Scan Input Vs file output resolution

[alanmcd]

At Luminous-Landscape, the ratio on page 12
http://luminous-landscape.com/wp-content/uploads/2015/02/The-New-Epson-V850-Pro-Scanner-Final.pdf
is given as: 6400ppi scan of 6x7cm negative gives a printable 58x40in
So if all I want is to get 30x20 prints from a 4x5 negative, 1800ppi scans would provide an almost 1 for 1 ratio of input to digital file output ready for printing.
Am I understanding this correctly?
He is assuming a 360ppi printing. My service is asking asking for 254ppi file. I know I don't want to upsample (ie. invent pixels) but is there a problem with 'downsampling' or is there less issue with this. It doesn't have to be an exact one for one does it?

Also: The Luminous paper talks about outputting at 16bit/channel mode. But my printer is asking for 8bit/channel. What is the effect of doing this? The file size of half but does this reduce the quality of the print ?

Thanks
Alan

[alen]

Output 2 versions of the image, then do a test print print and find out exactly. Yes you will burn ink and paper but you will know exactly what you will get.

[RHITMrB]

There is no issue with downsampling, and in fact, depending on your workflow, it may be better to downsample. Photoshop's default downsampling algorithm produces sharpening as a side effect - in Photoshop you can choose "Bicubic" instead of "Automatic" or "Bicubic Sharper" if the added sharpening bothers you.

[Jeff T]

Scan at 16bit if your image needs heavy adjustments in Photoshop. Edit the 16bit file Photoshop, save a copy as 16bit file, reduce to 8bit and save a final copy for printing.

If you're scanning 4x5 films then 8bit is sufficient for printing in most cases.

[onnect17]

Alan,
Allow me to make a couple of suggestions.

Try to scan at closest native resolution of the scanner.
254 x 30" = 7620
7620 / 5" = 1524
So the closest resolution above should be 2400 dpi, if using an Epson.

PS is not my first choice for interpolation work. Search for "QImage" or "Perfect Resize". Both do a decent job.
Double check the proportions. 20x30 will require some cropping in the 4x5.
Ask the printer for the preferred profile and convert the final image to it before reducing the file to 8 bits.

Good luck.

[alanmcd]

Scan at 16bit if your image needs heavy adjustments in Photoshop. Edit the 16bit file Photoshop, save a copy as 16bit file, reduce to 8bit and save a final copy for printing.

If you're scanning 4x5 films then 8bit is sufficient for printing in most cases.

Good point - thank you.
Alan

[alanmcd]

Alan,
Allow me to make a couple of suggestions.

Try to scan at closest native resolution of the scanner.
254 x 30" = 7620
7620 / 5" = 1524
So the closest resolution above should be 2400 dpi, if using an Epson.

PS is not my first choice for interpolation work. Search for "QImage" or "Perfect Resize". Both do a decent job.
Double check the proportions. 20x30 will require some cropping in the 4x5.
Ask the printer for the preferred profile and convert the final image to it before reducing the file to 8 bits.

Good luck.

Thanks - I want to stick to LR which sets the profile at the same time as the 8 bit reduction in the export process. Not sure if that makes a difference but I'll keep my eye on that.
Alan

[alanmcd]

I will say something else I do notice. And that's the need to leave the Automatic Orange Mask Expansion option ticked. It makes a difference all for the better. And the Unsharp Masking can be strengthened with good results. I can see the result of using this option before I import into LR so it doesn't force any backtracking in my workflow. All other settings I can leave as standard.
thanks for all the help.
Alan

[alanmcd]

At Luminous-Landscape, the ratio on page 12
http://luminous-landscape.com/wp-content/uploads/2015/02/The-New-Epson-V850-Pro-Scanner-Final.pdf
is given as: 6400ppi scan of 6x7cm negative gives a printable 58x40in
So if all I want is to get 30x20 prints from a 4x5 negative, 1800ppi scans would provide an almost 1 for 1 ratio of input to digital file output ready for printing.
Am I understanding this correctly?
He is assuming a 360ppi printing. My service is asking asking for 254ppi file. I know I don't want to upsample (ie. invent pixels) but is there a problem with 'downsampling' or is there less issue with this. It doesn't have to be an exact one for one does it?

Also: The Luminous paper talks about outputting at 16bit/channel mode. But my printer is asking for 8bit/channel. What is the effect of doing this? The file size of half but does this reduce the quality of the print ?

Thanks
Alan

Let me ask another question for comment on this subject:
If my V800 can deliver 6400ppi without breaching TIF filesize limits, this gives me an 8 x 10 ft print.
Can someone tell me why they would then jump to a drum scan?
It seems that drum scanning would be reserved for billboards or something. And even then, a billboard is viewed from such a long distance that this sort of resolution is totally unnecessary.
So why do we need drum scans?
Alan

[alanmcd]

What I am saying is that, my V800 has a non-interpolated resolution of 6400ppi.
This means that each pixel scanned, placed on a piece of paper at the same distance apart as it was when scanned, will result in an output of 8ft x 10ft (from 4x5" negative).
What megapixel camera would you need to do the same same thing?
Full frame digital - 55 Megapixel?
Am I understanding this paradigm correctly?
Alan

[RHITMrB]

What I am saying is that, my V800 has a non-interpolated resolution of 6400ppi.
This means that each pixel scanned, placed on a piece of paper at the same distance apart as it was when scanned, will result in an output of 8ft x 10ft (from 4x5" negative).
What megapixel camera would you need to do the same same thing?
Full frame digital - 55 Megapixel?
Am I understanding this paradigm correctly?
Alan

The sensor in a V700/750/800/850 is capable of resolving 6400ppi, but the lens is most certainly not. In my and others' experience the effective resolution is closer to 2400dpi. This is still quite a bit.

[Ken Lee]

You might find this article helpful, particularly the part about resolution: http://www.kennethleegallery.com/html/scanning/index.php

[onnect17]

Let me ask another question for comment on this subject:
If my V800 can deliver 6400ppi without breaching TIF filesize limits, this gives me an 8 x 10 ft print.
Can someone tell me why they would then jump to a drum scan?
It seems that drum scanning would be reserved for billboards or something. And even then, a billboard is viewed from such a long distance that this sort of resolution is totally unnecessary.
So why do we need drum scans?
Alan

First, let me say drum scanners are not perfect by any means. Quite exposed to the mechanics of the system.
On the other hand, they capture the info from the emulsion in a different way compared to the CCD based scanner, not relaying so heavily and widely in the lens. But optical resolution is not the only issue. Flare in the CCD based scanners also impacts the color purity.

As other members mentioned, IMHO the resulting optical resolution of the epsons is subtantially lower than 6400 dpi.

[fishbulb]

As other members mentioned, IMHO the resulting optical resolution of the epsons is subtantially lower than 6400 dpi.

Yes, the various tests out there measure the actual resolution of the Epson lineup (4990, 700/750, 800/850) at around 2000-2400 dpi depending on the model, the test, etc.

A drum scanner (properly set up, trained operator etc.) can deliver far more realized dpi, as well as better color rendition etc.

[Tin Can]

If we print at 300 dpi and have Epson scan with 1800 dpi minimal isn't that a possible 6x enlargement?

Which is 48x60" and bigger than most anybody prints.

Of course Drum is better, but is it worth it for amateur work, especially considering how cheap inkjet prints can be when done in quantity?

And what happened to fractal extrapolation?

[fishbulb]

What I am saying is that, my V800 has a non-interpolated resolution of 6400ppi.
This means that each pixel scanned, placed on a piece of paper at the same distance apart as it was when scanned, will result in an output of 8ft x 10ft (from 4x5" negative).
What megapixel camera would you need to do the same same thing?
Full frame digital - 55 Megapixel?
Am I understanding this paradigm correctly?
Alan

If you want to print 8x10ft at 254 ppi, you are looking at about a 24380 x 30480 pixel image, or 743 megapixels. To get that kind of actual resolution you'd need to be scanning an 8x10 sheet of film at over 4000 real dpi, and under ideal conditions (both photographic and scanning). No matter how high the dpi of your scanner, or the fineness of your film grain, you are never going to get that kind of resolution out of 4x5, and it would be a challenge for 8x10 too.

Realistically the available resolution from film depends on a ton of factors - type of film, aperture used, lens type, any motion blur, film flatness etc. - not to mention the quality and type of the scan. For example, you can get significant resolution improvements with a flatbed by using a calibrated film holder, or significant resolution losses with a drum scanner if it isn't focused correctly.

With ideal conditions and a good drum scanner, you can get 320+ megapixels of real resolution out of 4x5. This would be fine-grained black and white film, like Delta 100, a larger aperture (f/11 to f/16), and a drum scanner at 4000+ dpi. The same image, scanned with an Epson flatbed, you should be able to get about 100 megapixels of real resolution out of it (320/(4000/2400*2))=96

Under less ideal resolution conditions - color film and a smaller aperture (f/32-ish) - you're looking at more like 100 megapixels with a 4000dpi drum scanner, and correspondingly less with a flatbed. Aperture and film choice have a HUGE impact on available resolution for a scan, I can't stress that enough. (f/64 is all well and good, but if you're trying to maximize resolution, the diffraction is going to kill it for you)

See the tables on this page (https://www.onlandscape.co.uk/2011/12/big-camera-comparison/) for the details on those resolution numbers and how they were tested. (I'm not just making up numbers here. :) )

[Jac@stafford.net]

And what happened to fractal extrapolation?

I don't believe it ever worked using fractal mathematics. I have used it with surprising success an image having a relatively short tonal range, but that was, IMHO, the exception. ...oh, it too hours to process. :)

[onnect17]

I don't believe it ever worked using fractal mathematics. I have used it with surprising success an image having a relatively short tonal range, but that was, IMHO, the exception. ...oh, it too hours to process. :)

Actually, I think that's what "Perfect Resize" does (or uses). Qimage is more dedicated to printing but it allows file-to-file interpolation. Both are really good, IMHO, and much better than PS.

Also quite useful for QuadtoneRIP users.

[lorithorn]

At Luminous-Landscape, the ratio on page 12
http://luminous-landscape.com/wp-content/uploads/2015/02/The-New-Epson-V850-Pro-Scanner-Final.pdf
is given as: 6400ppi scan of 6x7cm negative gives a printable 58x40in
So if all I want is to get 30x20 prints from a 4x5 negative, 1800ppi scans would provide an almost 1 for 1 ratio of input to digital file output ready for printing.
Am I understanding this correctly?
He is assuming a 360ppi printing. My service is asking asking for 254ppi file. I know I don't want to upsample (ie. invent pixels) but is there a problem with 'downsampling' or is there less issue with this. It doesn't have to be an exact one for one does it?

Also: The Luminous paper talks about outputting at 16bit/channel mode. But my printer is asking for 8bit/channel. What is the effect of doing this? The file size of half but does this reduce the quality of the print ?

Thanks
Alan

Yes you will burn ink and paper but you will know exactly what you will get.

http://hautavis.net/128/o.png