time of processing, as these low resolution scans are not good enough quality for an enlargement print.

Phil.


Last edited by gofour3; 11-20-2012 at 12:11 PM.
11-20-2012, 12:04 PM   #5
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Scanning terminology and print requirements can be very confusing for most folks. I assume you are working with 645 film?

The shorthand DPI is often misused in plain old post-processing speak; with scanning it is even worse. It is best to think of your scanning quality levels in terms of pixel density.

For an 8x10 printing requirement, a scan producing 4800x3200 pixels would work. This translates to 2000 DPI and a print of greater than 300 PPI (pixels per inch). The total size of the entire file would be 40 MB if 48-bit scanning was not used. if 48-bit scanning is used, then your tiff file would be 80 MB.. 48-bit scanning is better for editing but you better have the computer horsepower.

Some houses scan at greater resolutions which are useful to a point for larger prints. At a certain point you are just enlarging film grain and a higher res is unneeded. Fr your needs I'd declare victory at 2000 DPI.

Also, I would recommend letting shops scan stuff rather than you getting a scanner. It is a real skill that takes a lot of time and more..most flat bed scanners do an inferior job with medium format than a good lab can, especially if prints are your goal.

I'd get my film rescanned by a better lab in Korea and then develop a good relationship with the shop so they can help you in the future.

M
11-20-2012, 01:15 PM   #6
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It all depends on the final print size and the way you will look at the print. It is one thing to print an 8 x 10, hold it and use a magnifier to see the pixel structure, and another to frame it, hang it on the wall and look at it from 3 or 4 feet distance. The type of paper will play also a significant role. Smooth paper can show details, so high dpi can provide an advantage, while canvas with its texture can hide details, so a lower resolution may be just fine.

Here are some basic guidelines:

A good quality film scanner will provide better results than a flatbed one, so given a choice go with a dedicated film scanner.

The scans should be in high enough resolution to extract all the film info without going below the grain size. Depending on film type, exposure and development, anything in the 2,000 to 4,000 dpi is good. The resulted scan must be in lossless format (e.g. TIFF) either in 8-bit or 16-bit (if significant post processing will take place) per RGB color. A good starting point is 2,400 dpi, which for a 35mm frame will give an 8-bit uncompressed file size of approximately 7.4 Mpixels or 22 Mbytes (keeping in mind that TIFF can be compressed like ZIP without losing any data).

Each printer has a native max resolution for printing (e.g. 2,880 dpi) that does not directly relate to the image file, but it will print best if fed images in integer fractions of that resolution. For Epson printers which will print at 1,440 or 2,880 dpi, the image should be in multiples of 180 dpi (e.g. 180 or 360). For some HP printers with 1,200dpi, the image should be at 150 or 300. This way the printer driver does not have to scale the image using floating point math that can introduce artifacts.

Note that the image should never be at the printing resolution unless it is line art. The printer needs extra pixels in its dithering process to reproduce millions of colors using only a few inks. Limiting the image resolution to one quarter (or less) of the printer resolution is desirable (e.g. 360 dpi image for a 1,440 dpi print).
It is best to, either to resize the image before printing to the proper dpi using your image editing software and its best re-sampling option (e.g. bi-cubic), or to use dedicated RIP software (Raster Image Processor) which includes advanced re-sampling algorithms to do the printing.

For images that you plan to hold and view, try to stay over 200dpi if possible. For images that will be framed and viewed from a distance anything in the 100-200 range will be good.
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