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Author Topic: Scanning resolution  (Read 4073 times)

richardw

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Scanning resolution
« on: November 10, 2020, 12:52:00 pm »

Dear All,

I am digitising a large photography archive, to be used in potential publications and exhibitions. The archive consists of several hundred black and white photographs taken in the 1940s-60s. I’m using the Epson V850 Pro flatbed scanner with either Epson Scan 2 or Silverfast SE Plus 8

Although I have access to the medium and large format negatives, my preference is to scan from the prints (which are mostly 8 x 10 inches). This preference is mainly due to the fact that the negatives are not all in good condition, and I would also like to capture the photographer’s darkroom adjustments.

I have scanned similar photographs over many years, usually opting for very high resolution scans, scanning at 2400 dpi and resulting in scanned image sizes of well over 1Gb. This is to make sure that when I print exhibition sized prints, up to 1 metre in size, I am getting the very best image quality possible from the original photographs.

However, the huge file size does dramatically slow down scanning and subsequent processing. It also means that the removal of dust and other marks requires much more work due to the increased resolution.

I have three questions relating to this:

1. Should I re-think my preference for scanning prints rather than negatives? Would I obtain a better technical quality from the negatives?

2. Am I scanning the images at an unnecessarily high resolution? What would be the optimum quality vs size compromise?

3. If scanning from prints, is there any particular advantage in using Silverfast over the Epson Scan software? Would I obtain a better dynamic range in the shadows or highlights in Silverfast?

I’d be very interested and grateful to hear the various opinions of the experienced users on this list.

Thanks and best wishes,

Richard
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tsinsf

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Re: Scanning resolution
« Reply #1 on: November 10, 2020, 01:16:32 pm »

I have no experience scanning negatives, but have a lot of experiencing scanning prints. With a little editing I am almost always able to produce a copy that is better than the original. I use Viewscan software to do the scan and editing. It is an excellent program and it is easy to make adjustments to the photos without taking them into Photoshop. You can try it for free. The pro edition costs $99. Sorry, can't give you advice about what resolution to use.The link is below:

https://www.hamrick.com
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Alan Klein

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Re: Scanning resolution
« Reply #2 on: November 10, 2020, 01:37:01 pm »

I have no experience scanning negatives, but have a lot of experiencing scanning prints. With a little editing I am almost always able to produce a copy that is better than the original. I use Viewscan software to do the scan and editing. It is an excellent program and it is easy to make adjustments to the photos without taking them into Photoshop. You can try it for free. The pro edition costs $99. Sorry, can't give you advice about what resolution to use.The link is below:

https://www.hamrick.com
Original prints are 300dpi.  So scan at 300 dpi, or 600 at the most.  You can always uprez later for secondary printing, posting on the web, making slideshows, etc.  If you use Epsonscan, you can use ICE which will correct many scratches, tears, hairs,  and imperfections in the print.  If you have color prints, Epsonscan can use auto color correction which improves faded color prints as well.  Epsonscan will pick up the full range of tones in one scan.  You can also adjust contrast, exposure and levels or adjust the tones after the scan of either negatives or prints. I've never used Silverfast, so I can't comment on its capability. 

You should get better results from the negatives.  But you will have more processing to do.  Negatives might be in better shape than old photo prints as well. ICE does not work with most BW negative film or Kodachrome color film, only with E6 Ektachrome type color film.  It works with prints however. ICE doubles scan time.  The scanner has to scan twice to compare normal lighting against IR lighting.  That's how it knows where the tears and other imperfections are.

Try a couple of different methods on different type shots and see what works best for you.  Enlarge the results to see what that looks like too.  Good luck and be patient.  This is going to take a lot of work. 

digitaldog

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Re: Scanning resolution
« Reply #3 on: November 10, 2020, 01:37:16 pm »

1. The film has a far greater dynamic range than a print. It's also (if a neg) un rendered which allows you to control the rendering.
2. Scan an archive at the highest optical resolution, bit depth, color gamut. You can go down, you can't go back up.
3 Silverfast is excellent and powerful, albeit with a steep(er) learning curve.
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digitaldog

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Re: Scanning resolution
« Reply #4 on: November 10, 2020, 01:38:42 pm »

Original prints are 300dpi. 
Maybe your prints are, not all prints are 300dpi.
"All generalizations are false, including this one." -Mark Twain
Quote
You can always uprez later for secondary printing, posting on the web, making slideshows, etc.
And lose image quality (interpolation up).
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Alan Klein

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Re: Scanning resolution
« Reply #5 on: November 10, 2020, 02:08:05 pm »

Maybe your prints are, not all prints are 300dpi.
"All generalizations are false, including this one." -Mark TwainAnd lose image quality (interpolation up).
OK, if 300 or 600 isn't good enough, how far do you go?  One could try let's say 600 and then compare uprezing against scanning at the same final resolution and see if there are any differences.  But to scan let's say at 2400 as the OP suggested seems like a waste of time, especially since he doesn;t intent to enlarge very much, if at all.  Plus his prints are 8x10, pretty large to begin with.  Such large files may not be able to be handled by post processing programs. I think 600 would do the job, but he can compare results himself. 

I do agree with you that he should use 16 bit grayscale to get the most from tones.

Alan Klein

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Re: Scanning resolution
« Reply #6 on: November 10, 2020, 02:12:21 pm »

If you scan the negatives, than you should scan at higher resolutions.  I use 2400 with my V850 on 35mm, 6x7 medium format and 4x5 film.

digitaldog

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Re: Scanning resolution
« Reply #7 on: November 10, 2020, 02:21:58 pm »

I never said 300DPI isn't ”good enough” I corrected your incorrect generalization that all prints are. Absolutely not so.
Do you also believe all displays are 72PPI? Equally untrue.
Quality for some, specific printers? Read this:
https://www.digitalphotopro.com/technique/photography-workflow/the-right-resolution/
What makes you believe that 16 bit grayscale has ”more tones”?
More device values; yes.
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Alan Klein

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Re: Scanning resolution
« Reply #8 on: November 10, 2020, 02:48:47 pm »

I gave him some concrete starting points.  If mine aren't OK, then what do you suggest?  Scanning at 8x10 print at 2400 is not necessary.  Might not work because the file is too big.  What would you suggest?

digitaldog

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Re: Scanning resolution
« Reply #9 on: November 10, 2020, 02:58:11 pm »

I gave him some concrete starting points.
Some based on generalizations that are often not what you suggest. And now, maybe you know.
I made recommendations. Specific ones. IF the OP required more detail from my recommendations, I hope he asks.
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David Sutton

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Re: Scanning resolution
« Reply #10 on: November 10, 2020, 03:49:46 pm »

A second vote for Viewscan.
I set it to scan twice for each image, once for the shadow detail and once for the highlights.
There are two downsides. The file sizes are huge, as you say, and the scan pulls a remarkable amount of detail out of the shadows, and you may need to create a custom curve to crush some of that back when you print, if you want the result to not look too “digital” but closer to an original print from film. If that makes sense.
The original prints will definitely not be 300dpi. I've scanned an ancient postcard sized print of a couple riding a tandem, and been able to read the brand of the bike on the frame.
Scanning the prints is probably less work, but it depends on the quality there. If I was creating a vital archive I'd bite the bullet and scan both the prints and the negatives. Otherwise I'd decide how much of my life I wanted to spend on the project and go from there.
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JRSmit

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Re: Scanning resolution
« Reply #11 on: November 11, 2020, 10:59:58 am »

My suggestion is to scan at the native resolution of the scanner, which I the case of a v850 is probably 1200dpi.
The highest number of dpi is normally an interpolated result.
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digitaldog

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Re: Scanning resolution
« Reply #12 on: November 11, 2020, 11:03:56 am »

My suggestion is to scan at the native resolution of the scanner, which I the case of a v850 is probably 1200dpi.
The highest number of dpi is normally an interpolated result.
Exactly. If one sees a spec like 1200x2400, the second value is interpolation.
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Alan Klein

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Re: Scanning resolution
« Reply #13 on: November 11, 2020, 12:02:48 pm »

My suggestion is to scan at the native resolution of the scanner, which I the case of a v850 is probably 1200dpi.
The highest number of dpi is normally an interpolated result.

These are the specs.  So what's the native resolution?  Note that this scanner has two lenses - a better one for scanning everything in film holders except 8x10.  And a less quality lens that scans 8x10 on the flatbed glass.

I scan at 2400.  That seems to work best for me whether I'm scanning 35mm., MF or 4x5.

Specs:
Maximum Resolution   6400 dpi (Optical)
4800 x 9600 dpi (Hardware)
6400 x 9600 dpi (Hardware)
12,800 x 12,800 dpi (Interpolated)
https://www.bhphotovideo.com/c/product/1083201-REG/epson_b11b224201_perfection_v850_pro_scanner.html/specs



digitaldog

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Re: Scanning resolution
« Reply #14 on: November 11, 2020, 12:28:20 pm »

These are the specs.  So what's the native resolution? 
We told you, the first!
There is a linear CCD with a fixed number of sensors to create a pixel.
There is a stepper motor that moves that linear sensor down the scan bed.
One is optical, the other isn't. Pixels are square. You either get 4800x4800 or you get 9600 interpolated by 9600 as one example; 4800 x 9600 dpi (Hardware)
Quote
I scan at 2400.  That seems to work best for me whether I'm scanning 35mm., MF or 4x5.
The statement without further data is meaningless. IF your scanner has a higher optical resolution than 2400, and we have no idea since you didn't specify above what scanner, then no, it might work best for YOU but it's not producing all the actual data available IF it's optical resolution is higher. 
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degrub

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Re: Scanning resolution
« Reply #15 on: November 11, 2020, 12:55:16 pm »

Alan,

from the Epson spec sheet:

Technology
Scanner Type    Flatbed Scanner
Optical Resolution    6,400 DPI (Horizontal x Vertical)
Dual Lens System - scanning resolutions    Super Resolution Lens 6,400x 9,600 DPI, High Resolution Lens 4,800x 9,600 DPI

If you are using the Super Resolution Lens - 6400 is the optical
If you are using the High Resolution lens - 4800 is the optical.

so depending on the lens used, you would change settings for the scan to retain the most available "real" data.
If the sensor head actually has 6400 sensels, then the scan is limited by the optics and you would adjust accordingly.  Epson would be oversampling  the High resolution lens path and then reducing the resolution either in driver software  or more likely the scanner firmware. It is possible the sensor sensel arrangement is such that can get native 4800, but i don't know.

Using the High resolution lens at 2400 is just keeping every other sensel value and throwing the other one away.  Using the Super resolution at 2400 would require down sampling and interpolation, not always desirable, but may not have any practical effect.

If the medium being sampled does not have enough resolution, then both cases would be oversampling. Oversampling can be a good thing if you can tolerate the file size. This, i think, would likely be true for prints. Transparencies, maybe not, but depends on the film and the camera optics.

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Alan Klein

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Re: Scanning resolution
« Reply #16 on: November 11, 2020, 01:18:03 pm »

Alan,

from the Epson spec sheet:

Technology
Scanner Type    Flatbed Scanner
Optical Resolution    6,400 DPI (Horizontal x Vertical)
Dual Lens System - scanning resolutions    Super Resolution Lens 6,400x 9,600 DPI, High Resolution Lens 4,800x 9,600 DPI

If you are using the Super Resolution Lens - 6400 is the optical
If you are using the High Resolution lens - 4800 is the optical.

so depending on the lens used, you would change settings for the scan to retain the most available "real" data.
If the sensor head actually has 6400 sensels, then the scan is limited by the optics and you would adjust accordingly.  Epson would be oversampling  the High resolution lens path and then reducing the resolution either in driver software  or more likely the scanner firmware. It is possible the sensor sensel arrangement is such that can get native 4800, but i don't know.

Using the High resolution lens at 2400 is just keeping every other sensel value and throwing the other one away.  Using the Super resolution at 2400 would require down sampling and interpolation, not always desirable, but may not have any practical effect.

If the medium being sampled does not have enough resolution, then both cases would be oversampling. Oversampling can be a good thing if you can tolerate the file size. This, i think, would likely be true for prints. Transparencies, maybe not, but depends on the film and the camera optics.


I never saw better resolution above 2400 on a V850.  So their higher resolution specs may provide the pixels but not actually resolve that high.  Additionally, I tried sharpening a 4800 4x5 scan. I found that sharpening a 2400 scan gave me better results.
https://www.largeformatphotography.info/forum/showthread.php?158728-Howtek-8000-Drum-vs-Epson-V850-flatbed-scanners&highlight=howtek

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Re: Scanning resolution
« Reply #17 on: November 11, 2020, 01:24:27 pm »

I never saw better resolution above 2400 on a V850.  So their higher resolution specs may provide the pixels but not actually resolve that high.  Additionally, I tried sharpening a 4800 4x5 scan. I found that sharpening a 2400 scan gave me better results.
https://www.largeformatphotography.info/forum/showthread.php?158728-Howtek-8000-Drum-vs-Epson-V850-flatbed-scanners&highlight=howtek
Well at least one issue with what you provided (other than the Howtek, which I've owned blew the Epson away as expected): only ONE of your screen captures provided was at 1:1 (100% zoom) and that affects the perception of sharpness and other visual attributes. Any preview less than 100% is subsampled down which is really not the way to ever evaluate, on-screen, image quality.
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Alan Klein

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Re: Scanning resolution
« Reply #18 on: November 11, 2020, 01:44:09 pm »

Well at least one issue with what you provided (other than the Howtek, which I've owned blew the Epson away as expected): only ONE of your screen captures provided was at 1:1 (100% zoom) and that affects the perception of sharpness and other visual attributes. Any preview less than 100% is subsampled down which is really not the way to ever evaluate, on-screen, image quality.
My scans are for the web and digital display.  If I want a print of a specific shot, I would probably have a proscan made.  So for practical results, I've found 2400 very good.  The comparison with the Howtek is pretty good in the test.  Of course, it's not going to be as good, but 2400 works very well.  On a color 4x5 that's about 600mb.  It would be 4x higher I believe at 4800 and I don't think Lightroom can handle such a large file.  I'm satisfied with what I'm getting at 2400. Of course the following was downsampled for 1600 on the long side.


Lake Topanemus
by Alan Klein, on Flickr]

degrub

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Re: Scanning resolution
« Reply #19 on: November 11, 2020, 01:54:44 pm »

I never saw better resolution above 2400 on a V850.  So their higher resolution specs may provide the pixels but not actually resolve that high.  Additionally, I tried sharpening a 4800 4x5 scan. I found that sharpening a 2400 scan gave me better results.
https://www.largeformatphotography.info/forum/showthread.php?158728-Howtek-8000-Drum-vs-Epson-V850-flatbed-scanners&highlight=howtek

That may well be because the film could not record higher resolution than that or the camera optics limited the film recorded image.
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