Problems with photo import pixelation

[StewDay]

Hi,

 

I'm a relative newb to Affinity Photo but have some photo editing experience with Photoshop & others.

 

The issue I'm having is with scanning an image at the highest resolution for editing in AP.

 

I have a Brother Ds-720D and am using NAPS2 as the scanner software on a Windows 10 machine. I am scanning at 1200 DPI.

Scanned images when viewed in NAPS2 when zoomed to the extreme (1000%) show almost no sign of pixelation.

When I try to export in any photo image format - png, jpeg or tiff - the output file is quite pixelated.

Viewing the file properties of the exported file shows it's reduced the image to 200DPI.

From what I can see I've set the NAPS2 preferences for the highest quality output.

 

So ... I tried exporting as PDF and the output file when viewed using Adobe Reader with extreme zoom (1000%) looks identical to the image as viewed in NAPS2.

 

Ok, so now I seem to be getting somewhere ...

 

However, when I try to open the PDF in Affinity Photo the maximum DPI I can select for the import is 400.

If I go with that setting the imported PDF is significantly better than the tiff import but is still quite a bit more pixelated than viewing the PDF in Adobe Reader.

[example below with the AP import on top with the Adobe Reader view below]

 

BTW, I've set the View Quality setting in AP to Bilinear (Best Quality), so that is not the issue.

 

Is there any way to import my PDF at 120DPI?

If not, can anyone suggest a better way to get the highest quality scan into AP?

 

The image is a crusty old, low-quality set of four snaps from a photo booth (yeah, a real one) from when my wife & I first started dating over 20 years ago. We'd like to crop the four images, clean them up somewhat and blow up prints from them. I realise they'll always look like low-quality photos and I'm happy to roll with those artefacts. What I want to try to avoid is adding additional processing artefacts.

 

Hope you can help.

 

Cheers,

 

Stew

[walt.farrell]

I installed NAPS2 to check the files it produces, and when I tell it to scan at 1200dpi, save as TIFF, and then examine the image properties the file claims to be 1200dpi. So, if you're only getting 200dpi I'm not sure what's happening. Sorry.

[StewDay]

Hi Walt ,

 

Don't be sorry. I now have one more piece of information. So either I haven't got the settings right in NAPS2 or there is some kind of incompatibility with my scanner. 

 

I'll investigate further what's going on with the initial scan as I'd imagine AP has no issues importing a 1200DPI Tiff.

 

Stew

[StewDay]

Ok, so I've had another look at NAPS2 and have been able to get it to spit out a 600DPI Tiff ... even though 1200 was appearing in the options my scanner is limited to 600 so that may have had something to do with it defaulting to 200 ... who knows.

 

Anyway, I still had a similar issue. After completing the scan if I zoomed in while previewing in NAPS2 the scan looks excellent. When I save as tiff I'm seeing pixelation.

The properties of that tiff tell me it's 600DPI and the quality was the best so far ... but still not as good as when viewing in NAPS2.

 

Shouldn't it be the same? Tiff is lossless right?

 

Anyway, I thought I'd try saving as a png, just for the heck of it ... and guess what? Perfect!

I can't see a difference between the saved png and the preview in NAPS2.

 

So, I don't know why, but there's something weird going on with saving to Tiff from NAPS2 on my machine. PNG, however, works perfectly.

 

Thanks again Walt for pointing me back to the source of the issue.

 

[walt.farrell]

I have no idea why TIFF would behave differently from PNG, as both are (as far as I know) lossless formats. But congratulations on having found a working solution

[v_kyr]

That C# tool uses the .Net framework Bitmap class to save to various bitmap formats, so it writes a TIFF file by reusing the default MS .Net library routines here.

[firstdefence]

Your scanners scanning specs are (See Below) maybe you got the 1200dpi from this. Have you tried any other software? what about Hamrick's Vuescan

 

[StewDay]

Hi firstdefence,

 

No, I haven't tried any other software. I'm too cheap to spend money on something like Vuescan when I can get NAPS2 for free!

 

So from that screen grab you posted does that mean I should be able to scan at 1200 dpi? I'm not sure what Interpolated scan resolution and Scan resolution from ADF refer to???

 

[v_kyr]

That Brother model is a mobile pocket scanner isn't it? - It's Scan resolution (optical) is up to 600 x 600 dpi according to Brother specs, so that's the physical (optical) max resolution it scans. -- See the following more detailed explanations to get an idea:

1. What does interpolation mean?

Interpolate means that between real, scanned pixels the software will set those whose color value is an average of the neighboring pixels. This gives a scan in a higher resolution than the max. possible optical resolution of the scanner. However, the file does not contain any additional information: details that can not be captured at the highest optical resolution will not, if interpolated!

For example, if a scanned pixel has the value 202 and the next scanned pixel has the value 206, then the interpolated interpolated pixel is calculated to be 204 [1]. At this point, therefore, there is no information that would be taken from the template.

A problem arises in the following case: On the template is a black field with a very thin white line that goes through the field. Put the case, the scanner detects at its max. optical resolution respectively left and right of the line the outermost edge of the black field. When interpolating, he will then also set the intermediate pixel black, since the average of two black pixels again results in a black (interpolated) pixel. This thin white line will therefore not be present in the scan because it was not optically detected.

 

NOTE: details that can not be captured at the highest physical resolution will not work if interpolated!

 

2. What exactly is the "optical" resolution?

If this is the case, your scanner has a maximum optical resolution of 600 x 600 ppi. This means there are 600 CCDs per inch horizontally scanning your original. That's the maximum, which is optically possible. He really can not scan anything more.

The same applies to a 600 x 1200 ppi scanner. However, it looks a bit different with the vertical resolution, which is not limited by a number of CCDs. Here, the resolution is controlled by a step motor, d. H. a motor moves the car gradually. The more steps per inch, the higher the resolution.

Scanning with 1200 x 1200 ppi also results in a problem here: Since there are only 600 CCDs horizontally and interpolated to 1200 ppi, the following happens: Horizontally, every second pixel is scanned and the intermediate interpolated. Vertical is scanned 1200 steps per inch. However, since the CCDs have a diameter of one-sixth of an inch, the scanned pixels overlap each by 50%, which somewhat distorts the result.

That's why the maximum optical resolution of a 600 x 1200 ppi scanner is 600 ppi! The phrase "1200 ppi" means only that the motor can make 1200 steps per inch. More details than 600 ppi can not be scanned with it.

The advantage of 600x1200 ppi scanners over 600x600 ppi is that if a stepper motor is capable of 1200 steps per inch, it probably works very well at 600 steps.

3. Why is interpolation mostly not useful?

Interpolating is therefore not useful because increasing the resolution potentially increases the amount of data without including additional information. The doubling of the resolution corresponds to z. Eg a quadrupling (2 squared) the amount of data. So you get partially extremely larger files without any benefit.

If you have a max. optical resolution of 300 ppi and interpolate to 600 ppi, this means that about 75% of your data did not result from the template, but were calculated. 75% of the data do not contain any additional information! With an interpolation to 1200 ppi 93.8% of the data are already without additional information!

The following graphic serves as an example. The black boxes symbolize the pixels that were actually scanned. Since it was interpolated to twice the resolution, every second pixel is horizontally and vertically an interpolated pixel, here shown in gray.

For a scanner with 300 x 600 ppi, the 2nd line would not be interpolated, but scanned, but due to the overlap, this line is still an average of the 1st and 3rd line. The result is the same.

For example, with a 9 x 13 cm color photo, this example (1200 ppi) would give you a file about 74.7 MB in size, with all the consequences mentioned. And only about 4.7 MB contain "real" information. Around 70 MB are interpolated data!

You can now calculate for yourself how high the proportion of "real" data is at an interpolated resolution of 9600 ppi, which is advertised so often. Incidentally, this file would be about 4.7 GB in size. How many of them do you bring back to your hard drive? And how do you want to print this file? How do you want to open them in your application?

So why do you want to waste your memory space with this superfluous, informal MByte (or GByte)? Apart from the fact that these amounts of data can slow your computer to a standstill, at the latest when it comes to printing.

Since, as explained in the previous chapter, when scanning lower resolutions are sufficient than many scanners optically possible, I keep interpolating i. d. R. does not make sense. You only get more data that your printer can not handle.

 

4. No rule without exception: when is interpolation still useful?

However, it is not the case that interpolating is completely meaningless. For example, it may be necessary if the calculated scan resolution is the opt. Resolution of the scanner exceeds, z. For example, if you want to greatly enlarge the scan. Although this does not give you any additional information, it reduces the effect of stairs because there is a larger number of pixels.

This is likely to occur when scanning line originals, as you are scanning at higher resolutions than with grayscale or color originals. In spite of the lower color depth, you will get larger files than when scanning as a gray level and then anti-aliasing, but the gray tones would have to be rasterized!

Also, interpolating may be necessary if you are scanning slides or negatives and the necessary resolution can only be achieved by interpolating.

Basically, with line drawings, it may be useful to interpolate when the opt. Resolution of the scanner is not enough. For grayscale and color charts, it's usually not a good idea and usually not necessary. Interpolation never reaches a higher information content!

The maximum interpolated resolution of a scanner is therefore the least important technical feature of a scanner. Only it can be advertised so well ...

By the way: If your scanner is max. "optical" resolution 300 x 600 ppi indicates you can only scan with a resolution of 300 x 300 ppi [2], if you want to avoid interpolation. At a resolution of 600 x 600 ppi, it has to interpolate in one direction (the maximum resolution of 300 ppi resolution) to 600 ppi, otherwise the image would be compressed. To prevent stretching or upsetting, the horizontal and vertical resolution must always be the same. In the case of vertical resolution, as already mentioned, the pixels overlap, which amounts to an interpolation.

 

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[1] This example describes the "Linear Interpolation". In addition, there are also the "square" and the "cubic interpolation". Although they require more computing time, they deliver better results. Nevertheless, the pixels thus calculated without correspondence on the original.

[2] The statement is only correct for resolutions higher than the optical resolution. However, there are also cases where interpolation is performed although the optical resolution has not yet been reached.

 

 

 

 

 

 

 

 

 

[StewDay]

Thanks v_kyr ... but you're hurting my brain  

 

This is enough for me: 

Quote

It's Scan resolution (optical) is up to 600 x 600 dpi according to Brother specs, so that's the physical (optical) max resolution it scans