Plustek 8100 Resolution

[Stealth3kpl]

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I read on a forum that the published resolution for the 8100i of 7200ppi is achieved using interpolation, so there is little point in scanning greater than 3600ppi (the actual scanner resolution) as it merely gives you bloated files. Is this correct?

 

Pete

[Stealth3kpl]

I've been scanning at full resolution (in Vuescan). I was doing so to gain as much information as possible before downsizing to about 2000 pixels along the long edge. Is this a waste of time?

Pete

[philipus]

Hi Pete,

 

I'm no expert on that scanner but I've read at filmscanner.info that the effective resolution is about half of 7200. If that's true, I'm wondering if scanning at 7200 isn't just bloating the file without meaningful information being added. As for scanning at a higher resolution, whether in your case 7200 or half that, and later downsizing, that can be useful in certain situations. For instance it can deal with noise in the shadows, which is also 'shrunk' as one downsizes. Personally I don't do this, though, but scan at 2000dpi because it simplifies my workflow and is big enough for internet use. I will scan higher if I need to print larger, for instance.

 

Br
Philip

[pop]

I read on a forum that the published resolution for the 8100i of 7200ppi is achieved using interpolation, so there is little point in scanning greater than 3600ppi (the actual scanner resolution) as it merely gives you bloated files. Is this correct?

 

Pete

The technical data on Plustek's site state that 7200ppi is the optical resolution of the device. 

[Stealth3kpl]

Hi Pete,

 

I'm no expert on that scanner but I've read at filmscanner.info that the effective resolution is about half of 7200. If that's true, I'm wondering if scanning at 7200 isn't just bloating the file without meaningful information being added. As for scanning at a higher resolution, whether in your case 7200 or half that, and later downsizing, that can be useful in certain situations. For instance it can deal with noise in the shadows, which is also 'shrunk' as one downsizes. Personally I don't do this, though, but scan at 2000dpi because it simplifies my workflow and is big enough for internet use. I will scan higher if I need to print larger, for instance.

 

Br

Philip

 

 

 

 

I suspect this is the approach I'll take in future.

Thanks to all who responded.

Pete

Edited December 29, 2017 by Stealth3kpl

[Mr.Prime]

I tried scanning some b&w negs at 3600 and at 7200 and subjectively there was more detail at full resolution. I’m wondering if there is some pixel-shifting going on or if perhaps the resolution in higher in the scan direction and interpolated between pixels orthogonal to the scan direction.

Edited December 18, 2020 by Mr.Prime

[pop]

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vor 3 Stunden schrieb Mr.Prime:

I’m wondering if there is some pixel-shifting going on

Why would that be? As said above, the device has an optical resolution of 7200 dpi. That is, if it merely records what the scan head sees, you will fetch  a genuine resolution of 7200. Hence, you are bound to see more detail than at 3600.

[Mr.Prime]

7 hours ago, pop said:

Why would that be? 

I was under the mis-apprehension  that somebody said that the optical resolution was only 3600dpi. This corresponds to 7um pixel size. 

Edited December 18, 2020 by Mr.Prime

[bags27]

Here's a test 

https://www.dpreview.com/forums/thread/4547755

Plustek 8200i
Expected 7200
Actual 3505

Plustek 8200i
Expected 3600
Actual 2794

Canon FS4000US
Expected 4000
Actual 3150

Epson V550
Expected 3600
Actual 1575

Nikon D610 + f/2.8 50mm D + ES2
Expected 4233 (based on 4000 pixels per 24mm)
Actual 2794

 

[giannis]

On 12/18/2020 at 3:27 PM, Mr.Prime said:

I was under the mis-apprehension  that somebody said that the optical resolution was only 3600dpi. This corresponds to 7um pixel size. 

The optical resolution is 7200dpi. That is for the sensor only. The real, achievable resolution, when scanning at 7200dpi, is around 3800dpi as tested with a target. The discrepancy is due to:

• lens quality (in the scanner)

• focus quality (in the scanner)

• stepper motor quality (the thing that moves the sensor line across the film to scan it)

Long story short, you get better resolution when scanning at 7200dpi, but that's a small difference compared to filesizes and scan times. The way to get the best res at the best filesize, is to scan at 7200dpi and resize (say with Bicubic) by a factor of 3 or so (roughly 1,8x in each dimension). In practice, scanning at 3600dpi (which will yield 3200-3400dpi tested with a target) is the best compromise in terms of resolution, scanning speed and file size.