Info on Scanning & Printing Negs

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ghoti

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Let's say I have a 2400ppi jpg scanned from a 35mm negative using a fairly cheap Epson V370 (I believe) desktop scanner. The image "size" is reading as 4x6 and approximately 130MP. After a bit of curves and levels TLC in photoshop, it looks rather nice...as a jpg on a computer screen.

My question, being a dreadful ignoramus on such matters, is: what are the limits of quality and size I can expect if I decide to print this image? How big can I make a top quality print?

I know in theory I can make (roughly) a 32x48 from this 130MP image at 300ppi, but the scan quality will, I imagine, be a bigger limiting factor than the resolution.
 
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I think you might be confusing something for the image size as the maximum a 2400 dpi scan of a 35mm neg will reach is 3456 x 2304 (~8mp). The quality of a print any size will depend on a number of factors, perhaps most importantly the distance away that your viewing it as most large prints look sharp from a few metres back, but are somewhat softer up close.
 
well, lets see...

35mm frame size is 36mm x 24mm

2400 ppi = 2400 / 25.4 = 94.5 ppmm (or very near)

so 35mm scan would be 36*94.5 by 24*94.5 = 3402 x 2268 pixels

and printed at 300dpi on a inkjet, that's coming out at 11.34" x 7.56"

(I normally work on a 300dpi resolution for anything that's likely to be viewed hand-held rather than a wall hanger)

frankly, IMO, scanning at 2400ppi you're hitting pixelation issues printing anything much larger than A4, maybe A3 depending on the image complexity...
 
TheBigYin said:
well, lets see...

35mm frame size is 36mm x 24mm

2400 ppi = 2400 / 25.4 = 94.5 ppmm (or very near)

so 35mm scan would be 36*94.5 by 24*94.5 = 3402 x 2268 pixels

and printed at 300dpi on a inkjet, that's coming out at 11.34" x 7.56"

(I normally work on a 300dpi resolution for anything that's likely to be viewed hand-held rather than a wall hanger)

frankly, IMO, scanning at 2400ppi you're hitting pixelation issues printing anything much larger than A4, maybe A3 depending on the image complexity...
Click to expand...

Just to add:- you can use programs that smooth out the annoying pixels because of scanning, but go too far and you end up more like a digital image :eek:
 
PMN said:
Smooth out annoying pixels? You mean noise?
Click to expand...

That had me wondering as well...

I think he may be referring to software that allows you to increase the pixel count of an image, upsizing it, and using software interpolatinon so you don't just get "bigger squares", much the same as "overscanning" on the scanner will do (i.e. if the scanner will only physically / optically produce 2400, sometimes the software will allow you to overscan at 4800 or even 9600) but perhaps with slightly more finesse in the upsizing algorithms...
 
Most of the vastly inflated '6400' dpi or '9600' dpi resolutions quoted on the specs are true at the sensor (ie. it can resolve it), but not at the actual slide/neg as the optics in the scanning path limit the resolution. Its not really so much 'upscaling' as the images are produced at that resolution on the sensor, but if you were to compare a 2400 dpi and a 6400 dpi scan on a V700/V750 for instance then there would be no more detail actually resolved so it is sort of like 'hardware upscaling' really even if its not upscaling in the sense that most would use it!
 
Interesting stuff, thank you.

I now totally understand why max resolution should be about 8MP from a 35mm neg at 2400dpi, so why is the file I have ~130MP? How might that have come about?

I'm new to all of this...
 
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Are you sure it's not 130 Mb?
 
Are you sure you've not accidentally selected the maximum scanning resolution (which would be an interpolated figure) as 14000/1.44 (the long side of a 35mm neg in inches) comes out as 9722 dpi which the V370 cannot produce optically (max 4800 dpi) so you must have selected one of the interpolated resolutions (9600 dpi is an interpolated resolution option on thw V370 according to the specifications).

Check that you've not set the output DPI to 2400 rather than the scanning dpi (the output dpi has no effect on quality).
 
s162216 said:
Are you sure you've not accidentally selected the maximum scanning resolution (which would be an interpolated figure) as 14000/1.44 (the long side of a 35mm neg in inches) comes out as 9722 dpi which the V370 cannot produce optically (max 4800 dpi) so you must have selected one of the interpolated resolutions (9600 dpi is an interpolated resolution option on thw V370 according to the specifications).

Check that you've not set the output DPI to 2400 rather than the scanning dpi (the output dpi has no effect on quality).
Click to expand...
I didn't scan the negative, so I really don't know what's been done. All I know is what it's telling me when I stick the jpg into photoshop.
So we have a huge file: something like 14000x9600 pixels.
The dpi field (in photoshop) is saying 2,400, but I guess that's irrelevant as it's not a physical image. The image looks nice on the screen.

I'm just trying to figure out how (if) I can get a very high quality print* from this file and, if so, how large I can feasibly make it.

*for display in a departmental reception hall/lobby in an academic organisation
 
If it has been scanned with an interpolated resolution, is that a disaster for final print quality? Let's say I'd ideally like a print no smaller than 12" along its shortest edge, but willing to go smaller for higher quality.
 
The person who scanned it probably thought that selecting the top resolution was the best idea which is why you have such a big file (also just check, is it in 24/8 bit or 48/16 bit?) - realistically the size you can go to will depend on how close you want it to be viewed at, most billboards for instance look sharp from a few metres away, but up close you can see the low resolution nature of them (less than 100 dpi printing is typical for them ).

If possible I would get the negative re-scanned using more realistic settings, but for a 12" on the shortest edge print I don't think you'll have too much of a quality problem with your existing scan unless your expecting a person to be viewing it 30cm or something in front of them.
 
s162216 said:
The person who scanned it probably thought that selecting the top resolution was the best idea which is why you have such a big file (also just check, is it in 24/8 bit or 48/16 bit?) - realistically the size you can go to will depend on how close you want it to be viewed at, most billboards for instance look sharp from a few metres away, but up close you can see the low resolution nature of them (less than 100 dpi printing is typical for them ).

If possible I would get the negative re-scanned using more realistic settings, but for a 12" on the shortest edge print I don't think you'll have too much of a quality problem with your existing scan unless your expecting a person to be viewing it 30cm or something in front of them.
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Okay. Thank you. I appreciate your patience...

Just for future reference: what scanning settings would we select for maximum print size & quality on a cheap scanner like the v370? What are the tangible advantages of spending more on a scanner?
 
Cheap scanners generally don't resolve very much resolution (~1700 dpi is usual), despite what they may claim. As I described above although the sensor may be able to resolve the massive DPI's claimed, the optics in the scanning path (especially the high pass filter) limit the actual resolution that the scanner resolves so you can end up having massive files with no tangible difference in detail compared to ones 25% of the size! More expensive scanners resolve more detail (which for the fairly small 35mm negative is fairly important) and also have better density (e.g how dark they can get detail out of which is important when scanning high contrast slides). For 35mm a dedicated (non flatbed) scanner is key for getting quality out in my opinion.

Obviously scanning at 1700 dpi is not going to get you anywhere near the size you want so you could just scan it at 4800 dpi (the maximim optical resolution of the V370) which should give a fairly decent result, or (I don't know how/where your getting the print done) you could just send the negative into the lab where they will have scanning equipment which can easily outstrip anything consumer based and ask them to print it to 18x12 or whatever (that will give you a better result for a large print). I would recommend Peak Imaging for the job as they always do everything to exceptional quality.
 
PMN said:
Smooth out annoying pixels? You mean noise?
Click to expand...

Well what ever it is called (aliasing? ) e.g. quite a large blow up...one without noise reduction and one with:-




 
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