Resizing After Scanning Black & White Negative

[IanBarber]

Just looking for clarification that the method I am currently using for resizing after scanning with an Epson V800 scanner is considered to be the most optimal way.

Step 1
Scan at 2400ppi and bring into Photoshop.
Note: I have recently started to scan at 4800 wondering if this will give give me closer to the scanners optimal resolution of 2400.



Step2
Uncheck the resample checkbox and change the Resolution to match the printer (360 for the Epson R3880)



Step 3
Recheck the Resample checkbox, enter the desired output size and choose Bicubic Sharper (reduction) for the resample method.

[mdarnton]

Maybe someone will respond to this: I'm not sure that it's such a bad idea to let the printer handle resampling rather than do it yourself. It should know what it wants. That's not an informed comment, so I welcome qualified answers!

[Alan9940]

Ian, that's a fine method to down-sample an image file. It's best if you don't let the printer driver resample the image in any way. FWIW, the method I established years ago is:

1. Test to determine the optimal optical resolution for your particular scanner; not always what the manufacturer claims as the max optical resolution.

2. Scan all film at your pre-determined optimal scanner resolution, thereby creating a master file that is never modified (think of it as a raw file.)

3. Edit, as needed, then target output for whatever is needed.

Note: Bicubic Sharper may not always be the best choice when down-sampling. Depending on the image, a simple Bicubic will provide better tonal transitions.

[faberryman]

What method does PS use for downsampling when Auto is selected?

[Alan9940]

What method does PS use for downsampling when Auto is selected?

Don't know for sure, but I'd assume Bicubic Smoother since that algorithm was Adobe's recommendation for reducing image size back when it was added to the Image Size dialog.

[rdeloe]

Jeff Schewe, author of The Digital Print, recommends preparing the file in the resolution needed by the printer rather than letting the printer driver do the re-sizing; this includes resizing through the print dialogue box. For downsampling, he suggests bicubic smoother. For upsizing a lot, he recommends preserve detail. For small amounts up or down, he recommends using the automatic setting and letting Photoshop decide. In his testing with Epson printers, he claims to be able to see the difference between 720 ppi and 360 ppi (so don't throw away the extra pixels is his advice). I use Lightroom, which takes care of up- and down-sizing "under the hood". I'm creating a TIFF at export, which I send to Quadtone RIP. In my experience it does a good job. There are also specialized applications out there that claim to have various kinds of secret sauce to produce better results.

[Pere Casals]

What method does PS use for downsampling when Auto is selected?

This is undisclosed, I think: "Automatic: Photoshop chooses the resampling method based on the document type and whether the document is scaling up or down." (document type ? different for indexed color, etc?)

A good guess is that it depends on if we are increasing or decreasing the pixel count, Bicubic Smoother (enlargement), Bicubic Sharper (reduction), for those situations, ...also I'm suspecting they use Bicubic (smoother gradients) if the new size is close to the original.

After any resize a sharpening should follow... but IMHO the sharpenings included in the Ps resizing algorithms are conservative to not destroy things, so my view is that anyway we should try a final manual sharpening just before moving from 16 bits/channel to 8 bits/channel for the image release.

[Pere Casals]

I would point that Nik Collection has a nice sharpening tool, it allows to pick control points in the image and to ajust settings for those points to teach the tool what we want, so many times we can craft and advanced custom sharpening in a very straight way:

https://luminous-landscape.com/3-ste...mal-sharpness/
https://web.archive.org/web/20190102...mal-sharpness/

[Peter De Smidt]

As others have said, minimize what is thrown away. If you're scan is big enough for 720dpi at the printing size, then use that. If the size is between 720 and 360, then there are three choices, all of which you can test for yourself. Upsize to 720, send the file straight to the printer, and downsize to 360. Give it a whirl. Each method will require different levels of sharpening.

Regarding interpolation, I'd use bicubric for making smaller. bicurbric sharper simply adds sharpening. I'd rather sharpen separately. For enlargement, the best built in method with Photoshop is Preserve Details. Some versions of Lancros are better, but they invovle 3rd party software. The best that I've used is Topaz Gigapixel AI. I just had a 36"x48" print made from a 24 mp digital file, and Topaz did the best job. I tested all of the versions mentioned, as well as Genuine Fractals.

[Pere Casals]

The best that I've used is Topaz Gigapixel AI.

I guess this one falls in the convolutional neural networks category https://en.wikipedia.org/wiki/Compar...ing_algorithms